8. Stock-Based Compensation

Equity Plans

In May 2021 the Company adopted the 2021 Equity Incentive Plan (the “2021 Plan”). As amended and restated in February 2025, the 2021 Plan has an aggregate of 3,340,000 authorized shares.

The 2021 Plan provides for the grant of incentive stock options (“ISOs”), non-statutory stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards, performance-based stock awards, other forms of equity compensation and performance cash awards. ISOs may be granted only to employees. All other awards may be granted to employees, including officers, and to non-employee directors and consultants of the Company and its affiliates. Service-based awards generally vest over a four-year period, with the first 25% of such awards vesting following twelve months of continued employment or service with the remaining awards vesting monthly in equal installments over the following thirty-six months. Certain other awards vest monthly over thirty-six months for subsequent grants. For certain service-based awards to the board of directors, vesting occurs in thirty-six equal monthly installments over a three-year period for initial grants and in twelve equal monthly installments over a twelve-month period for subsequent grants. As of March 31, 2026, there were 3,969 shares available for issuance under the 2021 Plan.

On July 26, 2020, the Company adopted the 2020 Inducement Equity Incentive Plan (the “2020 Inducement Plan”) and reserved 20,000 shares for future grant under the 2020 Inducement Plan. The 2020 Inducement Plan, as amended and restated in January 2026, has an aggregate of 300,000 authorized shares. As of March 31, 2026, there were 275,000 shares available for issuance under the 2020 Inducement Plan.

Stock Options

The risk-free interest rate valuation assumption for options is based on the U.S. Treasury yield curve rate at the date of grant with a maturity approximating the expected term of the option.

All option awards generally expire ten years from the date of grant. The expected term assumption for options granted to employees is determined using the simplified method that represents the average of the contractual term

of the option and the weighted average vesting period of the option. The Company uses the simplified method because it does not have sufficient historical option exercise data to provide a reasonable basis upon which to estimate the expected term.

The expected volatility is based on the historical volatility of the Company's common stock over the most recent period commensurate with the estimated expected term of the stock option.

The assumed dividend yield is based upon the Company’s expectation of not paying dividends in the foreseeable future.

The weighted average grant-date fair value of stock options granted in the three months ended March 31, 2026 and 2025 was $25.96 and $6.33, respectively.

The aggregate intrinsic value of stock options as of March 31, 2026 is based on the Company’s closing stock price of $25.90 per share.

Restricted Stock Unit Awards

Restricted stock units vest over four years with one sixteenth of the restricted stock units vesting every quarter.

The aggregate fair value of RSUs vested during the three months ended March 31, 2026 was $747 thousand.

2017 Employee Stock Purchase Plan

In May 2021, the Company's board of directors reactivated the Company’s 2017 Employee Stock Purchase Plan (“ESPP”) which had previously been suspended. The ESPP allows eligible employees to withhold up to 15% of their earnings to purchase shares of the Company’s common stock at a price per share equal to the lower of (i) 85% of the fair market value of a share of the Company’s common stock on the first date of an offering, or (ii) 85% of the fair market value of a share of the Company’s common stock on the date of purchase. The Company had 32,562 shares available for future issuance under the ESPP as of March 31, 2026. The number of shares of common stock reserved for issuance will automatically increase on January 1 of each calendar year through January 1, 2027, by the lesser of (a) 1% of the total number of shares of the Company’s common stock outstanding on December 31 of the preceding calendar year, (b) 12,000 shares, or (c) a number determined by the Company's board of directors that is less than (a) and (b). The Company issued 9,263 and 818 shares under the ESPP during the three months ended March 31, 2026 and 2025, respectively. The ESPP is considered a compensatory plan. The Company recorded stock-based compensation expense related to its ESPP of $13 thousand and $7 thousand for the three months ended March 31, 2026 and 2025, respectively.

Stock-Based Compensation Expense