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      <link:linkbaseRef xlink:type="simple" xlink:href="ptn-20240331_def.xml" xlink:role="http://www.xbrl.org/2003/role/definitionLinkbaseRef" xlink:arcrole="http://www.w3.org/1999/xlink/properties/linkbase" />
    </appinfo>
  </annotation>
  <import namespace="http://www.xbrl.org/2003/instance" schemaLocation="http://www.xbrl.org/2003/xbrl-instance-2003-12-31.xsd" />
  <import namespace="http://www.xbrl.org/2003/linkbase" schemaLocation="http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" />
  <import namespace="http://xbrl.org/2005/xbrldt" schemaLocation="http://www.xbrl.org/2005/xbrldt-2005.xsd" />
  <import namespace="http://xbrl.sec.gov/country/2023" schemaLocation="https://xbrl.sec.gov/country/2023/country-2023.xsd" />
  <import namespace="http://xbrl.sec.gov/currency/2023" schemaLocation="https://xbrl.sec.gov/currency/2023/currency-2023.xsd" />
  <import namespace="http://xbrl.sec.gov/dei/2023" schemaLocation="https://xbrl.sec.gov/dei/2023/dei-2023.xsd" />
  <import namespace="http://www.xbrl.org/dtr/type/non-numeric" schemaLocation="http://www.xbrl.org/dtr/type/nonNumeric-2009-12-16.xsd" />
  <import namespace="http://www.xbrl.org/dtr/type/numeric" schemaLocation="http://www.xbrl.org/dtr/type/numeric-2009-12-16.xsd" />
  <import namespace="http://xbrl.sec.gov/exch/2023" schemaLocation="https://xbrl.sec.gov/exch/2023/exch-2023.xsd" />
  <import namespace="http://www.xbrl.org/2009/arcrole/fact-explanatoryFact" schemaLocation="http://www.xbrl.org/lrr/arcrole/factExplanatory-2009-12-16.xsd" />
  <import namespace="http://www.xbrl.org/2009/role/negated" schemaLocation="http://www.xbrl.org/lrr/role/negated-2009-12-16.xsd" />
  <import namespace="http://www.xbrl.org/2009/role/net" schemaLocation="http://www.xbrl.org/lrr/role/net-2009-12-16.xsd" />
  <import namespace="http://xbrl.sec.gov/naics/2023" schemaLocation="https://xbrl.sec.gov/naics/2023/naics-2023.xsd" />
  <import namespace="http://xbrl.sec.gov/sic/2023" schemaLocation="https://xbrl.sec.gov/sic/2023/sic-2023.xsd" />
  <import namespace="http://fasb.org/srt-roles/2023" schemaLocation="https://xbrl.fasb.org/srt/2023/elts/srt-roles-2023.xsd" />
  <import namespace="http://fasb.org/srt-types/2023" schemaLocation="https://xbrl.fasb.org/srt/2023/elts/srt-types-2023.xsd" />
  <import namespace="http://www.xbrl.org/dtr/type/2020-01-21" schemaLocation="https://www.xbrl.org/dtr/type/2020-01-21/types.xsd" />
  <import namespace="http://xbrl.sec.gov/stpr/2023" schemaLocation="https://xbrl.sec.gov/stpr/2023/stpr-2023.xsd" />
  <import namespace="http://fasb.org/us-roles/2023" schemaLocation="https://xbrl.fasb.org/us-gaap/2023/elts/us-roles-2023.xsd" />
  <import namespace="http://fasb.org/us-types/2023" schemaLocation="https://xbrl.fasb.org/us-gaap/2023/elts/us-types-2023.xsd" />
  <import namespace="http://fasb.org/srt/2023" schemaLocation="https://xbrl.fasb.org/srt/2023/elts/srt-2023.xsd" />
  <import namespace="http://fasb.org/us-gaap/2023" schemaLocation="https://xbrl.fasb.org/us-gaap/2023/elts/us-gaap-2023.xsd" />
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  <element id="ptn_PreferredStockAbstract" name="PreferredStockAbstract" nillable="true" abstract="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_GainLossOnPurchaseCommitment" name="GainLossOnPurchaseCommitment" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_EarningPerShareBasicAndDiluted" name="EarningPerShareBasicAndDiluted" nillable="true" xbrli:periodType="duration" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_WeightedAverageNumberOfCommonSharesOutstandingUsedInComputingBasicAndDiluted" name="WeightedAverageNumberOfCommonSharesOutstandingUsedInComputingBasicAndDiluted" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_CumulativeEffectOfAccountingChange" name="CumulativeEffectOfAccountingChange" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_StockBasedCompensationShares" name="StockBasedCompensationShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_StockBasedCompensationAmount" name="StockBasedCompensationAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_WithholdingTaxesRelatedToRestrictedStockUnitsShares" name="WithholdingTaxesRelatedToRestrictedStockUnitsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_WithholdingTaxesRelatedToRestrictedStockUnitsAmount" name="WithholdingTaxesRelatedToRestrictedStockUnitsAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_RedemptionOfConvertibleSeriesBSeriesCPreferredStockShares" name="RedemptionOfConvertibleSeriesBSeriesCPreferredStockShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_RedemptionOfConvertibleSeriesBSeriesCPreferredStockAmount" name="RedemptionOfConvertibleSeriesBSeriesCPreferredStockAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_SaleOfCommonStockAndWarrantsNetOfCostsShares" name="SaleOfCommonStockAndWarrantsNetOfCostsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_SaleOfCommonStockAndWarrantsNetOfCostsAmount" name="SaleOfCommonStockAndWarrantsNetOfCostsAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ConversionOfLiabilityClassifiedWarrants" name="ConversionOfLiabilityClassifiedWarrants" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_WarrantExcercisesShares" name="WarrantExcercisesShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_WarrantExcercisesAmount" name="WarrantExcercisesAmount" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ReverseStockSplitFractionalSharesShares" name="ReverseStockSplitFractionalSharesShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ReverseStockSplitFractionalSharesAmount" name="ReverseStockSplitFractionalSharesAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ReclassificationOfContingentlyRedeemableWarrants" name="ReclassificationOfContingentlyRedeemableWarrants" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_RedemptionOfConvertibleSeriesBSeriesCPreferredStock" name="RedemptionOfConvertibleSeriesBSeriesCPreferredStock" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_WarrantExercisesShares" name="WarrantExercisesShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_WarrantExercisesAmount" name="WarrantExercisesAmount" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_SaleOfCommonStockAndWarrantsNetOfCosts" name="SaleOfCommonStockAndWarrantsNetOfCosts" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_SaleOfCommonStockNetOfCostsShares" name="SaleOfCommonStockNetOfCostsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_SaleOfCommonStockNetOfCostsAmount" name="SaleOfCommonStockNetOfCostsAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ConversionOfLiabilityClassifiedWarrantsUponWarrantExerciseShares" name="ConversionOfLiabilityClassifiedWarrantsUponWarrantExerciseShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ConversionOfLiabilityClassifiedWarrantsUponWarrantExerciseAmount" name="ConversionOfLiabilityClassifiedWarrantsUponWarrantExerciseAmount" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_AdjustmentsToReconcileNetLossToNetCashNewAbstract" name="AdjustmentsToReconcileNetLossToNetCashNewAbstract" nillable="true" abstract="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_UnrealizedForeignCurrencyTransactionGain" name="UnrealizedForeignCurrencyTransactionGain" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ChangeInFairValueOfLiabilityClassifiedWarrants" name="ChangeInFairValueOfLiabilityClassifiedWarrants" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ProceedsFromSaleOfBusiness" name="ProceedsFromSaleOfBusiness" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ConversionOfLiabilitiesClassifiedAsWarrants" name="ConversionOfLiabilitiesClassifiedAsWarrants" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ConversionOfLiabilityClassifiedWarrantsUponWarrantExercise" name="ConversionOfLiabilityClassifiedWarrantsUponWarrantExercise" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_BasisOfPresentationDisclosureTextBlock" name="BasisOfPresentationDisclosureTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_NewAccountingPronouncementsAndChangesInAccountingPrinciplesDisclosureTextBlock" name="NewAccountingPronouncementsAndChangesInAccountingPrinciplesDisclosureTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_AssetPurchaseAgreementDisclosureTextBlock" name="AssetPurchaseAgreementDisclosureTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ManufacturingSupplyAgreementsTextBlock" name="ManufacturingSupplyAgreementsTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_AgreementWithFosunTextBlock" name="AgreementWithFosunTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_AgreementWithKwangdongTextBlock" name="AgreementWithKwangdongTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_PreviouslyIssuedFinancialStatementsPolicyTextBlock" name="PreviouslyIssuedFinancialStatementsPolicyTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_AccruedLiabilitiesPolicyTextBlock" name="AccruedLiabilitiesPolicyTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ScheduleOfSalesTableTextBlock" name="ScheduleOfSalesTableTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ScheduleOfInventoryPurchaseCommitmentsTableTextBlock" name="ScheduleOfInventoryPurchaseCommitmentsTableTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ScheduleOfEquityDistributionAgreementTableTextBlock" name="ScheduleOfEquityDistributionAgreementTableTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ScheduleOfStockPurchaseWarrantsTableTextBlock" name="ScheduleOfStockPurchaseWarrantsTableTextBlock" nillable="true" xbrli:periodType="duration" type="nonnum:textBlockItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_DescriptionOfSalesBasedPayments" name="DescriptionOfSalesBasedPayments" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_RevenuesGross" name="RevenuesGross" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ProductSalesAllowancesAndAccruals" name="ProductSalesAllowancesAndAccruals" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_OfferingExpenses" name="OfferingExpenses" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_MoneyMarketAccountsAndTreasuryBills" name="MoneyMarketAccountsAndTreasuryBills" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_PaymentsToSalesBasedMilestonePayments" name="PaymentsToSalesBasedMilestonePayments" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_TaxExpense" name="TaxExpense" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_UpfrontPaymentOfLess" name="UpfrontPaymentOfLess" nillable="true" xbrli:balance="credit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_taxexpenses" name="taxexpenses" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_PrepaidClinicalStudyCosts" name="PrepaidClinicalStudyCosts" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_PrepaidInsurancePremiums" name="PrepaidInsurancePremiums" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_VyleesiContractualAdvances" name="VyleesiContractualAdvances" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_CashEquivalentsTreasuryBillAtCarryingValue" name="CashEquivalentsTreasuryBillAtCarryingValue" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_MarketableSecuritiesTreasuryBillAtCarryingValue" name="MarketableSecuritiesTreasuryBillAtCarryingValue" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_CarryingValueDuringTheYear" name="CarryingValueDuringTheYear" nillable="true" xbrli:balance="debit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_CostClinicalStudy" name="CostClinicalStudy" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_OtherResearchRelatedExpenses" name="OtherResearchRelatedExpenses" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_PersonalCost" name="PersonalCost" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_AccruedSellingExpenses" name="AccruedSellingExpenses" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_TotaAcrruedLiabilities" name="TotaAcrruedLiabilities" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_AccruedOtherLongTermLiabilities" name="AccruedOtherLongTermLiabilities" nillable="true" xbrli:balance="credit" xbrli:periodType="instant" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_EquityGrossProceedsShares" name="EquityGrossProceedsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_EquityFeesShares" name="EquityFeesShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_EquityExpensesShares" name="EquityExpensesShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_EquityExpensesProceeds" name="EquityExpensesProceeds" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_EquityNetProceedsShares" name="EquityNetProceedsShares" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_EquityNetProceedsProceeds" name="EquityNetProceedsProceeds" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_SharesOfCommonStock" name="SharesOfCommonStock" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ExercisePricePerShareWarrantsOutstanding" name="ExercisePricePerShareWarrantsOutstanding" nillable="true" xbrli:periodType="duration" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_LatestTerminationDate" name="LatestTerminationDate" nillable="true" xbrli:periodType="duration" type="xbrli:stringItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumberBeginningBalance" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumberBeginningBalance" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumberEndingBalance" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisableNumberEndingBalance" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumberEndingBalance" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingNumberEndingBalance" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumberEndingBalance" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumberEndingBalance" nillable="true" xbrli:periodType="duration" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceBeginningBalance" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceBeginningBalance" nillable="true" xbrli:periodType="duration" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceEndingBalance" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceEndingBalance" nillable="true" xbrli:periodType="duration" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionExercisableWeightedAverageExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionExercisableWeightedAverageExercisePrice" nillable="true" xbrli:periodType="duration" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedExercisePrice" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsVestedAndExpectedToVestOutstandingWeightedExercisePrice" nillable="true" xbrli:periodType="duration" type="num:perShareItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementBySharesBasedPaymentAwardOptionsVestedAndOutstandingAggregateIntrinsicValue" name="ShareBasedCompensationArrangementBySharesBasedPaymentAwardOptionsVestedAndOutstandingAggregateIntrinsicValue" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
  <element id="ptn_ShareBasedCompensationArrangementBySharesBasedPaymentAwardOptionsOutstandingAndOutstandingAggregateIntrinsicValue" name="ShareBasedCompensationArrangementBySharesBasedPaymentAwardOptionsOutstandingAndOutstandingAggregateIntrinsicValue" nillable="true" xbrli:balance="debit" xbrli:periodType="duration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" />
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