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Stock-based Compensation (Tables) | 12 Months Ended
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Dec. 31, 2023
Share-Based Payment Arrangement [Abstract] |
Summary of Recognized Stock-Based Compensation | The Company recognized stock-based compensation as follows (in thousands):
|  | Year Ended December 31, |
|  | 2023 |  |  | 2022 |  |  | 2021 |
Research and development |  | $ | 22,407 |  |  | $ | 24,895 |  |  | $ | 21,443 |
General and administrative |  |  | 20,391 |  |  |  | 21,251 |  |  |  | 19,342 |
Total stock-based compensation |  | $ | 42,798 |  |  | $ | 46,146 |  |  | $ | 40,785 |
Summary of Share-based Payment Award, Stock Options, Valuation Assumptions | The estimated grant-date fair value of all the Company’s options to purchase common stock was calculated using the Black-Scholes option pricing model, based on the following assumptions:
|  | Year Ended December 31,
|  | 2023 |  | 2022 |  | 2021
Expected term (in years) |  | 5.3 – 6.0 |  | 5.3 – 6.1 |  | 5.2 – 6.1
Expected volatility |  | 79% – 80% |  | 79% – 80% |  | 78% – 81%
Risk free interest rate |  | 3.5% – 4.6% |  | 1.5% – 4.3% |  | 0.5% – 1.3%
Dividend yield |  | — |  | — |  | —
Summary of Options to Purchase Common Stock | Option activity is shown below:
|  | Number of Options |  |  | Weighted Average Exercise Price Per Share |  |  | Weighted Average Remaining Contractual Term |  |  | Aggregate Intrinsic Value |
|  |  |  |  |  |  |  | (In years) |  |  | (In thousands) |
Outstanding as of December 31, 2021 |  |  | 11,644,070 |  |  | $ | 16.41 |  |  |  |  |  |  |
Granted |  |  | 4,996,366 |  |  |  | 12.11 |  |  |  |  |  |  |
Exercised |  |  | (298,239 | ) |  |  | 10.26 |  |  |  |  |  |  |
Forfeited |  |  | (2,628,925 | ) |  |  | 18.28 |  |  |  |  |  |  |
Outstanding as of December 31, 2022 |  |  | 13,713,272 |  |  |  | 14.62 |  |  |  |  |  |  |
Granted |  |  | 572,538 |  |  |  | 6.98 |  |  |  |  |  |  |
Exercised |  |  | (132,192 | ) |  |  | 8.16 |  |  |  |  |  |  |
Forfeited |  |  | (2,057,381 | ) |  |  | 14.21 |  |  |  |  |  |  |
Outstanding as of December 31, 2023 |  |  | 12,096,237 |  |  | $ | 14.40 |  |  |  | 6.7 |  |  | $ | 676 |
Exercisable as of December 31, 2023 |  |  | 8,467,987 |  |  | $ | 14.80 |  |  |  | 6.0 |  |  | $ | 62 |
Vested and expected to vest as of December 31, 2023 |  |  | 12,096,237 |  |  | $ | 14.40 |  |  |  | 6.7 |  |  | $ | 676 |
Summary of Restricted Stock Awards and Restricted Stock Units | Activity for the RSUs is shown below.
|  | Number of Shares |  |  | Weighted Average Grant Date Fair Value per Share |
Unvested restricted stock units as of December 31, 2021 |  |  | 1,373,874 |  |  | $ | 18.35 |
Granted |  |  | 2,539,014 |  |  |  | 10.02 |
Vested |  |  | (414,577 | ) |  |  | 18.63 |
Forfeited |  |  | (453,693 | ) |  |  | 16.21 |
Unvested restricted stock units as of December 31, 2022 |  |  | 3,044,618 |  |  |  | 11.68 |
Granted |  |  | 5,142,444 |  |  |  | 6.62 |
Vested |  |  | (1,584,448 | ) |  |  | 10.41 |
Forfeited |  |  | (510,513 | ) |  |  | 10.03 |
Unvested restricted stock units as of December 31, 2023 |  |  | 6,092,101 |  |  | $ | 7.78 |

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