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  <element name="DocumentAndEntityInformationAbstract" id="ardx_DocumentAndEntityInformationAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="DomesticCorporateDebtSecuritiesIncludingCashEquivalentsMember" id="ardx_DomesticCorporateDebtSecuritiesIncludingCashEquivalentsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="EmployeeStockPurchasePlanMember" id="ardx_EmployeeStockPurchasePlanMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="PerformanceBasedRestrictedStockUnitsMember" id="ardx_PerformanceBasedRestrictedStockUnitsMember" type="nonnum:domainItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
  <element name="SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract" id="ardx_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsOutstandingWeightedAverageExercisePriceAndAdditionalDisclosuresAbstract" type="xbrli:stringItemType" abstract="true" xbrli:periodType="duration" nillable="true" substitutionGroup="xbrli:item"/>
</schema>
