3.20.2 html 144 260 1 false 30 0 false 6 false false R1.htm 100000 - Document - Document and Entity Information Sheet http://preludetx.com/20200930/taxonomy/role/DocumentDocumentAndEntityInformation Document and Entity Information Cover 1 false false R2.htm 100010 - Statement - STATEMENT OF BALANCE SHEETS (UNAUDITED) Sheet http://preludetx.com/20200930/taxonomy/role/StatementSTATEMENTOFBALANCESHEETSUNAUDITED STATEMENT OF BALANCE SHEETS (UNAUDITED) Statements 2 false false R3.htm 100020 - Statement - STATEMENT OF BALANCE SHEETS (PARENTHETICAL) (UNAUDITED) Sheet http://preludetx.com/20200930/taxonomy/role/StatementSTATEMENTOFBALANCESHEETSPARENTHETICALUNAUDITED STATEMENT OF BALANCE SHEETS (PARENTHETICAL) (UNAUDITED) Statements 3 false false R4.htm 100030 - Statement - STATEMENTS OF OPERATIONS (UNAUDITED) Sheet http://preludetx.com/20200930/taxonomy/role/StatementSTATEMENTSOFOPERATIONSUNAUDITED STATEMENTS OF OPERATIONS (UNAUDITED) Statements 4 false false R5.htm 100040 - Statement - STATEMENTS OF CHANGES IN CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (UNAUDITED) Sheet http://preludetx.com/20200930/taxonomy/role/StatementSTATEMENTSOFCHANGESINCONVERTIBLEPREFERREDSTOCKANDSTOCKHOLDERSEQUITYDEFICITUNAUDITED STATEMENTS OF CHANGES IN CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (UNAUDITED) Statements 5 false false R6.htm 100050 - Statement - STATEMENTS OF CHANGES IN CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (PARENTHETICAL) (UNAUDITED) Sheet http://preludetx.com/20200930/taxonomy/role/StatementSTATEMENTSOFCHANGESINCONVERTIBLEPREFERREDSTOCKANDSTOCKHOLDERSEQUITYDEFICITPARENTHETICALUNAUDITED STATEMENTS OF CHANGES IN CONVERTIBLE PREFERRED STOCK AND STOCKHOLDERS' EQUITY (DEFICIT) (PARENTHETICAL) (UNAUDITED) Statements 6 false false R7.htm 100060 - Statement - STATEMENTS OF CASH FLOWS (UNAUDITED) Sheet http://preludetx.com/20200930/taxonomy/role/StatementSTATEMENTSOFCASHFLOWSUNAUDITED STATEMENTS OF CASH FLOWS (UNAUDITED) Statements 7 false false R8.htm 100070 - Disclosure - Background Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureBackground Background Notes 8 false false R9.htm 100080 - Disclosure - Risks and Liquidity Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureRisksAndLiquidity Risks and Liquidity Notes 9 false false R10.htm 100090 - Disclosure - Summary of Significant Accounting Policies Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies Summary of Significant Accounting Policies Notes 10 false false R11.htm 100100 - Disclosure - Fair Value of Financial Instruments Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstruments Fair Value of Financial Instruments Notes 11 false false R12.htm 100110 - Disclosure - Accrued Expenses and Other Current Liabilities Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities Accrued Expenses and Other Current Liabilities Notes 12 false false R13.htm 100120 - Disclosure - Convertible Preferred Stock and Common Stock Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureConvertiblePreferredStockAndCommonStock Convertible Preferred Stock and Common Stock Notes 13 false false R14.htm 100130 - Disclosure - Stock-Based Compensation Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensation Stock-Based Compensation Notes 14 false false R15.htm 100140 - Disclosure - Subsequent Events Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureSubsequentEvents Subsequent Events Notes 15 false false R16.htm 100150 - Disclosure - Summary of Significant Accounting Policies (Policies) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesPolicies Summary of Significant Accounting Policies (Policies) Policies http://preludetx.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies 16 false false R17.htm 100160 - Disclosure - Summary of Significant Accounting Policies (Tables) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesTables Summary of Significant Accounting Policies (Tables) Tables http://preludetx.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPolicies 17 false false R18.htm 100170 - Disclosure - Fair Value of Financial Instruments (Tables) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsTables Fair Value of Financial Instruments (Tables) Tables http://preludetx.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstruments 18 false false R19.htm 100180 - Disclosure - Accrued Expenses and Other Current Liabilities (Tables) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesTables Accrued Expenses and Other Current Liabilities (Tables) Tables http://preludetx.com/20200930/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilities 19 false false R20.htm 100190 - Disclosure - Stock-Based Compensation (Tables) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensationTables Stock-Based Compensation (Tables) Tables http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensation 20 false false R21.htm 100200 - Disclosure - Background - Additional Information (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureBackgroundAdditionalInformationDetails Background - Additional Information (Details) Details 21 false false R22.htm 100210 - Disclosure - Risks and Liquidity - Additional Information (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureRisksAndLiquidityAdditionalInformationDetails Risks and Liquidity - Additional Information (Details) Details 22 false false R23.htm 100220 - Disclosure - Summary of Significant Accounting Policies - Additional Information (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesAdditionalInformationDetails Summary of Significant Accounting Policies - Additional Information (Details) Details 23 false false R24.htm 100230 - Disclosure - Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-average Shares of Common Stock Outstanding (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureSummaryOfSignificantAccountingPoliciesScheduleOfPotentiallyDilutiveSecuritiesExcludedFromComputationOfDilutedWeightedAverageSharesOfCommonStockOutstandingDetails Summary of Significant Accounting Policies - Schedule of Potentially Dilutive Securities Excluded from Computation of Diluted Weighted-average Shares of Common Stock Outstanding (Details) Details 24 false false R25.htm 100240 - Disclosure - Fair Value of Financial Instruments - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureFairValueOfFinancialInstrumentsScheduleOfAssetsAndLiabilitiesMeasuredAtFairValueOnRecurringBasisDetails Fair Value of Financial Instruments - Schedule of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) Details 25 false false R26.htm 100250 - Disclosure - Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureAccruedExpensesAndOtherCurrentLiabilitiesSummaryOfAccruedExpensesAndOtherCurrentLiabilitiesDetails Accrued Expenses and Other Current Liabilities - Summary of Accrued Expenses and Other Current Liabilities (Details) Details 26 false false R27.htm 100260 - Disclosure - Convertible Preferred Stock and Common Stock - Additional Information (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureConvertiblePreferredStockAndCommonStockAdditionalInformationDetails Convertible Preferred Stock and Common Stock - Additional Information (Details) Details 27 false false R28.htm 100270 - Disclosure - Stock-Based Compensation - Additional Information (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensationAdditionalInformationDetails Stock-Based Compensation - Additional Information (Details) Details 28 false false R29.htm 100280 - Disclosure - Stock-Based Compensation - Schedule of Stock-Based Compensation Expense Recorded in Statements of Operations (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensationScheduleOfStockBasedCompensationExpenseRecordedInStatementsOfOperationsDetails Stock-Based Compensation - Schedule of Stock-Based Compensation Expense Recorded in Statements of Operations (Details) Details 29 false false R30.htm 100290 - Disclosure - Stock-Based Compensation - Summary of Stock Option Activity (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensationSummaryOfStockOptionActivityDetails Stock-Based Compensation - Summary of Stock Option Activity (Details) Details 30 false false R31.htm 100300 - Disclosure - Stock-Based Compensation - Summary of Information about Stock Options Outstanding (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensationSummaryOfInformationAboutStockOptionsOutstandingDetails Stock-Based Compensation - Summary of Information about Stock Options Outstanding (Details) Details 31 false false R32.htm 100310 - Disclosure - Stock-Based Compensation - Schedule of Fair Value of Each Option Estimated on Date of Grant Using Weighted Average Assumptions (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensationScheduleOfFairValueOfEachOptionEstimatedOnDateOfGrantUsingWeightedAverageAssumptionsDetails Stock-Based Compensation - Schedule of Fair Value of Each Option Estimated on Date of Grant Using Weighted Average Assumptions (Details) Details 32 false false R33.htm 100320 - Disclosure - Stock-Based Compensation - Summary of Activity related to RSA Stock-Based Payment Awards (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureStockBasedCompensationSummaryOfActivityRelatedToRSAStockBasedPaymentAwardsDetails Stock-Based Compensation - Summary of Activity related to RSA Stock-Based Payment Awards (Details) Details 33 false false R34.htm 100330 - Disclosure - Subsequent Events - Additional Information (Details) Sheet http://preludetx.com/20200930/taxonomy/role/DisclosureSubsequentEventsAdditionalInformationDetails Subsequent Events - Additional Information (Details) Details 34 false false All Reports Book All Reports prld-20200930.xml prld-20200930.xsd prld-20200930_cal.xml prld-20200930_def.xml prld-20200930_lab.xml prld-20200930_pre.xml http://fasb.org/srt/2020-01-31 http://fasb.org/us-gaap/2020-01-31 http://xbrl.sec.gov/dei/2019-01-31 true true