Stock-based compensation (Tables)

3 Months Ended

Mar. 31, 2024

Stock-based compensation

Summary of stock option activity and related information

A summary of the Company’s stock option activity and related information for the three months ended March 31, 2024 is as follows:

	Shares	Weighted-average exercise price per share		Weighted-average remaining contractual term (years)	Aggregate intrinsic value (in thousands)
Outstanding at December 31, 2023	2,270,359	$	19.81	7.8	$	559
Granted	31,751		9.77
Exercised	(4,600)		7.97
Forfeited/cancelled	(151,695)		12.89
Expired	(22,914)		163.77
Cancelled under the Option Exchange Program	(603,330)		30.58
Granted under the Option Exchange Program	603,330		11.44
Outstanding at March 31, 2024	2,122,901	$	13.18	8.7	$	4,539
Vested at March 31, 2024	565,008	$	20.83	7.3	$	1,084

Schedule of assumptions used to estimate fair value of each stock option on grant date

The fair value of each stock option granted during the three months ended March 31, 2024 and 2023 was estimated on the grant date using the Black-Scholes option-pricing model using the following weighted-average assumptions:

	Three months ended March 31,
	2024		2023
Risk-free interest rate	4.08	%	3.56	%
Volatility	95	%	90	%
Dividend yield	—		—
Expected term (years)	5.8		6.2

Schedule of restricted stock units

A summary of the Company’s restricted stock unit activity and related information for the three months ended March 31, 2024 is as follows:

	Shares	Weighted-average grant date fair value per share
Outstanding at December 31, 2023	209,289	$	18.05
Granted	254,574	$	10.00
Vested	(14,279)	$	25.97
Forfeited/cancelled	(23,192)	$	18.12
Outstanding at March 31, 2024	426,392	$	12.98

Schedule of assumptions used to estimate fair value of each employee stock purchase plan on grant date

	Three months ended March 31,
	2024		2023
Risk-free interest rate	5.24	%	4.77	%
Volatility	60	%	106	%
Dividend yield	—		—
Expected term (years)	0.5		0.5