Share-based compensation (Tables)

9 Months Ended

Sep. 30, 2023

Share-based compensation

Schedule of stock-based compensation expense

Share-based compensation expense recorded for stock options and restricted stock awards 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,
	2023		2022		2023		2022
Research and development	$	466	$	480	$	1,323	$	1,387
General and administrative		617		860		2,017		2,590
	$	1,083	$	1,340	$	3,340	$	3,977

Schedule of 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,
	2023			2022
Expected volatility		88.5	%		85.6	%
Risk-free interest rate		3.8	%		2.7	%
Expected term (in years)		6.03			5.97
Expected dividend yield		—			—
Fair value of common stock	$	4.87		$	3.64

Schedule of option activity

A summary of option activity under the 2020 Plan and prior Plans during the nine months ended September 30, 2023 was as follows:

		Weighted
		average
	Number of	exercise price
	shares	per share
Outstanding at January 1, 2023	2,519,405		9.60
Granted	658,900		4.87
Forfeited	(98,216)		11.56
Expired	(55,670)		16.59
Outstanding at September 30, 2023	3,024,419		8.38
Exercisable at September 30, 2023	1,669,562		8.76