The Company has two equity incentive plans: the 2016 Equity Incentive Plan, as amended, and the 2020 Equity Incentive Plan. New awards can only be granted under the 2020 Equity Incentive Plan (the “Plan”). The number of shares of the Company’s common stock that may be issued pursuant to rights granted under the Plan shall automatically increase on January 1st of each year and continuing for ten years beginning on January 1, 2021, in an amount equal to five percent of the total number of shares of the Company’s common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the Company's board of directors or compensation committee to determine a lesser number of shares shall be added for such year. On January 1, 2026, 3,147,681 shares were added to the Plan. As of March 31, 2026, 7,332,525 shares were available for future grants. The Plan provides for the granting of common stock, incentive stock options, nonqualified stock options, restricted stock awards, restricted stock units and/or stock appreciation rights to employees, directors, and other persons, as determined by the Company’s board of directors. The Company’s stock options vest based on the terms in each award agreement, generally over four-year periods with 25% of options vesting after one year and then monthly thereafter, and have a term of ten years.

The Company measures stock-based awards at their grant-date fair value and records compensation expense on a straight-line basis over the vesting period of the awards. The Company recorded stock-based compensation expense in the following expense categories in its accompanying statements of operations:


	Three Months Ended March 31,
(in thousands)	2026		2025
Research and development	$	1,089	$	2,270
General and administrative		911		1,562
	$	2,000	$	3,832

The following table summarizes stock option activity for the periods indicated:


	Number of shares			Weighted average exercise price per share		Weighted average remaining contractual term (years)
Outstanding at December 31, 2025		14,727,692		$	7.68		6.80
Granted		3,570,250		$	2.30
Exercised		(26,463	)	$	1.16
Forfeited		(583,766	)	$	12.95
Outstanding at March 31, 2026		17,687,713		$	6.43		7.21
Exercisable at March 31, 2026		10,101,993		$	9.34		5.86

At March 31, 2026, the aggregate intrinsic value of outstanding options and exercisable options was $14.0 million and $4.7 million, respectively.

The following table summarizes information about stock options outstanding at March 31, 2026 under the Plan:


	Options Outstanding						Options Exercisable
Range of Exercise Prices	Number Outstanding		Weighted Average Remaining Contractual Life (in years)		Weighted Average Exercise Price		Number Exercisable		Weighted Average Exercise Price
$0.31 - $2.09		4,864,197		6.88	$	1.37		2,558,956	$	1.60
$2.10 - $4.43		4,277,350		9.53		2.55		432,778		3.79
$4.44 - $7.50		4,714,930		7.21		5.53		3,280,908		5.66
$7.51 - $74.45		3,831,236		5.06		18.29		3,829,351		18.30
		17,687,713						10,101,993

The weighted-average grant date fair value of options granted was $1.97 and $1.11 per option for the three months ended March 31, 2026 and 2025, respectively. The Company recorded stock-based compensation expense of $1.9 million and $3.7 million for the three months ended March 31, 2026 and 2025, respectively, related to stock options. As of March 31, 2026, the total unrecognized compensation expense related to unvested stock option awards was $14.5 million, which the Company expects to recognize over a weighted-average period of 2.60 years.

The fair value of each option was estimated on the date of grant using the weighted average assumptions in the table below:


	Three months ended March 31,
	2026			2025
Expected volatility		114.01	%		86.50	%
Risk-free interest rate		3.91	%		4.32	%
Expected life (in years)		6.07			6.07
Expected dividend yield		—			—

The Company granted restricted stock units (“RSUs”) to employees that generally vest over a four-year period with 25% of awards vesting after one year and then quarterly thereafter. Any unvested units will be forfeited upon termination of services.

The following table summarizes activity related to RSU stock-based payment awards:


	Number of shares			Weighted-average grant date fair value
Unvested balance at December 31, 2025		220,500		$	1.43
Granted		292,325		$	2.30
Vested		(59,557	)	$	1.70
Forfeited		(14,188	)	$	1.82
Unvested balance at March 31, 2026		439,080		$	1.96

The Company recorded stock-based compensation expense of $0.1 million for both the three months ended March 31, 2026 and 2025, related to RSUs. At March 31, 2026, the total unrecognized expense related to the RSUs was $0.8 million, which the Company expects to recognize over a weighted-average period 3.64 years.

The Company has an Employee Stock Purchase Plan (the “ESPP”). The number of shares of the Company’s common stock that may be issued pursuant to rights granted under the ESPP shall automatically increase on January 1st of each year and continuing for ten years beginning in 2021, in an amount equal to one percent of the total number of shares of all classes of the Company’s common stock outstanding on December 31st of the preceding calendar year, subject to the discretion of the Company's board of directors or compensation committee to determine a lesser number of shares shall be added for such year. On January 1, 2026, 629,536 shares were added to the ESPP and as of March 31, 2026, the ESPP had 2,936,805 shares of common stock reserved for future issuance.

Under the ESPP, eligible employees can purchase the Company’s common stock through accumulated payroll deductions at such times as are established by the Company's compensation committee. Eligible employees may purchase the Company’s common stock at 85% of the lower of the fair market value of the Company’s common stock on the first day of the offering period or on the last day of the offering period. Eligible employees may contribute up to 15% of their eligible compensation. Under the ESPP, a participant may not accrue rights to purchase more than $25,000 worth of the Company’s common stock for each calendar year in which such right is outstanding.

The ESPP is considered compensatory under the FASB stock compensation rules. Accordingly, share-based compensation expense is determined based on the option’s grant-date fair value as estimated by applying the Black Scholes option-pricing model and is recognized over the withholding period. The Company recognized share-based compensation expense of $40 thousand for each of the three months ended March 31, 2026 and 2025, related to the ESPP.