2015 Equity Incentive Plan

In 2015, we adopted the 2015 Equity Incentive Plan (the "2015 Plan") that authorized the granting of options for shares of common stock. Our 2015 Plan provided for the grant of incentive stock options, non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit ("RSU") awards, and other stock awards. The 2015 Plan was terminated in connection with the adoption of the 2021 Equity Incentive Plan (the "2021 Plan") in November 2021 in connection with the initial public offering ("IPO"), and we will not grant any additional awards under the 2015 Plan. However, the 2015 Plan will continue to govern the terms and conditions of the outstanding awards previously granted thereunder.

2021 Equity Incentive Plan

In September 2021, our Board of Directors adopted, and our stockholders approved, the 2021 Plan, which became effective in connection with the IPO in November 2021. The 2021 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, RSU awards, performance awards, and other forms of equity compensation. In addition, the number of shares of our Class A common stock reserved for issuance under the 2021 Plan will automatically increase on January 1 of each year for a period of 10 years, beginning on January 1, 2022 and continuing through (and including) January 1, 2031, in an amount equal to 4% of the total number of share of our common stock (both Class A and Class B) outstanding on December 31 of the immediately preceding year, except that, before the date of any such increase, our Board of Directors may determine that the increase for such year will be a lesser number of shares. Additionally, to the extent that any stock options outstanding under the 2015 Plan expire, terminate prior to exercise, are not issued because the award is settled in cash, are forfeited because of the failure to vest, or are reacquired or withheld (or not issued) to satisfy a tax withholding obligation or the purchase or exercise price, if any, the shares of Class B common stock reserved for issuance pursuant to such equity awards will become available for issuance as shares of Class A common stock under the 2021 Plan. The maximum number of shares of our Class A common stock that may be issued on the exercise of incentive stock options under the 2021 Plan is 100,000,000 shares.

2021 Employee Stock Purchase Plan

In September 2021, our Board of Directors adopted, and our stockholders approved, the 2021 Employee Stock Purchase Plan (the "2021 ESPP"), which became effective in connection with the IPO in November 2021. The 2021 ESPP authorizes the issuance of shares of Class A common stock pursuant to purchase rights granted to employees. The number of shares of our Class A common stock reserved for issuance will automatically increase on January 1 of each year for a period of 10 years, beginning on January 1, 2022 and continuing through (and including) January 1, 2031, by the lesser of (1) 1% of the total number of shares of our common stock (both Class A and Class B) outstanding on December 31 of the immediately preceding year and (2) 142,500 shares, except that, before the date of any such increase, our Board of Directors may determine that such increase will be less than the amount set forth in clauses (1) and (2). The price at which Class A common stock is purchased under the 2021 ESPP is equal to 85% of the fair market value of a share of our Class A common stock on the first day of the offering period, or the date of purchase, whichever is lower. Offering periods are six months long and begin on November 3 and May 3 of each year.

Stock Options

A summary of the status of the 2015 Plan and 2021 Plan as of  December 31, 2025 and  June 30, 2026, and changes during the six month period ended  June 30, 2026, is presented below:

There were no stock options granted for the three and six months ended June 30, 2026 and 2025.

2021 ESPP

The following table summarizes the weighted-average assumptions used in estimating the fair value of the 2021 ESPP grants for the following offering periods presented, using the Black Scholes option-pricing model:

RSUs

The Company grants RSUs to certain employees. The RSUs granted have service-based vesting conditions. The service-based vesting condition for awards to new employees is typically satisfied over four years, with a cliff vesting period of one year and continued vesting quarterly thereafter. The service-based vesting condition for refresh grants of RSUs to existing employees is typically satisfied over three years with vesting occurring quarterly, subject to the employees' continued service to us. RSUs and the related stock-based compensation are recognized on a straight-line basis over the requisite service period. 

As a material inducement to Dr. Carlsten entering into employment with the Company, the Compensation Committee of the Board of Directors approved an inducement grant (granted outside the 2021 Equity Incentive Plan) in the form of an RSU award comprised of 1,532,379 RSUs converting into an equal number of shares of the Company's Class A common stock. 255,397 shares underlying the award vested as of the initial date of grant in June, 2026 and the remaining shares underlying award will vest in 16 equal quarterly installments on each vesting date thereafter, subject to Dr. Carlsten's continuous service to the Company as of each such vesting date.

RSU activity during the six months ended June 30, 2026 was as follows:

Performance Stock Units

In March 2025, we granted certain members of our executive leadership team 50 thousand RSUs with performance-based and service-based vesting conditions (the "PSUs"). The awards vest based on the achievement of certain financial performance targets as well as the individuals' continued employment with us. The total grant date fair value of the awards was determined to be $0.3 million. Stock-based compensation expense is recognized on a straight-line basis over their requisite service periods, if it is probable the performance condition will be met. Stock-based compensation expense is reversed if the achievement of the performance condition does not occur. As of June 30, 2026, it is not probable that the PSUs will vest.

PSU activity during the six months ended June 30, 2026 was as follows:

Stock-Based Compensation Expense

Stock-based compensation expense, recognized as selling, general, and administrative expenses in the condensed consolidated statements of operations and comprehensive loss for the three and six months ended June 30, 2026 and 2025, was $2.0 million and $2.4 million respectively, and $0.4 million and $0.8 million for the three and six months ended June 30, 2025, respectively. 

As of  June 30, 2026, there was approximately $0.3 million of total unrecognized compensation cost related to unvested stock options granted under both equity incentive plans, which is expected to be recognized over the weighted-average remaining vesting period of approximately 0.94 years. There was approximately $14.4 million of total unrecognized compensation cost related to outstanding unvested RSUs under the 2021 Plan, which is expected to be recognized over the weighted-average remaining vesting period of approximately 3.83 years.