3.23.3 html 91 126 1 false 23 0 false 3 false false R1.htm 100000 - Document - Document and Entity Information Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 100010 - Statement - Condensed Consolidated Balance Sheets Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_StatementCondensedConsolidatedBalanceSheets Condensed Consolidated Balance Sheets Statements 2 false false R3.htm 100020 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_StatementCondensedConsolidatedBalanceSheetsParenthetical Condensed Consolidated Balance Sheets (Parenthetical) Statements 3 false false R4.htm 100030 - Statement - Condensed Consolidated Statements of Operations and Comprehensive (Loss) Income Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfOperationsAndComprehensiveLossIncome Condensed Consolidated Statements of Operations and Comprehensive (Loss) Income Statements 4 false false R5.htm 100040 - Statement - Condensed Consolidated Statements of Stockholders' Equity Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfStockholdersEquity Condensed Consolidated Statements of Stockholders' Equity Statements 5 false false R6.htm 100050 - Statement - Condensed Consolidated Statements of Cash Flows Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_StatementCondensedConsolidatedStatementsOfCashFlows Condensed Consolidated Statements of Cash Flows Statements 6 false false R7.htm 100060 - Disclosure - Nature of the Business Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureNatureOfBusiness Nature of the Business Notes 7 false false R8.htm 100070 - Disclosure - Summary of Significant Accounting Policies Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 8 false false R9.htm 100080 - Disclosure - Fair Value of Financial Instruments Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureFairValueOfFinancialInstruments Fair Value of Financial Instruments Notes 9 false false R10.htm 100090 - Disclosure - Accounts Payable, Accrued Expenses and Other Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureAccountsPayableAccruedExpensesAndOther Accounts Payable, Accrued Expenses and Other Notes 10 false false R11.htm 100100 - Disclosure - Stock-Based Compensation Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureStockBasedCompensation Stock-Based Compensation Notes 11 false false R12.htm 100110 - Disclosure - Net Loss Per Common Share Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureNetLossPerCommonShare Net Loss Per Common Share Notes 12 false false R13.htm 100120 - Disclosure - Recent Accounting Pronouncements Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureRecentAccountingPronouncements Recent Accounting Pronouncements Notes 13 false false R14.htm 100130 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureSummaryOfSignificantAccountingPolicies 14 false false R15.htm 100140 - Disclosure - Fair Value of Financial Instruments (Tables) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsTables Fair Value of Financial Instruments (Tables) Tables http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureFairValueOfFinancialInstruments 15 false false R16.htm 100150 - Disclosure - Accounts Payable, Accrued Expenses and Other (Tables) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureAccountsPayableAccruedExpensesAndOtherTables Accounts Payable, Accrued Expenses and Other (Tables) Tables http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureAccountsPayableAccruedExpensesAndOther 16 false false R17.htm 100160 - Disclosure - Net Loss Per Common Share (Tables) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureNetLossPerCommonShareTables Net Loss Per Common Share (Tables) Tables http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureNetLossPerCommonShare 17 false false R18.htm 100170 - Disclosure - Nature of the Business - Additional Information (Detail) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureNatureOfBusinessAdditionalInformationDetail Nature of the Business - Additional Information (Detail) Details 18 false false R19.htm 100180 - Disclosure - Fair Value of Financial Instruments - Summary of Assets Measured at Fair Value on a Recurring Basis (Detail) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsSummaryOfAssetsMeasuredAtFairValueOnRecurringBasisDetail Fair Value of Financial Instruments - Summary of Assets Measured at Fair Value on a Recurring Basis (Detail) Details 19 false false R20.htm 100190 - Disclosure - Fair Value of Financial Instruments - Additional Information (Detail) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsAdditionalInformationDetail Fair Value of Financial Instruments - Additional Information (Detail) Details 20 false false R21.htm 100200 - Disclosure - Fair Value of Financial Instruments - Summary of Carrying Values and Fair Values of Financial Instruments (Detail) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsSummaryOfCarryingValuesAndFairValuesOfFinancialInstrumentsDetail Fair Value of Financial Instruments - Summary of Carrying Values and Fair Values of Financial Instruments (Detail) Details 21 false false R22.htm 100210 - Disclosure - Accounts Payable, Accrued Expenses and Other - Schedule of Accounts Payable, Accrued Expenses and Other (Detail) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureAccountsPayableAccruedExpensesAndOtherScheduleOfAccountsPayableAccruedExpensesAndOtherDetail Accounts Payable, Accrued Expenses and Other - Schedule of Accounts Payable, Accrued Expenses and Other (Detail) Details 22 false false R23.htm 100220 - Disclosure - Stock-Based Compensation - Additional Information (Detail) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureStockBasedCompensationAdditionalInformationDetail Stock-Based Compensation - Additional Information (Detail) Details 23 false false R24.htm 100230 - Disclosure - Net Loss Per Common Share - Schedule of Outstanding Options Excluded from Computation of Diluted Loss Per Share (Detail) Sheet http://www.merrimackpharma.com/20230930/taxonomy/role/Role_DisclosureNetLossPerCommonShareScheduleOfOutstandingOptionsExcludedFromComputationOfDilutedLossPerShareDetail Net Loss Per Common Share - Schedule of Outstanding Options Excluded from Computation of Diluted Loss Per Share (Detail) Details 24 false false All Reports Book All Reports mack-20230930.htm mack-20230930.xsd mack-20230930_cal.xml mack-20230930_def.xml mack-20230930_lab.xml mack-20230930_pre.xml http://fasb.org/us-gaap/2023 http://xbrl.sec.gov/dei/2023 true true