The Company adopted the 2022 Equity Incentive Plan (the “2022 Plan”) effective upon the closing of the IPO, which provides for the granting of incentive stock options (“ISOs”) to the Company's employees, and for the grant of nonstatutory stock options (“NSOs”), stock appreciation rights, restricted stock awards, restricted stock unit awards, performance awards, and other forms of awards to employees, directors, and consultants. As of December 31, 2024, no stock appreciation rights or performance awards were issued.

The Company initially reserved for issuance 1,870,000 new shares of common stock pursuant to the 2022 Plan. The Company’s 2017 Equity Incentive Plan (the “2017 Plan”) was terminated in 2022; however, shares underlying outstanding stock awards granted under the 2017 Plan will continue to be governed by the 2017 Plan. Shares available under the 2017 Plan were added to the available shares in the 2022 Plan. Shares underlying outstanding stock awards granted under the 2017 Plan that expire or are repurchased by, forfeited to, cancelled or withheld by the Company will also be reserved for issuance under the 2022 Plan.

The initial number of shares of the Company’s common stock that may be issued under the 2022 Plan will not exceed 4,423,920 shares of the Company's common stock, which is the sum of (i) 1,870,000 new shares, plus (ii) 2,553,920 shares related to the 2017 Plan. In addition, the number of shares of the Company’s common stock reserved for issuance under the 2022 Plan will automatically increase on January 1 of each year for a period of ten years, beginning on January 1, 2023 and continuing through January 1, 2032, in an amount equal to (1) 4% of the total number of shares of the Company’s common stock outstanding on December 31 of the immediately preceding year, or (2) a lesser number of shares determined by the Company's board of directors no later than December 31 of the immediately preceding year. Accordingly, effective January 1, 2024, the number of shares in the 2022 Plan increased by 1,189,657 shares, representing 4% of the prior year end’s common stock outstanding. The maximum number of shares of the Company's common stock that may be issued on the exercise of stock options or vesting of RSUs and RSAs under the 2022 Plan is 13,271,760 shares.

Since the date of incorporation and through December 31, 2024, the Company issued stock options, RSUs and RSAs to its employees, directors and consultants. As of December 31, 2024, 859,841 shares of common stock remained available for future issuance under the 2022 Plan.

ISOs granted to newly hired employees under the 2022 Plan generally vest 25% after the completion of 12 months of service, and the balance vests in equal monthly installments over the next 36 months of service and expire ten years from the grant date, unless subject to provisions regarding 10% stockholders. ISOs granted to existing employees generally vest ratably over a 48-month period of service and expire ten years from the grant date. NSOs vest in accordance with the terms of the specific agreement under which the options were provided and expire ten years from the date of grant. RSUs granted to employees generally vest annually over a two to four year period of service and expire ten years from the grant date. RSAs granted to non-employees generally vest at the time of grant and expire ten years from the grant date.

The following table summarizes the components of stock-based compensation expense recognized in the Company’s statements of operations and comprehensive loss during the years ended December 31, 2024 and 2023 (in thousands):


	Year Ended December 31,
	2024		2023
Research and development expenses	$	3,798	$	4,236
General and administrative expenses		4,540		4,176
Total	$	8,338	$	8,412

The Company estimated the fair value of stock options using the Black-Scholes option pricing model. The fair value of employee and non-employee stock options is being amortized on the straight-line basis over the requisite service period of the awards.

The Black-Scholes option pricing model requires the use of highly subjective assumptions which determine the fair value of stock-based awards. These assumptions include:

The following weighted average assumptions were used to value options granted during the periods indicated:


	Year Ended December 31, 2024			Year Ended December 31, 2023
Expected term	5.94 years			5.98 years
Expected volatility		110.6	%		90.8	%
Risk-free interest rate		4.28	%		4.04	%
Expected dividend yield		—			—

A summary of the stock plan activity is as follows:


	Total Options Outstanding			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)		Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2023		3,930,306		$	10.86		8.14	$	37,853
Granted		1,700,899			2.42
Exercised		(28,930	)		7.78
Forfeited/expired		(711,432	)		8.91
Vested and expected to vest at December 31, 2024		4,890,843		$	8.23		6.66	$	330
Exercisable as of December 31, 2024		2,883,622		$	9.45		5.46	$	263

As of December 31, 2024, there was unrecognized stock-based compensation expense of $8.3 million related to unvested stock options which the Company expects to recognize over a weighted-average period of 1.6 years.

Weighted-average grant-date fair value of the options granted during the year ended December 31, 2024 was $2.05 per share.

RSUs entitle the holder to receive shares of the Company’s common stock upon vesting. The fair value of RSUs is based upon the closing sales price of the Company’s common stock on the grant date.

A summary of the RSU activity is as follows:


`	Number of Units			Weighted-Average Grant Date Fair Value
Unvested at December 31, 2023		—		$	—
Issued		762,346			2.59
Vested and released		(38,556	)		2.96
Forfeited		(207,279	)		2.63
Unvested at December 31, 2024		516,511		$	2.54

As of December 31, 2024, there was unrecognized stock-based compensation expense of $0.9 million related to unvested restricted stock units which the Company expects to recognize over a weighted-average period of 2.3 years.

RSAs entitle the holder to receive shares of the Company’s common stock upon vesting. The fair value of RSAs is based upon the closing sales price of the Company’s common stock on the grant date.

A summary of the RSA activity is as follows:


	Number of Units			Weighted-Average Grant Date Fair Value
Unvested at December 31, 2023		—		$	—
Issued		40,003			1.27
Vested and released		(40,003	)		1.27
Forfeited		—			—
Unvested at December 31, 2024		—		$	—

As of December 31, 2024, there was no unrecognized stock-based compensation expense related to unvested restricted stock awards.

The Company’s 2017 Plan permitted early exercise of certain stock options prior to vesting to certain directors, officers, and employees. Any shares issued pursuant to unvested options are restricted and subject to repurchase by the Company until the conditions for vesting are met. The amounts paid for shares purchased under an early exercise of stock options and subject to repurchase by the Company are reported as options subject to repurchase, short and long-term on the balance sheet and is reclassified to common stock and additional paid-in capital as such shares vest. Upon termination of employment of an option-holder, the Company has the right to repurchase, at the original purchase price, any unvested options.

As of December 31, 2024, and 2023, there were none and 5,040 unvested common shares outstanding that were issued upon the early exercise of stock options prior to the vesting of the underlying shares which are subject to repurchase by the Company at the original issuance price upon termination of the stockholders’ services. The right to repurchase these shares generally lapses with respect to 25% of the shares underlying the option after one year of service to the Company and 1/48th of the shares underlying the original grant per month for 36 months thereafter. The shares purchased by the option-holders pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be issued until those shares vest. As of December 31, 2023, the Company recorded an insignificant amount of liabilities associated with the cash received for shares issued subject to repurchase rights, recorded within the options subject to repurchase, short-term, and options subject to repurchase, long-term on the Company’s balance sheets.

The Company’s 2022 Employee Stock Purchase Plan (“ESPP”) has two components: a component that is intended to qualify as an “employee stock purchase plan” under Section 423 of the Code (the “423 Component”) and a component that is not intended to qualify (the “Non-423 Component”). The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation. At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock at the beginning of the offering period or at the end of each applicable purchase period.

Subject to adjustment in the case of certain capitalization events, 187,000 shares of the Company’s common stock were available for purchase at the adoption of the ESPP. Pursuant to the ESPP, the annual share increase pursuant to the evergreen provision is determined based on the least of (i) 1% of the Company’s common stock outstanding as of December 31 of the immediately preceding year, (ii) 561,000 shares, or (iii) such number of shares as determined by the Board. Accordingly, effective January 1, 2024, the number of shares in the ESPP increased by 297,414 shares, representing 1% of the prior year-end’s common stock outstanding. As of December 31, 2024, 563,731 shares of common stock remained available for issuance under the ESPP.

During the years ended December 31, 2024 and 2023, the Company recognized $0.1 million and $0.2 million, respectively, in stock-based compensation expense related to the ESPP.