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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 Stock-Based Compensation Expense | The following table presents stock-based compensation expense as reflected in the Company's consolidated statements of operations (in thousands):
|  | Year Ended December 31, |
|  | 2023 |  |  | 2022 |
Research and development |  | $ | 9,143 |  |  | $ | 7,225 |
General and administrative |  |  | 11,116 |  |  |  | 9,901 |
Total stock-based compensation |  | $ | 20,259 |  |  | $ | 17,126 |
The following table presents stock-based compensation expense by type of award (in thousands):
|  | Year Ended December 31, |
|  | 2023 |  |  | 2022 |
Stock options |  | $ | 18,060 |  |  | $ | 14,054 |
Restricted stock units (including performance-based RSUs) |  |  | 2,023 |  |  |  | 2,878 |
Employee Stock Purchase Plan |  |  | 176 |  |  |  | 194 |
Total |  | $ | 20,259 |  |  | $ | 17,126 |
Summary of Stock Option Activity | A summary of stock option activity for the year ended December 31, 2023 is set forth below (in thousands, except share and per share data):
|  | Number of Shares Underlying Outstanding Options |  |  | Weighted Average Exercise Price |  |  | Weighted- Average Remaining Contractual Term (in years) |  |  | Aggregate Intrinsic Value (in thousands) |
Outstanding, December 31, 2022 |  |  | 6,203,020 |  |  | $ | 14.44 |  |  |  | 8.4 |  |  | $ | 780 |
Options granted |  |  | 4,293,442 |  |  | $ | 5.36 |  |  |  |  |  |  |
Options exercised |  |  | (946 | ) |  | $ | 4.76 |  |  |  |  |  |  |
Options forfeited or cancelled |  |  | (1,112,411 | ) |  | $ | 10.59 |  |  |  |  |  |  |
Outstanding, December 31, 2023 |  |  | 9,383,105 |  |  | $ | 10.64 |  |  |  | 8.2 |  |  | $ | 45 |
Options exercisable, December 31, 2023 |  |  | 3,984,821 |  |  | $ | 13.65 |  |  |  | 7.4 |  |  | $ | 6 |
Vested and expected to vest, December 31, 2023 |  |  | 9,383,105 |  |  | $ | 10.64 |  |  |  | 8.2 |  |  | $ | 45 |
Schedule of Assumptions to Estimate Fair Value of Stock Options Using Black-Scholes Option Pricing Model | The assumptions used in the Black Scholes Model to calculate stock-based compensation are as follows:
|  | Year Ended December 31,
|  | 2023 |  | 2022
Fair value of common stock |  | $1.32 - $9.15 |  | $8.94 - $19.97
Expected term (years) |  | 5.5 - 6.1 years |  | 5.5 - 6.1 years
Volatility |  | 83.25% - 92.87% |  | 77.4% - 81.7%
Risk free rates |  | 3.5% - 4.86% |  | 1.6% - 4.22%
Dividend rate |  | 0.0% |  | 0.0%
Summary of Restricted Stock Unit Activity | The summary of RSU activity and related information for the year ended December 31, 2023 is set forth below:
|  | Number of Units Outstanding |  |  | Weighted Average Grant Date Fair Value |
Outstanding, December 31, 2022 |  |  | 197,580 |  |  | $ | 7.80 |
RSUs granted |  |  | 513,700 |  |  | $ | 7.47 |
RSUs vested |  |  | (194,455 | ) |  | $ | 7.43 |
RSUs forfeited |  |  | (62,625 | ) |  | $ | 7.07 |
Outstanding, December 31, 2023 |  |  | 454,200 |  |  | $ | 7.69 |

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