Stock-based compensation (Tables)

12 Months Ended

Dec. 31, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

A summary of the Company’s stock option activity is as follows:

	Number of Shares			Weighted Average Exercise Price		Weighted Remaining Contract Term (in years)		Aggregate Intrinsic Value (in thousands)
Balance as of December 31, 2021		1,688,789		$	8.69		9.0	$	1,651
Granted		3,112,681			0.90
Exercised		—			—
Forfeited/Expired		(1,492,818	)		8.06
Balance as of December 31, 2022		3,308,652		$	1.65		9.4	$	—
Exercisable and vested at December 31, 2022		493,804		$	4.52		8.8	$	—
Vested and expected to vest as of December 31, 2022		3,308,652		$	1.65		9.4	$	—

Schedule of Fair Value of Each Stock Option Award

The fair value of each stock option award is estimated on the grant-date using the Black-Scholes option pricing model. The inputs used below are subjective and require significant judgment to determine.

	Years Ended December 31,
	2022			2021
Expected term (in years)		6.0			5.7
Risk-free interest rate		3.2	%		0.8	%
Expected volatility		81.8	%		70.2	%
Dividend rate	—%			—%
Fair value of common stock	$	0.6		$	7.2

Schedule of Stock-Based Compensation Expense

The allocation of stock-based compensation expense was as follows (in thousands):

	Years Ended December 31,
	2022		2021
Research and development	$	638	$	2,545
General and administrative		1,333		1,573
Total stock-based compensation expense	$	1,971	$	4,118

At December 31, 2022, the unrecognized compensation cost related to outstanding time-based options was $2.0 million and is expected to be recognized as expense over approximately 3.2 years.