As of June 30, 2023, the Company had 796,957 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:


	Six Months Ended June 30,
	2023			2022
Fair value of common stock	$	3.76		$	8.30
Expected term (in years)		6.0			6.0
Expected volatility		81.9	%		78.4	%
Risk-free interest rate		3.7	%		1.8	%
Dividend yield		—			—

During the six months ended June 30, 2023 and 2022, the Company granted stock options to purchase 2,108,219 shares and 1,948,264 shares of its common stock, respectively, with a weighted-average grant-date fair value of $3.76 and $5.65 per share, respectively. As of June 30, 2023, total unrecognized compensation expense related to stock options was $19.2 million, which is expected to be recognized over a weighted-average period of 2.4 years.

As of June 30, 2023, options for 30,704 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 six months ended June 30, 2023 and 2022, the Company granted 645,360 restricted stock units and 1,040,500 restricted stock units, respectively, with a weighted-average grant date fair value of $5.55 and $6.00 per share, respectively. As of June 30, 2023, total unrecognized compensation expense related to restricted stock units was $6.2 million, which is expected to be recognized over a weighted-average period of 1.8 years.

As of June 30, 2023, the Company had 666,535 shares of its common stock available for issuance under its Employee Stock Purchase Plan (“ESPP”).

During the six months ended June 30, 2023, the Company issued 44,977 shares with a weighted-average purchase price of $3.76 under the ESPP, which resulted in an immaterial amount of compensation expense. The Company did not issue any shares under the ESPP during the six months ended June 30, 2022.

Stock-based compensation expense was allocated as follows:


	Three Months Ended June 30,				Six Months Ended June 30,
(in thousands)	2023		2022		2023		2022
Research and development	$	2,463	$	909	$	4,817	$	1,705
General and administrative		1,775		832		3,489		1,782
Total stock-based compensation expense	$	4,238	$	1,741	$	8,306	$	3,487