11. Equity Incentive Plans

2009 Equity Incentive Plan

We adopted an equity incentive plan in 2009 (the “2009 Plan”) that provided for the issuance of incentive and nonqualified common stock options and other share-based awards for employees, directors and consultants. Under the 2009 Plan, the exercise price for incentive and nonqualified stock options were not to be less than the fair market value of our common stock at the date of grant. Stock options granted under this plan expire no later than ten years from the grant date and vesting was established at the time of grant. Pursuant to the terms of the 2019 Plan, any shares subject to outstanding stock options originally granted under the 2009 Plan that terminate, expire or lapse for any reason without the delivery of shares to the holder thereof shall become available for issuance pursuant to awards granted under the 2019 Plan. While no shares are available for future grant under the 2009 Plan, it continues to govern outstanding equity awards granted thereunder.

2019 Equity Incentive Plan

The 2019 Plan became effective immediately prior to the closing of our initial public offering in July 2019. The 2019 Plan provides for the issuance of awards in the form of stock options and other share-based awards for employees, directors and consultants. Under the 2019 Plan, the stock option exercise price per share shall not be less than the fair market value of a share of stock on the effective date of grant, as defined by the 2019 Plan, unless explicitly qualified under the provisions of Section 409A or Section 424(a) of the Internal Revenue Code of 1986. Additionally, unless otherwise specified, stock options granted under this plan expire no later than ten years from the grant date and vesting is established at the time of grant. Except for certain awards granted to non-employee directors, stock options and restricted stock units granted under the 2019 Plan generally vest over a four-year period, subject to continuous service through each applicable vesting date. As of June 30, 2025, we had 36,324,901 shares of common stock authorized for issuance under the 2019 Plan.

Stock Options

The weighted-average remaining contractual life for stock options outstanding as of June 30, 2025 was 5.5 years. The weighted-average remaining contractual life for stock options vested and exercisable as of June 30, 2025 was 4.9 years.

Restricted Stock Units

Performance-Based Restricted Stock Units

In addition to the restricted stock units described above, one of our executive officers was granted an award of 124,976 shares of performance-based restricted stock units during the six months ended June 30, 2025. The shares will vest and be issued only if a certain financial metric is achieved for fiscal year 2025 and if the service conditions are met. If the performance condition is achieved, the shares will vest in three annual installments, subject to the grantee's continuous service through the respective vest dates.

Market-Based Restricted Stock Units

Separate from the restricted stock units described above, certain of our executive officers have been granted awards of market-based restricted stock units. The number of shares of common stock that may be earned under the respective awards range from zero shares to a defined maximum number of shares and are calculated based on our total shareholder return during a three-year performance period as measured against that of the group of companies comprising the S&P Biotechnology Select Industry Index as of the grant date or other applicable date, subject to certain adjustments to such index group. Except as expressly provided in the terms of each award's agreement, vesting is subject to the respective grantee's continuous service through the end of the three-year performance period.

Grant Date Fair Value of Stock Options, Restricted Stock Units, Performance-Based Restricted Stock Units and Market-Based Restricted Stock Units Granted

The determination of the grant date fair value of stock options granted using a Black-Scholes option-pricing model is affected by the fair value of our common stock, as well as assumptions regarding a number of variables that are subjective and generally require judgment to determine. The valuation assumptions were determined as follows:

Fair value of common stock—The fair value of each share of common stock is based on the closing price of our common stock on the date of grant, or other relevant determination date, as reported on The Nasdaq Global Select Market.

Expected term—The expected term of stock options granted to employees and non-employee directors is determined using the “simplified” method, as illustrated in ASC Topic 718, Compensation—Stock Compensation, as we do not have sufficient exercise history to determine a better estimate of expected term. Under this approach, the expected term is based on the midpoint between the vesting date and the end of the contractual term of the stock option.

Risk-free interest rate—We utilize a risk-free interest rate in the option valuation model based on U.S. Treasury zero-coupon issues with remaining terms similar to the expected terms of the stock options.

Expected volatility—Expected volatility is based on a weighted average of our historical volatility and the historical volatility of our publicly traded industry peers utilizing a period of time consistent with our estimate of expected term.

Expected dividend yield—We do not anticipate paying any cash dividends in the foreseeable future and, therefore, use an expected dividend yield of zero in the option valuation model.

The weighted-average grant date fair value per share of stock options granted during the six months ended June 30, 2025 and 2024 was $5.50 and $2.70, respectively.

The grant date fair value of restricted stock units granted is based on the closing price of our common stock on the date of grant, or other relevant determination date, as reported on The Nasdaq Global Select Market. The weighted-average grant date fair value per share of restricted stock units granted during the six months ended June 30, 2025 and 2024 was $8.13 and $3.99, respectively.

The weighted-average grant date fair value per share of the performance-based restricted stock units granted during the six months ended June 30, 2025 was $7.28 and was based on the closing price of our common stock on the date of grant, as reported on The Nasdaq Global Select market. Expense will be recognized ratably over the requisite service period only if achievement of the performance condition is deemed to be probable. Any compensation cost recognized will be reversed if achievement of the performance condition is deemed not probable or if the performance condition is not met. Probability of achievement will be assessed periodically. If the performance condition is met and the grantee ceases to provide continued service through any of the applicable vesting dates for reasons other than those expressly provided in the terms of the respective award, compensation cost recognized for unvested shares will be reversed in the period in which service ceased.

The weighted-average grant date fair value per share of the market-based restricted stock units granted during the six months ended June 30, 2025 and 2024 was $13.50 and $6.49, respectively, and was determined using a Monte Carlo valuation model, which uses assumptions such as volatility, risk-free interest rate and dividend estimated for the respective performance periods. The aggregate share-based compensation expense of the market-based restricted stock units granted during the six months ended June 30, 2025 and 2024 was $13.6 million and $7.2 million, respectively. Aggregate share-based compensation expense is calculated based on the target payout level of shares granted and is recognized on a straight-line basis over the respective grants' performance periods, which are also the requisite service periods. Attainment of each grant's respective market condition and the number of shares earned and vested does not impact the related share-based compensation expense recognized. Share-based compensation expense is reversed only if the respective grantee does not provide continuous service through the respective performance period for reasons other than those expressly provided in the terms of the respective award.