3.22.2 html 122 234 1 false 43 0 false 6 false false R1.htm 100000 - Document - Document and Entity Information Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 100010 - Statement - Condensed Consolidated Balance Sheets Sheet http://www.alxoncology.com/20220630/taxonomy/role/StatementCondensedConsolidatedBalanceSheets Condensed Consolidated Balance Sheets Statements 2 false false R3.htm 100030 - Statement - Condensed Consolidated Balance Sheets (Parenthetical) Sheet http://www.alxoncology.com/20220630/taxonomy/role/StatementCondensedConsolidatedBalanceSheetsParenthetical Condensed Consolidated Balance Sheets (Parenthetical) Statements 3 false false R4.htm 100050 - Statement - Condensed Consolidated Statements of Operations Sheet http://www.alxoncology.com/20220630/taxonomy/role/StatementCondensedConsolidatedStatementsOfOperations Condensed Consolidated Statements of Operations Statements 4 false false R5.htm 100060 - Statement - Condensed Consolidated Statements of Comprehensive Loss Sheet http://www.alxoncology.com/20220630/taxonomy/role/StatementCondensedConsolidatedStatementsOfComprehensiveLoss Condensed Consolidated Statements of Comprehensive Loss Statements 5 false false R6.htm 100070 - Statement - Condensed Consolidated Statements of Stockholders' Equity Sheet http://www.alxoncology.com/20220630/taxonomy/role/StatementCondensedConsolidatedStatementsOfStockholdersEquity Condensed Consolidated Statements of Stockholders' Equity Statements 6 false false R7.htm 100080 - Statement - Condensed Consolidated Statements of Cash Flows Sheet http://www.alxoncology.com/20220630/taxonomy/role/StatementCondensedConsolidatedStatementsOfCashFlows Condensed Consolidated Statements of Cash Flows Statements 7 false false R8.htm 100090 - Disclosure - Organization Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureOrganization Organization Notes 8 false false R9.htm 100100 - Disclosure - Significant Accounting Policies Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureSignificantAccountingPolicies Significant Accounting Policies Notes 9 false false R10.htm 100110 - Disclosure - Fair Value of Financial Instruments Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureFairValueOfFinancialInstruments Fair Value of Financial Instruments Notes 10 false false R11.htm 100120 - Disclosure - Balance Sheet Components Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureBalanceSheetComponents Balance Sheet Components Notes 11 false false R12.htm 100130 - Disclosure - Leases Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureLeases Leases Notes 12 false false R13.htm 100140 - Disclosure - Stockholders' Equity Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockholdersEquity Stockholders' Equity Notes 13 false false R14.htm 100150 - Disclosure - Stock-Based Compensation Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensation Stock-Based Compensation Notes 14 false false R15.htm 100160 - Disclosure - Related-Party Transactions Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureRelatedPartyTransactions Related-Party Transactions Notes 15 false false R16.htm 100170 - Disclosure - Net Loss Per Share Sheet http://www.alxoncology.com/20220630/taxonomy/role/DisclosureNetLossPerShare1 Net Loss Per Share Notes 16 false false R17.htm 100180 - Disclosure - Commitments and Contingencies Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureCommitmentsAndContingencies Commitments and Contingencies Notes 17 false false R18.htm 100190 - Disclosure - Subsequent Events Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureSubsequentEvents Subsequent Events Notes 18 false false R19.htm 100200 - Disclosure - Significant Accounting Policies (Policies) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureSignificantAccountingPoliciesPolicies Significant Accounting Policies (Policies) Policies http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureSignificantAccountingPolicies 19 false false R20.htm 100210 - Disclosure - Fair Value of Financial Instruments (Tables) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsTables Fair Value of Financial Instruments (Tables) Tables http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureFairValueOfFinancialInstruments 20 false false R21.htm 100220 - Disclosure - Balance Sheet Components (Tables) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureBalanceSheetComponentsTables Balance Sheet Components (Tables) Tables http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureBalanceSheetComponents 21 false false R22.htm 100230 - Disclosure - Leases (Tables) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureLeasesTables Leases (Tables) Tables http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureLeases 22 false false R23.htm 100240 - Disclosure - Stockholders' Equity (Tables) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockholdersEquityTables Stockholders' Equity (Tables) Tables http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockholdersEquity 23 false false R24.htm 100250 - Disclosure - Stock-Based Compensation (Tables) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationTables Stock-Based Compensation (Tables) Tables http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensation 24 false false R25.htm 100260 - Disclosure - Net Loss Per Share (Tables) Sheet http://www.alxoncology.com/20220630/taxonomy/role/DisclosureNetLossPerShareTables Net Loss Per Share (Tables) Tables http://www.alxoncology.com/20220630/taxonomy/role/DisclosureNetLossPerShare1 25 false false R26.htm 100270 - Disclosure - Fair Value of Financial Instruments - Additional Information (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureFairValueOfFinancialInstrumentsAdditionalInformationDetails Fair Value of Financial Instruments - Additional Information (Details) Details 26 false false R27.htm 100280 - Disclosure - Fair Value of Financial Instruments - Schedule of Available for Sale Investments Measured at Fair Value of Recurring Basis (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsScheduleOfAvailableForSaleInvestmentsMeasuredAtFairValueOfRecurringBasisDetails Fair Value of Financial Instruments - Schedule of Available for Sale Investments Measured at Fair Value of Recurring Basis (Details) Details 27 false false R28.htm 100290 - Disclosure - Fair Value of Financial Instruments - Schedule of Fair Value of Available for Sale Investments (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsScheduleOfFairValueOfAvailableForSaleInvestmentsDetails Fair Value of Financial Instruments - Schedule of Fair Value of Available for Sale Investments (Details) Details 28 false false R29.htm 100300 - Disclosure - Fair Value of Financial Instruments - Schedule of Fair Value of Available-for-sale Investments by Contractual Maturity (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsScheduleOfFairValueOfAvailableforsaleInvestmentsByContractualMaturityDetails Fair Value of Financial Instruments - Schedule of Fair Value of Available-for-sale Investments by Contractual Maturity (Details) Details 29 false false R30.htm 100310 - Disclosure - Balance Sheet Components - Schedule of Components of Property and Equipment (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureBalanceSheetComponentsScheduleOfComponentsOfPropertyAndEquipmentDetails Balance Sheet Components - Schedule of Components of Property and Equipment (Details) Details 30 false false R31.htm 100320 - Disclosure - Balance Sheet Components - Additional Information (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureBalanceSheetComponentsAdditionalInformationDetails Balance Sheet Components - Additional Information (Details) Details 31 false false R32.htm 100330 - Disclosure - Balance Sheet Components - Schedule of Components of Other Assets, Net (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureBalanceSheetComponentsScheduleOfComponentsOfOtherAssetsNetDetails Balance Sheet Components - Schedule of Components of Other Assets, Net (Details) Details 32 false false R33.htm 100340 - Disclosure - Balance Sheet Components - Components of Accrued Expenses and Other Current Liabilities (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureBalanceSheetComponentsComponentsOfAccruedExpensesAndOtherCurrentLiabilitiesDetails Balance Sheet Components - Components of Accrued Expenses and Other Current Liabilities (Details) Details 33 false false R34.htm 100350 - Disclosure - Leases - Additional Information (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureLeasesAdditionalInformationDetails Leases - Additional Information (Details) Details 34 false false R35.htm 100360 - Disclosure - Leases - Schedule of Maturities of Operating and Finance Lease Liabilities (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureLeasesScheduleOfMaturitiesOfOperatingAndFinanceLeaseLiabilitiesDetails Leases - Schedule of Maturities of Operating and Finance Lease Liabilities (Details) Details 35 false false R36.htm 100370 - Disclosure - Leases - Components of Lease Costs (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureLeasesComponentsOfLeaseCostsDetails Leases - Components of Lease Costs (Details) Details 36 false false R37.htm 100380 - Disclosure - Leases - Supplemental Cash Flow Disclosures for Cash Paid for Leases (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/DisclosureLeasesSupplementalCashFlowDisclosuresForCashPaidForLeasesDetails Leases - Supplemental Cash Flow Disclosures for Cash Paid for Leases (Details) Details 37 false false R38.htm 100390 - Disclosure - Stockholders' Equity - Additional Information (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockholdersEquityAdditionalInformationDetails Stockholders' Equity - Additional Information (Details) Details 38 false false R39.htm 100400 - Disclosure - Stockholders' Equity - Common Stock Reserved for Future Issuance (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockholdersEquityCommonStockReservedForFutureIssuanceDetails Stockholders' Equity - Common Stock Reserved for Future Issuance (Details) Details 39 false false R40.htm 100410 - Disclosure - Stock-Based Compensation - Additional Information (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationAdditionalInformationDetails Stock-Based Compensation - Additional Information (Details) Details 40 false false R41.htm 100430 - Disclosure - Stock-Based Compensation - Summary of Share-Based Compensation Expense (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationSummaryOfShareBasedCompensationExpenseDetails Stock-Based Compensation - Summary of Share-Based Compensation Expense (Details) Details 41 false false R42.htm 100440 - Disclosure - Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureStockBasedCompensationSummaryOfRestrictedStockUnitActivityDetails Stock-Based Compensation - Summary of Restricted Stock Unit Activity (Details) Details 42 false false R43.htm 100450 - Disclosure - Related-Party Transactions - Additional Information (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureRelatedPartyTransactionsAdditionalInformationDetails Related-Party Transactions - Additional Information (Details) Details 43 false false R44.htm 100460 - Disclosure - Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/DisclosureNetLossPerShareComputationOfBasicAndDilutedNetLossPerShareDetails Net Loss Per Share - Computation of Basic and Diluted Net Loss per Share (Details) Details 44 false false R45.htm 100470 - Disclosure - Net Loss Per Share - Summary of Outstanding Potentially Dilutive Securities Were Excluded from Computation of Diluted Net Loss Per Share (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/DisclosureNetLossPerShareSummaryOfOutstandingPotentiallyDilutiveSecuritiesWereExcludedFromComputationOfDilutedNetLossPerShareDetails Net Loss Per Share - Summary of Outstanding Potentially Dilutive Securities Were Excluded from Computation of Diluted Net Loss Per Share (Details) Details 45 false false R46.htm 100480 - Disclosure - Commitments and Contingencies - Additional Information (Details) Sheet http://www.alxoncology.com/20220630/taxonomy/role/Role_DisclosureCommitmentsAndContingenciesAdditionalInformationDetails Commitments and Contingencies - Additional Information (Details) Details 46 false false All Reports Book All Reports alxo-20220630.htm alxo-20220630.xsd alxo-20220630_cal.xml alxo-20220630_def.xml alxo-20220630_lab.xml alxo-20220630_pre.xml alxo-ex31_1.htm alxo-ex31_2.htm alxo-ex32_1.htm alxo-ex32_2.htm http://fasb.org/us-gaap/2022 http://xbrl.sec.gov/dei/2022 true true