2018 Stock Option and Grant Plan

In November 2018, the Company adopted the 2018 Stock Option and Grant Plan, or the 2018 Plan, which allowed for the granting of up to 1,763,303 equity awards to the founders, employees, members of the Board of Directors and consultants of the Company. The unvested shares of restricted common stock issued under the 2018 Plan are subject to repurchase by the Company at the original issuance price in the event of the holder’s termination, either voluntarily or involuntarily. Consideration received for unvested stock-based awards is initially recorded as a liability and subsequently reclassified into stockholders’ deficit as the related awards vest. Restricted common stock granted under the 2018 Plan generally vests over four years. Certain of the restricted common stock granted under the 2018 Plan vests upon achievement of certain performance conditions. The awards expire no more than 10 years from the date of grant.

Restricted stock awards (2018 Plan)

The total number of shares under the 2018 Plan that were vested as of December 31, 2025 and 2024 was 1,114,614. As of December 31, 2025 and 2024 , there were no amounts recorded in accrued expenses and other current liabilities related to shares held by employees and non-employees that were unvested and subject to repurchase under this plan. During the year ended December 31, 2024, any repurchased shares under the 2018 Plan were transferred to the 2019 Equity Incentive Plan. As of December 31, 2025 and 2024, no awards were available for issuance under the 2018 Plan.

Restricted stock awards (outside of the 2018 Plan)

In 2018, the Company issued 639,201 shares of restricted stock to founders and advisors outside of the 2018 Plan. The shares were issued under the terms of respective restricted common stock agreements, and unvested shares are subject to repurchase by the Company upon the holder’s termination of its relationship with the Company at the original purchase price per share.

The total number of shares outside of the 2018 Plan that were vested as of December 31, 2025 and 2024 was 628,829. As of December 31, 2025 and 2024, there were immaterial amounts recorded in accrued expenses and other current liabilities related to shares held by employees and non-employees that were unvested and subject to repurchase outside of the 2018 Plan. The unvested awards as of December 31, 2025 and 2024 vest upon the achievement of future performance milestones.

2019 Equity Incentive Plan

In August 2019, the Board of Directors approved the establishment of the 2019 Equity Incentive Plan, or the 2019 Plan. The 2019 Plan allows for the granting of restricted common stock, incentive stock options, or ISOs, and non-qualified stock options, or NSOs, to the employees, members of the Board of Directors and consultants of the Company. Restricted common stock granted under the 2019 Plan is generally vested upon issuance. Unvested shares of restricted common stock are subject to repurchase by the Company at the original issuance price in the event of the employee’s termination, either voluntarily or involuntarily. ISOs are granted only to the Company’s employees, including officers and directors who are also employees. NSOs are granted to consultants, employees, and non-employee directors of the Company. Stock options granted under the 2019 Plan generally expire 10 years from the date of grant. The 2019 Plan allows the holder of the stock option to early exercise the stock option in whole or in part prior to the full vesting of the stock option. Unvested stock options are subject to repurchase by the Company at the original issuance price in the event of the employee’s termination, either voluntarily or involuntarily. Early exercises of stock options are not deemed to be substantive exercises for accounting purposes and accordingly, consideration received for unvested stock options is initially recorded as a liability and subsequently reclassified into stockholders’ equity (deficit) as the related stock options vest.

There were 831,177 equity incentive awards authorized and available for issuance under the 2019 Plan as of December 31, 2024. No shares remained available for issuance under the 2019 Plan as of December 31, 2025 as the 2019 Plan was replaced by the 2025 Equity Incentive Plan, or 2025 Plan, which is further discussed below.

Stock option repricing (2019 Plan)

In December 2024, the Company completed a repricing of 3,415,997 outstanding stock options, which adjusted the exercise price of such stock options to $10.42 per share, including with respect to 1,969,902 outstanding stock options held by executive officers and members of the Board of Directors. Of those stock options, an option to purchase 51,861 shares held by the Company’s Chief Executive Officer was amended to change the market-based vesting condition such that the option will fully vest if (i) the Company’s stock price is equal to or greater than $38.57 per share (as may be adjusted for stock splits) on average over a 20-day trading period or (ii) the Company is acquired at a stock price equal to or greater than $38.57 per share (as may be adjusted for stock splits), in each case subject to the grantee’s continued service relationship with the Company. The stock option repricing was treated as a modification in accordance with ASC 718, Compensation — Stock Compensation, and resulted in incremental stock-based compensation expense of $0.7 million, of which $0.3 million was recognized for vested stock options in December 2024.

During the year ended December 31, 2025, the Company recognized $0.2 million of incremental stock-based compensation expense related to the vesting of shares included in the repricing. The remaining $0.2 million of incremental stock-based compensation expense will be recognized over the remainder of the vesting periods for unvested stock options.

Restricted stock awards (2019 Plan)

During the years ended December 31, 2025 and 2024, there were no shares and 14 shares, respectively, of restricted stock issued under the 2019 Plan. The weighted average grant-date fair value of restricted stock granted during the year ended December 31, 2024 was $14.89 per share.

2025 Equity Incentive Plan

The Board of Directors and stockholders approved the 2025 Plan, which became effective on January 29, 2025. The 2025 Plan replaced the 2019 Plan, and upon its effectiveness, the Company ceased granting awards under the 2019 Plan. The 2025 Plan allows the Company to make equity-based and cash-based incentive awards to its officers, employees, directors and consultants. The Company initially reserved 5,300,000 shares of its common stock under the 2025 Plan plus those shares of common stock previously reserved but unissued under the 2019 Plan. Any outstanding awards granted under the 2019 Plan will remain subject to the terms of the 2019 Plan and applicable award agreements. The number of shares reserved for issuance under the 2025 Plan will increase automatically on January 1st each year from 2026 through 2035 by the number of shares equal to the lesser of 5% of the sum of (a) the total number of outstanding shares of all classes of the Company’s common stock plus (b) the total number of shares of the Company’s common stock subject to pre-funded warrants (if any) and (c) the total number of shares of the Company’s common stock issuable upon conversion of preferred stock (if any), in each case as of the immediately preceding December 31st, or a number as may be determined by the Board of Directors or compensation committee thereof.

There were 4,790,225 equity incentive awards authorized and available for issuance under the 2025 Plan as of December 31, 2025.

Stock options (2019 Plan and 2025 Plan)

The total intrinsic value of options exercised during the year ended December 31, 2025 and 2024 was $11.2 million and $0.1 million, respectively. The intrinsic value is the difference between the fair value of the Company’s common stock at the time of exercise and the exercise price of the stock option.

The total fair value of options that vested during the years ended December 31, 2025 and 2024 was $11.1 million and $6.3 million, respectively.

The weighted average grant-date fair value of employee options granted during the years ended December 31, 2025 and 2024 was $12.34 per share and $9.51 per share, respectively.

As of December 31, 2025 and 2024, there were no options subject to repurchase under the 2019 Plan and 2025 Plan.

In December 2025, an option to purchase 51,861 shares held by the Company’s Chief Executive Officer met its market-based vesting condition and became fully vested as the Company’s stock price was equal to or greater than $38.57 per share on average over a 20-day trading period.

Restricted stock awards (2025 Plan)

During the year ended December 31, 2025, 4 shares of restricted stock were issued under the 2025 Plan. The weighted average grant-date fair value of restricted stock granted during the year ended December 31, 2025 was $17.47 per share.

2025 Employee Stock Purchase Plan

The Board of Directors and stockholders approved the 2025 Employee Stock Purchase Plan, or 2025 ESPP, which became effective on January 30, 2025. The number of shares initially available for issuance pursuant to the 2025 ESPP was 450,000 shares. The purchase price of common stock purchased under the ESPP is equal to 85% of the lesser of the fair market value of the common stock on (i) the first trading day of the applicable offering period or (ii) the last trading day of each purchase period in the applicable offering period. The aggregate number of shares reserved for sale under the ESPP will increase automatically on January 1st of each year from 2026 through 2035 by the number of shares equal to 1% of the sum of (a) the total number of outstanding shares of all classes of the Company’s common stock plus (b) the total number of shares of the Company’s common stock subject to pre-funded warrants (if any) and (c) the total number of shares of the Company’s common stock issuable upon conversion of preferred stock (if any), in each case outstanding as of the immediately preceding December 31st, provided that the Board of Directors or the compensation committee thereof may in its sole discretion reduce the amount of the increase in any particular calendar year. During the year ended December 31, 2025, 110,644 shares were purchased under the 2025 ESPP.

Fair value measurement

The Company estimated the fair value of service-based stock options and employee stock purchases using the Black-Scholes option-pricing model. The fair value of service-based stock options is being amortized on the straight-line basis over the requisite service period of the awards.

Prior to the IPO in January 2025, the Board of Directors determined the fair value of the common stock at the time of grant of the option by considering a number of objective and subjective factors including: (i) third-party valuations of the Company’s common stock; (ii) the Company’s stage of development; (iii) the status of research and development efforts; (iv) the rights, preferences, and privileges of the Company’s redeemable convertible preferred stock relative to those of the Company’s common stock; (v) the Company’s operating results and financial condition, including the Company’s levels of available capital resources; (vi) equity market conditions affecting comparable public companies; (vii) general U.S. market conditions; and (viii) the lack of marketability of the Company’s common stock. After completion of the IPO, the fair value of common stock is based on the closing market price on the date of grant.

The Black-Scholes option-pricing model requires the use of highly subjective assumptions which determine the fair value of stock-based awards. These assumptions include:

The fair value of the awards subject to the repricing in December 2024 was measured using a Monte-Carlo simulation analysis. For each simulation path, the fair value of the instrument was calculated using the Black-Scholes call option formula using input assumptions that include a risk-free rate of 4.15%, volatility of 116%, and a term of 9.65 years.

The fair value of awards that contain market-based conditions issued during fiscal year 2023 was measured using a Monte-Carlo option pricing model at the date of grant using input assumptions that include a risk-free rate of 4.35%, volatility of 80%, and a discount rate of 25%. Upon the repricing of awards that contain market-based conditions in December 2024, the fair value was measured using a Monte-Carlo option pricing model using input assumptions that include a risk-free rate of 4.08%, volatility of 113%, and a discount rate of 30%.

Stock-based compensation expense

For the years ended December 31, 2025 and 2024, the Company recognized $12.6 million and $9.6 million, respectively, in stock-based compensation related to stock option grants issued to employees and non-employees. For the year ended December 31, 2025, the Company recognized $1.8 million in stock-based compensation expense related to the 2025 ESPP. No comparable amount was recognized for the year ended December 31, 2024.

As of December 31, 2025 and 2024, there was $28.4 million and $30.0 million, respectively, of total unrecognized compensation cost related to unvested options for which the cost is expected to be recognized over a weighted-average period of 3.05 years and 3.11 years, respectively. As of December 31, 2025, there was $1.9 million of total unrecognized compensation cost related to the 2025 ESPP for which the cost is expected to be recognized over a weighted-average period of 1.16 years.

Restricted stock units

In September 2025, the Company issued 594,825 RSUs, under the 2025 Plan at a grant date fair value of $23.67 per share. These RSUs vest in equal annual installments over two years, subject to the holder's continued employment with, or services to, the Company on each vesting date. Each RSU represents the right to receive one share of the Company’s common stock when and if the applicable vesting conditions are satisfied.

For the year ended December 31, 2025, the Company recognized $2.0 million in stock-based compensation expense related to restricted stock issued. As of December 31, 2025, there was $12.1 million of total unrecognized compensation cost related to RSUs that is expected to be recognized over a weighted average period of 1.67 years.