STOCK-BASED COMPENSATION

3 Months Ended

Mar. 31, 2026

Share-Based Payment Arrangement [Abstract]

2021 Equity Incentive Plan

The 2021 Equity Incentive Plan (the “2021 Plan”), which provides for the grant of incentive stock options to employees and the grant of nonstatutory stock options, stock appreciation rights, restricted stock awards, RSUs, performance awards and other forms of stock awards to employees, directors and consultants, became effective on June 30, 2021. The 2021 Plan is a successor to the Company’s Amended and Restated Stock Performance Plan that was adopted by the Company’s board of directors and stockholders on April 8, 2013 (as amended from time to time, most recently on November 20, 2020, the “2013 Plan”). Following the effectiveness of the 2021 Plan, no further grants may be made under the 2013 Plan; however, any outstanding equity awards granted under the 2013 Plan continue to be governed by the terms of the 2013 Plan. As of March 31, 2026, there were 3,035,572 options outstanding under the 2013 Plan.

The number of shares of common stock reserved for issuance under the 2021 Plan automatically increases on January 1 of each calendar year through January 1, 2031, in an amount equal to 5% of the total number of shares of common stock outstanding on December 31 of the fiscal year before the date of each automatic increase, or a lesser number of shares determined by the board of directors prior to the applicable January 1. On January 1, 2026, the number of shares of common stock reserved for issuance under the 2021 Plan automatically increased by 3,028,768 shares.

The maximum number of shares of common stock that may be issued upon the exercise of incentive stock options under the 2021 Plan is 12,000,000. As of March 31, 2026, a total of 20,702,193 shares were authorized for issuance under the 2021 Plan and 1,392,371 shares remained available for issuance under the 2021 Plan.

The Company recorded stock-based compensation expense related to stock options and RSUs in the following expense categories of its condensed statements of operations and comprehensive loss for the periods shown (in thousands):


	Three Months Ended March 31,
		2026		2025
General and administrative		$	1,366	$	1,492
Research and development		1,030		982
Total stock-based compensation		$	2,396	$	2,474

Stock Options

The Black-Scholes option-pricing model was used to estimate the fair value of stock options granted during the three months ended March 31, 2026 and 2025 with the following weighted average assumptions:


	Three Months Ended March 31,
	2026	2025
Risk-free interest rate	3.92% - 3.97%	4.16% - 4.52%
Expected term (in years)	6.0	6.0
Expected volatility	90%	91% - 92%
Expected dividend yield	0%	0%

The weighted average grant date fair value of options granted during the three months ended March 31, 2026 and 2025 was $1.42 per share and $1.33 per share, respectively.

Stock options granted after December 31, 2017 generally vest monthly over a range of 12 to 48 months or vest monthly over a total of 48 months following a one-year cliff and all have a 10-year contractual term. Beginning January 1, 2024, stock options granted to consultants vest quarterly over a one-year period, provided that such consultants continue to perform services as dictated by their respective consulting agreements with the Company. Annual option awards issued to members of the Company’s board of directors vest in full on the first anniversary of the grant date. Stock options granted prior to December 31, 2017 were either fully vested upon grant or generally vested monthly over a range of three to 24 months and also have a 10-year term. The Company’s common stock became publicly traded in July 2021. Prior to January 1, 2025, the Company lacked sufficient company-specific historical and implied volatility information for its common stock and estimated its expected stock volatility using a weighted average blend of historical volatility of a publicly traded set of peer companies, as well as its own historical volatility. Beginning on January 1, 2025, based on the availability of sufficient historical trading data of the Company’s common stock, the Company began using its historical volatility to estimate expected stock volatility. Due to the lack of historical exercise history, the expected term of the Company’s stock options has been determined using the “simplified” method for awards. The risk-free interest rate is determined by reference to the U.S. Treasury yield curve in effect at the time of grant of the award for time periods approximately equal to the expected term of the award. Expected dividend yield is zero based on the fact that the Company has never paid cash dividends and does not expect to pay any cash dividends in the foreseeable future.

The following table reflects summarized stock option activity during the three months ended March 31, 2026:


	Stock Options	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value (in thousands)
Outstanding as of December 31, 2025	12,578,766	$	3.46
Granted	2,488,001	$	1.87
Exercised	(91,828)	$	1.58
Forfeited	(1,563)	$	3.77
Expired	(86,323)	$	2.34
Outstanding as of March 31, 2026	14,887,053	$	3.21	7.2	$	363
Vested and exercisable as of March 31, 2026	8,931,079	$	3.66	6.1	$	340

The intrinsic value of stock options exercised during the three months ended March 31, 2026 was $0.1 million and the intrinsic value of stock options exercised during the three months ended March 31, 2025 was immaterial. As of March 31, 2026, total unrecognized compensation costs related to unvested stock option awards were approximately $11.3 million, which the Company expects to recognize over a weighted-average period of approximately 2.5 years.

Restricted Stock Units

RSUs granted to employees vest in equal annual installments on the first three anniversaries of the grant date and RSUs granted to members of the Company’s board of directors vest in full on the first anniversary of the grant date.

The following table reflects summarized RSU activity during the three months ended March 31, 2026:


	Number of Shares	Weighted Average Grant Date Fair Value
Unvested as of December 31, 2025	1,907,976	$	2.93
Granted	1,658,433	$	1.87
Vested	(805,203)	$	3.45

Unvested as of March 31, 2026	2,761,206	$	2.14

As of March 31, 2026, total unrecognized compensation costs related to unvested RSUs were approximately $5.1 million, which the Company expects to recognize over a weighted-average period of approximately 2.2 years.

Employee Stock Purchase Plan

The 2021 Employee Stock Purchase Plan (the “ESPP”), which permits employees to purchase shares of common stock, became effective on June 30, 2021. The number of shares of common stock reserved for issuance automatically increases on January 1 of each calendar year through January 1, 2031, by the lesser of (1) 1% of the total number of shares of common stock outstanding on the last day of the fiscal year before the date of the automatic increase, and (2) 800,000 shares; provided, however, that before the date of any such increase, the board of directors may determine that such increase will be less than the amount set forth in clauses (1) and (2). On January 1, 2026, the number of shares of common stock reserved for issuance under the ESPP automatically increased by 605,754 shares. As of March 31, 2026, there are a total of 2,975,783 shares reserved for issuance under the ESPP and there have been no purchases of shares under the ESPP, as the ESPP has not yet been implemented.