As of March 31, 2023, the Company had 1,148,889 shares of its common stock available for future issuance under its stock incentive plan.

The Company’s stock options generally vest over 48 months with 25% vesting after one year followed by ratable monthly vesting over the remaining three years and have a contractual term of 10 years. The weighted-average assumptions used principally in determining the fair value of options granted were as follows:


	Three Months Ended March 31,
	2023			2022
Fair value of common stock	$	3.98		$	8.58
Expected term (in years)		6.0			6.0
Expected volatility		82.1	%		78.3	%
Risk-free interest rate		3.8	%		1.7	%
Dividend yield		—			—

During the three months ended March 31, 2023 and 2022, the Company granted stock options to purchase 1,543,219 shares and 1,818,298 shares of its common stock, respectively, with a weighted-average grant-date fair value of $5.53 and $5.84 per share, respectively. As of March 31, 2023, total unrecognized compensation expense related to stock options was $19.9 million, which is expected to be recognized over a weighted-average period of 2.4 years.

As of March 31, 2023, options for 56,162 shares of Company common stock with a weighted-average exercise price of $1.36 were exercised and unvested. The underlying proceeds from the unvested exercises of $0.1 million is recorded in other current liabilities on the condensed consolidated balance sheet.

During the three months ended March 31, 2023, the Company granted 645,360 restricted stock units with a weighted-average grant date fair value of $5.55 per share. As of March 31, 2023, total unrecognized compensation expense related to restricted stock units was $8.2 million, which is expected to be recognized over a weighted-average period of 1.6 years. The Company did not grant any restricted stock units during the three months ended March 31, 2022.

Stock-based compensation expense was allocated as follows:


	Three Months Ended March 31,
(in thousands)	2023		2022
Research and development	$	2,354	$	796
General and administrative		1,714		950
Total stock-based compensation expense	$	4,068	$	1,746