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Equity Incentive Plans and Stock-based Compensation | 12 Months Ended
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Dec. 31, 2025
Share-Based Payment Arrangement [Abstract] |
Equity Incentive Plans and Stock-based Compensation | Equity Incentive Plans and Stock-based Compensation On June 8, 2021, the stockholders of the Company approved the 2021 Equity Incentive Plan (“2021 Plan”) and the 2021 Employee Stock Purchase Plan (“2021 ESPP”). As of December 31, 2025, 29,341,567 and 5,518,072 shares were available for grant under the 2021 Plan and 2021 ESPP, respectively. 2021 Employee Stock Purchase Plan Under the 2021 ESPP, participants are permitted to purchase shares of Common Stock, up to the IRS allowable limit, through contributions (in the form of payroll deductions or otherwise to the extent permitted by the administrator of the 2021 ESPP) of up to 15% of their eligible compensation. Participants are permitted to purchase shares of the Company’s Common Stock at 85% of the lower of the fair market value of the Company’s Common Stock on the first trading day of an offering period or on the last trading date in each purchase period. The Company offers a six-month purchase period. Participants may end their participation at any time during an offering and will be paid their accrued contributions that have not yet been used to purchase shares. Participation ends automatically upon termination of employment with the Company. The number of shares of common stock available for issuance under the 2021 ESPP will be increased on the first day of each fiscal year, in an amount equal to the least of (i) 3,734,500 shares of common stock, (ii) a number of s hares of common stock equal to one percent (1%) of the total number of shares of all classes of common stock of the Company on the last day of the immediately preceding fiscal year, or (iii) such number of shares determined by the Administrator no later than the last day of the immediately preceding fiscal year. 2021 Equity Incentive Plan Under the 2021 Plan, the Company can grant incentive stock options, nonstatutory stock options, stock appreciation rig hts, restricted stock, restricted stock units and performance awards to employees, non-employee directors and consultants. Options generally expire ten years after the date of grant. The number of shares available for issuance under the 2021 Plan will be increased on the first day of each fiscal year, in an amount equal to the least of (i) 18,672,200 shares, (ii) a number of shares equal to five percent (5%) of the total number of shares of all classes of common stock of the Company outstanding on the last day of the immediately preceding fiscal year, or (iii) such number of shares determined by the Administrator no later than the last day of the immediately preceding fiscal year. 2017 Equity Incentive Plan At the time of adoption of the 2021 Plan and the 2021 ESPP, no further awards will be granted under the 2017 Equity Incentive Plan (“2017 Plan”). Stock-based awards forfeited or cancelled from the 2017 Plan are returned to the pool of shares of Common Stock available for issuance under the 2021 Plan. Grant Date Fair Value of Stock Options In determining the compensation cost of the option awards, the fair value for each option award has been estimated using the Black Scholes model. The significant assumptions used in these calculations are summarized as follows:
| Year Ended December 31, 2025 |  | Year Ended December 31, 2024 |  |
Expected term (in years) | 5.3 - 6.0 |  | 5.3 - 6.1 |  |
Expected volatility | 97.5% - 103.9% |  | 99.7% - 101.6% |  |
Expected dividend rate | 0.0% |  | 0.0% |  |
Risk free interest rate | 3.6% - 4.0% |  | 3.4% - 4.6% |  |
Expected term: The expected term of stock options represents the weighted-average period the stock options are expected to remain outstanding. The Company does not have sufficient historical exercise and post-vesting termination activity to provide accurate data for estimating the expected term of options and has opted to use the “simplified method,” whereby the expected term equals the arithmetic average of the vesting term and the original contractual term of the option. Expected volatility: Historically, the Company has been a private company and lacked company‑specific historical and implied volatility information for its common stock. Therefore, the expected volatility of the Company’s common stock was determined by using an average of historical volatilities of selected industry peers deemed to be comparable to the Company’s business corresponding to the expected term of the awards and the Company expects to continue to do so until such time as the Company has adequate historical data regarding the volatility of its traded common stock price. Expected dividend yield: The expected dividend rate is zero as the Company has no history or expectation of declaring dividends on its common stock. Risk-free interest rate: The risk-free interest rate is based on the U.S. Treasury yield curve in effect at the time of grant for zero-coupon U.S. Treasury notes with maturities corresponding to the expected term of the awards. The following table summarizes option award activity during the year ended December 31, 2025:
| Number of Stock Option Awards |  | Weighted Average Exercise Price |  | Weighted Average Remaining Contractual Life (Years) |  | Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2024 | 16,634,775 |  |  | $ | 3.57 |  |  |  |  |
Granted | 3,659,200 |  |  | $ | 1.01 |  |  |  |  |
Exercised | (112,085) |  |  | $ | 0.52 |  |  |  |  |
Forfeited | (2,911,020) |  |  | $ | 2.59 |  |  |  |  |
Outstanding as of December 31, 2025 | 17,270,870 |  |  | $ | 3.22 |  |  | 6.9 |  | $ | 5,696 |
Options vested and expected to vest as of December 31, 2025 | 17,270,870 |  |  | $ | 3.22 |  |  |  |  |
Vested and exercisable at December 31, 2025 | 11,281,386 |  |  | $ | 4.00 |  |  | 5.9 |  | $ | 2,581 |
As of December 31, 2025, there was $7.7 million of total unrecognized compensation expense expected to be recognized over a weighted average-period of 2.2 years. The total intrinsic value of options exercised during the years ended December 31, 2025 and 2024 was $0.1 million and $1.3 million, respectively. Aggregate intrinsic value represents the difference between the fair market value of the common stock and the exercise price of outstanding, in-the-money options. The weighted-average grant-date fair value of options granted during the years ended December 31, 2025 and 2024 was $0.82 and $2.16 per share, respectively. Stock-based Compensation Expense The following sets forth the total stock-based compensation expense for the Company’s stock options and ESPP included in the Company’s consolidated statements of operations:
(in thousands) | Year Ended December 31, 2025 |  | Year Ended December 31, 2024 |  |
Research and development | $ | 2,690 |  |  | $ | 4,626 |  |  |
General and administrative | 4,154 |  |  | 8,075 |  |  |
Total stock-based compensation expense | $ | 6,844 |  |  | $ | 12,701 |  |  |

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