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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashAndCashEquivalentsAtCarryingValue" xlink:to="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CashAndCashEquivalentsAtCarryingValue_lbl" xml:lang="en-US">Cash and Cash Equivalents, at Carrying Value</label>
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    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ShortTermBankDeposits" xlink:label="plx_ShortTermBankDeposits" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ShortTermBankDeposits" xlink:to="plx_ShortTermBankDeposits_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ShortTermBankDeposits_lbl" xml:lang="en-US">Carrying value of deposits held with banks for short period, usually less than one year or the normal operating cycle, whichever is longer.</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsReceivableNetCurrent" xlink:to="us-gaap_AccountsReceivableNetCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xml:lang="en-US">Accounts Receivable, Net, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xml:lang="en-US">Accounts receivable - Trade</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherAssetsCurrent" xlink:label="us-gaap_OtherAssetsCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherAssetsCurrent" xlink:to="us-gaap_OtherAssetsCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xml:lang="en-US">Other Assets, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xml:lang="en-US">Other assets</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_OtherAssetsCurrent_lbl" xml:lang="en-US">Other assets</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InventoryNet" xlink:label="us-gaap_InventoryNet" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InventoryNet" xlink:to="us-gaap_InventoryNet_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InventoryNet_lbl" xml:lang="en-US">Inventory, Net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_InventoryNet_lbl" xml:lang="en-US">Inventories</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_InventoryNet_lbl" xml:lang="en-US">Total inventory</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsCurrent" xlink:label="us-gaap_AssetsCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsCurrent" xlink:to="us-gaap_AssetsCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AssetsCurrent_lbl" xml:lang="en-US">Assets, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_AssetsCurrent_lbl" xml:lang="en-US">Total current assets</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AssetsNoncurrentAbstract" xlink:label="us-gaap_AssetsNoncurrentAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AssetsNoncurrentAbstract" xlink:to="us-gaap_AssetsNoncurrentAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AssetsNoncurrentAbstract_lbl" xml:lang="en-US">Assets, Noncurrent [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AssetsNoncurrentAbstract_lbl" xml:lang="en-US">NON-CURRENT ASSETS:</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent" xlink:label="us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent" xlink:to="us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_lbl" xml:lang="en-US">Assets for Plan Benefits, Defined Benefit Plan</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DefinedBenefitPlanAssetsForPlanBenefitsNoncurrent_lbl" xml:lang="en-US">Funds in respect of employee rights upon retirement</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="us-gaap_PropertyPlantAndEquipmentNet" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentNet" xlink:to="us-gaap_PropertyPlantAndEquipmentNet_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xml:lang="en-US">Property, Plant and Equipment, Net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xml:lang="en-US">Property and equipment, net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xml:lang="en-US">Property, Plant and Equipment, Net, Total</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseRightOfUseAsset" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseRightOfUseAsset" xlink:to="us-gaap_OperatingLeaseRightOfUseAsset_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xml:lang="en-US">Operating Lease, Right-of-Use Asset</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseRightOfUseAsset_lbl" xml:lang="en-US">Operating lease right of use assets</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Assets" xlink:label="us-gaap_Assets" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Assets" xlink:to="us-gaap_Assets_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_Assets_lbl" xml:lang="en-US">Assets</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_Assets_lbl" xml:lang="en-US">Total assets</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquityAbstract" xlink:to="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xml:lang="en-US">Liabilities and Equity [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xml:lang="en-US">LIABILITIES AND STOCKHOLDERS' EQUITY (NET OF CAPITAL DEFICIENCY)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrentAbstract" xlink:label="us-gaap_LiabilitiesCurrentAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrentAbstract" xlink:to="us-gaap_LiabilitiesCurrentAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xml:lang="en-US">Liabilities, Current [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xml:lang="en-US">CURRENT LIABILITIES:</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAbstract" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAbstract" xlink:to="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAbstract_lbl" xml:lang="en-US">Accounts Payable and Accrued Liabilities, Current [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAbstract_lbl" xml:lang="en-US">Accounts payable and accruals:</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_AccountsPayableAndAccruedLiabilitiesCurrentAbstract_lbl" xml:lang="en-US">Accounts payable and accruals - other:</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableTradeCurrent" xlink:label="us-gaap_AccountsPayableTradeCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableTradeCurrent" xlink:to="us-gaap_AccountsPayableTradeCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccountsPayableTradeCurrent_lbl" xml:lang="en-US">Accounts Payable, Trade, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AccountsPayableTradeCurrent_lbl" xml:lang="en-US">Trade</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableOtherCurrent" xlink:label="us-gaap_AccountsPayableOtherCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableOtherCurrent" xlink:to="us-gaap_AccountsPayableOtherCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccountsPayableOtherCurrent_lbl" xml:lang="en-US">Accounts Payable, Other, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AccountsPayableOtherCurrent_lbl" xml:lang="en-US">Other</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiabilityCurrent" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityCurrent" xlink:to="us-gaap_OperatingLeaseLiabilityCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xml:lang="en-US">Operating Lease, Liability, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xml:lang="en-US">Operating lease liabilities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityCurrent" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiabilityCurrent" xlink:to="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xml:lang="en-US">Contract with Customer, Liability, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ContractWithCustomerLiabilityCurrent_lbl" xml:lang="en-US">Contracts liability</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebtCurrent" xlink:label="us-gaap_ConvertibleDebtCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConvertibleDebtCurrent" xlink:to="us-gaap_ConvertibleDebtCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ConvertibleDebtCurrent_lbl" xml:lang="en-US">Convertible Debt, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ConvertibleDebtCurrent_lbl" xml:lang="en-US">Convertible notes</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NotesPayableCurrent" xlink:label="us-gaap_NotesPayableCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NotesPayableCurrent" xlink:to="us-gaap_NotesPayableCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NotesPayableCurrent_lbl" xml:lang="en-US">Notes Payable, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NotesPayableCurrent_lbl" xml:lang="en-US">Promissory note</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesCurrent" xlink:label="us-gaap_LiabilitiesCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesCurrent" xlink:to="us-gaap_LiabilitiesCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xml:lang="en-US">Liabilities, Current</label>
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityNoncurrent" xlink:label="us-gaap_ContractWithCustomerLiabilityNoncurrent" />
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent" xlink:label="us-gaap_PensionAndOtherPostretirementAndPostemploymentBenefitPlansLiabilitiesNoncurrent" />
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiabilityNoncurrent" xlink:to="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" />
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherLiabilitiesNoncurrent" xlink:label="us-gaap_OtherLiabilitiesNoncurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherLiabilitiesNoncurrent" xlink:to="us-gaap_OtherLiabilitiesNoncurrent_lbl" />
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesNoncurrent" xlink:label="us-gaap_LiabilitiesNoncurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesNoncurrent" xlink:to="us-gaap_LiabilitiesNoncurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesNoncurrent_lbl" xml:lang="en-US">Liabilities, Noncurrent</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LiabilitiesNoncurrent_lbl" xml:lang="en-US">Total long term liabilities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Liabilities" xlink:label="us-gaap_Liabilities" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Liabilities" xlink:to="us-gaap_Liabilities_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_Liabilities_lbl" xml:lang="en-US">Liabilities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_Liabilities_lbl" xml:lang="en-US">Total liabilities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommitmentsAndContingencies" xlink:label="us-gaap_CommitmentsAndContingencies" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommitmentsAndContingencies" xlink:to="us-gaap_CommitmentsAndContingencies_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommitmentsAndContingencies_lbl" xml:lang="en-US">Commitments and Contingencies</label>
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquityAbstract" xlink:label="us-gaap_StockholdersEquityAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityAbstract" xlink:to="us-gaap_StockholdersEquityAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xml:lang="en-US">Stockholders' Equity Attributable to Parent [Abstract]</label>
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockValue" xlink:label="us-gaap_CommonStockValue" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockValue" xlink:to="us-gaap_CommonStockValue_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockValue_lbl" xml:lang="en-US">Common Stock, Value, Issued</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockValue_lbl" xml:lang="en-US">Common Stock, $0.001 par value: Authorized - as of December 31, 2020 and 2021, 120,000,000 shares; issued and outstanding - as of December 31, 2020 and 2021, 34,765,280 and 45,556,647 shares, respectively</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalCommonStock" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalCommonStock" xlink:to="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AdditionalPaidInCapitalCommonStock_lbl" xml:lang="en-US">Additional Paid in Capital, Common Stock</label>
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquity" xlink:label="us-gaap_StockholdersEquity" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquity" xlink:to="us-gaap_StockholdersEquity_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockholdersEquity_lbl" xml:lang="en-US">Stockholders' Equity Attributable to Parent</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_StockholdersEquity_lbl" xml:lang="en-US">Beginning balance</label>
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LiabilitiesAndStockholdersEquity" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LiabilitiesAndStockholdersEquity" xlink:to="us-gaap_LiabilitiesAndStockholdersEquity_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xml:lang="en-US">Liabilities and Equity</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xml:lang="en-US">Total liabilities net of capital deficiency</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockParOrStatedValuePerShare" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xml:lang="en-US">Common Stock, issued</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockSharesOutstanding" xlink:label="us-gaap_CommonStockSharesOutstanding" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockSharesOutstanding" xlink:to="us-gaap_CommonStockSharesOutstanding_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xml:lang="en-US">Common Stock, Shares, Outstanding</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xml:lang="en-US">Common Stock, outstanding</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementAbstract" xlink:label="us-gaap_IncomeStatementAbstract" />
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductOrServiceAxis" xlink:label="srt_ProductOrServiceAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ProductOrServiceAxis" xlink:to="srt_ProductOrServiceAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_ProductOrServiceAxis_lbl" xml:lang="en-US">Product and Service [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ProductsAndServicesDomain" xlink:label="srt_ProductsAndServicesDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ProductsAndServicesDomain" xlink:to="srt_ProductsAndServicesDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_ProductsAndServicesDomain_lbl" xml:lang="en-US">Product and Service [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProductMember" xlink:label="us-gaap_ProductMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProductMember" xlink:to="us-gaap_ProductMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProductMember_lbl" xml:lang="en-US">Goods [Member]</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LicenseAndServiceMember_lbl" xml:lang="en-US">License and R&amp;D Services [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Revenues" xlink:label="us-gaap_Revenues" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Revenues" xlink:to="us-gaap_Revenues_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_Revenues_lbl" xml:lang="en-US">Revenues.</label>
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="us-gaap_ResearchAndDevelopmentExpense" />
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OtherNonoperatingIncome" xlink:label="us-gaap_OtherNonoperatingIncome" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OtherNonoperatingIncome" xlink:to="us-gaap_OtherNonoperatingIncome_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OtherNonoperatingIncome_lbl" xml:lang="en-US">Other Nonoperating Income</label>
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NonoperatingIncomeExpense" xlink:label="us-gaap_NonoperatingIncomeExpense" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NonoperatingIncomeExpense" xlink:to="us-gaap_NonoperatingIncomeExpense_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xml:lang="en-US">Nonoperating Income (Expense)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NonoperatingIncomeExpense_lbl" xml:lang="en-US">FINANCIAL EXPENSES - NET</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetIncomeLoss_lbl" xml:lang="en-US">Net Income (Loss) Attributable to Parent</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EarningsPerShareBasic" xlink:to="us-gaap_EarningsPerShareBasic_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xml:lang="en-US">Earnings Per Share, Basic</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_EarningsPerShareBasic_lbl" xml:lang="en-US">LOSS PER SHARE OF COMMON STOCK - BASIC</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EarningsPerShareDiluted" xlink:label="us-gaap_EarningsPerShareDiluted" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xml:lang="en-US">Earnings Per Share, Diluted</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_EarningsPerShareDiluted_lbl" xml:lang="en-US">LOSS PER SHARE OF COMMON STOCK - DILUTED</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic" xlink:to="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xml:lang="en-US">Weighted Average Number of Shares Outstanding, Basic</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_WeightedAverageNumberOfSharesOutstandingBasic_lbl" xml:lang="en-US">WEIGHTED AVERAGE NUMBER OF SHARES OF COMMON STOCK USED IN COMPUTING LOSS PER SHARE - BASIC</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_WeightedAverageNumberOfDilutedSharesOutstanding_lbl" xml:lang="en-US">WEIGHTED AVERAGE NUMBER OF SHARES OF COMMON STOCK USED IN COMPUTING LOSS PER SHARE - DILUTED</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementOfStockholdersEquityAbstract" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfStockholdersEquityAbstract" xlink:to="us-gaap_StatementOfStockholdersEquityAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StatementOfStockholdersEquityAbstract_lbl" xml:lang="en-US">CONSOLIDATED STATEMENTS OF CHANGES IN CAPITAL DEFICIENCY</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="us-gaap_StatementEquityComponentsAxis" />
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="us-gaap_EquityComponentDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EquityComponentDomain" xlink:to="us-gaap_EquityComponentDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EquityComponentDomain_lbl" xml:lang="en-US">Equity Component [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CommonStockMember" xlink:label="us-gaap_CommonStockMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CommonStockMember" xlink:to="us-gaap_CommonStockMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CommonStockMember_lbl" xml:lang="en-US">Common Stock [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="us-gaap_AdditionalPaidInCapitalMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdditionalPaidInCapitalMember" xlink:to="us-gaap_AdditionalPaidInCapitalMember_lbl" />
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="us-gaap_RetainedEarningsMember" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharesOutstanding_lbl" xml:lang="en-US">Shares, Outstanding</label>
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    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_IssuanceOfCommonStockAndWarrantsNetOfIssuanceCostValue" xlink:label="plx_IssuanceOfCommonStockAndWarrantsNetOfIssuanceCostValue" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_IssuanceOfCommonStockAndWarrantsNetOfIssuanceCostValue_lbl" xml:lang="en-US">Represents issuance of common stock, net of issuance cost, value.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_IssuanceOfCommonStockAndWarrantsNetOfIssuanceCostValue_lbl" xml:lang="en-US">Issuance Of Common Stock And Warrants, Net Of Issuance Cost, Value</label>
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    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_IssuanceOfCommonStockAndWarrantsNetOfIssuanceCostInShares" xlink:label="plx_IssuanceOfCommonStockAndWarrantsNetOfIssuanceCostInShares" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_IssuanceOfCommonStockAndWarrantsNetOfIssuanceCostInShares_lbl" xml:lang="en-US">Represents issuance of common stock, net of issuance cost, in shares.</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_IssuanceOfCommonStockAndWarrantsNetOfIssuanceCostInShares_lbl" xml:lang="en-US">Issuance of common stock and warrants, net of issuance cost (in shares)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueNewIssues" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xml:lang="en-US">Stock Issued During Period, Value, New Issues</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xml:lang="en-US">Issuance of common stock, net of issuance cost</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xml:lang="en-US">Stock Issued During Period, Shares, New Issues</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xml:lang="en-US">Issuance of common stock, net of issuance cost (in shares)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xml:lang="en-US">Number of shares issued (in shares)</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_StockIssuedDuringPeriodValueSalesAgreement_lbl" xml:lang="en-US">Equity impact of the value of new stock issued during the period. Includes shares issued in a sales agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_StockIssuedDuringPeriodValueSalesAgreement_lbl" xml:lang="en-US">Stock Issued During Period, Value, Sales Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_StockIssuedDuringPeriodValueSalesAgreement_lbl" xml:lang="en-US">Issuance of common stock under the Sales Agreement, net</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_StockIssuedDuringPeriodSharesSalesAgreement_lbl" xml:lang="en-US">Stock Issued During Period, Shares, Sales Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_StockIssuedDuringPeriodSharesSalesAgreement_lbl" xml:lang="en-US">Stock Issued During Period, Shares, Sales Agreement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_StockIssuedDuringPeriodSharesSalesAgreement_lbl" xml:lang="en-US">Issuance of common stock under the Sales Agreement, net (in shares)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" />
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    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeitures" xlink:label="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeitures" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeitures_lbl" xml:lang="en-US">Amount of recognized equity-based compensation during the period for restricted stock awards.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeitures_lbl" xml:lang="en-US">Share Based Compensation Restricted Stock Awards Net Of Forfeitures</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeitures_lbl" xml:lang="en-US">Share-based compensation related to restricted stock awards</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeituresShares" xlink:label="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeituresShares" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeituresShares" xlink:to="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeituresShares_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeituresShares_lbl" xml:lang="en-US">Share Based Compensation Restricted Stock Awards Net Of Forfeitures Shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeituresShares_lbl" xml:lang="en-US">Share Based Compensation Restricted Stock Awards Net Of Forfeitures Shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ShareBasedCompensationRestrictedStockAwardsNetOfForfeituresShares_lbl" xml:lang="en-US">Share-based compensation related to restricted stock awards (in shares)</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_StockIssuedDuringPeriodValueWarrantsExercises" xlink:label="plx_StockIssuedDuringPeriodValueWarrantsExercises" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_StockIssuedDuringPeriodValueWarrantsExercises" xlink:to="plx_StockIssuedDuringPeriodValueWarrantsExercises_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_StockIssuedDuringPeriodValueWarrantsExercises_lbl" xml:lang="en-US">Value of shares issued during period for exercise of warrants.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_StockIssuedDuringPeriodValueWarrantsExercises_lbl" xml:lang="en-US">Stock Issued During Period, Value, Warrants Exercises</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_StockIssuedDuringPeriodValueWarrantsExercises_lbl" xml:lang="en-US">Exercise of warrants</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_StockIssuedDuringPeriodSharesWarrantsExercises" xlink:label="plx_StockIssuedDuringPeriodSharesWarrantsExercises" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_StockIssuedDuringPeriodSharesWarrantsExercises" xlink:to="plx_StockIssuedDuringPeriodSharesWarrantsExercises_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_StockIssuedDuringPeriodSharesWarrantsExercises_lbl" xml:lang="en-US">Number of shares issued during period for exercise of warrants.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_StockIssuedDuringPeriodSharesWarrantsExercises_lbl" xml:lang="en-US">Stock Issued During Period, Shares, Warrants Exercises</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_StockIssuedDuringPeriodSharesWarrantsExercises_lbl" xml:lang="en-US">Exercise of warrants (in shares)</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ReacquisitionOfEquityComponentOfConvertibleNotes" xlink:label="plx_ReacquisitionOfEquityComponentOfConvertibleNotes" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ReacquisitionOfEquityComponentOfConvertibleNotes" xlink:to="plx_ReacquisitionOfEquityComponentOfConvertibleNotes_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ReacquisitionOfEquityComponentOfConvertibleNotes_lbl" xml:lang="en-US">Reacquisition Of Equity Component Of Convertible Notes</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ReacquisitionOfEquityComponentOfConvertibleNotes_lbl" xml:lang="en-US">Reacquisition Of Equity Component Of Convertible Notes</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="plx_ReacquisitionOfEquityComponentOfConvertibleNotes_lbl" xml:lang="en-US">Reacquisition of equity component of convertible notes</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ReacquisitionOfEquityComponentOfConvertibleNotes_lbl" xml:lang="en-US">Reacquisition of equity component of convertible notes</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_EquityComponentOfConvertibleNotesNetOfTransactionCosts" xlink:label="plx_EquityComponentOfConvertibleNotesNetOfTransactionCosts" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_EquityComponentOfConvertibleNotesNetOfTransactionCosts" xlink:to="plx_EquityComponentOfConvertibleNotesNetOfTransactionCosts_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_EquityComponentOfConvertibleNotesNetOfTransactionCosts_lbl" xml:lang="en-US">Equity Component Of Convertible Notes Net Of Transaction Costs</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_EquityComponentOfConvertibleNotesNetOfTransactionCosts_lbl" xml:lang="en-US">Equity Component Of Convertible Notes Net Of Transaction Costs</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_EquityComponentOfConvertibleNotesNetOfTransactionCosts_lbl" xml:lang="en-US">Equity component of convertible notes, net of transaction costs</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StatementOfCashFlowsAbstract" xlink:label="us-gaap_StatementOfCashFlowsAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StatementOfCashFlowsAbstract" xlink:to="us-gaap_StatementOfCashFlowsAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xml:lang="en-US">CONSOLIDATED STATEMENTS OF CASH FLOWS</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xml:lang="en-US">Net Cash Provided by (Used in) Operating Activities [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xml:lang="en-US">CASH FLOWS FROM OPERATING ACTIVITIES:</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract" xlink:to="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xml:lang="en-US">Adjustments to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xml:lang="en-US">Adjustments required to reconcile net loss to net cash used in operating activities:</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensation" xlink:label="us-gaap_ShareBasedCompensation" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensation" xlink:to="us-gaap_ShareBasedCompensation_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensation_lbl" xml:lang="en-US">Share-based Compensation</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensation_lbl" xml:lang="en-US">Share-based compensation</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_Depreciation" xlink:label="us-gaap_Depreciation" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_Depreciation" xlink:to="us-gaap_Depreciation_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_Depreciation_lbl" xml:lang="en-US">Depreciation</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_Depreciation_lbl" xml:lang="en-US">Depreciation</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ForeignCurrencyTransactionGainLossUnrealized" xlink:to="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xml:lang="en-US">Foreign Currency Transaction Gain (Loss), Unrealized</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossUnrealized_lbl" xml:lang="en-US">Financial income, net (mainly exchange differences)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PensionAndOtherPostretirementBenefitExpense" xlink:label="us-gaap_PensionAndOtherPostretirementBenefitExpense" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PensionAndOtherPostretirementBenefitExpense" xlink:to="us-gaap_PensionAndOtherPostretirementBenefitExpense_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PensionAndOtherPostretirementBenefitExpense_lbl" xml:lang="en-US">Pension and Other Postretirement Benefits Cost (Reversal of Cost)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PensionAndOtherPostretirementBenefitExpense_lbl" xml:lang="en-US">Changes in accrued liability for employee rights upon retirement</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_GainLossOnAmountsFundedInRespectOfEmployeeRightsUponRetirement" xlink:label="plx_GainLossOnAmountsFundedInRespectOfEmployeeRightsUponRetirement" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_GainLossOnAmountsFundedInRespectOfEmployeeRightsUponRetirement" xlink:to="plx_GainLossOnAmountsFundedInRespectOfEmployeeRightsUponRetirement_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_GainLossOnAmountsFundedInRespectOfEmployeeRightsUponRetirement_lbl" xml:lang="en-US">Gain (loss) on amounts funded in respect of employee rights upon retirement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_GainLossOnAmountsFundedInRespectOfEmployeeRightsUponRetirement_lbl" xml:lang="en-US">Gain Loss On Amounts Funded In Respect Of Employee Rights Upon Retirement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="plx_GainLossOnAmountsFundedInRespectOfEmployeeRightsUponRetirement_lbl" xml:lang="en-US">Gain on amounts funded in respect of employee rights upon retirement</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xlink:label="us-gaap_GainLossOnSaleOfPropertyPlantEquipment" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GainLossOnSaleOfPropertyPlantEquipment" xlink:to="us-gaap_GainLossOnSaleOfPropertyPlantEquipment_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_GainLossOnSaleOfPropertyPlantEquipment_lbl" xml:lang="en-US">Gain (Loss) on Disposition of Property Plant Equipment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_GainLossOnSaleOfPropertyPlantEquipment_lbl" xml:lang="en-US">Gain on sale of fixed assets</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_GainsLossesOnExtinguishmentOfDebt" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_GainsLossesOnExtinguishmentOfDebt" xlink:to="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xml:lang="en-US">Gain (Loss) on Extinguishment of Debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xml:lang="en-US">Loss on extinguishment of convertible notes</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_GainsLossesOnExtinguishmentOfDebt_lbl" xml:lang="en-US">Loss on extinguishment of convertible notes</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfFinancingCostsAndDiscounts" xlink:to="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xml:lang="en-US">Amortization of Debt Issuance Costs and Discounts</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AmortizationOfFinancingCostsAndDiscounts_lbl" xml:lang="en-US">Amortization of debt issuance costs and debt discount</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract" xlink:to="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xml:lang="en-US">Increase (Decrease) in Operating Capital [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xml:lang="en-US">Changes in operating assets and liabilities:</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInContractWithCustomerLiability" xlink:to="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl" xml:lang="en-US">Increase (Decrease) in Contract with Customer, Liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_IncreaseDecreaseInContractWithCustomerLiability_lbl" xml:lang="en-US">Increase (decrease) in contracts liability (including non-current portion)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsReceivable" xlink:to="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xml:lang="en-US">Increase (Decrease) in Accounts Receivable</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xml:lang="en-US">Decrease (increase) in accounts receivable and other assets</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ChangeInOperatingLeaseRightOfUseAssets" xlink:label="plx_ChangeInOperatingLeaseRightOfUseAssets" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ChangeInOperatingLeaseRightOfUseAssets" xlink:to="plx_ChangeInOperatingLeaseRightOfUseAssets_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ChangeInOperatingLeaseRightOfUseAssets_lbl" xml:lang="en-US">Amount of Net Change in Operating Lease Right Of use Assets.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ChangeInOperatingLeaseRightOfUseAssets_lbl" xml:lang="en-US">Change in Operating Lease Right Of use Assets</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="plx_ChangeInOperatingLeaseRightOfUseAssets_lbl" xml:lang="en-US">Changes in right of use assets</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInInventories" xlink:label="us-gaap_IncreaseDecreaseInInventories" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInInventories" xlink:to="us-gaap_IncreaseDecreaseInInventories_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseInInventories_lbl" xml:lang="en-US">Increase (Decrease) in Inventories</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_IncreaseDecreaseInInventories_lbl" xml:lang="en-US">Decrease (increase) in inventories</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities" xlink:to="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xml:lang="en-US">Increase (Decrease) in Accounts Payable and Accrued Liabilities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayableAndAccruedLiabilities_lbl" xml:lang="en-US">Increase in accounts payable and accruals</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities" xlink:to="us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_lbl" xml:lang="en-US">Increase (Decrease) in Other Noncurrent Liabilities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_IncreaseDecreaseInOtherNoncurrentLiabilities_lbl" xml:lang="en-US">Decrease in other long term liabilities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInOperatingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xml:lang="en-US">Net Cash Provided by (Used in) Operating Activities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xml:lang="en-US">Net cash used in operating activities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xml:lang="en-US">Net Cash Provided by (Used in) Investing Activities [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xml:lang="en-US">CASH FLOWS FROM INVESTING ACTIVITIES:</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_IncreaseDecreaseInBankDeposits" xlink:label="plx_IncreaseDecreaseInBankDeposits" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_IncreaseDecreaseInBankDeposits" xlink:to="plx_IncreaseDecreaseInBankDeposits_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_IncreaseDecreaseInBankDeposits_lbl" xml:lang="en-US">Amount of increase (decrease) in deposits held with banks.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_IncreaseDecreaseInBankDeposits_lbl" xml:lang="en-US">Increase (Decrease) in Bank Deposits</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="plx_IncreaseDecreaseInBankDeposits_lbl" xml:lang="en-US">Investment in bank deposits</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ProceedsFromSaleOfShortTermDeposits" xlink:label="plx_ProceedsFromSaleOfShortTermDeposits" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ProceedsFromSaleOfShortTermDeposits" xlink:to="plx_ProceedsFromSaleOfShortTermDeposits_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ProceedsFromSaleOfShortTermDeposits_lbl" xml:lang="en-US">Amount of cash inflow from sale of short-term deposits.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ProceedsFromSaleOfShortTermDeposits_lbl" xml:lang="en-US">Proceeds from Sale of Short-term Deposits</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ProceedsFromSaleOfShortTermDeposits_lbl" xml:lang="en-US">Proceeds from sale of short-term deposits</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment" xlink:to="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xml:lang="en-US">Payments to Acquire Property, Plant, and Equipment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xml:lang="en-US">Purchase of property and equipment</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" xlink:label="us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment" xlink:to="us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_lbl" xml:lang="en-US">Proceeds from Sale of Property, Plant, and Equipment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ProceedsFromSaleOfPropertyPlantAndEquipment_lbl" xml:lang="en-US">Proceeds from sale of property and equipment</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncreaseDecreaseOfRestrictedInvestments" xlink:label="us-gaap_IncreaseDecreaseOfRestrictedInvestments" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncreaseDecreaseOfRestrictedInvestments" xlink:to="us-gaap_IncreaseDecreaseOfRestrictedInvestments_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncreaseDecreaseOfRestrictedInvestments_lbl" xml:lang="en-US">Increase (Decrease) in Restricted Cash</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_IncreaseDecreaseOfRestrictedInvestments_lbl" xml:lang="en-US">Decrease (increase) in restricted deposit</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PaymentsForProceedsFromOtherInvestingActivities" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PaymentsForProceedsFromOtherInvestingActivities" xlink:to="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl" xml:lang="en-US">Payments for (Proceeds from) Other Investing Activities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_PaymentsForProceedsFromOtherInvestingActivities_lbl" xml:lang="en-US">Amounts funded in respect of employee rights upon retirement, net</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInInvestingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xml:lang="en-US">Net Cash Provided by (Used in) Investing Activities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xml:lang="en-US">Net cash provided by (used in) investing activities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xml:lang="en-US">CASH FLOWS FROM FINANCING ACTIVITIES:</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RepaymentsOfConvertibleDebt" xlink:label="us-gaap_RepaymentsOfConvertibleDebt" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfConvertibleDebt" xlink:to="us-gaap_RepaymentsOfConvertibleDebt_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RepaymentsOfConvertibleDebt_lbl" xml:lang="en-US">Repayments of Convertible Debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_RepaymentsOfConvertibleDebt_lbl" xml:lang="en-US">Payment for convertible notes redemption and transactions costs</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_RepaymentsOfConvertibleDebt_lbl" xml:lang="en-US">Net payment for convertible notes</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_RepaymentsOfConvertibleDebt_lbl" xml:lang="en-US">Debt conversion converted instrument amount, cash</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RepaymentsOfNotesPayable" xlink:label="us-gaap_RepaymentsOfNotesPayable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RepaymentsOfNotesPayable" xlink:to="us-gaap_RepaymentsOfNotesPayable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RepaymentsOfNotesPayable_lbl" xml:lang="en-US">Repayments of Notes Payable</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_RepaymentsOfNotesPayable_lbl" xml:lang="en-US">Payment for promissory note</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_RepaymentsOfNotesPayable_lbl" xml:lang="en-US">Payment for promissory note</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ProceedsFromIssuanceOfCommonStockAndWarrantsNet" xlink:label="plx_ProceedsFromIssuanceOfCommonStockAndWarrantsNet" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ProceedsFromIssuanceOfCommonStockAndWarrantsNet" xlink:to="plx_ProceedsFromIssuanceOfCommonStockAndWarrantsNet_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ProceedsFromIssuanceOfCommonStockAndWarrantsNet_lbl" xml:lang="en-US">Proceeds from issuance of common stock and warrants, net.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ProceedsFromIssuanceOfCommonStockAndWarrantsNet_lbl" xml:lang="en-US">Proceeds From Issuance Of Common Stock And Warrants, Net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ProceedsFromIssuanceOfCommonStockAndWarrantsNet_lbl" xml:lang="en-US">Proceeds from issuance of common stock and warrants, net</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfCommonStock" xlink:to="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xml:lang="en-US">Proceeds from Issuance of Common Stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xml:lang="en-US">Proceeds from issuance of common stock under the Sales Agreement, net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ProceedsFromIssuanceOfCommonStock_lbl" xml:lang="en-US">Gross proceeds</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromWarrantExercises" xlink:label="us-gaap_ProceedsFromWarrantExercises" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromWarrantExercises" xlink:to="us-gaap_ProceedsFromWarrantExercises_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromWarrantExercises_lbl" xml:lang="en-US">Proceeds from Warrant Exercises</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ProceedsFromWarrantExercises_lbl" xml:lang="en-US">Exercise of warrants</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NetCashProvidedByUsedInFinancingActivities" xlink:to="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xml:lang="en-US">Net Cash Provided by (Used in) Financing Activities</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xml:lang="en-US">Net cash provided by financing activities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" xlink:label="us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents" xlink:to="us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_lbl" xml:lang="en-US">Effect of Exchange Rate on Cash and Cash Equivalents</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_EffectOfExchangeRateOnCashAndCashEquivalents_lbl" xml:lang="en-US">EFFECT OF EXCHANGE RATE CHANGES ON CASH AND CASH EQUIVALENTS</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xml:lang="en-US">Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xml:lang="en-US">NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents" xlink:to="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xml:lang="en-US">Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xml:lang="en-US">BALANCE OF CASH AND CASH EQUIVALENTS AT END OF YEAR</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xml:lang="en-US">BALANCE OF CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_CollaborativeArrangementDisclosureTextBlock_lbl" xml:lang="en-US">COMMERCIALIZATION AGREEMENTS</label>
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    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ScheduleOfUsefulLifeTableTextBlock" xlink:label="plx_ScheduleOfUsefulLifeTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ScheduleOfUsefulLifeTableTextBlock" xlink:to="plx_ScheduleOfUsefulLifeTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ScheduleOfUsefulLifeTableTextBlock_lbl" xml:lang="en-US">Schedule Of Useful Life Table Text Block</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ScheduleOfUsefulLifeTableTextBlock_lbl" xml:lang="en-US">Schedule Of Useful Life [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ScheduleOfUsefulLifeTableTextBlock_lbl" xml:lang="en-US">Schedule of Useful Life</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTextBlock" xlink:to="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xml:lang="en-US">Property, Plant and Equipment [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xml:lang="en-US">Schedule of Property and Equipment</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfInventoryCurrentTableTextBlock" xlink:label="us-gaap_ScheduleOfInventoryCurrentTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfInventoryCurrentTableTextBlock" xlink:to="us-gaap_ScheduleOfInventoryCurrentTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfInventoryCurrentTableTextBlock_lbl" xml:lang="en-US">Schedule of Inventory, Current [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ScheduleOfInventoryCurrentTableTextBlock_lbl" xml:lang="en-US">Schedule of Inventory</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LeaseCostTableTextBlock" xlink:label="us-gaap_LeaseCostTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseCostTableTextBlock" xlink:to="us-gaap_LeaseCostTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xml:lang="en-US">Lease, Cost [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LeaseCostTableTextBlock_lbl" xml:lang="en-US">Schedule of Operating Leases</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" xml:lang="en-US">Lessee, Operating Lease, Liability, Maturity [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" xml:lang="en-US">Schedule of Maturity Analysis of Operating Leases</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DisaggregationOfRevenueTableTextBlock" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DisaggregationOfRevenueTableTextBlock" xlink:to="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" xml:lang="en-US">Disaggregation of Revenue [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" xml:lang="en-US">Schedule of Company's Disaggregation of Revenues</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ScheduleOfOptionsAndRestrictedStocksGrantedTableTextBlock" xlink:label="plx_ScheduleOfOptionsAndRestrictedStocksGrantedTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ScheduleOfOptionsAndRestrictedStocksGrantedTableTextBlock" xlink:to="plx_ScheduleOfOptionsAndRestrictedStocksGrantedTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ScheduleOfOptionsAndRestrictedStocksGrantedTableTextBlock_lbl" xml:lang="en-US">Tabular disclosure of options and restricted stocks granted during the period.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ScheduleOfOptionsAndRestrictedStocksGrantedTableTextBlock_lbl" xml:lang="en-US">Schedule Of Options And Restricted Stocks Granted [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ScheduleOfOptionsAndRestrictedStocksGrantedTableTextBlock_lbl" xml:lang="en-US">Schedule of Options and Restricted Stocks Granted</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" xml:lang="en-US">Share-based Compensation, Stock Options, Activity [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ScheduleOfShareBasedCompensationStockOptionsActivityTableTextBlock_lbl" xml:lang="en-US">Summary of Stock Option Activity</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock" xlink:label="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock" xlink:to="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock_lbl" xml:lang="en-US">Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ScheduleOfSharebasedCompensationRestrictedStockAndRestrictedStockUnitsActivityTableTextBlock_lbl" xml:lang="en-US">Summary of Restricted Stock Activity</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedGoodsAndNonemployeeServicesTransactionBySupplierTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedGoodsAndNonemployeeServicesTransactionBySupplierTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedGoodsAndNonemployeeServicesTransactionBySupplierTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedGoodsAndNonemployeeServicesTransactionBySupplierTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfShareBasedGoodsAndNonemployeeServicesTransactionBySupplierTextBlock_lbl" xml:lang="en-US">Schedule of Share-based Goods and Nonemployee Services Transaction by Supplier [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ScheduleOfShareBasedGoodsAndNonemployeeServicesTransactionBySupplierTextBlock_lbl" xml:lang="en-US">Summary of Options Granted to Consultants, Directors, and Other Service Providers</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTextBlock" xlink:label="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTextBlock" xlink:to="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTextBlock_lbl" xml:lang="en-US">Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTextBlock_lbl" xml:lang="en-US">Summary of Share Options Outstanding and Exercisable</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xml:lang="en-US">Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTextBlock_lbl" xml:lang="en-US">Schedule of Stock-Based Compensation Expense in Statement of Operations</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentAxis" xlink:label="us-gaap_DebtInstrumentAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentAxis" xlink:to="us-gaap_DebtInstrumentAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentAxis_lbl" xml:lang="en-US">Debt Instrument [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentNameDomain" xlink:label="us-gaap_DebtInstrumentNameDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentNameDomain" xlink:to="us-gaap_DebtInstrumentNameDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentNameDomain_lbl" xml:lang="en-US">Debt Instrument, Name [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ConvertibleNotesDue2021And2024Member" xlink:label="plx_ConvertibleNotesDue2021And2024Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ConvertibleNotesDue2021And2024Member" xlink:to="plx_ConvertibleNotesDue2021And2024Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ConvertibleNotesDue2021And2024Member_lbl" xml:lang="en-US">Represents information pertaining to convertible notes due 2021 and 2024.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ConvertibleNotesDue2021And2024Member_lbl" xml:lang="en-US">Notes 2021 and 2024</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SevenPointFivePercentageConvertibleNotesMember" xlink:label="plx_SevenPointFivePercentageConvertibleNotesMember" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SevenPointFivePercentageConvertibleNotesMember_lbl" xml:lang="en-US">2021 Notes</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SevenPointFivePercentageSeniorSecuredConvertibleNotesDue2024Member" xlink:label="plx_SevenPointFivePercentageSeniorSecuredConvertibleNotesDue2024Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SevenPointFivePercentageSeniorSecuredConvertibleNotesDue2024Member" xlink:to="plx_SevenPointFivePercentageSeniorSecuredConvertibleNotesDue2024Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_SevenPointFivePercentageSeniorSecuredConvertibleNotesDue2024Member_lbl" xml:lang="en-US">Represents the information pertaining to seven point five percentage senor secured convertible notes due 2024.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SevenPointFivePercentageSeniorSecuredConvertibleNotesDue2024Member_lbl" xml:lang="en-US">2024 Notes</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" xml:lang="en-US">Fair Value Measurement Inputs and Valuation Techniques [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTableTextBlock_lbl" xml:lang="en-US">Schedule of Fair Value Assumptions</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock" xlink:label="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock" xlink:to="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock_lbl" xml:lang="en-US">Interest Income and Interest Expense Disclosure [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_InterestIncomeAndInterestExpenseDisclosureTableTextBlock_lbl" xml:lang="en-US">Schedule of Interest Expense Recognized</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock" xlink:to="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock_lbl" xml:lang="en-US">Schedule of Deferred Tax Assets and Liabilities [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ScheduleOfDeferredTaxAssetsAndLiabilitiesTableTextBlock_lbl" xml:lang="en-US">Schedule of Deferred Tax Assets</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ScheduleOfOpenTaxYearsTableTextBlock" xlink:label="plx_ScheduleOfOpenTaxYearsTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ScheduleOfOpenTaxYearsTableTextBlock" xlink:to="plx_ScheduleOfOpenTaxYearsTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ScheduleOfOpenTaxYearsTableTextBlock_lbl" xml:lang="en-US">Schedule Of Open Tax Years Table Text Block</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ScheduleOfOpenTaxYearsTableTextBlock_lbl" xml:lang="en-US">Schedule Of Open Tax Years [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ScheduleOfOpenTaxYearsTableTextBlock_lbl" xml:lang="en-US">Schedule of Open Tax Years</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SupplementaryBalanceSheetsInformationTableTextBlock" xlink:label="plx_SupplementaryBalanceSheetsInformationTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SupplementaryBalanceSheetsInformationTableTextBlock" xlink:to="plx_SupplementaryBalanceSheetsInformationTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_SupplementaryBalanceSheetsInformationTableTextBlock_lbl" xml:lang="en-US">The tabular disclosure for supplemental balance sheets information.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SupplementaryBalanceSheetsInformationTableTextBlock_lbl" xml:lang="en-US">Supplementary Balance Sheets Information [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_SupplementaryBalanceSheetsInformationTableTextBlock_lbl" xml:lang="en-US">Supplemental Information, Balance Sheets</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock" xlink:to="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock_lbl" xml:lang="en-US">Schedule of Related Party Transactions [Table Text Block]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsTableTextBlock_lbl" xml:lang="en-US">Schedule of Related Party Transactions</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:to="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xml:lang="en-US">Property, Plant and Equipment [Table]</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:to="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xml:lang="en-US">Long-Lived Tangible Asset [Axis]</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:to="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xml:lang="en-US">Property, Plant and Equipment, Type [Domain]</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_LaboratoryEquipmentMember" xlink:to="plx_LaboratoryEquipmentMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_LaboratoryEquipmentMember_lbl" xml:lang="en-US">Laboratory Equipment [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_LaboratoryEquipmentMember_lbl" xml:lang="en-US">Laboratory Equipment [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FurnitureAndFixturesMember" xlink:label="us-gaap_FurnitureAndFixturesMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FurnitureAndFixturesMember" xlink:to="us-gaap_FurnitureAndFixturesMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FurnitureAndFixturesMember_lbl" xml:lang="en-US">Furniture [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ComputerEquipmentMember" xlink:label="us-gaap_ComputerEquipmentMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ComputerEquipmentMember" xlink:to="us-gaap_ComputerEquipmentMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xml:lang="en-US">Computer Equipment [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeAxis" xlink:label="srt_RangeAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeAxis" xlink:to="srt_RangeAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_RangeAxis_lbl" xml:lang="en-US">Range [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RangeMember" xlink:label="srt_RangeMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RangeMember" xlink:to="srt_RangeMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_RangeMember_lbl" xml:lang="en-US">Range [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MinimumMember" xlink:label="srt_MinimumMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MinimumMember" xlink:to="srt_MinimumMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_MinimumMember_lbl" xml:lang="en-US">Minimum</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MaximumMember" xlink:label="srt_MaximumMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MaximumMember" xlink:to="srt_MaximumMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_MaximumMember_lbl" xml:lang="en-US">Maximum</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentLineItems" xlink:to="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentLineItems_lbl" xml:lang="en-US">Property, Plant and Equipment [Line Items]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:to="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" xml:lang="en-US">Property, Plant and Equipment, Useful Life</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PropertyPlantAndEquipmentUsefulLife_lbl" xml:lang="en-US">Property and equipment, useful life</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SignificantAccountingPoliciesTable" xlink:label="plx_SignificantAccountingPoliciesTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SignificantAccountingPoliciesTable" xlink:to="plx_SignificantAccountingPoliciesTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_SignificantAccountingPoliciesTable_lbl" xml:lang="en-US">Significant Accounting Policies [Table].</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SignificantAccountingPoliciesTable_lbl" xml:lang="en-US">Significant Accounting Policies [Table]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsidiarySaleOfStockAxis" xlink:label="us-gaap_SubsidiarySaleOfStockAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsidiarySaleOfStockAxis" xlink:to="us-gaap_SubsidiarySaleOfStockAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsidiarySaleOfStockAxis_lbl" xml:lang="en-US">Sale of Stock [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SaleOfStockNameOfTransactionDomain" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SaleOfStockNameOfTransactionDomain" xlink:to="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xml:lang="en-US">Sale of Stock [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_AtMarketEquityOfferingMember" xlink:label="plx_AtMarketEquityOfferingMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_AtMarketEquityOfferingMember" xlink:to="plx_AtMarketEquityOfferingMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_AtMarketEquityOfferingMember_lbl" xml:lang="en-US">Represents the information pertaining to At The Market equity offering.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_AtMarketEquityOfferingMember_lbl" xml:lang="en-US">ATM Shares</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PrivatePlacementMember" xlink:label="us-gaap_PrivatePlacementMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PrivatePlacementMember" xlink:to="us-gaap_PrivatePlacementMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PrivatePlacementMember_lbl" xml:lang="en-US">Private Placement</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_TypeOfArrangementAxis" xlink:label="us-gaap_TypeOfArrangementAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_TypeOfArrangementAxis" xlink:to="us-gaap_TypeOfArrangementAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_TypeOfArrangementAxis_lbl" xml:lang="en-US">Type of Arrangement and Non-arrangement Transactions [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ArrangementsAndNonarrangementTransactionsMember" xlink:to="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xml:lang="en-US">Arrangements and Non-arrangement Transactions [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_AmendedPfizerAgreementMember" xlink:label="plx_AmendedPfizerAgreementMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_AmendedPfizerAgreementMember" xlink:to="plx_AmendedPfizerAgreementMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_AmendedPfizerAgreementMember_lbl" xml:lang="en-US">Amended Pfizer Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_AmendedPfizerAgreementMember_lbl" xml:lang="en-US">Amended Pfizer Agreement</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ChiesiUsAgreementAndChiesiExUsAgreementMember" xlink:label="plx_ChiesiUsAgreementAndChiesiExUsAgreementMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ChiesiUsAgreementAndChiesiExUsAgreementMember" xlink:to="plx_ChiesiUsAgreementAndChiesiExUsAgreementMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ChiesiUsAgreementAndChiesiExUsAgreementMember_lbl" xml:lang="en-US">n/a</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ChiesiUsAgreementAndChiesiExUsAgreementMember_lbl" xml:lang="en-US">Chiesi US Agreement and Chiesi Ex US Agreement [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ChiesiUSAgreementMember" xlink:label="plx_ChiesiUSAgreementMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ChiesiUSAgreementMember" xlink:to="plx_ChiesiUSAgreementMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ChiesiUSAgreementMember_lbl" xml:lang="en-US">Chiesi US Agreement [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ChiesiExUSAgreementMember" xlink:label="plx_ChiesiExUSAgreementMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ChiesiExUSAgreementMember" xlink:to="plx_ChiesiExUSAgreementMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ChiesiExUSAgreementMember_lbl" xml:lang="en-US">Chiesi Ex US Agreement [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_LegalEntityAxis" xlink:label="dei_LegalEntityAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_LegalEntityAxis" xlink:to="dei_LegalEntityAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_LegalEntityAxis_lbl" xml:lang="en-US">Legal Entity [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/dei/2021q4/dei-2021q4.xsd#dei_EntityDomain" xlink:label="dei_EntityDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="dei_EntityDomain" xlink:to="dei_EntityDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="dei_EntityDomain_lbl" xml:lang="en-US">Entity [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ProtalixBioTherapeuticsIncorporationMember" xlink:label="plx_ProtalixBioTherapeuticsIncorporationMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ProtalixBioTherapeuticsIncorporationMember" xlink:to="plx_ProtalixBioTherapeuticsIncorporationMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ProtalixBioTherapeuticsIncorporationMember_lbl" xml:lang="en-US">Protalix Bio Therapeutics Incorporation [Member].</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ProtalixBioTherapeuticsIncorporationMember_lbl" xml:lang="en-US">Protalix Bio Therapeutics Incorporation [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_StatementGeographicalAxis" xlink:label="srt_StatementGeographicalAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_StatementGeographicalAxis" xlink:to="srt_StatementGeographicalAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_StatementGeographicalAxis_lbl" xml:lang="en-US">Geographical [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_SegmentGeographicalDomain" xlink:label="srt_SegmentGeographicalDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_SegmentGeographicalDomain" xlink:to="srt_SegmentGeographicalDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_SegmentGeographicalDomain_lbl" xml:lang="en-US">Geographical [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.sec.gov/country/2021/country-2021.xsd#country_BR" xlink:label="country_BR" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="country_BR" xlink:to="country_BR_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="country_BR_lbl" xml:lang="en-US">Brazil [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_MajorCustomersAxis" xlink:label="srt_MajorCustomersAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_MajorCustomersAxis" xlink:to="srt_MajorCustomersAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_MajorCustomersAxis_lbl" xml:lang="en-US">Customer [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_NameOfMajorCustomerDomain" xlink:label="srt_NameOfMajorCustomerDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_NameOfMajorCustomerDomain" xlink:to="srt_NameOfMajorCustomerDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_NameOfMajorCustomerDomain_lbl" xml:lang="en-US">Customer [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_FiocruzMember" xlink:label="plx_FiocruzMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_FiocruzMember" xlink:to="plx_FiocruzMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_FiocruzMember_lbl" xml:lang="en-US">Fiocruz [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ChiesiMember" xlink:label="plx_ChiesiMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ChiesiMember" xlink:to="plx_ChiesiMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ChiesiMember_lbl" xml:lang="en-US">Global except Brazil and Italy</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ChiesiMember_lbl" xml:lang="en-US">Chiesi [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SignificantAccountingPoliciesLineItems" xlink:label="plx_SignificantAccountingPoliciesLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SignificantAccountingPoliciesLineItems" xlink:to="plx_SignificantAccountingPoliciesLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SignificantAccountingPoliciesLineItems_lbl" xml:lang="en-US">Significant Accounting Policies [Line Items]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharesIssuedPricePerShare" xlink:label="us-gaap_SharesIssuedPricePerShare" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharesIssuedPricePerShare" xlink:to="us-gaap_SharesIssuedPricePerShare_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xml:lang="en-US">Shares Issued, Price Per Share</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharesIssuedPricePerShare_lbl" xml:lang="en-US">Shares Issued, Price Per Share</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharePrice" xlink:label="us-gaap_SharePrice" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharePrice" xlink:to="us-gaap_SharePrice_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharePrice_lbl" xml:lang="en-US">Share Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharePrice_lbl" xml:lang="en-US">Share price</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SaleOfStockMaximumOfferingPrice" xlink:label="plx_SaleOfStockMaximumOfferingPrice" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SaleOfStockMaximumOfferingPrice" xlink:to="plx_SaleOfStockMaximumOfferingPrice_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_SaleOfStockMaximumOfferingPrice_lbl" xml:lang="en-US">Sale of stock, maximum offering price.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SaleOfStockMaximumOfferingPrice_lbl" xml:lang="en-US">Sale Of Stock Maximum Offering Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_SaleOfStockMaximumOfferingPrice_lbl" xml:lang="en-US">Sale of stock, maximum offering price</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_StockIssuedDuringPeriodIssuePricePerShareNewIssues" xlink:label="plx_StockIssuedDuringPeriodIssuePricePerShareNewIssues" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_StockIssuedDuringPeriodIssuePricePerShareNewIssues" xlink:to="plx_StockIssuedDuringPeriodIssuePricePerShareNewIssues_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_StockIssuedDuringPeriodIssuePricePerShareNewIssues_lbl" xml:lang="en-US">Per share price at which the new stock issued during the period.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_StockIssuedDuringPeriodIssuePricePerShareNewIssues_lbl" xml:lang="en-US">Stock Issued During Period, Issue Price Per Share, New Issues</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_StockIssuedDuringPeriodIssuePricePerShareNewIssues_lbl" xml:lang="en-US">Purchase price (in dollars per share)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights" xlink:to="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xml:lang="en-US">Class of Warrant or Right, Number of Securities Called by Warrants or Rights</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByWarrantsOrRights_lbl" xml:lang="en-US">Number of warrants issued (in shares)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1" xlink:to="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xml:lang="en-US">Class of Warrant or Right, Exercise Price of Warrants or Rights</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightExercisePriceOfWarrantsOrRights1_lbl" xml:lang="en-US">Exercise price of warrants (in dollars per share)</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_WarrantsAndRightsCommencementPeriodForExerciseOfWarrants" xlink:label="plx_WarrantsAndRightsCommencementPeriodForExerciseOfWarrants" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_WarrantsAndRightsCommencementPeriodForExerciseOfWarrants" xlink:to="plx_WarrantsAndRightsCommencementPeriodForExerciseOfWarrants_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_WarrantsAndRightsCommencementPeriodForExerciseOfWarrants_lbl" xml:lang="en-US">Period following the issuance date, the warrants become exercisable, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_WarrantsAndRightsCommencementPeriodForExerciseOfWarrants_lbl" xml:lang="en-US">Warrants And Rights, Commencement Period For Exercise Of Warrants</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_WarrantsAndRightsCommencementPeriodForExerciseOfWarrants_lbl" xml:lang="en-US">Exercise of warrants, commencement period</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_WarrantsAndRightsOutstandingTerm" xlink:label="us-gaap_WarrantsAndRightsOutstandingTerm" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_WarrantsAndRightsOutstandingTerm" xlink:to="us-gaap_WarrantsAndRightsOutstandingTerm_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_WarrantsAndRightsOutstandingTerm_lbl" xml:lang="en-US">Warrants and Rights Outstanding, Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_WarrantsAndRightsOutstandingTerm_lbl" xml:lang="en-US">Term of warrants</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromIssuanceOfPrivatePlacement" xlink:label="us-gaap_ProceedsFromIssuanceOfPrivatePlacement" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromIssuanceOfPrivatePlacement" xlink:to="us-gaap_ProceedsFromIssuanceOfPrivatePlacement_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromIssuanceOfPrivatePlacement_lbl" xml:lang="en-US">Proceeds from Issuance of Private Placement</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ProceedsFromIssuanceOfPrivatePlacement_lbl" xml:lang="en-US">Proceeds from private placement</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_UpfrontNonrefundableNoncreditablePaymentReceivable" xlink:label="plx_UpfrontNonrefundableNoncreditablePaymentReceivable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_UpfrontNonrefundableNoncreditablePaymentReceivable" xlink:to="plx_UpfrontNonrefundableNoncreditablePaymentReceivable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_UpfrontNonrefundableNoncreditablePaymentReceivable_lbl" xml:lang="en-US">The amount of upfront, non refundable and non creditable payment receivable under the agreement for licensing rights.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_UpfrontNonrefundableNoncreditablePaymentReceivable_lbl" xml:lang="en-US">Upfront Nonrefundable Noncreditable Payment Receivable</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_UpfrontNonrefundableNoncreditablePaymentReceivable_lbl" xml:lang="en-US">Non-refundable Payment Receivable</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_AdditionalAmountsPayableToCoverDevelopmentCosts" xlink:label="plx_AdditionalAmountsPayableToCoverDevelopmentCosts" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_AdditionalAmountsPayableToCoverDevelopmentCosts" xlink:to="plx_AdditionalAmountsPayableToCoverDevelopmentCosts_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_AdditionalAmountsPayableToCoverDevelopmentCosts_lbl" xml:lang="en-US">The maximum amount payable to the entity to cover development costs under agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_AdditionalAmountsPayableToCoverDevelopmentCosts_lbl" xml:lang="en-US">Additional Amounts Payable To Cover Development Costs</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PaymentOnNetSalesPercentage" xlink:label="plx_PaymentOnNetSalesPercentage" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PaymentOnNetSalesPercentage" xlink:to="plx_PaymentOnNetSalesPercentage_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PaymentOnNetSalesPercentage_lbl" xml:lang="en-US">Represents the payment as a percentage of future net sales.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PaymentOnNetSalesPercentage_lbl" xml:lang="en-US">Payment On Net Sales Percentage</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_CollaborativeArrangementRevenuesExpensesSharingPercentage" xlink:label="plx_CollaborativeArrangementRevenuesExpensesSharingPercentage" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_CollaborativeArrangementRevenuesExpensesSharingPercentage" xlink:to="plx_CollaborativeArrangementRevenuesExpensesSharingPercentage_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_CollaborativeArrangementRevenuesExpensesSharingPercentage_lbl" xml:lang="en-US">Collaborative arrangement revenues and expense sharing percentage.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_CollaborativeArrangementRevenuesExpensesSharingPercentage_lbl" xml:lang="en-US">Collaborative Arrangement Revenues Expenses Sharing Percentage</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:to="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xml:lang="en-US">Debt Instrument, Interest Rate, Stated Percentage</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xml:lang="en-US">Interest rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DebtInstrumentInterestRateStatedPercentage_lbl" xml:lang="en-US">Interest rate (as a percent)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ConvertibleDebt" xlink:label="us-gaap_ConvertibleDebt" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ConvertibleDebt" xlink:to="us-gaap_ConvertibleDebt_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ConvertibleDebt_lbl" xml:lang="en-US">Convertible Debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ConvertibleDebt_lbl" xml:lang="en-US">Aggregate principal amount</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_TaxRateAssumptionRelatedToDeferredTaxDifferenceReversal" xlink:label="plx_TaxRateAssumptionRelatedToDeferredTaxDifferenceReversal" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_TaxRateAssumptionRelatedToDeferredTaxDifferenceReversal" xlink:to="plx_TaxRateAssumptionRelatedToDeferredTaxDifferenceReversal_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_TaxRateAssumptionRelatedToDeferredTaxDifferenceReversal_lbl" xml:lang="en-US">Deferred taxes are computed using the tax rates expected to be in effect when those differences reverse.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_TaxRateAssumptionRelatedToDeferredTaxDifferenceReversal_lbl" xml:lang="en-US">Tax Rate Assumption Related To Deferred Tax Difference Reversal</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount" xlink:to="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xml:lang="en-US">Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseLiability" xlink:label="us-gaap_OperatingLeaseLiability" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseLiability" xlink:to="us-gaap_OperatingLeaseLiability_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xml:lang="en-US">Operating Lease, Liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xml:lang="en-US">Present value of operating lease liabilities</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_RevenuePerformanceObligationNumber" xlink:label="plx_RevenuePerformanceObligationNumber" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_RevenuePerformanceObligationNumber" xlink:to="plx_RevenuePerformanceObligationNumber_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_RevenuePerformanceObligationNumber_lbl" xml:lang="en-US">Revenue, Performance Obligation, Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_RevenuePerformanceObligationNumber_lbl" xml:lang="en-US">Revenue, Performance Obligation, Number</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PfizerMember" xlink:label="plx_PfizerMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PfizerMember" xlink:to="plx_PfizerMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PfizerMember_lbl" xml:lang="en-US">Global except for Brazil</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PfizerMember_lbl" xml:lang="en-US">Pfizer [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_KirinHoldingsCompanyLimitedMember" xlink:label="plx_KirinHoldingsCompanyLimitedMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_KirinHoldingsCompanyLimitedMember" xlink:to="plx_KirinHoldingsCompanyLimitedMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_KirinHoldingsCompanyLimitedMember_lbl" xml:lang="en-US">Kirin Holdings Company, Limited [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_KirinHoldingsCompanyLimitedMember_lbl" xml:lang="en-US">Kirin Holdings Company, Limited [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_CollaborativeArrangementProfitSharePercentage" xlink:label="plx_CollaborativeArrangementProfitSharePercentage" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_CollaborativeArrangementProfitSharePercentage" xlink:to="plx_CollaborativeArrangementProfitSharePercentage_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_CollaborativeArrangementProfitSharePercentage_lbl" xml:lang="en-US">Collaborative arrangement profit sharing percentage.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_CollaborativeArrangementProfitSharePercentage_lbl" xml:lang="en-US">Collaborative Arrangement Profit Share Percentage</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="us-gaap_DebtInstrumentFaceAmount" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentFaceAmount" xlink:to="us-gaap_DebtInstrumentFaceAmount_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xml:lang="en-US">Debt Instrument, Face Amount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xml:lang="en-US">Face amount</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromRepaymentsOfNotesPayable" xlink:label="us-gaap_ProceedsFromRepaymentsOfNotesPayable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromRepaymentsOfNotesPayable" xlink:to="us-gaap_ProceedsFromRepaymentsOfNotesPayable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromRepaymentsOfNotesPayable_lbl" xml:lang="en-US">Proceeds from (Repayments of) Notes Payable</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_ProceedsFromRepaymentsOfNotesPayable_lbl" xml:lang="en-US">Payment on notes payable</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_MaximumEntitlementOfDevelopmentCostsToCoverPerYear" xlink:label="plx_MaximumEntitlementOfDevelopmentCostsToCoverPerYear" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_MaximumEntitlementOfDevelopmentCostsToCoverPerYear" xlink:to="plx_MaximumEntitlementOfDevelopmentCostsToCoverPerYear_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_MaximumEntitlementOfDevelopmentCostsToCoverPerYear_lbl" xml:lang="en-US">The maximum amount payable to entity to cover development costs in any year under agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_MaximumEntitlementOfDevelopmentCostsToCoverPerYear_lbl" xml:lang="en-US">Maximum Entitlement Of Development Costs To Cover Per Year</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_AgreementAmendmentPaymentReceivable" xlink:label="plx_AgreementAmendmentPaymentReceivable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_AgreementAmendmentPaymentReceivable" xlink:to="plx_AgreementAmendmentPaymentReceivable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_AgreementAmendmentPaymentReceivable_lbl" xml:lang="en-US">Agreement Amendment Payment Receivable</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_AgreementAmendmentPaymentReceivable_lbl" xml:lang="en-US">Agreement Amendment Payment Receivable</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ChangeInAmountReceivableForAchievementOfRegulatoryAndCommercialMilestones" xlink:label="plx_ChangeInAmountReceivableForAchievementOfRegulatoryAndCommercialMilestones" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ChangeInAmountReceivableForAchievementOfRegulatoryAndCommercialMilestones" xlink:to="plx_ChangeInAmountReceivableForAchievementOfRegulatoryAndCommercialMilestones_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ChangeInAmountReceivableForAchievementOfRegulatoryAndCommercialMilestones_lbl" xml:lang="en-US">Change In Amount Receivable For Achievement Of Regulatory And Commercial Milestones</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ChangeInAmountReceivableForAchievementOfRegulatoryAndCommercialMilestones_lbl" xml:lang="en-US">Change In Amount Receivable For Achievement Of Regulatory And Commercial Milestones</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_AdditionalAmountPayableForAchievementOfRegulatoryAndCommercialMilestones" xlink:label="plx_AdditionalAmountPayableForAchievementOfRegulatoryAndCommercialMilestones" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_AdditionalAmountPayableForAchievementOfRegulatoryAndCommercialMilestones" xlink:to="plx_AdditionalAmountPayableForAchievementOfRegulatoryAndCommercialMilestones_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_AdditionalAmountPayableForAchievementOfRegulatoryAndCommercialMilestones_lbl" xml:lang="en-US">The total amount payable to entity for the achievement of regulatory and commercial milestones.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_AdditionalAmountPayableForAchievementOfRegulatoryAndCommercialMilestones_lbl" xml:lang="en-US">Additional Amount Payable For Achievement Of Regulatory And Commercial Milestones</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PaymentInConsiderationForDevelopmentServicesPerformed" xlink:label="plx_PaymentInConsiderationForDevelopmentServicesPerformed" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PaymentInConsiderationForDevelopmentServicesPerformed" xlink:to="plx_PaymentInConsiderationForDevelopmentServicesPerformed_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PaymentInConsiderationForDevelopmentServicesPerformed_lbl" xml:lang="en-US">The cash inflow from consideration received for development services performed.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PaymentInConsiderationForDevelopmentServicesPerformed_lbl" xml:lang="en-US">Payment in Consideration for Development Services Performed</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_PaymentInConsiderationForDevelopmentServicesPerformed_lbl" xml:lang="en-US">Payments in consideration for development services performed</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PaymentsInConnectionWithPerformanceOfAdditionalStudies" xlink:label="plx_PaymentsInConnectionWithPerformanceOfAdditionalStudies" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PaymentsInConnectionWithPerformanceOfAdditionalStudies" xlink:to="plx_PaymentsInConnectionWithPerformanceOfAdditionalStudies_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PaymentsInConnectionWithPerformanceOfAdditionalStudies_lbl" xml:lang="en-US">The cash inflow in connection with performance of additional studies.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PaymentsInConnectionWithPerformanceOfAdditionalStudies_lbl" xml:lang="en-US">Payments in Connection with Performance of Additional Studies</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_PaymentsInConnectionWithPerformanceOfAdditionalStudies_lbl" xml:lang="en-US">Payments in connection with performance of additional studies</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiabilityRevenueRecognized" xlink:to="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xml:lang="en-US">Contract with Customer, Liability, Revenue Recognized</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xml:lang="en-US">Recognized revenues related to non-refundable payment</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ContractWithCustomerLiability" xlink:label="us-gaap_ContractWithCustomerLiability" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ContractWithCustomerLiability" xlink:to="us-gaap_ContractWithCustomerLiability_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xml:lang="en-US">Contract with Customer, Liability</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xml:lang="en-US">Future milestone payment</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_NonRefundableFutureServicePayment" xlink:label="plx_NonRefundableFutureServicePayment" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_NonRefundableFutureServicePayment" xlink:to="plx_NonRefundableFutureServicePayment_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_NonRefundableFutureServicePayment_lbl" xml:lang="en-US">Amount of non refundable payment received for future service.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_NonRefundableFutureServicePayment_lbl" xml:lang="en-US">Non-Refundable Future Service Payment</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PercentageOfAdultGaucherPatientsTreatedWithAlfataliglicerase" xlink:label="plx_PercentageOfAdultGaucherPatientsTreatedWithAlfataliglicerase" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PercentageOfAdultGaucherPatientsTreatedWithAlfataliglicerase" xlink:to="plx_PercentageOfAdultGaucherPatientsTreatedWithAlfataliglicerase_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PercentageOfAdultGaucherPatientsTreatedWithAlfataliglicerase_lbl" xml:lang="en-US">Represents the percentage of adult Gaucher patients treated with Uplyso.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PercentageOfAdultGaucherPatientsTreatedWithAlfataliglicerase_lbl" xml:lang="en-US">Percentage Of Adult Gaucher Patients Treated With alfataliglicerase</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_FurnitureAndComputerEquipmentMember" xlink:label="plx_FurnitureAndComputerEquipmentMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_FurnitureAndComputerEquipmentMember" xlink:to="plx_FurnitureAndComputerEquipmentMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_FurnitureAndComputerEquipmentMember_lbl" xml:lang="en-US">Furniture And Computer Equipment Member</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_FurnitureAndComputerEquipmentMember_lbl" xml:lang="en-US">Furniture And Computer Equipment [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LeaseholdImprovementsMember" xlink:label="us-gaap_LeaseholdImprovementsMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LeaseholdImprovementsMember" xlink:to="us-gaap_LeaseholdImprovementsMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xml:lang="en-US">Leasehold Improvements [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="us-gaap_PropertyPlantAndEquipmentGross" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PropertyPlantAndEquipmentGross" xlink:to="us-gaap_PropertyPlantAndEquipmentGross_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PropertyPlantAndEquipmentGross_lbl" xml:lang="en-US">Property, Plant and Equipment, Gross</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:to="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xml:lang="en-US">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2009/role/negatedLabel" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xml:lang="en-US">Less - accumulated depreciation and amortization</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InventoryRawMaterialsNetOfReserves" xlink:label="us-gaap_InventoryRawMaterialsNetOfReserves" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InventoryRawMaterialsNetOfReserves" xlink:to="us-gaap_InventoryRawMaterialsNetOfReserves_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InventoryRawMaterialsNetOfReserves_lbl" xml:lang="en-US">Inventory, Raw Materials, Net of Reserves</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_InventoryRawMaterialsNetOfReserves_lbl" xml:lang="en-US">Raw materials</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InventoryWorkInProcessNetOfReserves" xlink:label="us-gaap_InventoryWorkInProcessNetOfReserves" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InventoryWorkInProcessNetOfReserves" xlink:to="us-gaap_InventoryWorkInProcessNetOfReserves_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InventoryWorkInProcessNetOfReserves_lbl" xml:lang="en-US">Inventory, Work in Process, Net of Reserves</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_InventoryWorkInProcessNetOfReserves_lbl" xml:lang="en-US">Work in progress</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InventoryFinishedGoodsNetOfReserves" xlink:label="us-gaap_InventoryFinishedGoodsNetOfReserves" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InventoryFinishedGoodsNetOfReserves" xlink:to="us-gaap_InventoryFinishedGoodsNetOfReserves_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InventoryFinishedGoodsNetOfReserves_lbl" xml:lang="en-US">Inventory, Finished Goods, Net of Reserves</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_InventoryFinishedGoodsNetOfReserves_lbl" xml:lang="en-US">Finished goods</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InventoryWriteDown" xlink:label="us-gaap_InventoryWriteDown" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InventoryWriteDown" xlink:to="us-gaap_InventoryWriteDown_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InventoryWriteDown_lbl" xml:lang="en-US">Inventory Write-down</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetirementPlanTypeAxis" xlink:label="us-gaap_RetirementPlanTypeAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetirementPlanTypeAxis" xlink:to="us-gaap_RetirementPlanTypeAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RetirementPlanTypeAxis_lbl" xml:lang="en-US">Retirement Plan Type [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RetirementPlanTypeDomain" xlink:label="us-gaap_RetirementPlanTypeDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RetirementPlanTypeDomain" xlink:to="us-gaap_RetirementPlanTypeDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RetirementPlanTypeDomain_lbl" xml:lang="en-US">Retirement Plan Type [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DefinedBenefitPostretirementLifeInsuranceMember" xlink:label="us-gaap_DefinedBenefitPostretirementLifeInsuranceMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedBenefitPostretirementLifeInsuranceMember" xlink:to="us-gaap_DefinedBenefitPostretirementLifeInsuranceMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DefinedBenefitPostretirementLifeInsuranceMember_lbl" xml:lang="en-US">Contribution to Insurance Companies [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ContributionPlansMember" xlink:label="plx_ContributionPlansMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ContributionPlansMember" xlink:to="plx_ContributionPlansMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ContributionPlansMember_lbl" xml:lang="en-US">Contribution to Defined Contribution Plans [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_EmployeeSeveranceObligationPayment" xlink:label="plx_EmployeeSeveranceObligationPayment" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_EmployeeSeveranceObligationPayment" xlink:to="plx_EmployeeSeveranceObligationPayment_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_EmployeeSeveranceObligationPayment_lbl" xml:lang="en-US">Employee severance obligation payment.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_EmployeeSeveranceObligationPayment_lbl" xml:lang="en-US">Employee Severance Obligation Payment</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_EmployeeSeveranceObligationPayment_lbl" xml:lang="en-US">Employee severance obligation payments</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PostemploymentBenefitsPeriodExpense" xlink:label="us-gaap_PostemploymentBenefitsPeriodExpense" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PostemploymentBenefitsPeriodExpense" xlink:to="us-gaap_PostemploymentBenefitsPeriodExpense_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PostemploymentBenefitsPeriodExpense_lbl" xml:lang="en-US">Postemployment Benefits, Period Expense</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_PostemploymentBenefitsPeriodExpense_lbl" xml:lang="en-US">Severance expense</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount" xlink:label="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount" xlink:to="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount_lbl" xml:lang="en-US">Defined Contribution Plan, Employer Discretionary Contribution Amount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DefinedContributionPlanEmployerDiscretionaryContributionAmount_lbl" xml:lang="en-US">Contributions</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax" xlink:label="us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax" xlink:to="us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_lbl" xml:lang="en-US">Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), after Reclassification Adjustment, before Tax</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DefinedBenefitPlanAmountsRecognizedInOtherComprehensiveIncomeLossNetGainLossBeforeTax_lbl" xml:lang="en-US">Gain for the period</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear" xlink:label="us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear" xlink:to="us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DefinedBenefitPlanExpectedFutureEmployerContributionsNextFiscalYear_lbl" xml:lang="en-US">Defined Benefit Plan, Expected Future Employer Contributions, Next Fiscal Year</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_NumberOfEmployeesToReceiveBenefitsDuringNextFiveYears" xlink:label="plx_NumberOfEmployeesToReceiveBenefitsDuringNextFiveYears" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_NumberOfEmployeesToReceiveBenefitsDuringNextFiveYears" xlink:to="plx_NumberOfEmployeesToReceiveBenefitsDuringNextFiveYears_lbl" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_NumberOfEmployeesToReceiveBenefitsDuringNextFiveYears_lbl" xml:lang="en-US">Number Of Employees To Receive Benefits During Next Five Years</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_BenefitsPayableDuringNextFiveYears" xlink:to="plx_BenefitsPayableDuringNextFiveYears_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_BenefitsPayableDuringNextFiveYears_lbl" xml:lang="en-US">Amount of benefits payable during next five years.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_BenefitsPayableDuringNextFiveYears_lbl" xml:lang="en-US">Benefits Payable During Next Five Years</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable" xlink:label="us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable" xlink:to="us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfResearchAndDevelopmentArrangementContractToPerformForOthersTable_lbl" xml:lang="en-US">Schedule of Research and Development Arrangement, Contract to Perform for Others [Table]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersByTypeAxis_lbl" xml:lang="en-US">Research and Development Arrangement, Contract to Perform for Others, Type [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain" xlink:to="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ResearchAndDevelopmentArrangementContractToPerformForOthersTypeDomain_lbl" xml:lang="en-US">Research and Development Arrangement, Contract to Perform for Others, Type [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RoyaltyAgreementTermsMember" xlink:label="us-gaap_RoyaltyAgreementTermsMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RoyaltyAgreementTermsMember" xlink:to="us-gaap_RoyaltyAgreementTermsMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RoyaltyAgreementTermsMember_lbl" xml:lang="en-US">Royalty Agreement Terms [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_CounterpartyNameAxis" xlink:label="srt_CounterpartyNameAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_CounterpartyNameAxis" xlink:to="srt_CounterpartyNameAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_CounterpartyNameAxis_lbl" xml:lang="en-US">Counterparty Name [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_RepurchaseAgreementCounterpartyNameDomain" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_RepurchaseAgreementCounterpartyNameDomain" xlink:to="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" xml:lang="en-US">Counterparty Name [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_OfficeOfIsraeliInnovationAuthorityMember" xlink:label="plx_OfficeOfIsraeliInnovationAuthorityMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_OfficeOfIsraeliInnovationAuthorityMember" xlink:to="plx_OfficeOfIsraeliInnovationAuthorityMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_OfficeOfIsraeliInnovationAuthorityMember_lbl" xml:lang="en-US">Office of the Israeli Innovation Authority [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_OfficeOfIsraeliInnovationAuthorityMember_lbl" xml:lang="en-US">Office of the Israeli Innovation Authority [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_OutsideOfIsraelMember" xlink:label="plx_OutsideOfIsraelMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_OutsideOfIsraelMember" xlink:to="plx_OutsideOfIsraelMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_OutsideOfIsraelMember_lbl" xml:lang="en-US">Outside of Israel [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_OutsideOfIsraelMember_lbl" xml:lang="en-US">Outside of Israel [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_NoncollaborativeArrangementTransactionsMember" xlink:label="us-gaap_NoncollaborativeArrangementTransactionsMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_NoncollaborativeArrangementTransactionsMember" xlink:to="us-gaap_NoncollaborativeArrangementTransactionsMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_NoncollaborativeArrangementTransactionsMember_lbl" xml:lang="en-US">Arrangement Other than Collaborative [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_CommitmentsAndContingenciesLineItems" xlink:label="plx_CommitmentsAndContingenciesLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_CommitmentsAndContingenciesLineItems" xlink:to="plx_CommitmentsAndContingenciesLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_CommitmentsAndContingenciesLineItems_lbl" xml:lang="en-US">Commitments And Contingencies [Line Items]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_CommitmentsAndContingenciesLineItems_lbl" xml:lang="en-US">Commitments And Contingencies [Line Items]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_RoyaltiesOnSaleOfProducts" xlink:label="plx_RoyaltiesOnSaleOfProducts" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_RoyaltiesOnSaleOfProducts" xlink:to="plx_RoyaltiesOnSaleOfProducts_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_RoyaltiesOnSaleOfProducts_lbl" xml:lang="en-US">Percentage of royalties based on sale of products developed from projects funded.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_RoyaltiesOnSaleOfProducts_lbl" xml:lang="en-US">Royalties On Sale Of Products</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_RoyaltiesOnSaleOfProducts_lbl" xml:lang="en-US">Royalties based on sale of products developed from funded projects, percentage</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RoyaltyExpense" xlink:label="us-gaap_RoyaltyExpense" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RoyaltyExpense" xlink:to="us-gaap_RoyaltyExpense_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RoyaltyExpense_lbl" xml:lang="en-US">Royalty Expense</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_RoyaltyExpense_lbl" xml:lang="en-US">Royalty expense included in cost of revenue</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedRoyaltiesCurrentAndNoncurrent" xlink:label="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent" xlink:to="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent_lbl" xml:lang="en-US">Accrued Royalties</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AccruedRoyaltiesCurrentAndNoncurrent_lbl" xml:lang="en-US">Accrued royalties</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_CommitmentAmount" xlink:label="plx_CommitmentAmount" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_CommitmentAmount" xlink:to="plx_CommitmentAmount_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_CommitmentAmount_lbl" xml:lang="en-US">Commitment amount.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_CommitmentAmount_lbl" xml:lang="en-US">Commitment Amount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_CommitmentAmount_lbl" xml:lang="en-US">Subcontracting commitment amount</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PercentageOfRoyaltiesToGrantReceived" xlink:label="plx_PercentageOfRoyaltiesToGrantReceived" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PercentageOfRoyaltiesToGrantReceived" xlink:to="plx_PercentageOfRoyaltiesToGrantReceived_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PercentageOfRoyaltiesToGrantReceived_lbl" xml:lang="en-US">Required royalty payments represented as a percentage to grants received.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PercentageOfRoyaltiesToGrantReceived_lbl" xml:lang="en-US">Percentage of Royalties to Grant Received</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_DisclosureOfLeasesOperatingLineItems" xlink:label="plx_DisclosureOfLeasesOperatingLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_DisclosureOfLeasesOperatingLineItems" xlink:to="plx_DisclosureOfLeasesOperatingLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_DisclosureOfLeasesOperatingLineItems_lbl" xml:lang="en-US">Disclosure of Leases Operating</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_DisclosureOfLeasesOperatingLineItems_lbl" xml:lang="en-US">Disclosure of Leases Operating [Line Items]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseCost" xlink:label="us-gaap_OperatingLeaseCost" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseCost" xlink:to="us-gaap_OperatingLeaseCost_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseCost_lbl" xml:lang="en-US">Operating Lease, Cost</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseCost_lbl" xml:lang="en-US">Operating lease costs</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeasePayments" xlink:label="us-gaap_OperatingLeasePayments" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeasePayments" xlink:to="us-gaap_OperatingLeasePayments_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeasePayments_lbl" xml:lang="en-US">Operating Lease, Payments</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeasePayments_lbl" xml:lang="en-US">Cash paid for amounts included in the measurement of lease liabilities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1" xlink:to="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xml:lang="en-US">Operating Lease, Weighted Average Remaining Lease Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xml:lang="en-US">Weighted average remaining lease term (in years)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent" xlink:to="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xml:lang="en-US">Operating Lease, Weighted Average Discount Rate, Percent</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xml:lang="en-US">Weighted average discount rate</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xml:lang="en-US">Operating Leases, Future Minimum Payments Due, Next Twelve Months</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xml:lang="en-US">2022</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xml:lang="en-US">Lessee, Operating Lease, Liability, Payments, Due Year Two</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xml:lang="en-US">2023</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xml:lang="en-US">Lessee, Operating Lease, Liability, Payments, Due Year Three</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xml:lang="en-US">2024</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xml:lang="en-US">Lessee, Operating Lease, Liability, Payments, Due Year Four</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xml:lang="en-US">2025</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xml:lang="en-US">Lessee, Operating Lease, Liability, Payments, Due Year Five</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFive_lbl" xml:lang="en-US">2026</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xml:lang="en-US">Lessee, Operating Lease, Liability, Payments, Due after Year Five</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive_lbl" xml:lang="en-US">2027 and thereafter</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xml:lang="en-US">Lessee, Operating Lease, Liability, Payments, Due</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xml:lang="en-US">Total undiscounted cash flows</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount" xlink:to="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xml:lang="en-US">Lessee, Operating Lease, Liability, Undiscounted Excess Amount</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xml:lang="en-US">Less: imputed interest</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeLeaseDescriptionTable" xlink:label="us-gaap_LesseeLeaseDescriptionTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeLeaseDescriptionTable" xlink:to="us-gaap_LesseeLeaseDescriptionTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeLeaseDescriptionTable_lbl" xml:lang="en-US">Lessee, Lease, Description [Table]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_VehiclesMember" xlink:label="us-gaap_VehiclesMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_VehiclesMember" xlink:to="us-gaap_VehiclesMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_VehiclesMember_lbl" xml:lang="en-US">Vehicles [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseOptionToExtend" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseOptionToExtend" xlink:to="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xml:lang="en-US">Lessee, Operating Lease, Option to Extend</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_LesseeOperatingLeaseNumberOfRenewalTermExtensions" xlink:label="plx_LesseeOperatingLeaseNumberOfRenewalTermExtensions" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_LesseeOperatingLeaseNumberOfRenewalTermExtensions" xlink:to="plx_LesseeOperatingLeaseNumberOfRenewalTermExtensions_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_LesseeOperatingLeaseNumberOfRenewalTermExtensions_lbl" xml:lang="en-US">Lessee Operating Lease, Number Of Renewal Term Extensions</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_LesseeOperatingLeaseNumberOfRenewalTermExtensions_lbl" xml:lang="en-US">Lessee Operating Lease, Number Of Renewal Term Extensions</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_LesseeOperatingLeaseRenewalTerm" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_LesseeOperatingLeaseRenewalTerm" xlink:to="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xml:lang="en-US">Lessee, Operating Lease, Renewal Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xml:lang="en-US">Operating lease, term of agreement</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SecurityDeposit" xlink:label="us-gaap_SecurityDeposit" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SecurityDeposit" xlink:to="us-gaap_SecurityDeposit_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SecurityDeposit_lbl" xml:lang="en-US">Security Deposit</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PercentageOfChangeInOperatingLeaseMonthlyRentalPayments" xlink:label="plx_PercentageOfChangeInOperatingLeaseMonthlyRentalPayments" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PercentageOfChangeInOperatingLeaseMonthlyRentalPayments" xlink:to="plx_PercentageOfChangeInOperatingLeaseMonthlyRentalPayments_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PercentageOfChangeInOperatingLeaseMonthlyRentalPayments_lbl" xml:lang="en-US">Percentage of Change in Operating Lease Monthly Rental Payments.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PercentageOfChangeInOperatingLeaseMonthlyRentalPayments_lbl" xml:lang="en-US">Percentage of Change in Operating Lease Monthly Rental Payments</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:to="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xml:lang="en-US">Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="us-gaap_AwardTypeAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AwardTypeAxis" xlink:to="us-gaap_AwardTypeAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AwardTypeAxis_lbl" xml:lang="en-US">Award Type [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_lbl" xml:lang="en-US">Equity Award [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="us-gaap_EmployeeStockOptionMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeStockOptionMember" xlink:to="us-gaap_EmployeeStockOptionMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeStockOptionMember_lbl" xml:lang="en-US">Option to purchase shares of common stock</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="us-gaap_RestrictedStockMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedStockMember" xlink:to="us-gaap_RestrictedStockMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RestrictedStockMember_lbl" xml:lang="en-US">Restricted Stock</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_lbl" xml:lang="en-US">Exercise Price Range [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_lbl" xml:lang="en-US">Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice4.69Member" xlink:label="plx_ExercisePrice4.69Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice4.69Member" xlink:to="plx_ExercisePrice4.69Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice4.69Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 4.69.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice4.69Member_lbl" xml:lang="en-US">Exercise Price 4.69</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice2.00Member" xlink:label="plx_ExercisePrice2.00Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice2.00Member" xlink:to="plx_ExercisePrice2.00Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice2.00Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 2.00.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice2.00Member_lbl" xml:lang="en-US">Exercise Price 2.00</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice3.59OneMember" xlink:label="plx_ExercisePrice3.59OneMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice3.59OneMember" xlink:to="plx_ExercisePrice3.59OneMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice3.59OneMember_lbl" xml:lang="en-US">Represents the information pertaining to exercise price one 3.59 .</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice3.59OneMember_lbl" xml:lang="en-US">Exercise Price 3.59 One</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice3.66Member" xlink:label="plx_ExercisePrice3.66Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice3.66Member" xlink:to="plx_ExercisePrice3.66Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice3.66Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 3.66.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice3.66Member_lbl" xml:lang="en-US">Exercise Price 3.66</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice3.73Member" xlink:label="plx_ExercisePrice3.73Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice3.73Member" xlink:to="plx_ExercisePrice3.73Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice3.73Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 3.73</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice3.73Member_lbl" xml:lang="en-US">Exercise Price 3.73</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_NoExercisePriceMember" xlink:label="plx_NoExercisePriceMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_NoExercisePriceMember" xlink:to="plx_NoExercisePriceMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_NoExercisePriceMember_lbl" xml:lang="en-US">No Exercise Price [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_NoExercisePriceMember_lbl" xml:lang="en-US">No Exercise Price</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice3.59TwoMember" xlink:label="plx_ExercisePrice3.59TwoMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice3.59TwoMember" xlink:to="plx_ExercisePrice3.59TwoMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice3.59TwoMember_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 3.59 two.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice3.59TwoMember_lbl" xml:lang="en-US">Exercise Price 3.59 Two</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice1.57Member" xlink:label="plx_ExercisePrice1.57Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice1.57Member" xlink:to="plx_ExercisePrice1.57Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice1.57Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 1.57.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice1.57Member_lbl" xml:lang="en-US">Exercise Price 1.57</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award [Line Items]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/definitionGuidance" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xml:lang="en-US">Number of options granted</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Gross</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_lbl" xml:lang="en-US">Granted (in shares)</label>
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Granted</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Exercise price</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1_lbl" xml:lang="en-US">Vesting period</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue" xlink:to="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/definitionGuidance" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue_lbl" xml:lang="en-US">Fair value at grant</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue_lbl" xml:lang="en-US">Share based compensation arrangement by share based payment award grant date fair value.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue_lbl" xml:lang="en-US">Share Based Compensation Arrangement By Share Based Payment Award Grant Date Fair Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValue_lbl" xml:lang="en-US">Fair value at grant</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedContractualTerm" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedContractualTerm" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedContractualTerm" xlink:to="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedContractualTerm_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedContractualTerm_lbl" xml:lang="en-US">Share based compensation arrangement by share based payment award granted contractual term.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedContractualTerm_lbl" xml:lang="en-US">Share Based Compensation Arrangement By Share Based Payment Award Granted Contractual Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantedContractualTerm_lbl" xml:lang="en-US">Expiration period</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_TitleOfIndividualAxis" xlink:label="srt_TitleOfIndividualAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_TitleOfIndividualAxis" xlink:to="srt_TitleOfIndividualAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_TitleOfIndividualAxis_lbl" xml:lang="en-US">Title of Individual [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:label="srt_TitleOfIndividualWithRelationshipToEntityDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_TitleOfIndividualWithRelationshipToEntityDomain" xlink:to="srt_TitleOfIndividualWithRelationshipToEntityDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_TitleOfIndividualWithRelationshipToEntityDomain_lbl" xml:lang="en-US">Relationship to Entity [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_EmployeeMember" xlink:label="plx_EmployeeMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_EmployeeMember" xlink:to="plx_EmployeeMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_EmployeeMember_lbl" xml:lang="en-US">Employee [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_EmployeeMember_lbl" xml:lang="en-US">Employee</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_lbl" xml:lang="en-US">Number of options</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xml:lang="en-US">Outstanding at end of year</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber_lbl" xml:lang="en-US">Outstanding at beginning of year</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriod_lbl" xml:lang="en-US">Forfeited and Expired</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumber_lbl" xml:lang="en-US">Exercisable at end of year</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceRollforward_lbl" xml:lang="en-US">Weighted average exercise price</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xml:lang="en-US">Outstanding at end of year</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePrice_lbl" xml:lang="en-US">Outstanding at beginning of year</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsForfeituresAndExpirationsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Forfeited and Expired</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xml:lang="en-US">Exercise Price (in dollars per share)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableWeightedAverageExercisePrice_lbl" xml:lang="en-US">Exercisable at end of year</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xml:lang="en-US">Non vested at end of year</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_lbl" xml:lang="en-US">Outstanding at beginning of year</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_lbl" xml:lang="en-US">Granted</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_lbl" xml:lang="en-US">Vested</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_OptionsGrantedToConsultantsDirectorsAndOtherServiceProvidersMember" xlink:label="plx_OptionsGrantedToConsultantsDirectorsAndOtherServiceProvidersMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_OptionsGrantedToConsultantsDirectorsAndOtherServiceProvidersMember" xlink:to="plx_OptionsGrantedToConsultantsDirectorsAndOtherServiceProvidersMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_OptionsGrantedToConsultantsDirectorsAndOtherServiceProvidersMember_lbl" xml:lang="en-US">Represents information pertaining to options  granted to consultants directors and other service providers.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_OptionsGrantedToConsultantsDirectorsAndOtherServiceProvidersMember_lbl" xml:lang="en-US">Options granted to consultants, directors and other service providers</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingRollForward_lbl" xml:lang="en-US">Number of options or restricted stock</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_StockIssuedDuringPeriodSharesStockExpired" xlink:label="plx_StockIssuedDuringPeriodSharesStockExpired" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_StockIssuedDuringPeriodSharesStockExpired" xlink:to="plx_StockIssuedDuringPeriodSharesStockExpired_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_StockIssuedDuringPeriodSharesStockExpired_lbl" xml:lang="en-US">Number of share options (or share units) expired during the current period.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_StockIssuedDuringPeriodSharesStockExpired_lbl" xml:lang="en-US">Stock Issued During Period Shares Stock Expired</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_StockIssuedDuringPeriodSharesStockExpired_lbl" xml:lang="en-US">Expired</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Share-based Compensation Arrangements by Share-based Payment Award, Options, Expirations in Period, Weighted Average Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardOptionsExpirationsInPeriodWeightedAverageExercisePrice_lbl" xml:lang="en-US">Expired</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable" xlink:label="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable" xlink:to="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable_lbl" xml:lang="en-US">Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range [Table]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice3.55Member" xlink:label="plx_ExercisePrice3.55Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice3.55Member" xlink:to="plx_ExercisePrice3.55Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice3.55Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 3.55.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice3.55Member_lbl" xml:lang="en-US">Exercise Price 3.55</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice3.59Member" xlink:label="plx_ExercisePrice3.59Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice3.59Member" xlink:to="plx_ExercisePrice3.59Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice3.59Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 3.59.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice3.59Member_lbl" xml:lang="en-US">Exercise Price 3.59</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice3.70Member" xlink:label="plx_ExercisePrice3.70Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice3.70Member" xlink:to="plx_ExercisePrice3.70Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice3.70Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price 3.70.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice3.70Member_lbl" xml:lang="en-US">Exercise Price 3.70</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice5.10Member" xlink:label="plx_ExercisePrice5.10Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice5.10Member" xlink:to="plx_ExercisePrice5.10Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice5.10Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price $5.10.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice5.10Member_lbl" xml:lang="en-US">Exercise Price 5.10</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice5.60Member" xlink:label="plx_ExercisePrice5.60Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice5.60Member" xlink:to="plx_ExercisePrice5.60Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice5.60Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price $5.60.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice5.60Member_lbl" xml:lang="en-US">Exercise Price 5.60</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ExercisePrice17.20Member" xlink:label="plx_ExercisePrice17.20Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ExercisePrice17.20Member" xlink:to="plx_ExercisePrice17.20Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ExercisePrice17.20Member_lbl" xml:lang="en-US">Represents the information pertaining to exercise price $17.20.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ExercisePrice17.20Member_lbl" xml:lang="en-US">Exercise Price 17.20</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_lbl" xml:lang="en-US">Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_lbl" xml:lang="en-US">Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_lbl" xml:lang="en-US">Exercise price</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions_lbl" xml:lang="en-US">Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Outstanding Options</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions_lbl" xml:lang="en-US">Number of options outstanding at end of year</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2" xlink:to="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_lbl" xml:lang="en-US">Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_lbl" xml:lang="en-US">Weighted average remaining contractual life</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions" xlink:to="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions_lbl" xml:lang="en-US">Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Number of Exercisable Options</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions_lbl" xml:lang="en-US">Number of options exercisable</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageRemainingContractualTerm2" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageRemainingContractualTerm2" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageRemainingContractualTerm2" xlink:to="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageRemainingContractualTerm2_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageRemainingContractualTerm2_lbl" xml:lang="en-US">Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageRemainingContractualTerm2_lbl" xml:lang="en-US">Weighted average remaining contractual life</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable" xlink:to="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfEmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsTable_lbl" xml:lang="en-US">Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationAxis" xlink:label="us-gaap_IncomeStatementLocationAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationAxis" xlink:to="us-gaap_IncomeStatementLocationAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xml:lang="en-US">Income Statement Location [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_IncomeStatementLocationDomain" xlink:label="us-gaap_IncomeStatementLocationDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_IncomeStatementLocationDomain" xlink:to="us-gaap_IncomeStatementLocationDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xml:lang="en-US">Income Statement Location [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_CostOfSalesMember" xlink:label="us-gaap_CostOfSalesMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_CostOfSalesMember" xlink:to="us-gaap_CostOfSalesMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_CostOfSalesMember_lbl" xml:lang="en-US">Cost of goods sold</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ResearchAndDevelopmentExpenseMember" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ResearchAndDevelopmentExpenseMember" xlink:to="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xml:lang="en-US">Research and development expenses</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SellingGeneralAndAdministrativeExpensesMember" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpensesMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SellingGeneralAndAdministrativeExpensesMember" xlink:to="us-gaap_SellingGeneralAndAdministrativeExpensesMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SellingGeneralAndAdministrativeExpensesMember_lbl" xml:lang="en-US">Selling, general and administrative expenses</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsLineItems_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AllocatedShareBasedCompensationExpense" xlink:to="us-gaap_AllocatedShareBasedCompensationExpense_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xml:lang="en-US">Allocated Share-based Compensation Expense</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RestrictedStockUnitsRSUMember" xlink:label="us-gaap_RestrictedStockUnitsRSUMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RestrictedStockUnitsRSUMember" xlink:to="us-gaap_RestrictedStockUnitsRSUMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RestrictedStockUnitsRSUMember_lbl" xml:lang="en-US">Restricted Stock Units</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PresidentAndChiefExecutiveOfficerMember" xlink:label="plx_PresidentAndChiefExecutiveOfficerMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PresidentAndChiefExecutiveOfficerMember" xlink:to="plx_PresidentAndChiefExecutiveOfficerMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PresidentAndChiefExecutiveOfficerMember_lbl" xml:lang="en-US">This member stands for President and Chief Executive Officer.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PresidentAndChiefExecutiveOfficerMember_lbl" xml:lang="en-US">President and Chief Executive Officer</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SeniorVicePresidentAndChiefDevelopmentOfficerMember" xlink:label="plx_SeniorVicePresidentAndChiefDevelopmentOfficerMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SeniorVicePresidentAndChiefDevelopmentOfficerMember" xlink:to="plx_SeniorVicePresidentAndChiefDevelopmentOfficerMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_SeniorVicePresidentAndChiefDevelopmentOfficerMember_lbl" xml:lang="en-US">This member stands for Senior Vice President and Chief Development Officer.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SeniorVicePresidentAndChiefDevelopmentOfficerMember_lbl" xml:lang="en-US">Sr. Vice President And Chief Development Officer</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SeniorVicePresidentAndChiefFinancialOfficerMember" xlink:label="plx_SeniorVicePresidentAndChiefFinancialOfficerMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SeniorVicePresidentAndChiefFinancialOfficerMember" xlink:to="plx_SeniorVicePresidentAndChiefFinancialOfficerMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_SeniorVicePresidentAndChiefFinancialOfficerMember_lbl" xml:lang="en-US">Sr. Vice President And Chief Financial Officer</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SeniorVicePresidentAndChiefFinancialOfficerMember_lbl" xml:lang="en-US">Senior Vice President And Chief Financial Officer</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SeniorVicePresidentOperationsMember" xlink:label="plx_SeniorVicePresidentOperationsMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SeniorVicePresidentOperationsMember" xlink:to="plx_SeniorVicePresidentOperationsMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_SeniorVicePresidentOperationsMember_lbl" xml:lang="en-US">Senior Vice President, Operations [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SeniorVicePresidentOperationsMember_lbl" xml:lang="en-US">Senior Vice President, Operations</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_VicePresidentResearchAndDevelopmentMember" xlink:label="plx_VicePresidentResearchAndDevelopmentMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_VicePresidentResearchAndDevelopmentMember" xlink:to="plx_VicePresidentResearchAndDevelopmentMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_VicePresidentResearchAndDevelopmentMember_lbl" xml:lang="en-US">This member stands for vice president research and development.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_VicePresidentResearchAndDevelopmentMember_lbl" xml:lang="en-US">Vice President Research And Development</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ChiefExecutiveOfficerMember" xlink:label="srt_ChiefExecutiveOfficerMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ChiefExecutiveOfficerMember" xlink:to="srt_ChiefExecutiveOfficerMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_ChiefExecutiveOfficerMember_lbl" xml:lang="en-US">Chief Executive Officer</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ChiefFinancialOfficerMember" xlink:label="srt_ChiefFinancialOfficerMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ChiefFinancialOfficerMember" xlink:to="srt_ChiefFinancialOfficerMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_ChiefFinancialOfficerMember_lbl" xml:lang="en-US">Chief Financial Officer</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_CertainEmployeesMember" xlink:label="plx_CertainEmployeesMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_CertainEmployeesMember" xlink:to="plx_CertainEmployeesMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_CertainEmployeesMember_lbl" xml:lang="en-US">Certain Employees [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_CertainEmployeesMember_lbl" xml:lang="en-US">Certain Employees</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_BoardOfDirectorsChairmanMember" xlink:label="srt_BoardOfDirectorsChairmanMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_BoardOfDirectorsChairmanMember" xlink:to="srt_BoardOfDirectorsChairmanMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_BoardOfDirectorsChairmanMember_lbl" xml:lang="en-US">Chairman, Board of Directors</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_DirectorMember" xlink:label="srt_DirectorMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_DirectorMember" xlink:to="srt_DirectorMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="srt_DirectorMember_lbl" xml:lang="en-US">Director</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_AtmEquityOfferingSalesAgreementMember" xlink:label="plx_AtmEquityOfferingSalesAgreementMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_AtmEquityOfferingSalesAgreementMember" xlink:to="plx_AtmEquityOfferingSalesAgreementMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_AtmEquityOfferingSalesAgreementMember_lbl" xml:lang="en-US">Represents information pertaining to ATM Equity Offering Sales Agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_AtmEquityOfferingSalesAgreementMember_lbl" xml:lang="en-US">ATM Equity Offering Sales Agreement [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_AtmEquityOfferingSalesAgreementMember_lbl" xml:lang="en-US">BofA Securities</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_OverAllotmentOptionMember" xlink:label="us-gaap_OverAllotmentOptionMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_OverAllotmentOptionMember" xlink:to="us-gaap_OverAllotmentOptionMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_OverAllotmentOptionMember_lbl" xml:lang="en-US">Over-Allotment Option</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="us-gaap_PlanNameAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameAxis" xlink:to="us-gaap_PlanNameAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PlanNameAxis_lbl" xml:lang="en-US">Plan Name [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="us-gaap_PlanNameDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_PlanNameDomain" xlink:to="us-gaap_PlanNameDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_PlanNameDomain_lbl" xml:lang="en-US">Plan Name [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_EmployeeStockIncentivePlan2006Member" xlink:label="plx_EmployeeStockIncentivePlan2006Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_EmployeeStockIncentivePlan2006Member" xlink:to="plx_EmployeeStockIncentivePlan2006Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_EmployeeStockIncentivePlan2006Member_lbl" xml:lang="en-US">It represent the employee stock incentive plan for the particular period.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_EmployeeStockIncentivePlan2006Member_lbl" xml:lang="en-US">2006 Employee Stock Incentive Plan</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_CommonStockNumberOfVotingRights" xlink:label="plx_CommonStockNumberOfVotingRights" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_CommonStockNumberOfVotingRights" xlink:to="plx_CommonStockNumberOfVotingRights_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_CommonStockNumberOfVotingRights_lbl" xml:lang="en-US">Represents the number of votes for each share of common stock is entitled.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_CommonStockNumberOfVotingRights_lbl" xml:lang="en-US">Common Stock, Number Of Voting Rights</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockholdersEquityNoteStockSplitConversionRatio1" xlink:label="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1" xlink:to="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_lbl" xml:lang="en-US">Stockholders' Equity Note, Stock Split, Conversion Ratio</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_StockholdersEquityNoteStockSplitConversionRatio1_lbl" xml:lang="en-US">Reverse stock split ratio</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_NumberOfDirectors" xlink:label="plx_NumberOfDirectors" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_NumberOfDirectors" xlink:to="plx_NumberOfDirectors_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_NumberOfDirectors_lbl" xml:lang="en-US">Number Of Directors</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_NumberOfDirectors_lbl" xml:lang="en-US">Number Of Directors</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Authorized</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xml:lang="en-US">Number of shares authorized for issuance under share-based payment arrangement</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xml:lang="en-US">Shares of Common Stock remain available for grant under the plan</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsVestedNumberOfShares_lbl" xml:lang="en-US">Number of shares vested</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares" xlink:to="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsNonvestedNumberOfShares_lbl" xml:lang="en-US">Number of non-vested shares</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfQuarterlyIncrements" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfQuarterlyIncrements" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfQuarterlyIncrements" xlink:to="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfQuarterlyIncrements_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfQuarterlyIncrements_lbl" xml:lang="en-US">Number of equal quarterly increments over which the awards vest under the share based payment arrangement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfQuarterlyIncrements_lbl" xml:lang="en-US">Share-Based Compensation Arrangement By Share-Based Payment Award, Number Of Quarterly Increments</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfQuarterlyIncrements_lbl" xml:lang="en-US">Number of equal quarterly increments</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Exercise Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExercisePrice_lbl" xml:lang="en-US">Share price</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_lbl" xml:lang="en-US">Dividend Yield</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate" xlink:to="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedVolatilityRate_lbl" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsRiskFreeInterestRate_lbl" xml:lang="en-US">Risk Free Interest Rate</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardFairValueAssumptionsExpectedTerm1_lbl" xml:lang="en-US">Expected Term</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsContingentUponCertainConditionsAggregateValue" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsContingentUponCertainConditionsAggregateValue" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsContingentUponCertainConditionsAggregateValue" xlink:to="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsContingentUponCertainConditionsAggregateValue_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsContingentUponCertainConditionsAggregateValue_lbl" xml:lang="en-US">The aggregate value of non option equity instruments, that will be granted contingent upon certain conditions, on an annual basis.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsContingentUponCertainConditionsAggregateValue_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Non Option Equity Instruments, Grants, Contingent Upon Certain Conditions, Aggregate Value</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ShareBasedCompensationArrangementByShareBasedPaymentAwardNonOptionEquityInstrumentsGrantsContingentUponCertainConditionsAggregateValue_lbl" xml:lang="en-US">Aggregate value of Restricted Stock Units that will be granted, contingent upon certain conditions</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xml:lang="en-US">Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized_lbl" xml:lang="en-US">Unrecognized compensation cost</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:to="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xml:lang="en-US">Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_lbl" xml:lang="en-US">Unrecognized weighted average period</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised" xlink:to="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xml:lang="en-US">Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xml:lang="en-US">Exercised</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtConversionConvertedInstrumentSharesIssued1" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtConversionConvertedInstrumentSharesIssued1" xlink:to="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" xml:lang="en-US">Debt Conversion, Converted Instrument, Shares Issued</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DebtConversionConvertedInstrumentSharesIssued1_lbl" xml:lang="en-US">Converted instrument, shares issued</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight" xlink:to="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xml:lang="en-US">Class of Warrant or Right, Number of Securities Called by Each Warrant or Right</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_ClassOfWarrantOrRightNumberOfSecuritiesCalledByEachWarrantOrRight_lbl" xml:lang="en-US">Number of shares per warrant issued</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PercentageOfCommissionOnSaleOfShares" xlink:label="plx_PercentageOfCommissionOnSaleOfShares" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PercentageOfCommissionOnSaleOfShares" xlink:to="plx_PercentageOfCommissionOnSaleOfShares_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PercentageOfCommissionOnSaleOfShares_lbl" xml:lang="en-US">Percentage of commission on sale of shares.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PercentageOfCommissionOnSaleOfShares_lbl" xml:lang="en-US">Percentage of Commission on Sale of Shares</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_PercentageOfCommissionOnSaleOfShares_lbl" xml:lang="en-US">Commission (as a percent)</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputTypeAxis" xlink:label="us-gaap_MeasurementInputTypeAxis" />
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    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MeasurementInputTypeAxis_lbl" xml:lang="en-US">Measurement Input Type [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputTypeDomain" xlink:label="us-gaap_MeasurementInputTypeDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputTypeDomain" xlink:to="us-gaap_MeasurementInputTypeDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MeasurementInputTypeDomain_lbl" xml:lang="en-US">Measurement Input Type [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputSharePriceMember" xlink:label="us-gaap_MeasurementInputSharePriceMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputSharePriceMember" xlink:to="us-gaap_MeasurementInputSharePriceMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MeasurementInputSharePriceMember_lbl" xml:lang="en-US">Share Price.</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputExpectedTermMember" xlink:label="us-gaap_MeasurementInputExpectedTermMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputExpectedTermMember" xlink:to="us-gaap_MeasurementInputExpectedTermMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MeasurementInputExpectedTermMember_lbl" xml:lang="en-US">Expected term</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputRiskFreeInterestRateMember" xlink:label="us-gaap_MeasurementInputRiskFreeInterestRateMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputRiskFreeInterestRateMember" xlink:to="us-gaap_MeasurementInputRiskFreeInterestRateMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_MeasurementInputRiskFreeInterestRateMember_lbl" xml:lang="en-US">Risk free rate</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_MeasurementInputPriceVolatilityMember" xlink:label="us-gaap_MeasurementInputPriceVolatilityMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_MeasurementInputPriceVolatilityMember" xlink:to="us-gaap_MeasurementInputPriceVolatilityMember_lbl" />
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    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_MeasurementInputYieldMember" xlink:label="plx_MeasurementInputYieldMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_MeasurementInputYieldMember" xlink:to="plx_MeasurementInputYieldMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_MeasurementInputYieldMember_lbl" xml:lang="en-US">Yield</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_MeasurementInputYieldMember_lbl" xml:lang="en-US">Yield</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:to="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueByFairValueHierarchyLevelAxis_lbl" xml:lang="en-US">Fair Value Hierarchy and NAV [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:to="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueMeasurementsFairValueHierarchyDomain_lbl" xml:lang="en-US">Fair Value Hierarchy and NAV [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueInputsLevel3Member" xlink:label="us-gaap_FairValueInputsLevel3Member" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueInputsLevel3Member" xlink:to="us-gaap_FairValueInputsLevel3Member_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueInputsLevel3Member_lbl" xml:lang="en-US">Level 3</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentMeasurementInput" xlink:to="us-gaap_DebtInstrumentMeasurementInput_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentMeasurementInput_lbl" xml:lang="en-US">Debt Instrument, Measurement Input</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestExpenseDebtExcludingAmortization" xlink:label="us-gaap_InterestExpenseDebtExcludingAmortization" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestExpenseDebtExcludingAmortization" xlink:to="us-gaap_InterestExpenseDebtExcludingAmortization_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InterestExpenseDebtExcludingAmortization_lbl" xml:lang="en-US">Interest Expense, Debt, Excluding Amortization</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_InterestExpenseDebtExcludingAmortization_lbl" xml:lang="en-US">Contractual interest expense</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AmortizationOfDebtDiscountPremium" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AmortizationOfDebtDiscountPremium" xlink:to="us-gaap_AmortizationOfDebtDiscountPremium_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium_lbl" xml:lang="en-US">Amortization of Debt Discount (Premium)</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_AmortizationOfDebtDiscountPremium_lbl" xml:lang="en-US">Debt discount amortization</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_InterestExpenseDebtOther" xlink:label="plx_InterestExpenseDebtOther" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_InterestExpenseDebtOther" xlink:to="plx_InterestExpenseDebtOther_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_InterestExpenseDebtOther_lbl" xml:lang="en-US">Interest Expense, Debt, Other</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_InterestExpenseDebtOther_lbl" xml:lang="en-US">Interest Expense, Debt, Other</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_InterestExpenseDebtOther_lbl" xml:lang="en-US">Other expenses</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestCostsIncurred" xlink:label="us-gaap_InterestCostsIncurred" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestCostsIncurred" xlink:to="us-gaap_InterestCostsIncurred_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InterestCostsIncurred_lbl" xml:lang="en-US">Interest Income (Expense), Net</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_InterestCostsIncurred_lbl" xml:lang="en-US">Total</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_FourPointFivePercentageConvertibleNotesMember" xlink:label="plx_FourPointFivePercentageConvertibleNotesMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_FourPointFivePercentageConvertibleNotesMember" xlink:to="plx_FourPointFivePercentageConvertibleNotesMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_FourPointFivePercentageConvertibleNotesMember_lbl" xml:lang="en-US">4.5% Convertible Notes [Member]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ConvertibleNotesDueTwoThousandTwentyOneMember" xlink:label="plx_ConvertibleNotesDueTwoThousandTwentyOneMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ConvertibleNotesDueTwoThousandTwentyOneMember" xlink:to="plx_ConvertibleNotesDueTwoThousandTwentyOneMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ConvertibleNotesDueTwoThousandTwentyOneMember_lbl" xml:lang="en-US">Convertible Notes Due Two Thousand Twenty One [Member]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentCarryingAmount" xlink:label="us-gaap_DebtInstrumentCarryingAmount" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentCarryingAmount" xlink:to="us-gaap_DebtInstrumentCarryingAmount_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xml:lang="en-US">Long-term Debt, Gross</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DebtInstrumentCarryingAmount_lbl" xml:lang="en-US">Debt Instrument Carrying Amount</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_DebtConversionConvertedInstrumentExchangeInCashAccruedAndUnpaidInterest" xlink:label="plx_DebtConversionConvertedInstrumentExchangeInCashAccruedAndUnpaidInterest" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_DebtConversionConvertedInstrumentExchangeInCashAccruedAndUnpaidInterest" xlink:to="plx_DebtConversionConvertedInstrumentExchangeInCashAccruedAndUnpaidInterest_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_DebtConversionConvertedInstrumentExchangeInCashAccruedAndUnpaidInterest_lbl" xml:lang="en-US">Amount of accrued and unpaid interest exchanged in cash in debt conversion.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_DebtConversionConvertedInstrumentExchangeInCashAccruedAndUnpaidInterest_lbl" xml:lang="en-US">Debt Conversion, Converted Instrument, Exchange in Cash, Accrued and Unpaid Interest</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_DebtConversionConvertedInstrumentExchangeInCashAccruedAndUnpaidInterest_lbl" xml:lang="en-US">Convertible notes exchange in cash, accrued and unpaid interest</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_DebtInstrumentConvertibleBaseValueForConversionRate" xlink:label="plx_DebtInstrumentConvertibleBaseValueForConversionRate" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_DebtInstrumentConvertibleBaseValueForConversionRate" xlink:to="plx_DebtInstrumentConvertibleBaseValueForConversionRate_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_DebtInstrumentConvertibleBaseValueForConversionRate_lbl" xml:lang="en-US">Debt Instrument Convertible Base Value For Conversion Rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_DebtInstrumentConvertibleBaseValueForConversionRate_lbl" xml:lang="en-US">Debt Instrument Convertible Base Value For Conversion Rate</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_DebtInstrumentConvertibleBaseValueForConversionRate_lbl" xml:lang="en-US">Base value for conversion rate</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ProceedsFromConvertibleDebt" xlink:label="us-gaap_ProceedsFromConvertibleDebt" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ProceedsFromConvertibleDebt" xlink:to="us-gaap_ProceedsFromConvertibleDebt_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ProceedsFromConvertibleDebt_lbl" xml:lang="en-US">Proceeds from Convertible Debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_ProceedsFromConvertibleDebt_lbl" xml:lang="en-US">Net proceeds from issuance of convertible notes</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_DebtInstrumentConvertibleConversionShareNumber" xlink:label="plx_DebtInstrumentConvertibleConversionShareNumber" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_DebtInstrumentConvertibleConversionShareNumber" xlink:to="plx_DebtInstrumentConvertibleConversionShareNumber_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_DebtInstrumentConvertibleConversionShareNumber_lbl" xml:lang="en-US">Debt Instrument Convertible Conversion Share Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_DebtInstrumentConvertibleConversionShareNumber_lbl" xml:lang="en-US">Debt Instrument Convertible Conversion Share Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_DebtInstrumentConvertibleConversionShareNumber_lbl" xml:lang="en-US">Number of shares for basis conversion</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleConversionPrice1" xlink:to="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" xml:lang="en-US">Debt Instrument, Convertible, Conversion Price</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentConvertibleConversionPrice1_lbl" xml:lang="en-US">Conversion price per share</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PercentageOfPremiumToClosingPriceOfStock" xlink:label="plx_PercentageOfPremiumToClosingPriceOfStock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PercentageOfPremiumToClosingPriceOfStock" xlink:to="plx_PercentageOfPremiumToClosingPriceOfStock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PercentageOfPremiumToClosingPriceOfStock_lbl" xml:lang="en-US">Percentage of premium to closing price of stock.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PercentageOfPremiumToClosingPriceOfStock_lbl" xml:lang="en-US">Percentage of Premium to Closing Price of Stock</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentTerm" xlink:label="us-gaap_DebtInstrumentTerm" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentTerm" xlink:to="us-gaap_DebtInstrumentTerm_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentTerm_lbl" xml:lang="en-US">Debt Instrument, Term</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentTerm_lbl" xml:lang="en-US">Mature term</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_DebtConversionTransactionCostsInConnectionWithExchangeOfConvertibleDebt" xlink:label="plx_DebtConversionTransactionCostsInConnectionWithExchangeOfConvertibleDebt" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_DebtConversionTransactionCostsInConnectionWithExchangeOfConvertibleDebt" xlink:to="plx_DebtConversionTransactionCostsInConnectionWithExchangeOfConvertibleDebt_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_DebtConversionTransactionCostsInConnectionWithExchangeOfConvertibleDebt_lbl" xml:lang="en-US">The transaction costs in connection with exchange of convertible notes.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_DebtConversionTransactionCostsInConnectionWithExchangeOfConvertibleDebt_lbl" xml:lang="en-US">Debt Conversion, Transaction Costs in Connection with Exchange of Convertible Debt</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_DebtConversionTransactionCostsInConnectionWithExchangeOfConvertibleDebt_lbl" xml:lang="en-US">Transactions costs in connection with the exchange of convertible notes</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_MaintainOfMinimumCashBalance" xlink:label="plx_MaintainOfMinimumCashBalance" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_MaintainOfMinimumCashBalance" xlink:to="plx_MaintainOfMinimumCashBalance_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_MaintainOfMinimumCashBalance_lbl" xml:lang="en-US">Minimum cash balance required to be maintained under long term debt agreements.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_MaintainOfMinimumCashBalance_lbl" xml:lang="en-US">Maintain of Minimum Cash Balance</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_MaintainOfMinimumCashBalance_lbl" xml:lang="en-US">Minimum cash balance required</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_MaximumDebtInstrumentConvertibleConversionShareNumber" xlink:label="plx_MaximumDebtInstrumentConvertibleConversionShareNumber" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_MaximumDebtInstrumentConvertibleConversionShareNumber" xlink:to="plx_MaximumDebtInstrumentConvertibleConversionShareNumber_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_MaximumDebtInstrumentConvertibleConversionShareNumber_lbl" xml:lang="en-US">The maximum price per share of the conversion feature embedded in the debt instrument.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_MaximumDebtInstrumentConvertibleConversionShareNumber_lbl" xml:lang="en-US">Maximum Debt Instrument Convertible Conversion Share Number</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_MaximumDebtInstrumentConvertibleConversionShareNumber_lbl" xml:lang="en-US">Maximum price per share of the conversion feature</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionDescription" xlink:label="us-gaap_DebtInstrumentRedemptionDescription" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentRedemptionDescription" xlink:to="us-gaap_DebtInstrumentRedemptionDescription_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentRedemptionDescription_lbl" xml:lang="en-US">Debt Instrument, Redemption, Description</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DebtInstrumentRedemptionDescription_lbl" xml:lang="en-US">Redemption, description</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdTradingDays" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdTradingDays" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleThresholdTradingDays" xlink:to="us-gaap_DebtInstrumentConvertibleThresholdTradingDays_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdTradingDays_lbl" xml:lang="en-US">Debt Instrument, Convertible, Threshold Trading Days</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdTradingDays_lbl" xml:lang="en-US">Threshold trading days</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1" xlink:to="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_lbl" xml:lang="en-US">Debt Instrument, Convertible, Threshold Consecutive Trading Days</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_DebtInstrumentConvertibleThresholdConsecutiveTradingDays1_lbl" xml:lang="en-US">Threshold consecutive trading days</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ThresholdPercentageOfConversionPrice" xlink:label="plx_ThresholdPercentageOfConversionPrice" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ThresholdPercentageOfConversionPrice" xlink:to="plx_ThresholdPercentageOfConversionPrice_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ThresholdPercentageOfConversionPrice_lbl" xml:lang="en-US">Threshold percentage of conversion price on sale price of the company's common stock.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ThresholdPercentageOfConversionPrice_lbl" xml:lang="en-US">Threshold Percentage Of Conversion Price</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_DebtInstrumentAggregatePercentageOfPrincipleAmountOutstanding" xlink:label="plx_DebtInstrumentAggregatePercentageOfPrincipleAmountOutstanding" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_DebtInstrumentAggregatePercentageOfPrincipleAmountOutstanding" xlink:to="plx_DebtInstrumentAggregatePercentageOfPrincipleAmountOutstanding_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_DebtInstrumentAggregatePercentageOfPrincipleAmountOutstanding_lbl" xml:lang="en-US">Aggregate percentage of principle amount of debt outstanding.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_DebtInstrumentAggregatePercentageOfPrincipleAmountOutstanding_lbl" xml:lang="en-US">Debt Instrument, Aggregate Percentage Of Principle Amount Outstanding</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_DebtInstrumentAggregatePercentageOfPrincipleAmountOutstanding_lbl" xml:lang="en-US">Aggregate percentage of principle amount</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_DebtInstrumentRedemption" xlink:label="plx_DebtInstrumentRedemption" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_DebtInstrumentRedemption" xlink:to="plx_DebtInstrumentRedemption_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_DebtInstrumentRedemption_lbl" xml:lang="en-US">The amount of redemption of debt as at the end of the reporting period.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_DebtInstrumentRedemption_lbl" xml:lang="en-US">Debt Instrument, Redemption</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_DebtInstrumentRedemption_lbl" xml:lang="en-US">Amount of redemption of debt</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_PercentageOfOutstandingCapitalStock" xlink:label="plx_PercentageOfOutstandingCapitalStock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_PercentageOfOutstandingCapitalStock" xlink:to="plx_PercentageOfOutstandingCapitalStock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_PercentageOfOutstandingCapitalStock_lbl" xml:lang="en-US">Percentage of outstanding capital stock.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_PercentageOfOutstandingCapitalStock_lbl" xml:lang="en-US">Percentage of Outstanding Capital Stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_PercentageOfOutstandingCapitalStock_lbl" xml:lang="en-US">Percentage of outstanding capital stock</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock" xlink:label="plx_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock" xlink:to="plx_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock_lbl" xml:lang="en-US">Represents the denomination of the principal amount of debt that is used in conversion calculations.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock_lbl" xml:lang="en-US">Debt Instrument Principal Amount Denomination for Conversion Into Common Stock</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="plx_DebtInstrumentPrincipalAmountDenominationForConversionIntoCommonStock_lbl" xml:lang="en-US">Denomination of the principal amount of debt</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_NumberOfCalendarDaysAfterDateOfApplicableFundamentalChange" xlink:label="plx_NumberOfCalendarDaysAfterDateOfApplicableFundamentalChange" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_NumberOfCalendarDaysAfterDateOfApplicableFundamentalChange" xlink:to="plx_NumberOfCalendarDaysAfterDateOfApplicableFundamentalChange_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_NumberOfCalendarDaysAfterDateOfApplicableFundamentalChange_lbl" xml:lang="en-US">Number of calendar days after the date of applicable fundamental change purchase date.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_NumberOfCalendarDaysAfterDateOfApplicableFundamentalChange_lbl" xml:lang="en-US">Number Of Calendar Days After Date Of Applicable Fundamental Change</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_NumberOfCalendarDaysAfterDateOfApplicableFundamentalChange_lbl" xml:lang="en-US">Number of calendar days after the date of applicable fundamental change purchase date</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed" xlink:label="us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed" xlink:to="us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_lbl" xml:lang="en-US">Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_DebtInstrumentRedemptionPricePercentageOfPrincipalAmountRedeemed_lbl" xml:lang="en-US">Redemption price, percentage</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable" xlink:to="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisValuationTechniquesTable_lbl" xml:lang="en-US">Fair Value Measurement Inputs and Valuation Techniques [Table]</label>
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_UsIsraelMember" xlink:to="plx_UsIsraelMember_lbl" />
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    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/srt/2021/elts/srt-2021-01-31.xsd#srt_ConsolidatedEntitiesDomain" xlink:label="srt_ConsolidatedEntitiesDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="srt_ConsolidatedEntitiesDomain" xlink:to="srt_ConsolidatedEntitiesDomain_lbl" />
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    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_EmployeeRelatedLiabilitiesCurrent" xlink:to="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xml:lang="en-US">Employee-related Liabilities, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xml:lang="en-US">Payroll and related expenses</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_InterestPayableCurrent" xlink:label="us-gaap_InterestPayableCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_InterestPayableCurrent" xlink:to="us-gaap_InterestPayableCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_InterestPayableCurrent_lbl" xml:lang="en-US">Interest Payable, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_InterestPayableCurrent_lbl" xml:lang="en-US">Interest payable</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedVacationCurrent" xlink:label="us-gaap_AccruedVacationCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedVacationCurrent" xlink:to="us-gaap_AccruedVacationCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccruedVacationCurrent_lbl" xml:lang="en-US">Accrued Vacation, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AccruedVacationCurrent_lbl" xml:lang="en-US">Provision for vacation</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedLiabilitiesCurrent" xlink:label="us-gaap_AccruedLiabilitiesCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedLiabilitiesCurrent" xlink:to="us-gaap_AccruedLiabilitiesCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xml:lang="en-US">Accrued Liabilities, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xml:lang="en-US">Accrued expenses</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccruedRoyaltiesCurrent" xlink:label="us-gaap_AccruedRoyaltiesCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccruedRoyaltiesCurrent" xlink:to="us-gaap_AccruedRoyaltiesCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccruedRoyaltiesCurrent_lbl" xml:lang="en-US">Accrued Royalties, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="us-gaap_AccruedRoyaltiesCurrent_lbl" xml:lang="en-US">Royalties payable</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_AccountsPayablePropertyAndEquipmentSuppliersCurrent" xlink:label="plx_AccountsPayablePropertyAndEquipmentSuppliersCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_AccountsPayablePropertyAndEquipmentSuppliersCurrent" xlink:to="plx_AccountsPayablePropertyAndEquipmentSuppliersCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_AccountsPayablePropertyAndEquipmentSuppliersCurrent_lbl" xml:lang="en-US">Carrying value as of the balance sheet date of obligations incurred and payable to property and equipment suppliers. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_AccountsPayablePropertyAndEquipmentSuppliersCurrent_lbl" xml:lang="en-US">Accounts Payable, Property And Equipment Suppliers, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_AccountsPayablePropertyAndEquipmentSuppliersCurrent_lbl" xml:lang="en-US">Property and equipment suppliers</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_AccountsPayableCurrent" xlink:label="us-gaap_AccountsPayableCurrent" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_AccountsPayableCurrent" xlink:to="us-gaap_AccountsPayableCurrent_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xml:lang="en-US">Accounts Payable, Current</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/totalLabel" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xml:lang="en-US">Accounts payable and accruals - other</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:to="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xml:lang="en-US">Schedule of Related Party Transactions, by Related Party [Table]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:to="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xml:lang="en-US">Related Party [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="us-gaap_RelatedPartyDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyDomain" xlink:to="us-gaap_RelatedPartyDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RelatedPartyDomain_lbl" xml:lang="en-US">Related Party [Domain]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_CompensationToNonExecutiveDirectorsMember" xlink:label="plx_CompensationToNonExecutiveDirectorsMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_CompensationToNonExecutiveDirectorsMember" xlink:to="plx_CompensationToNonExecutiveDirectorsMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_CompensationToNonExecutiveDirectorsMember_lbl" xml:lang="en-US">Compensation To The Non-Executive Directors [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_CompensationToNonExecutiveDirectorsMember_lbl" xml:lang="en-US">Compensation to the non-executive directors</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="us-gaap_RelatedPartyTransactionLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionLineItems" xlink:to="us-gaap_RelatedPartyTransactionLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xml:lang="en-US">Related Party Transaction [Line Items]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_RelatedPartyTransactionAmountsOfTransaction" xlink:label="us-gaap_RelatedPartyTransactionAmountsOfTransaction" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_RelatedPartyTransactionAmountsOfTransaction" xlink:to="us-gaap_RelatedPartyTransactionAmountsOfTransaction_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_RelatedPartyTransactionAmountsOfTransaction_lbl" xml:lang="en-US">Related Party Transaction, Amounts of Transaction</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/verboseLabel" xlink:label="us-gaap_RelatedPartyTransactionAmountsOfTransaction_lbl" xml:lang="en-US">Compensation (including share based compensation) to the non-executive directors</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="us-gaap_SubsequentEventTable" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTable" xlink:to="us-gaap_SubsequentEventTable_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventTable_lbl" xml:lang="en-US">Subsequent Event [Table]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="us-gaap_SubsequentEventTypeAxis" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeAxis" xlink:to="us-gaap_SubsequentEventTypeAxis_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xml:lang="en-US">Subsequent Event Type [Axis]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="us-gaap_SubsequentEventTypeDomain" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventTypeDomain" xlink:to="us-gaap_SubsequentEventTypeDomain_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xml:lang="en-US">Subsequent Event Type [Domain]</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="us-gaap_SubsequentEventMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventMember" xlink:to="us-gaap_SubsequentEventMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventMember_lbl" xml:lang="en-US">Subsequent Event</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ChiesiAgreementsMember" xlink:label="plx_ChiesiAgreementsMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ChiesiAgreementsMember" xlink:to="plx_ChiesiAgreementsMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ChiesiAgreementsMember_lbl" xml:lang="en-US">Chiesi Agreements [Member]</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ChiesiAgreementsMember_lbl" xml:lang="en-US">Chiesi Agreements</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_SupplyAndTechnologyTransferAgreementWithFiocruzMember" xlink:label="plx_SupplyAndTechnologyTransferAgreementWithFiocruzMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_SupplyAndTechnologyTransferAgreementWithFiocruzMember" xlink:to="plx_SupplyAndTechnologyTransferAgreementWithFiocruzMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_SupplyAndTechnologyTransferAgreementWithFiocruzMember_lbl" xml:lang="en-US">Represents information pertaining to supply and technology transfer agreement with Fiocruz.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_SupplyAndTechnologyTransferAgreementWithFiocruzMember_lbl" xml:lang="en-US">Brazil Agreement with Fiocruz</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_AlfataligliceraseMember" xlink:label="plx_AlfataligliceraseMember" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_AlfataligliceraseMember" xlink:to="plx_AlfataligliceraseMember_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_AlfataligliceraseMember_lbl" xml:lang="en-US">This member stands for the product, alfataliglicerase.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_AlfataligliceraseMember_lbl" xml:lang="en-US">Alfataliglicerase</label>
    <loc xlink:type="locator" xlink:href="https://xbrl.fasb.org/us-gaap/2021/elts/us-gaap-2021-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="us-gaap_SubsequentEventLineItems" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="us-gaap_SubsequentEventLineItems" xlink:to="us-gaap_SubsequentEventLineItems_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="us-gaap_SubsequentEventLineItems_lbl" xml:lang="en-US">Subsequent Event [Line Items]</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ProceedsFromExpenseReimbursements" xlink:label="plx_ProceedsFromExpenseReimbursements" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ProceedsFromExpenseReimbursements" xlink:to="plx_ProceedsFromExpenseReimbursements_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ProceedsFromExpenseReimbursements_lbl" xml:lang="en-US">The cash inflow from expense reimbursements in a collaboration agreement.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ProceedsFromExpenseReimbursements_lbl" xml:lang="en-US">Proceeds from Expense Reimbursements</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ProceedsFromExpenseReimbursements_lbl" xml:lang="en-US">Proceeds from expense reimbursements</label>
    <loc xlink:type="locator" xlink:href="plx-20211231.xsd#plx_ProceedsFromSaleOfProducts" xlink:label="plx_ProceedsFromSaleOfProducts" />
    <labelArc xlink:type="arc" xlink:arcrole="http://www.xbrl.org/2003/arcrole/concept-label" xlink:from="plx_ProceedsFromSaleOfProducts" xlink:to="plx_ProceedsFromSaleOfProducts_lbl" />
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/documentation" xlink:label="plx_ProceedsFromSaleOfProducts_lbl" xml:lang="en-US">The amount of proceeds from sale of products.</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/label" xlink:label="plx_ProceedsFromSaleOfProducts_lbl" xml:lang="en-US">Proceeds From Sale Of Products</label>
    <label xlink:type="resource" xlink:role="http://www.xbrl.org/2003/role/terseLabel" xlink:label="plx_ProceedsFromSaleOfProducts_lbl" xml:lang="en-US">Proceeds from sales</label>
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