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<!-- Creation Date      : 2014-11-25T17:41:34.8750298+00:00 -->
<!-- Version            : 2.0.0.4 -->
<!-- Package ID         : 3DA2D8FF6B1C0086C1E3846ED70A38CF-0000879407-001408 -->
<!-- Copyright (c) 2014 R. R. Donnelley & Sons Company. All Rights Reserved. -->
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  <element id="arwr_AggregatePriceOnIssuanceOrSaleOfEquity" name="AggregatePriceOnIssuanceOrSaleOfEquity" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="arwr_RemainingLifeOfWarrant" name="RemainingLifeOfWarrant" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_WarrantOneMember" name="WarrantOneMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_WarrantTwoMember" name="WarrantTwoMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_WarrantThreeMember" name="WarrantThreeMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_WarrantFourMember" name="WarrantFourMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_WarrantFiveMember" name="WarrantFiveMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_WarrantSixMember" name="WarrantSixMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_WarrantSevenMember" name="WarrantSevenMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_WarrantEightMember" name="WarrantEightMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_PercentageOfIncreaseInAnnualRentalCost" name="PercentageOfIncreaseInAnnualRentalCost" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_CorporateHeadquartersInPasadenaMember" name="CorporateHeadquartersInPasadenaMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_ResearchFacilityInMadisonMember" name="ResearchFacilityInMadisonMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_OtherRentalExpenses" name="OtherRentalExpenses" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="arwr_PaymentsUnderCapitalLease" name="PaymentsUnderCapitalLease" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="arwr_IncreaseInMonthlyExpenditureDueToUtilitiesCosts" name="IncreaseInMonthlyExpenditureDueToUtilitiesCosts" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="arwr_FacilityAndEquipmentRentExpense" name="FacilityAndEquipmentRentExpense" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="arwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardInducementGrants" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardInducementGrants" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_TwoThousandsStockOptionPlanMember" name="TwoThousandsStockOptionPlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_TwoThousandsFourEquityIncentivePlanMember" name="TwoThousandsFourEquityIncentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_TwoThousandsThirteenIncentivePlanMember" name="TwoThousandsThirteenIncentivePlanMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_ArrowheadMember" name="ArrowheadMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue" name="ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="arwr_FairValueMeasurementsDisclosureLineItems" name="FairValueMeasurementsDisclosureLineItems" type="xbrli:stringItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_FairValueMeasurementsDisclosureTable" name="FairValueMeasurementsDisclosureTable" type="xbrli:stringItemType" substitutionGroup="xbrldt:hypercubeItem" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_TwoThousandTenWarrantMember" name="TwoThousandTenWarrantMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_TwoThousandTwelveWarrantMember" name="TwoThousandTwelveWarrantMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_TwoThousandThirteenWarrantMember" name="TwoThousandThirteenWarrantMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_WarrantsIssuedToAcquireCommonStock" name="WarrantsIssuedToAcquireCommonStock" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" />
  <element id="arwr_TermOfExchangeRights" name="TermOfExchangeRights" type="xbrli:durationItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_ExchangeRightConvertibleConversionRatioForFirstYear" name="ExchangeRightConvertibleConversionRatioForFirstYear" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_ExchangeRightConvertibleConversionRatioForTwoYear" name="ExchangeRightConvertibleConversionRatioForTwoYear" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_ExchangeRightConvertibleConversionRatioForThreeYear" name="ExchangeRightConvertibleConversionRatioForThreeYear" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_ExchangeRightConvertibleConversionRatioForFourYear" name="ExchangeRightConvertibleConversionRatioForFourYear" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_ExchangeRightConvertibleConversionRatioForFiveYear" name="ExchangeRightConvertibleConversionRatioForFiveYear" type="xbrli:pureItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_NumberOfExchangeRightAreSold" name="NumberOfExchangeRightAreSold" type="xbrli:sharesItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_BusinessCombinationPurchasePriceContingentConsiderationFairValue" name="BusinessCombinationPurchasePriceContingentConsiderationFairValue" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="arwr_BusinessCombinationContingentConsiderationPayments" name="BusinessCombinationContingentConsiderationPayments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="arwr_BusinessCombinationFairValueOfChangeInContingentConsideration" name="BusinessCombinationFairValueOfChangeInContingentConsideration" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="arwr_DeferredTaxAssetFairValueAdjustments" name="DeferredTaxAssetFairValueAdjustments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="debit" />
  <element id="arwr_DeferredTaxLiabilitiesStateTaxes" name="DeferredTaxLiabilitiesStateTaxes" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="arwr_DeferredTaxLiabilitiesEquityInvestments" name="DeferredTaxLiabilitiesEquityInvestments" type="xbrli:monetaryItemType" substitutionGroup="xbrli:item" xbrli:periodType="instant" nillable="true" abstract="false" xbrli:balance="credit" />
  <element id="arwr_PercentageOfValuationAllowance" name="PercentageOfValuationAllowance" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_EffectiveIncomeTaxRateReconciliationMarkToMarketAdjustments" name="EffectiveIncomeTaxRateReconciliationMarkToMarketAdjustments" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_EffectiveIncomeTaxRateReconciliationWriteOffNetOperatingLosses" name="EffectiveIncomeTaxRateReconciliationWriteOffNetOperatingLosses" type="num:percentItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="false" />
  <element id="arwr_DiscretionaryContributionsMember" name="DiscretionaryContributionsMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_EmployeeContributionsUpToThreePercentMember" name="EmployeeContributionsUpToThreePercentMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_FiftyPercentageOfMatchingContributionMember" name="FiftyPercentageOfMatchingContributionMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
  <element id="arwr_EmployeeContributionUpToFirstTwoPercentageMember" name="EmployeeContributionUpToFirstTwoPercentageMember" type="nonnum:domainItemType" substitutionGroup="xbrli:item" xbrli:periodType="duration" nillable="true" abstract="true" />
</schema>
