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Fair Value Measurements - Summary of Estimated Fair Value of Success Payment Liability Assumptions (Details) | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2021 USD ($) | Dec. 31, 2020 USD ($)
Fred Hutch |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Fair value of common stock Series A convertible preferred stock | $ 14.80 | $ 9.07
Fred Hutch | Risk-Free Interest Rate |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Risk-free interest rate minimum | 0.07 | 0.10
Risk-free interest rate maximum | 2.24 | 1.52
Fred Hutch | Expected Volatility |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Expected volatility | 75.00% | 80.00%
Fred Hutch | Expected Term | Minimum |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Expected term (in years) | 8 months 15 days | 1 year
Fred Hutch | Expected Term | Maximum [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Expected term (in years) | 6 years 2 months 19 days | 6 years 11 months 19 days
Stanford |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Fair value of common stock Series A convertible preferred stock | $ 14.80 | $ 9.07
Stanford | Risk-Free Interest Rate |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Risk-free interest rate minimum | 0.07 | 0.10
Risk-free interest rate maximum | 2.24 | 1.53
Stanford | Expected Volatility |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Expected volatility | 75.00% | 80.00%
Stanford | Expected Term | Minimum |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Expected term (in years) | 8 months 15 days | 1 year
Stanford | Expected Term | Maximum [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Expected term (in years) | 8 years | 8 years 9 months

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