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  <element name="CommonStockSharesAvailableToSellUnderAgreement" id="cprx_CommonStockSharesAvailableToSellUnderAgreement" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DocumentAndEntityInformationAbstract" id="cprx_DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EstimatedTimeFromEnteringLicenseAgreementToCompletionOfDoubleBlindTreatmentPhasePeriodOfProductPhaseThreeTrial" id="cprx_EstimatedTimeFromEnteringLicenseAgreementToCompletionOfDoubleBlindTreatmentPhasePeriodOfProductPhaseThreeTrial" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueAssumptionsForfeitureRate" id="cprx_FairValueAssumptionsForfeitureRate" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueInputsAssetsLiabilitiesQuantitativeInformationLineItems" id="cprx_FairValueInputsAssetsLiabilitiesQuantitativeInformationLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="FairValueInputsAssetsLiabilitiesQuantitativeInformationTable" id="cprx_FairValueInputsAssetsLiabilitiesQuantitativeInformationTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="InterimFinancialStatementsPolicyTextBlock" id="cprx_InterimFinancialStatementsPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InvestmentForDevelopment" id="cprx_InvestmentForDevelopment" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="InvestmentPursuantToStrategicCollaboration" id="cprx_InvestmentPursuantToStrategicCollaboration" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="LicenseAgreementWithBiomarinMember" id="cprx_LicenseAgreementWithBiomarinMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaturityPeriodOfCertificatesOfDeposit" id="cprx_MaturityPeriodOfCertificatesOfDeposit" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumAmortizationPeriodOfCompensationCostOnStraightLineBasis" id="cprx_MaximumAmortizationPeriodOfCompensationCostOnStraightLineBasis" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumAmountOfCommonStockThatCanBeIssuedUnderShelfRegistrationStatement" id="cprx_MaximumAmountOfCommonStockThatCanBeIssuedUnderShelfRegistrationStatement" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumMaturityPeriodOfCashAndCashEquivalent" id="cprx_MaximumMaturityPeriodOfCashAndCashEquivalent" type="xbrli:stringItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MaximumPercentageOfOutstandingSharesThatCompanyCanSellUnderShelfRegistrationStatement" id="cprx_MaximumPercentageOfOutstandingSharesThatCompanyCanSellUnderShelfRegistrationStatement" type="num:percentItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MilestonePaymentDueUponNewDrugApplicationsAcceptance" id="cprx_MilestonePaymentDueUponNewDrugApplicationsAcceptance" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MilestonePaymentDueUponNewDrugApplicationsApproval" id="cprx_MilestonePaymentDueUponNewDrugApplicationsApproval" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MinimumAmortizationPeriodOfCompensationCostOnStraightLineBasis" id="cprx_MinimumAmortizationPeriodOfCompensationCostOnStraightLineBasis" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="MinimumAmountToBeSpentForProductPhaseThreeTrial" id="cprx_MinimumAmountToBeSpentForProductPhaseThreeTrial" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NorthwesternLicenseAgreementMember" id="cprx_NorthwesternLicenseAgreementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="NumberOfWarrantsExercised" id="cprx_NumberOfWarrantsExercised" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OctoberTwentyEightTwoThousandAndElevenWarrantsMember" id="cprx_OctoberTwentyEightTwoThousandAndElevenWarrantsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OptionsToPurchaseCommonStockMember" id="cprx_OptionsToPurchaseCommonStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OrganizationAndDescriptionOfBusinessLineItems" id="cprx_OrganizationAndDescriptionOfBusinessLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="OrganizationAndDescriptionOfBusinessTable" id="cprx_OrganizationAndDescriptionOfBusinessTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="PaidCostsInConnectionWithProductPhaseThreeTrial" id="cprx_PaidCostsInConnectionWithProductPhaseThreeTrial" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PaymentsForProceedsFromCertificatesOfDeposit" id="cprx_PaymentsForProceedsFromCertificatesOfDeposit" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PrepaidExpensesPolicyTextBlock" id="cprx_PrepaidExpensesPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PrepaidExpensesTableTextBlock" id="cprx_PrepaidExpensesTableTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PrepaidResearchFee" id="cprx_PrepaidResearchFee" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PrepaidSubscriptionFees" id="cprx_PrepaidSubscriptionFees" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ProceedsFromIssuanceOfCommonStockAndWarrantsNet" id="cprx_ProceedsFromIssuanceOfCommonStockAndWarrantsNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ProceedsFromIssuanceOfCommonStockGross" id="cprx_ProceedsFromIssuanceOfCommonStockGross" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ProceedsFromIssuanceOfCommonStockNet" id="cprx_ProceedsFromIssuanceOfCommonStockNet" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="duration" xbrli:balance="credit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PropertyPlantAndEquipmentUsefulLifeAndValuesAbstract" id="cprx_PropertyPlantAndEquipmentUsefulLifeAndValuesAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SaleOfStockAxis" id="cprx_SaleOfStockAxis" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:dimensionItem"/>
  <element name="SaleOfStockDomain" id="cprx_SaleOfStockDomain" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ShareBasedCompensationArrangementByShareBasedPaymentsAwardAwardTerm" id="cprx_ShareBasedCompensationArrangementByShareBasedPaymentsAwardAwardTerm" type="xbrli:durationItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SharesIssuedDuringPeriodWarrantsExercised" id="cprx_SharesIssuedDuringPeriodWarrantsExercised" type="xbrli:sharesItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="StockholdersEquityLineItems" id="cprx_StockholdersEquityLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="StockholdersEquityTable" id="cprx_StockholdersEquityTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="StrategicCollaborationDate" id="cprx_StrategicCollaborationDate" type="xbrli:dateItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SummaryOfBasisOfPresentationAndSignificantAccountingPoliciesLineItems" id="cprx_SummaryOfBasisOfPresentationAndSignificantAccountingPoliciesLineItems" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SummaryOfBasisOfPresentationAndSignificantAccountingPoliciesTable" id="cprx_SummaryOfBasisOfPresentationAndSignificantAccountingPoliciesTable" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrldt:hypercubeItem"/>
  <element name="TwoThousandFourteenShelfRegistrationStatementMember" id="cprx_TwoThousandFourteenShelfRegistrationStatementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="TwoThousandTenShelfRegistrationStatementMember" id="cprx_TwoThousandTenShelfRegistrationStatementMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="UnderwrittenPublicOfferingMember" id="cprx_UnderwrittenPublicOfferingMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="ValueOfPublicFloatBelowWhichAgreedLimitationArise" id="cprx_ValueOfPublicFloatBelowWhichAgreedLimitationArise" type="xbrli:monetaryItemType" abstract="false" xbrli:periodType="instant" xbrli:balance="debit" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WarrantLiabilityMember" id="cprx_WarrantLiabilityMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WarrantsLiabilityAtFairValueTextBlock" id="cprx_WarrantsLiabilityAtFairValueTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WarrantsLiabilityPolicyTextBlock" id="cprx_WarrantsLiabilityPolicyTextBlock" type="nonnum:textBlockItemType" abstract="false" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="WarrantsToPurchaseCommonStockMember" id="cprx_WarrantsToPurchaseCommonStockMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
</schema>


