Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2023

Stock-Based Compensation

Schedule of stock-based compensation expense

	Three Months Ended September 30,				Nine Months Ended September 30,
	2023		2022		2023		2022
Research and development expense	$	548	$	594	$	1,670	$	1,827
General and administrative expense		1,313		1,277		3,782		4,782
Total stock-based compensation expense	$	1,861	$	1,871	$	5,452	$	6,609

Summary of stock option activity

				Weighted
				Average
				Remaining	Aggregate
		Weighted		Contractual	Intrinsic
	Number of	Average		Term	Value (1)
	Stock Options	Exercise Price		(In years)	(In thousands)
Outstanding as of December 31, 2022	4,960,553	$	8.04	8.59	$	89
Granted	3,738,555	$	2.75
Exercised	(2,757)	$	2.82
Cancelled/forfeited	(872,873)	$	6.77
Outstanding as of September 30, 2023	7,823,478	$	5.66	8.54	$	-
Exercisable as of September 30, 2023	2,768,685	$	7.19	7.66	$	-

Schedule of assumptions used in determining fair value of options granted

	Nine Months Ended September 30,
	2023			2022
Risk-free interest rate		3.57 - 4.40	%		1.47 – 3.63	%
Expected dividend yield		0	%		0	%
Expected term (in years)		5.50 - 6.08			5.27 – 6.08
Expected volatility		81.69 - 87.32	%		80.75 – 87.64	%

Summary of restricted stock activity

	Number	Weighted
	of Shares	Average
	of Restricted	Grant Date
	Stock	Fair Value
Unvested as of December 31, 2022	46,160	$	5.51
Vested	(31,793)	$	5.51
Canceled/Forfeited	(1,293)	$	5.51
Unvested as of September 30, 2023	13,074	$	5.51