For stock options requiring an assessment of value during the three months ended March 31, 2025 and 2024, the fair value of each stock option award was estimated using the Black-Scholes option-pricing model utilizing the following assumptions:


		March 31, 2025
Risk-free interest rate		4.05% - 4.46%
Expected dividend yield		0%
Expected volatility		86.46% - 87.69%
Expected life		5.50 to 6.25 years

		March 31, 2024
Risk-free interest rate		3.83% - 4.28%
Expected dividend yield		0%
Expected volatility		66.27% - 109.86%
Expected life		5.50 to 8.91 years

A summary of stock option activity for the three months ended March 31, 2025 is as follows:


	Number of Shares			Weighted Average Exercise Price		Weighted Average Remaining Contractual Life (in Years)
Stock options outstanding at December 31, 2024		10,471,724		$	5.61		7.27
Granted		1,889,300			0.99		—
Exercised		—			—		—
Cancelled		(22,563	)		3.42		—
Stock options outstanding at March 31, 2025		12,338,461			4.91		7.48
Stock options exercisable at March 31, 2025		5,982,995		$	8.41		5.63

The aggregate intrinsic value of exercisable but unexercised in-the-money stock options at March 31, 2025 was less than $0.1 million based on a weighted average exercise price of $8.41 per share. The aggregate intrinsic value of options is calculated as the difference of the market close price of $0.91 on March 31, 2025, and the weighted average exercise price of $8.41, with a weighted average remaining contractual term of 5.63 years.

Stock-based compensation for the three months ended March 31, 2025 and 2024 was included in the Company’s condensed consolidated statements of operations and comprehensive loss as follows:


	Three Months Ended March 31,
(in thousands)	2025		2024
General and administrative	$	695	$	956
Research and development		643		990
Total stock-based compensation	$	1,338	$	1,946

As of March 31, 2025, total unrecognized stock-based compensation expense was $6.0 million, which is expected to be recognized as an operating expense in the Company’s condensed consolidated statements of operations and comprehensive loss over the weighted average remaining period of 2.15 years.