In April 2022, we entered into an Open Market Sale AgreementSM with Jefferies implementing the Jefferies ATM Offering Program. In December 2024, we amended the Jefferies ATM Offering Program. Under the Jefferies ATM Offering Program we may offer and sell, from time to time and at our option, up to an aggregate of $215.0 million of shares of our common stock (inclusive of $65.0 million of sales made prior to the amendment) through Jefferies, acting as sales agent. Jefferies is entitled to a fixed commission rate of up to 3.0% of the gross sales proceeds of shares sold under the Jefferies ATM Offering Program. During the year ended December 31, 2025, we sold an aggregate of 13,887,177 shares of common stock at a weighted-average price of $4.94 per share for net proceeds of approximately $66.4 million under the Jefferies ATM Offering Program. We did not utilize the Jefferies ATM Offering Program during the six months ended June 30, 2026.

Common Stock Reserved for Future Issuance

Common stock reserved for future issuance was as follows:


	June 30, 2026
Common stock options and restricted stock units		13,976,293
Shares available under the 2015 equity incentive plan		6,164,361
Shares available under the 2022 inducement plan		167,675
Shares available under the employee stock purchase plan		537,999
		20,846,328

The following table summarizes our stock option activity under all equity incentive plans for the six months ended June 30, 2026:


	Number of Outstanding Stock Options			Weighted- Average Exercise Price
Outstanding as of December 31, 2025		9,591,504		$	3.82
Granted		4,274,091		$	0.73
Canceled/forfeited/expired		(296,519	)	$	8.00
Outstanding as of June 30, 2026		13,569,076		$	2.75

The assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows:


	Three Months Ended June 30,		Six Months Ended June 30,
	2026	2025	2026	2025
Expected term (in years)	5.50	5.50 – 6.00	5.50 – 6.08	5.50 – 6.08
Risk-free interest rate	4.2%	3.9% – 4.1%	3.7% – 4.2%	3.9% – 4.5%
Expected volatility	107.5%	76.9% – 77.5%	105.5% – 107.5%	75.9% – 77.5%
Expected dividend yield	0.0%	0.0%	0.0%	0.0%

The following table summarizes our restricted stock unit activity under all equity incentive plans for the six months ended June 30, 2026:


	Number of Outstanding Restricted Stock Units			Weighted-Average Grant Date Fair Value
Balance as of December 31, 2025		20,108		$	5.52
Granted		446,940		$	0.71
Released		(20,108	)	$	5.52
Cancelled		(39,723	)	$	0.71
Balance as of June 30, 2026		407,217		$	0.71

The allocation of stock-based compensation for all options and restricted stock units and stock issued pursuant to our employee stock purchase plan is as follows (in thousands):


	Three Months Ended June 30,				Six Months Ended June 30,
	2026		2025		2026		2025
Research and development	$	264	$	325	$	547	$	629
General and administrative		881		980		1,905		1,854
Total stock-based compensation expense	$	1,145	$	1,305	$	2,452	$	2,483