Share-based compensation (Tables)

9 Months Ended

Sep. 30, 2022

Share-based compensation

Schedule of Stock-based compensation expense

Share-based compensation expense recorded as research and development and general and administrative expenses in the condensed statements of operations is as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development	$	480	$	402	$	1,387	$	924
General and administrative		860		753		2,590		1,305
	$	1,340	$	1,155	$	3,977	$	2,229

Weighted average assumptions used in option-pricing

The weighted average assumptions used in the Black-Scholes option-pricing model for stock options granted were:

	Nine Months Ended September 30,
	2022			2021
Expected volatility		85.6	%		83.1	%
Risk-free interest rate		2.7	%		1.0	%
Expected term (in years)		5.97			6.04
Expected dividend yield		—			—
Fair value of common stock	$	3.64		$	23.61

Summary of option activity

A summary of option activity under the Plans and 2020 Plan during the nine months ended September 30, 2022 is as follows:

				Weighted
		Weighted		average
		average		remaining
	Number of	exercise price		contractual
	shares	per share		term (years)
Outstanding at January 1, 2022	2,005,756	$	11.26	8.50
Granted	543,900		3.64	9.45
Forfeited	(22,042)		12.20	—
Expired	(634)		17.96	—
Exercised	(17,221)		1.85	7.34
Outstanding at September 30, 2022	2,509,759		9.66	8.12
Exercisable at September 30, 2022	1,111,573		8.41	7.41