Equity Incentive Plans
2021 Employment Inducement Incentive Award Plan
The Company adopted the 2021 Employment Inducement Incentive Award Plan (the "2021 Inducement Plan") in December 2021. In December 2024, the Company amended the 2021 Inducement Plan to increase the number of shares of the Company’s common stock available for future issuance under the 2021 Inducement Plan to 9,500,000 shares. The Company reserved 9,500,000 shares, as amended, of the Company’s common stock for issuance pursuant to awards granted under the 2021 Inducement Plan. The terms of the 2021 Inducement Plan are substantially similar to the terms of the Company’s 2018 Incentive Award Plan below with the exception that awards may only be made to an employee who has not previously been an employee or member of the board of directors of the Company if the award is in connection with commencement of employment. As of December 31, 2025, 1,982,536 shares of common stock were available for future issuance under the 2021 Inducement Plan.
2018 Incentive Award Plan
The Company adopted the 2018 Incentive Award Plan (the “2018 Plan”) in July 2018. Under the 2018 Plan, which expires in July 2028, the Company may grant equity-based awards to individuals who are employees, officers, directors or consultants of the Company. Options issued under the 2018 Plan will generally expire ten years from the date of grant and vest over a four-year period. As of December 31, 2025, 5,494,874 shares of common stock were available for future issuance under the 2018 Plan.
The 2018 Plan contains a provision that allows annual increases in the number of shares available for issuance on the first day of each calendar year through January 1, 2028 in an amount equal to the lesser of: (i) 5% of the aggregate number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding calendar year, or (ii) such lesser amount determined by the Company. Under this evergreen provision, on January 1, 2026, an additional 4,778,774 shares became available for future issuance under the 2018 Plan.
2015 Stock Incentive Plan
The Company adopted the 2015 Stock Incentive Plan (the “2015 Plan”) in February 2015, which provided for the issuance of equity awards to the Company’s employees, members of its board of directors and consultants. In general, options issued under this plan vest over four years and expire after 10 years. Subsequent to the adoption of the 2018 Plan, no additional equity awards can be made under the 2015 Plan. The 2015 Plan expired in February 2025.
2018 Employee Stock Purchase Plan
The Company adopted the 2018 Employee Stock Purchase Plan (the “ESPP”) in July 2018. The ESPP, which expires in July 2028, permits participants to purchase common stock through payroll deductions of up to 20% of their eligible compensation. As of December 31, 2025, 2,773,650 shares of common stock were available for issuance under the ESPP.
The ESPP contains a provision that allows annual increases in the number of shares available for issuance on the first day of each calendar year through January 1, 2028 in an amount equal to the lesser of: (i) 1% of the aggregate number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding calendar year, or (ii) such
lesser amount determined by the Company. The Company elected to not increase the number of shares available for issuance under the ESPP on January 1, 2026.
Stock Awards
Stock Options
Activity under the Company’s stock option plans during the year ended December 31, 2025 was as follows:
| | | | | | | | | | | | | | | | | | | | | | | |
| Options Outstanding | | Weighted- Average Exercise Price | | Weighted- Average Remaining Term (in years) | | Aggregate Intrinsic Value (000’s) |
| Balance on December 31, 2024 | 13,665,771 | | $ | 26.57 | | | | | |
| Granted | 3,038,153 | | $ | 35.85 | | | | | |
| Exercised | (2,027,378) | | $ | 17.46 | | | | | |
| Forfeited and expired | (1,045,472) | | $ | 33.27 | | | | | |
| Balance on December 31, 2025 | 13,631,074 | | $ | 29.54 | | | 7.2 | | $ | 237,015 | |
| Exercisable on December 31, 2025 | 7,695,416 | | $ | 25.28 | | | 6.3 | | $ | 165,272 | |
Aggregate intrinsic value is calculated as the difference at a specific point in time between the closing price of the Company’s common stock at December 31, 2025 and the exercise price of stock options that had exercise prices below the closing price. The aggregate intrinsic value of options exercised during 2025, 2024 and 2023 was $46.5 million, $72.1 million and $16.2 million, respectively.
Restricted Stock Units
The Company’s restricted stock unit activity during the year ended December 31, 2025 was as follows:
| | | | | | | | | | | |
| Restricted Stock Units Outstanding | | Weighted- Average Grant Date Fair Value |
| Balance on December 31, 2024 | 1,334,635 | | | $ | 34.30 | |
| Granted | 1,624,023 | | | $ | 35.43 | |
| Vested | (415,264) | | | $ | 32.51 | |
| Forfeited | (221,662) | | | $ | 36.19 | |
| Balance on December 31, 2025 | 2,321,732 | | | $ | 35.23 | |
The weighted average grant date fair value for restricted stock units granted during 2024 and 2023 was $43.56 and $19.62, respectively. The total fair value of restricted stock units that vested during 2025, 2024, and 2023 was $14.3 million and $10.0 million, and $1.4 million respectively.
Employee Stock Purchase Plan
During the year ended December 31, 2025, the Company issued 206,428 shares of our common stock under the ESPP. The shares were purchased by employees at an average purchase price of $25.28 per share, resulting in proceeds to the Company of approximately $5.2 million.
Fair Value of Stock Awards
The following table summarizes the weighted average assumptions used to estimate the fair value of stock options granted under the Company’s stock option plans for the periods presented below:
| | | | | | | | | | | | | | | | | |
| Stock Option Awards | Year ended December 31, |
| 2025 | | 2024 | | 2023 |
| Expected option term | 6.0 years | | 6.0 years | | 6.0 years |
| Expected volatility | 64 | % | | 66 | % | | 66 | % |
| Risk free interest rate | 4.3 | % | | 4.2 | % | | 4.1 | % |
| Expected dividend yield | — | % | | — | % | | — | % |
The weighted-average fair value of stock options awarded during the years ended December 31, 2025, 2024 and 2023 was $22.26, $28.96 and $13.09 per share, respectively.
The following table summarizes the weighted average assumptions used to estimate the fair value of the ESPP awards for the periods presented below:
| | | | | | | | | | | | | | | | | |
| ESPP | Year ended December 31, |
| 2025 | | 2024 | | 2023 |
| Expected term | 1.3 years | | 1.3 years | | 1.1 years |
| Expected volatility | 57 | % | | 72 | % | | 66 | % |
| Risk free interest rate | 3.8 | % | | 5.0 | % | | 5.0 | % |
| Expected dividend yield | — | % | | — | % | | — | % |
The weighted-average fair value of awards under the ESPP during the years ended December 31, 2025, 2024 and 2023 was $13.40, $22.09 and $11.49 per share, respectively.
Restricted stock units are valued using the closing sale price of our common stock on the date of grant and recognizes forfeitures as they occur.
Stock-Based Compensation Expense
Stock-based compensation expense for the equity awards issued by the Company to employees and non-employees for the periods presented below was as follows:
| | | | | | | | | | | | | | | | | |
| Year ended December 31, |
| 2025 | | 2024 | | 2023 |
| Included in research and development | $ | 50,344 | | | $ | 40,667 | | | $ | 22,633 | |
| Included in general and administrative | 40,680 | | | 28,719 | | | 18,304 | |
| Total stock-based compensation expense | $ | 91,024 | | | $ | 69,386 | | | $ | 40,937 | |
Total stock-based compensation expense capitalized during 2025 was not significant and not separately broken out above.
A summary of the Company's total unrecognized stock-based compensation expense, as of December 31, 2025, is as follows:
| | | | | | | | | | | |
| Unrecognized Stock-Based Compensation Expense (in thousands) | | Average Remaining Vesting Period (in years) |
| Stock option awards | $ | 122,413 | | | 2.4 |
| RSU awards | $ | 61,297 | | | 2.7 |
| ESPP | $ | 6,600 | | | 1.4 |