Note 6. Stock-Based Compensation

Effective January 1, 2026, the number of shares of common stock available under the 2021 Incentive Award Plan (the 2021 Plan) increased by 3,614,972 shares pursuant to the evergreen provision. As of March 31, 2026, 6,360,083 shares of common stock remained available for issuance under the 2021 Plan.

Effective January 1, 2026, the number of shares of common stock available under the 2021 Employee Stock Purchase Plan (the ESPP) increased by 722,994 shares pursuant to the evergreen provision of the ESPP. As of March 31, 2026, 1,528,002 shares of common stock remained available for issuance under the ESPP.

As of March 31, 2026, 1,860,000 shares of common stock remained available for issuance under the 2023 Inducement Equity Plan as adopted in November 2023.

Repricing

On August 11, 2025 (the Repricing Effective Date), the Company's Board approved a repricing of certain outstanding vested and unvested stock option awards under the 2021 Plan for eligible non-executive employees and certain other service providers (the Repricing Participants). The per share exercise price of eligible stock option awards was reduced to $4.50. To receive the benefit of the repricing, Repricing Participants were required to remain an employee or service provider through the period (the Retention Period) that began on the Repricing Effective Date and ended on September 12, 2025 (the Retention Date). No other changes were made to the terms and conditions of the eligible stock option awards. The stock option repricing impacted approximately 2.6 million shares of common stock subject to stock option awards and affected 48 employees and service providers.

The repricing resulted in a total incremental stock-based compensation expense of $0.4 million, which was calculated using the Black-Scholes option pricing model, of which $0.3 million is associated with vested repriced options as of the Retention Date and was recognized on a straight-line basis over the Retention Period. The remaining $0.1 million of the incremental stock-based compensation expense is associated with unvested repriced options beyond the Retention Period and will be recognized on a straight-line basis over the remaining original vesting periods. For the three months ended March 31, 2026 and 2025, the Company did not recognize any incremental stock-based compensation expense related to the repricing.

Stock-Based Compensation Expense

As of March 31, 2026, there was $9.0 million of total unrecognized stock-based compensation expense which is expected to be recognized over a weighted-average period of 2.7 years.

Stock Options