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Stock-Based Compensation

12 Months Ended

Dec. 31, 2024

Stock-Based Compensation

Stock-Based Compensation

8. Stock-Based Compensation

2015 Second Amended and Restated Equity Incentive Plan

Prior to the Company’s initial public offering in June 2015 (the “IPO”), the Company granted awards to eligible participants under its 2008 Equity Incentive Plan. In May 2015, the Board of Directors adopted and, in June 2015, the Company’s stockholders approved the 2015 Stock Incentive Plan, as amended and amended and restated since the IPO (“2015 Plan”), which became effective immediately prior to the effectiveness of the IPO. Subsequent to the IPO, no option grants have been awarded to eligible participants under the 2008 Equity Incentive Plan.

The 2015 Plan provides for the grant of incentive stock options, non-statutory stock options, restricted stock awards, restricted stock units, stock appreciation rights and other stock-based awards. The Company’s employees, officers, directors and consultants and advisors are eligible to receive awards under the 2015 Plan.

Terms of stock option agreements, including vesting requirements, are determined by the Company’s board of directors, subject to the provisions of the applicable stock incentive plan. Options granted by the Company generally vest ratably over four years, with a one-year cliff, and options are exercisable from the date of grant for a period of ten years. As of December 31, 2024, options to purchase 5,378,672 shares of common stock are outstanding and 7,554,324 shares of common stock remain available for issuance under the 2015 Plan, all of which shares of common stock are reserved for issuance.

2022 Inducement Stock Incentive Plan

On February 17, 2022, the Board of Directors adopted the 2022 Inducement Stock Incentive Plan (the “Inducement Plan”). The Inducement Plan provides for the grant of nonstatutory stock options, stock appreciation rights, restricted stock, restricted stock units and other stock-based awards with respect to an aggregate of 300,000 shares of the Company’s common stock. Awards under the Inducement Plan may only be granted to persons who (a) were not previously an employee or director of the Company or (b) are commencing employment with the Company following a bona fide period of non-employment, in either case as an inducement material to the individual’s entering into employment with the Company and in accordance with the requirements of Nasdaq Stock Market Rule 5635(c)(4).

The Board of Directors approved amendments to the Inducement Plan to increase the number of shares of common stock authorized for issuance by 1,400,000 shares of common stock in the year ended December 31, 2023 and 1,100,000 shares of common stock in the year ended December 31, 2024. As of December 31, 2024, options to purchase 1,472,217 shares of common stock are outstanding and 1,294,846 shares of common stock remain available for issuance under the Inducement Plan, all of which shares of common stock are reserved for issuance.

Stock Option Activity

A summary of the Company’s stock option activity and related information for employees and non-employees follows:


							Weighted
				Weighted-			Average		Aggregate
				Average			Remaining		Intrinsic
				Exercise			Contractual		Value
		Shares		Price			Term (years)		(in thousands)
Outstanding at December 31, 2023		3,553,969		$	13.59		8.39		$	1,912
Granted		3,644,675		$	13.90
Exercised		(36,539)		$	5.21
Cancelled or forfeited		(309,544)		$	12.52
Expired		(1,672)		$	414.04
Outstanding at December 31, 2024		6,850,889		$	13.75		8.31		$	2,946
Vested and exercisable at December 31, 2024		2,206,580		$	15.15		7.05		$	1,878
Vested and expected to vest at December 31, 2024		6,850,889		$	13.75		8.31		$	2,946

The total intrinsic value of options exercised in the years ended December 31, 2024 and 2023 was $0.2 million and $0.5 million, respectively. The total grant date fair value of stock options vested for the year ended December 31, 2024 and 2023 was $8.6 million and $4.4 million, respectively. The weighted-average grant date fair value of options granted to employees and non-employees for the years ended December 31, 2024 and 2023 was $9.51 and $7.20 per share, respectively.

At December 31, 2024, the total unrecognized compensation expense related to unvested stock option awards was $33.2 million. The Company expects to recognize that cost over a weighted-average period of approximately 2.9 years.

Stock-Based Compensation Expense

During the years ended December 31, 2024 and 2023, the Company recorded stock-based compensation expense for employee and non-employee stock options and restricted stock, which was allocated as follows in the statements of operations (in thousands):


		Year Ended December 31,
		2024			2023
Research and development		$	3,782		$	1,304
General and administrative			9,260			5,010
Total		$	13,042		$	6,314

No related tax benefits were recognized for the years ended December 31, 2024 and 2023.

The fair value of stock options granted to employees and non-employees was estimated using the Black-Scholes option-pricing model based on the following assumptions:


		Year Ended December 31,
		2024		2023
Weighted-average expected volatility		74.32%-76.4%		65.86%-73.68%
Expected term (in years)		5.5-6.25		5.5-6.25
Risk-free interest rate		3.53%-4.59%		3.42%-4.67%
Expected dividend yield		0%		0%