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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioForecastMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Forecast [Member]</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Loss from operations</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock purchased</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardSharesPurchasedForAward_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Shares Purchased For Award</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraExpenseIncludedInResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contra expense included in research and development expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraExpenseIncludedInResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contra Expense Included In Research And Development Expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraExpenseIncludedInResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contra expense included in research and development expense.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VinbiocareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vinbiocare [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VinbiocareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vinbiocare [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VinbiocareMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Vinbiocare.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_SeptemberTwoThousandAndTwentyOneLeaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">September 2021 Lease Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_SeptemberTwoThousandAndTwentyOneLeaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">September Two Thousand And Twenty One Lease Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_SeptemberTwoThousandAndTwentyOneLeaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">September two thousand and twenty one lease agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Foreign currency transaction gain</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossRealized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Foreign Currency Transaction Gain Loss Realized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_COVIDNineteenVaccineDevelopmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">COVID-19 Vaccine Development</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_COVIDNineteenVaccineDevelopmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">C O V I D Nineteen Vaccine Development [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_COVIDNineteenVaccineDevelopmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">COVID-19 vaccine development.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Emerging Growth Company</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityEmergingGrowthCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Emerging Growth Company</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Prepaid Expense and Other Assets, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Prepaid expense and other assets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInPrepaidDeferredExpenseAndOtherAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Prepaid Deferred Expense And Other Assets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCashAndCashEquivalentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Cash and Cash Equivalents and Restricted Cash</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfCashAndCashEquivalentsTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Cash And Cash Equivalents Table [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of shares available</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Available For Grant</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Payments to Acquire Property, Plant, and Equipment, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Acquisition of property and equipment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquirePropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments To Acquire Property Plant And Equipment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-term Debt [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Debt [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Revenue, Noncurrent, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue, net of current portion</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Revenue Noncurrent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Geographical</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementGeographicalAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement Geographical [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock: $0.001 par value; 60,000 shares authorized;; 26,407 issued and outstanding at March 31,2022 and 26,372 issued and outstanding at December 31,2021</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Value, Issued, Beginning Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Common Stock, Value, Issued, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Value</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, State or Province</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressStateOrProvince_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address State Or Province</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Liabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForAdvanceToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments for advance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForAdvanceToAffiliate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments For Advance To Affiliate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_BillingReceivedAmountRelatedToClinicalTrial_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Billing received amount from third party related to clinical trial</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_BillingReceivedAmountRelatedToClinicalTrial_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Billing Received Amount Related to Clinical Trial</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_BillingReceivedAmountRelatedToClinicalTrial_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Billing received amount related to clinical trial.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Revenue</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation Of Revenue Table [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationPartnerCureVacEnteredIntoCoDevelopmentAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaboration Partner Cure Vac Entered Into Co Development Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationPartnerCureVacEnteredIntoCoDevelopmentAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaboration Partner Cure Vac Entered Into Co Development Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationPartnerCureVacEnteredIntoCoDevelopmentAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Collaboration Partner Cure Vac entered into Co-Development Agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RoyaltyPaymentTermDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Royalty payment term description</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RoyaltyPaymentTermDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Royalty Payment Term Description</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RoyaltyPaymentTermDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Royalty payment term description.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_JanssenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Janssen [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_JanssenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Janssen [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_JanssenMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Janssen.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average shares outstanding, basic and diluted</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_WeightedAverageNumberOfShareOutstandingBasicAndDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Weighted Average Number Of Share Outstanding Basic And Diluted</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CommitmentAndContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitment And Contingencies [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CommitmentAndContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitment And Contingencies [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CommitmentAndContingenciesLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commitment and contingencies.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToPurchaseOfAdditionalSharesOfCommonStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase of additional shares of common stock price per share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToPurchaseOfAdditionalSharesOfCommonStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option To Purchase Of Additional Shares Of Common Stock Price Per Share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToPurchaseOfAdditionalSharesOfCommonStockPricePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Option to purchase of additional shares of common stock price per share.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and Administrative [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General And Administrative Expense [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts Receivable, after Allowance for Credit Loss, Current, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts receivable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsReceivableNetCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Receivable Net Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementContractualTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contractual term</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementContractualTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaboration Agreement Contractual Term</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementContractualTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Collaboration agreement contractual term.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiabilityRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deductions for promised services provided in current period</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Related Party Transactions By Related Party [Table]</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Liabilities, Current, Total</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CityAreaCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">City Area Code</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontFeeReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront fee received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontFeeReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Fee Received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontFeeReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront fee received.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCollateral_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, collateral</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCollateral_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Collateral</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LiquidityPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liquidity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LiquidityPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liquidity Policy Policy [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LiquidityPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Liquidity.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodValueUnderEquityPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under equity plans</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodValueUnderEquityPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value Under Equity Plan</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodValueUnderEquityPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock issued during period value under equity plan.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireInterestInJointVenture_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash consideration paid for equity interest in joint venture</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsToAcquireInterestInJointVenture_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments To Acquire Interest In Joint Venture</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockConsiderationReceivedPerTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consideration received for common stock purchase</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockConsiderationReceivedPerTransaction_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale Of Stock Consideration Received Per Transaction</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Contract with Customer, Liability, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Contract Liabilities, Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Contract Liabilities, Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract With Customer Liability</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PotentialPrincipalRepaymentsOfDebtInstrument_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Potential principal repayment of loan</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PotentialPrincipalRepaymentsOfDebtInstrument_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Potential Principal Repayments Of Debt Instrument</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PotentialPrincipalRepaymentsOfDebtInstrument_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Potential Principal Repayments Of Debt Instrument.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Issuance of common stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of issuance costs (in shares)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares New Issues</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Interest of the prime rate plus</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentBasisSpreadOnVariableRate1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Basis Spread On Variable Rate1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContractWithCustomerAssetAdditionsForRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contract Assets, Additions for revenue recognized from billings</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContractWithCustomerAssetAdditionsForRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract With Customer Asset Additions For Revenue Recognized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContractWithCustomerAssetAdditionsForRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contract with customer asset additions for revenue recognized.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_StatementScenarioAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement Scenario [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonRareDiseaseTargetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-Rare Disease Targets [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonRareDiseaseTargetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Rare Disease Targets [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonRareDiseaseTargetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-rare disease targets.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Basis of Presentation</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BasisOfAccountingPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Basis Of Accounting Policy Policy [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash and cash equivalents, including restricted cash</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total cash, cash equivalents and restricted cash shown in the statement of cash flows</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Cash, cash equivalents and restricted cash at beginning of the period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Cash, cash equivalents and restricted cash at end of the period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CysticFibrosisFoundationTherapeuticsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cystic Fibrosis Foundation [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CysticFibrosisFoundationTherapeuticsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cystic Fibrosis Foundation Therapeutics Inc [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CysticFibrosisFoundationTherapeuticsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Cystic Fibrosis Foundation Therapeutics, Inc.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Noncash Income (Expense), Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Other non-cash expenses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherNoncashIncomeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Noncash Income Expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Share Based Compensation Arrangements By Share Based Payment Award [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash used in investing activities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Investing Activities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalExpendituresIncurredButNotYetPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase of property and equipment in accounts payable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CapitalExpendituresIncurredButNotYetPaid_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Capital Expenditures Incurred But Not Yet Paid</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_IL_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Israeli Ministry of Health ("MOH") [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_IL_lbl" xlink:role="http://www.xbrl.org/2003/role/label">I L</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodSharesOptionExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock to Ultragenyx on option exercise (in shares)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodSharesOptionExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares Option Exercised</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodSharesOptionExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock issued during period shares option exercised.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PaymentsForMatchingFundsForRemainingBudgetedCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Payments for matching funds for remaining budgeted costs</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PaymentsForMatchingFundsForRemainingBudgetedCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payments For Matching Funds For Remaining Budgeted Costs</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PaymentsForMatchingFundsForRemainingBudgetedCosts_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payments for matching funds for remaining budgeted costs.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Employee-related Liabilities, Current, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued compensation</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeRelatedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Related Liabilities Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">General and Administrative Expense, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">General and administrative</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GeneralAndAdministrativeExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">General And Administrative Expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Property, Plant and Equipment, Net, Ending Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Property, Plant and Equipment, Net, Beginning Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Property and equipment, net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Property and equipment, net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common stock, shares issued</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesIssued_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Purchase of common stock, shares</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestExpenseLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Interest Expense, Long-term Debt, Total</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfIncomeAndComprehensiveIncomeAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement Of Income And Comprehensive Income [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PaymentsForProceedsFromTenantAllowance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Tenant improvement allowance</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="country_SG_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Singapore Economic Development Board [Member]</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security Exchange Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_SecurityExchangeName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Security Exchange Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTaxAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Comprehensive loss:</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_FebruaryTwoThousandAndTwentyLeaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">February Two Thousand And Twenty Lease Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_FebruaryTwoThousandAndTwentyLeaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">February two thousand and twenty lease agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revenue.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Other Liabilities, Noncurrent, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other long-term liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OtherLiabilitiesNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Liabilities Noncurrent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event Type</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Disclosure [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionExerciseRevenueRangePerTarget_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Option exercise revenue range per target</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionExerciseRevenueRangePerTarget_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option Exercise Revenue Range Per Target</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionExerciseRevenueRangePerTarget_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Option exercise revenue range per target.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Period End Date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentPeriodEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Period End Date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Non-current restricted cash</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-current restricted cash</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RestrictedCashNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Restricted Cash Noncurrent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement Location [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disbursement Due July 2020 [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disbursement Period Three [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodThreeMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Disbursement period three.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Liabilities Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ResearchCollaborationAndExclusiveLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research Collaboration And Exclusive License Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ResearchCollaborationAndExclusiveLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research Collaboration And Exclusive License Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ResearchCollaborationAndExclusiveLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Research Collaboration and Exclusive License Agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares authorized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Shares Authorized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Transaction price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaboration Agreement Transaction Price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Collaboration agreement transaction price.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current portion of operating lease liability</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Liability Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions By Related Party [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNet_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Contract with Customer, Asset, after Allowance for Credit Loss, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Contract Assets, Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNet_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Contract Assets, Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract With Customer Asset Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodValueOptionExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock to Ultragenyx on option exercise</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodValueOptionExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value Option Exercised</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodValueOptionExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock issued during period value option exercised.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Supplemental disclosure of cash flow information</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalCashFlowInformationAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Cash Flow Information [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BalanceSheetRelatedDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Balance Sheet Related Disclosures [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remaining</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due After Year Four</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lessee operating lease liability payments due after year four.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to reconcile net loss to net cash used in operating activities:</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToReconcileNetIncomeLossToCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments To Reconcile Net Income Loss To Cash Provided By Used In Operating Activities [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Antidilutive securities excluded from computation of earnings per share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDiscountedPurchasePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum discounted purchase price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDiscountedPurchasePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Maximum Discounted Purchase Price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDiscountedPurchasePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share-based compensation arrangement by share-based payment award, maximum discounted purchase price.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loan maturity date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Maturity Date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalanceShares_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of shares owned</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedBalanceShares_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned Balance Shares</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MaximumSalesRequiredForLoansForgivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum LUNAR-COVID 19 sales required for Loans forgivable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MaximumSalesRequiredForLoansForgivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum Sales Required For Loans Forgivable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MaximumSalesRequiredForLoansForgivable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Maximum sales required for loans forgivable .</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Cash paid for interest</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InterestPaidNet_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Interest Paid Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LoanAndSecurityAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loan and Security Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LoanAndSecurityAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Loan And Security Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LoanAndSecurityAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Loan and security agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line Two</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine2_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address Address Line2</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current Fiscal Year End Date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_CurrentFiscalYearEndDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Current Fiscal Year End Date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">NET (DECREASE) INCREASE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryCashFlowPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement of Cash Flows</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InventoryCashFlowPolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Inventory Cash Flow Policy</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remaining research period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionPeriod1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Period1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease costs</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Cost</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PrepaymentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Prepayment fee percentage</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PrepaymentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Prepayment Fee Percentage</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PrepaymentFeePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Prepayment fee percentage.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionExerciseFeeRevenueReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Option exercise fee received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionExerciseFeeRevenueReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option Exercise Fee Revenue Received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionExerciseFeeRevenueReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Option exercise fee revenue received.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity method ownership percentage</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentOwnershipPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Method Investment Ownership Percentage</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AdjustmentsToTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Adjustments to transaction price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AdjustmentsToTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments To Transaction Price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AdjustmentsToTransactionPrice_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Adjustments to transaction price.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disaggregation Of Revenue [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation Of Revenue [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CounterpartyNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Counterparty Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_CounterpartyNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Counterparty Name [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Assets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContractWithCustomerAssetDeductionsForCashCollections_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contract Assets, Deductions for cash collections</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContractWithCustomerAssetDeductionsForCashCollections_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract With Customer Asset Deductions For Cash Collections</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContractWithCustomerAssetDeductionsForCashCollections_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contract with customer asset deductions for cash collections.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Lessee Operating Lease Liability Payments Due Next Twelve Months, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due Next Twelve Months</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accounts Payable, Current, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountsPayableCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounts Payable Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UltragenyxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Ultragenyx [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UltragenyxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Ultragenyx [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UltragenyxMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Ultragenyx.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Term loan</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentFaceAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Face Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, par value</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockParOrStatedValuePerShare_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Par Or Stated Value Per Share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DevelopmentAndOptionAgreementDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Development and option agreement date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DevelopmentAndOptionAgreementDate_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Development And Option Agreement Date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DevelopmentAndOptionAgreementDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Development and option agreement date.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment, Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Equity Method Investment Equity Method Investee Name [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance (in shares)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance (in shares)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Shares Outstanding</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraExpenseRemainingAmountIncludedInAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contra expense remaining amount included in accrued expenses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraExpenseRemainingAmountIncludedInAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contra Expense Remaining Amount Included In Accrued Expenses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraExpenseRemainingAmountIncludedInAccruedExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contra expense remaining amount included in accrued expenses.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders Equity Note [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and Development, Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpensePolicy_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research And Development Expense Policy</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Type</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentType_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Type</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenuePracticalExpedientRemainingPerformanceObligationDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue, practical expedient description</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenuePracticalExpedientRemainingPerformanceObligationDescription_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Practical Expedient Remaining Performance Obligation Description</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease liability, net of current portion</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiabilityNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Liability Noncurrent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Accrued Liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfAccruedLiabilitiesTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Accrued Liabilities Table [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current assets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disaggregation Of Revenue [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisaggregationOfRevenueLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disaggregation Of Revenue [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeStockOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stock Option [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EmployeeStockOptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Employee Stock Option [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ClinicalAccrualsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Clinical accruals</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ClinicalAccrualsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Clinical Accruals Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ClinicalAccrualsCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Clinical accruals current.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-term Debt, Type</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Longterm Debt Type [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OctoberTwoThousandAndSeventeenLeaseAmendmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">October 2017 Lease Amendment [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OctoberTwoThousandAndSeventeenLeaseAmendmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">October Two Thousand And Seventeen Lease Amendment [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OctoberTwoThousandAndSeventeenLeaseAmendmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">October 2017 lease amendment.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentAggregateCost_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment in joint venture</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentAggregateCost_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Method Investment Aggregate Cost</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Method Investment, Nonconsolidated Investee</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Method Investment Nonconsolidated Investee [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Income Tax Expense (Benefit), Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income tax expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxExpenseBenefit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Expense Benefit</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash investing activities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CashFlowNoncashInvestingAndFinancingActivitiesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cash Flow Noncash Investing And Financing Activities Disclosure [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_SummaryOfSignificantAccountingPolicyLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary Of Significant Accounting Policy [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_SummaryOfSignificantAccountingPolicyLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Summary Of Significant Accounting Policy [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_SummaryOfSignificantAccountingPolicyLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Summary of significant accounting policy.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Earnings Per Share, Basic and Diluted, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net loss per share, basic and diluted</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerShareBasicAndDiluted_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Basic And Diluted</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeasesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leases [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_WesternAllianceBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Western Alliance Bank [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_WesternAllianceBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Western Alliance Bank [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_WesternAllianceBankMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Western Alliance Bank.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToPurchaseOfAdditionalSharesOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Purchase of additional shares of common stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToPurchaseOfAdditionalSharesOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option To Purchase Of Additional Shares Of Common Stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToPurchaseOfAdditionalSharesOfCommonStock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Option to purchase of additional shares of common stock.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disbursement Due April 2020 [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disbursement Period Two [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodTwoMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Disbursement period two.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OtherMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Common Stock, Shares, Outstanding, Ending Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Common Stock, Shares, Outstanding, Beginning Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock, shares outstanding</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock Shares Outstanding</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Underwritten Public Offering [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underwritten Public Offering [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UnderwrittenPublicOfferingMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Underwritten public offering.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Beginning Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less accumulated depreciation and amortization</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accumulated Depreciation Depletion And Amortization Property Plant And Equipment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRecognitionPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue Recognition</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRecognitionPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Recognition Policy [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total operating expenses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Expenses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RareDiseaseTargetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Rare Disease Targets [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RareDiseaseTargetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Rare Disease Targets [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RareDiseaseTargetsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Rare disease targets.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">OPERATING ACTIVITIES:</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Operating Activities [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueRecognitionPotentialMilestoneRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue recognition potential milestone revenue recognized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueRecognitionPotentialMilestoneRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Recognition Potential Milestone Revenue Recognized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueRecognitionPotentialMilestoneRevenueRecognized_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revenue recognition potential milestone revenue recognized.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentInProcess_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Acquired in-process research and development expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentInProcess_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-cash charge recorded in acquired in-process research and development expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentInProcess_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research And Development In Process</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwentyTwentyOneInducementEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2021 Inducement Equity Incentive Plan [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwentyTwentyOneInducementEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Twenty Twenty One Inducement Equity Incentive Plan [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwentyTwentyOneInducementEquityIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">2021 Inducement equity incentive plan.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remaining Payments of Operating Lease Liability</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityMaturityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Maturity Table [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2024</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearTwo_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due Year Two</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDateOfFirstRequiredPayment1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loan first principal payment extended maturity date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentDateOfFirstRequiredPayment1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Date Of First Required Payment1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net loss</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net loss</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetIncomeLoss_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Income Loss</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Description of Business, Basis of Presentation and Summary of Significant Accounting Policies</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OrganizationConsolidationBasisOfPresentationBusinessDescriptionAndAccountingPoliciesTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average discount rate</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseWeightedAverageDiscountRatePercent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Weighted Average Discount Rate Percent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research and Development [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ResearchAndDevelopmentExpenseMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research And Development Expense [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Period Focus</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalPeriodFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Period Focus</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingPoliciesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Policies [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Address Line One</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressAddressLine1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address Address Line1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrantsReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Grant awarded</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_GrantsReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Grants Receivable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PotentialTargetLicenseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Potential target license term</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PotentialTargetLicenseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Potential Target License Term</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PotentialTargetLicenseTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Potential target license term.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of owned shares</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_InvestmentOwnedPercentOfNetAssets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Investment Owned Percent Of Net Assets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total current liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, Postal Zip Code</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressPostalZipCode_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address Postal Zip Code</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfReservedVaccineDoses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of reserved vaccine doses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfReservedVaccineDoses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Reserved Vaccine Doses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfReservedVaccineDoses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of reserved vaccine doses.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PreLaunchInventoryPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pre-Launch Inventory</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PreLaunchInventoryPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pre Launch Inventory Policy Policy [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PreLaunchInventoryPolicyPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pre-launch inventory policy.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total remaining lease payments</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Due</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductsAndServicesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Product and Service</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ProductsAndServicesDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Products And Services [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TakedaPharmaceuticalCompanyLimitedAndProvidenceTherapeuticsIncorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Takeda Pharmaceutical Company Limited [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TakedaPharmaceuticalCompanyLimitedAndProvidenceTherapeuticsIncorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Takeda Pharmaceutical Company Limited And Providence Therapeutics Incorporation [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TakedaPharmaceuticalCompanyLimitedAndProvidenceTherapeuticsIncorporationMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Takeda Pharmaceutical Company Limited and Providence Therapeutics Incorporation.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research equipment [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equipment [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Collaborative Arrangement and Arrangement Other than Collaborative</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ArrangementsAndNonarrangementTransactionsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Arrangements And Nonarrangement Transactions [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash used in operating activities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInOperatingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Operating Activities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront payment received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Payment Received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront payment received.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common Stock [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementEquityComponentsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement Equity Components [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Proceeds from Issuance of Long-term Debt, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from long-term debt agreement</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfLongTermDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Issuance Of Long Term Debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current assets:</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AssetsCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets Current [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Registrant Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityRegistrantName_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Registrant Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Revenue.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RevenueTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementConsiderationReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Consideration received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementConsiderationReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Collaboration Agreement Consideration Received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CollaborationAgreementConsiderationReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Collaboration agreement consideration received.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCollateralAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt instrument, collateral amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentCollateralAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument Collateral Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Stockholders' Equity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityNoteDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders Equity Note Disclosure [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ADAIRTechnologyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ADAIR Technology [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ADAIRTechnologyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">A D A I R Technology [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ADAIRTechnologyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">ADAIR Technology.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Interactive Data Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityInteractiveDataCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Interactive Data Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_FebruaryTwoThousandAndTwentyOneLeaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">February 2021 Lease Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_FebruaryTwoThousandAndTwentyOneLeaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">February Two Thousand And Twenty One Lease Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_FebruaryTwoThousandAndTwentyOneLeaseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">February two thousand and twenty one lease agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Address, City or Town</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityAddressCityOrTown_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Address City Or Town</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Contra research and development expense recognized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contra Research And Development Expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ContraResearchAndDevelopmentExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Contra research and development expense.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ResearchCollaborationAndLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Research Collaboration And Exclusive License Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ResearchCollaborationAndLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Research Collaboration And License Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ResearchCollaborationAndLicenseAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Research collaboration and license agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalRemainderOfFiscalYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Debt Maturities Repayments Of Principal Remainder Of Fiscal Year</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfPerformanceObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of performance obligations</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfPerformanceObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Performance Obligations</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfPerformanceObligations_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of performance obligations.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalBalanceSheetDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Balance Sheet Details</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SupplementalBalanceSheetDisclosuresTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Supplemental Balance Sheet Disclosures [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Trading Symbol</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_TradingSymbol_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Trading Symbol</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transactions</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions Disclosure [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">INVESTING ACTIVITIES:</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInInvestingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Investing Activities [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Less: imputed interest</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityUndiscountedExcessAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Undiscounted Excess Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Local Phone Number</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_LocalPhoneNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Local Phone Number</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total stockholders&#8217; equity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders Equity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Subsequent Event Type</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event Type [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AgreementAmountAgreedToFund_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Amount agreed to fund</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AgreementAmountAgreedToFund_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Agreement Amount Agreed To Fund</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AgreementAmountAgreedToFund_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Agreement amount agreed to fund.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statistical Measurement</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RangeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Range [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Small Business</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntitySmallBusiness_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Small Business</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leases</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeLeasesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Leases Policy [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SharePrice_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Price</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">APIC, Share-based Payment Arrangement, Increase for Cost Recognition, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based compensation expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Adjustments To Additional Paid In Capital Sharebased Compensation Requisite Service Period Recognition Value</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Long-term Debt, Excluding Current Maturities, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-term debt, net of current portion</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtNoncurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Debt Noncurrent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_GrantOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Grant 1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_GrantOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Grant One [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_GrantOneMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Grant one.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccruedLiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accrued Liabilities Current [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Deferred Revenue, Current, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Deferred revenue</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DeferredRevenueCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Deferred Revenue Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfReserveTargets_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Number of targets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfReserveTargets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Number Of Reserve Targets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NumberOfReserveTargets_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Number of reserve targets.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CureVacAGMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">CureVac [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CureVacAGMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Cure Vac A G [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CureVacAGMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">CureVac AG.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdate201409Member_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">ASC 606 [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AccountingStandardsUpdate201409Member_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Accounting Standards Update201409 [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AlexionPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Alexion [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AlexionPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Alexion Pharmaceuticals Inc [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_AlexionPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Alexion Pharmaceuticals, Inc.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Additional Paid in Capital, Ending Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Additional Paid in Capital, Beginning Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Additional Paid in Capital, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional paid-in capital</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapital_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid In Capital</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontFeeAndConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Upfront fee/consideration</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontFeeAndConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Upfront Fee And Consideration</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UpfrontFeeAndConsideration_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Upfront fee/consideration.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VallonPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vallon Pharmaceuticals, Inc. [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VallonPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vallon Pharmaceuticals Inc [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VallonPharmaceuticalsIncMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Vallon Pharmaceuticals, Inc.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Sale of Stock</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SaleOfStockNameOfTransactionDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Sale Of Stock Name Of Transaction [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Related Party Transaction [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transaction [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue From Contract With Customer [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Plan Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Plan Name [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Class Of Stock [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ClassOfStockLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Class Of Stock [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2023</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Debt Maturities Repayments Of Principal In Next Twelve Months</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_WarrantFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Warrant fee payable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_WarrantFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Warrant Fee Payable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_WarrantFeePayable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Warrant fee payable.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Unamortized Loan Commitment and Origination Fees and Unamortized Discounts or Premiums, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loan origination fee paid</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_UnamortizedLoanCommitmentAndOriginationFeesAndUnamortizedDiscountsOrPremiums_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Unamortized Loan Commitment And Origination Fees And Unamortized Discounts Or Premiums</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lessee, operating lease, term of contract</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseTermOfContract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Term Of Contract</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MonthlyBaseRent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Monthly base rent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MonthlyBaseRent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Monthly Base Rent</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MonthlyBaseRent_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Monthly base rent.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock, net of issuance costs</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueNewIssues_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value New Issues</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LackOfMarketabilityDiscountRestrictedPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lack of marketability discount restricted period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LackOfMarketabilityDiscountRestrictedPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lack Of Marketability Discount Restricted Period</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LackOfMarketabilityDiscountRestrictedPeriod_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Lack of marketability discount restricted period.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligationExpectedTimingOfSatisfactionStartDateAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Remaining Performance Obligation Expected Timing Of Satisfaction Start Date [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OtherAccruedResearchAndDevelopmentExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Other accrued research and development expenses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OtherAccruedResearchAndDevelopmentExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Other Accrued Research And Development Expenses</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OtherAccruedResearchAndDevelopmentExpenses_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Other accrued research and development expenses.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueIssuedForServices_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Common stock issued, value</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueIssuedForServices_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value Issued For Services</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Gain from foreign currency</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Foreign currency transaction gain</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Foreign Currency Transaction Gain (Loss), before Tax, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ForeignCurrencyTransactionGainLossBeforeTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Foreign Currency Transaction Gain Loss Before Tax</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Share-based Payment Arrangement, Noncash Expense, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based compensation expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PercentageRequiredToBeMaintainedInConsolidatedUnrestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage required to be maintain in consolidated, unrestricted cash</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PercentageRequiredToBeMaintainedInConsolidatedUnrestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Required To Be Maintained In Consolidated Unrestricted Cash</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PercentageRequiredToBeMaintainedInConsolidatedUnrestrictedCash_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage required to be maintained in consolidated unrestricted cash.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTypeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment Type [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RelatedPartyTransactionsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Related Party Transactions [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDiscountedAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum discounted amount per year</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDiscountedAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Maximum Discounted Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ShareBasedCompensationArrangementByShareBasedPaymentAwardMaximumDiscountedAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Share based compensation arrangement by share based payment award maximum discounted amount.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Long-term Debt, Current Maturities, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current portion of long-term debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongTermDebtCurrent_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Long Term Debt Current</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disbursement Due October 2020 [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disbursement Period Four [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPeriodFourMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Disbursement period four.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Net cash provided by financing activities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Financing Activities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitments And Contingencies Disclosure [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Right-of-use asset obtained in exchange for lease liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Right Of Use Asset Obtained In Exchange For Operating Lease Liability</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total assets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Assets_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Assets</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock upon exercise of stock options (in shares)</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Shares Stock Options Exercised</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Total liabilities and stockholders&#8217; equity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquity_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Liabilities And Stockholders Equity</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Quarterly Report</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentQuarterlyReport_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Quarterly Report</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Dividends, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Dividends declared or paid</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_Dividends_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Dividends</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfCashFlowsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement Of Cash Flows [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Additional Paid-In Capital [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdditionalPaidInCapitalMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Additional Paid In Capital [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Title of 12(b) Security</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_Security12bTitle_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Security12b Title</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Comprehensive loss</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComprehensiveIncomeNetOfTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Comprehensive Income Net Of Tax</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwoThousandTwentyEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2020 Employee Stock Purchase Plan [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwoThousandTwentyEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Twenty Employee Stock Purchase Plan [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwoThousandTwentyEmployeeStockPurchasePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two Thousand Twenty Employee Stock Purchase Plan.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Debt Instrument [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Award Type</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangements By Share Based Payment Award Award Type And Plan Name [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Components of Property and Equipment, Net</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Property Plant And Equipment [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PercentageOfEquityInterestInJointVenture_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Percentage of equity interest in joint venture</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PercentageOfEquityInterestInJointVenture_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Percentage Of Equity Interest In Joint Venture</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PercentageOfEquityInterestInJointVenture_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Percentage of equity interest in joint venture.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule of Maturities of Long-term Debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfMaturitiesOfLongTermDebtTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Schedule Of Maturities Of Long Term Debt Table [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2026</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearFour_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee, Operating Lease, Liability, to be Paid, Year Four</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VinbiocareAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Vinbiocare Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VinbiocareAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Vinbiocare Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_VinbiocareAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Vinbiocare agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Current Reporting Status</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCurrentReportingStatus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Current Reporting Status</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue From Contract With Customer [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Remaining performance obligation</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueRemainingPerformanceObligation_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue Remaining Performance Obligation</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Scenario</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_ScenarioUnspecifiedDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Scenario Unspecified [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_EquityMethodInvesteeNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Investment, Name</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_EquityMethodInvesteeNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Method Investee Name [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentIncreaseAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued interest added to principal debt balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentIncreaseAccruedInterest_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Debt Instrument, Increase, Accrued Interest</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lessee, operating leases, option to extend</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseOptionToExtend_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Option To Extend</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net Loss per Share</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EarningsPerSharePolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Earnings Per Share Policy [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LUNARCFMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">LUNAR-CF [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LUNARCFMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">L U N A R C F [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_LUNARCFMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">LUNAR-CF.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2022</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsRemainderOfFiscalYear_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lessee Operating Lease Liability Payments Remainder Of Fiscal Year</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Proceeds from debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Net increase in indebtedness</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromIssuanceOfDebt_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Proceeds From Issuance Of Debt</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Computer and software [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ComputerEquipmentMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Computer Equipment [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BorrowingsUnderGuaranteedInvestmentAgreements_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Term loan draw down</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_BorrowingsUnderGuaranteedInvestmentAgreements_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Borrowings Under Guaranteed Investment Agreements</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ReductionInNumberOfCommonStockCapitalSharesAvailableForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Reduction in number of common stock shares available for future issuance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ReductionInNumberOfCommonStockCapitalSharesAvailableForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Reduction in Number of Common Stock Capital Shares Available for Future Issuance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_ReductionInNumberOfCommonStockCapitalSharesAvailableForFutureIssuance_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Reduction in number of common stock capital shares available for future issuance.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-term Debt, Type</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LongtermDebtTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Longterm Debt Type [Axis]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Statement Location</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeStatementLocationDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Statement Location [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Accrued Liabilities, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accrued liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccruedLiabilities_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accrued Liabilities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Minimum [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MinimumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Minimum [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwoThousandNineteenOmnibusIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2019 Omnibus Equity Incentive Plan [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwoThousandNineteenOmnibusIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Two Thousand Nineteen Omnibus Incentive Plan [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_TwoThousandNineteenOmnibusIncentivePlanMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Two thousand nineteen omnibus incentive plan.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PharmaceuticalCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Pharmaceutical Company [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PharmaceuticalCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Pharmaceutical Company [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PharmaceuticalCompanyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Pharmaceutical company.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecurityDeposit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Security deposit</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SecurityDeposit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Security Deposit</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock upon exercise of stock options</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value Stock Options Exercised</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">FINANCING ACTIVITIES:</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_NetCashProvidedByUsedInFinancingActivitiesAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Net Cash Provided By Used In Financing Activities [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Filer Category</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFilerCategory_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Filer Category</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Fiscal Year Focus</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentFiscalYearFocus_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Document Fiscal Year Focus</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConstructionInProgressMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Construction in progress [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ConstructionInProgressMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Construction In Progress [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/periodEndLabel">Retained Earnings (Accumulated Deficit), Ending Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/periodStartLabel">Retained Earnings (Accumulated Deficit), Beginning Balance</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Retained Earnings (Accumulated Deficit), Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accumulated deficit</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated deficit</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsAccumulatedDeficit_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings Accumulated Deficit</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Income Taxes</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncomeTaxDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Income Tax Disclosure [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Depreciation, Depletion and Amortization, Nonproduction, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Depreciation and amortization</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DepreciationAndAmortization_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Depreciation And Amortization</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_FairValueDisclosuresAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Fair Value Disclosures [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonrefundableUpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Nonrefundable upfront payment received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonrefundableUpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Nonrefundable Upfront Payment Received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonrefundableUpfrontPaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Nonrefundable upfront payment received.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Maximum [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_MaximumMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Maximum [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetAndLiabilityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Summary of Changes in Balances of Contract Assets and Contract Liability</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ContractWithCustomerAssetAndLiabilityTableTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Contract With Customer Asset And Liability Table [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Central Index Key</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCentralIndexKey_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Central Index Key</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock related to acquired in-process research and development</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodValueAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stock Issued During Period Value Acquisitions</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PaymentReceivedFirstInstallment_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Received first installment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PaymentReceivedFirstInstallment_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Payment Received First Installment</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_PaymentReceivedFirstInstallment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Payment received first installment.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Tax Identification Number</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityTaxIdentificationNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Tax Identification Number</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Component</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityComponentDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Component [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_FinalPaymentOfDisbursementAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Final payment of disbursement amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_FinalPaymentOfDisbursementAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Final Payment Of Disbursement Amount</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_FinalPaymentOfDisbursementAmount_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Final payment of disbursement amount.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToExtendInitialTermOnAnAnnualBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Option to extend initial term on an annual basis</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToExtendInitialTermOnAnAnnualBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Option To Extend Initial Term On An Annual Basis</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_OptionToExtendInitialTermOnAnAnnualBasis_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Option to extend initial term on an annual basis.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:role="http://www.xbrl.org/2009/role/negatedLabel">Accounts receivable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsReceivable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accounts Receivable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Leasehold improvements [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseholdImprovementsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Leasehold Improvements [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CommitmentAndContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitment And Contingencies [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CommitmentAndContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Commitment And Contingencies [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_CommitmentAndContingenciesTable_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Commitment and contingencies.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-based compensation number of shares authorized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award Number Of Shares Authorized</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Statement [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementTable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement [Table]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Weighted-average remaining lease term</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseWeightedAverageRemainingLeaseTerm1_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Operating Lease Weighted Average Remaining Lease Term1</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity File Number</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityFileNumber_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity File Number</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonRefundablePaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Non-refundable payment received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonRefundablePaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Non Refundable Payment Received</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_NonRefundablePaymentReceived_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Non-refundable payment received.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Share Based Compensation Arrangement By Share Based Payment Award [Line Items]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MRNATechnologyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">mRNA Technology [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MRNATechnologyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">M R N A Technology [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_MRNATechnologyMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">mRNA technology.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accumulated Deficit [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RetainedEarningsMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Retained Earnings [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_TypeOfAdoptionMember_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounting Standards Update</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AdjustmentsForNewAccountingPronouncementsAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounting Standards Update</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Revenue from Contract with Customer, Excluding Assessed Tax, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Total revenue</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Revenue</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_RevenueFromContractWithCustomerExcludingAssessedTax_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Revenue From Contract With Customer Excluding Assessed Tax</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Increase (Decrease) in Accounts Payable, Total</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Accounts payable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInAccountsPayable_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Increase Decrease In Accounts Payable</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesCurrentAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Current liabilities:</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsShareBasedPaymentsTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Share-Based Compensation Expense</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_SubsequentEventMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Subsequent Event [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommitmentsAndContingenciesDisclosureTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Commitments and Contingencies</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_OperatingLeaseLiability_lbl" xlink:role="http://www.xbrl.org/2003/role/totalLabel">Operating Lease, Liability, Total</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_CommonStockMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Common Stock [Member]</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Schedule Of Property Plant And Equipment [Table]</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DisclosureOfCompensationRelatedCostsSharebasedPaymentsAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Equity Method Investment, Nonconsolidated Investee</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_EquityMethodInvestmentNonconsolidatedInvesteeDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Equity Method Investment Nonconsolidated Investee [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_PropertyPlantAndEquipmentByTypeAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Long-Lived Tangible Asset</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_DocumentTransitionReport_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Document Transition Report</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_RoyaltyPaymentPercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Royalty payment percentage.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_ProceedsFromStockOptionsExercised_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Proceeds from exercise of stock options</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseRenewalTerm_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Operating lease extended additional term</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursedAmountUponExecutionOfAmendment_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Disbursed amount upon execution of amendment.</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UnderlyingAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Underlying Agreement [Member]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_UnderlyingAgreementMember_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Underlying agreement.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockIssuedDuringPeriodSharesAcquisitions_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock related to acquired in-process research and development (in shares)</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DebtInstrumentInterestOnlyPaymentExtendedMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loan interest-only payment extended maturity date</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DebtInstrumentInterestOnlyPaymentExtendedMaturityDate_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Debt instrument interest only payment extended maturity date.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/verboseLabel">Share-based compensation expenses</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_AllocatedShareBasedCompensationExpense_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Allocated Share Based Compensation Expense</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_JointVenturesEquityMethodInvestmentsAndVariableInterestEntitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Joint Ventures, Equity Method Investments and Variable Interest Entities</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_JointVenturesEquityMethodInvestmentsAndVariableInterestEntitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Joint Ventures Equity Method Investments And Variable Interest Entities Policy [Text Block]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_JointVenturesEquityMethodInvestmentsAndVariableInterestEntitiesPolicyTextBlock_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Joint ventures, equity method investments and variable interest entities.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodSharesUnderEquityPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Issuance of common stock under equity plans (in shares)</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_StockIssuedDuringPeriodSharesUnderEquityPlan_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Stock issued during period shares under equity plan.</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StatementOfFinancialPositionAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Statement Of Financial Position [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseContractualTermAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease Contractual Term</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseContractualTermAxis_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Contractual Term [Axis]</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_StockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Stockholders Equity [Abstract]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseContractualTermDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Lease Contractual Term</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LeaseContractualTermDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Lease Contractual Term [Domain]</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPaymentUponAchievementOfRequiredManufacturingPracticesAndINDApplication_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Disbursement payment upon achievement of required manufacturing practices and IND application</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="arct_DisbursementPaymentUponAchievementOfRequiredManufacturingPracticesAndINDApplication_lbl" xlink:role="http://www.xbrl.org/2003/role/documentation">Disbursement payment upon achievement of required manufacturing practices and IND application.</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_IncreaseDecreaseInOperatingCapitalAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Changes in operating assets and liabilities</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LesseeOperatingLeaseLiabilityPaymentsDueYearThree_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">2025</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Common Stock, Shares Outstanding</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityCommonStockSharesOutstanding_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Common Stock Shares Outstanding</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Shell Company</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityShellCompany_lbl" xlink:role="http://www.xbrl.org/2003/role/label">Entity Shell Company</link:label>
    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_LiabilitiesAndStockholdersEquityAbstract_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Liabilities and stockholders&#8217; equity</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="us-gaap_DebtInstrumentInterestRateEffectivePercentage_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Loan accrues interest rate per annum, percentage</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="dei_EntityIncorporationStateCountryCode_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Entity Incorporation, State or Country Code</link:label>
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    <link:label xml:lang="en-US" xlink:type="resource" xlink:label="srt_RepurchaseAgreementCounterpartyNameDomain_lbl" xlink:role="http://www.xbrl.org/2003/role/terseLabel">Counterparty Name</link:label>
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