Equity (Tables)

9 Months Ended

Sep. 30, 2022

Equity [Abstract]

Summary of Stock-based Compensation Expense

Stock-based compensation expense is classified in the condensed statements of operations as follows:

(in thousands)	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Research and development expenses	$	973	$	1,423	$	3,288	$	3,850
General and administrative expenses	1,058		1,787		3,501		4,698
Total stock-based compensation expense	$	2,031	$	3,210	$	6,789	$	8,548

Schedule of Weighted Average Assumptions

The fair values of stock options granted are estimated using the Black-Scholes option pricing model with the following weighted average assumptions:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2022		2021		2022		2021
Expected volatility	84.18	%	89.17	%	83.80	%	89.18	%
Expected dividends	0	%	0	%	0	%	0	%
Expected terms (years)	6.08		6.07		6.04		6.03
Risk free rate	2.83	%	0.83	%	2.63	%	0.89	%

Schedule of Stock Option Activity

A summary of the Company’s stock option activity and related information for the nine months ended September 30, 2022 is as follows:

	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Life  (in Years)	Aggregate Intrinsic Value (in Thousands)
Outstanding at December 31, 2021	8,963,945	$	7.20	8.32	$	6,912
Options granted	3,360,450	$	1.34
Options exercised	(36,500)	$	3.67
Options cancelled/forfeited	(2,871,996)	$	7.86
Outstanding at September 30, 2022	9,415,899	$	4.92	8.30	$	—
Exercisable as of September 30, 2022	3,729,902	$	6.04	7.16	$	—

Summary of RSU Activity

A summary of the Company’s RSU activity and related information for the nine months ended September 30, 2022 is as follows:

	Number of Shares	Weighted Average Grant Date Fair Value
Non-vested at December 31, 2021	132,000	$	9.97
Restricted stock units granted	700,000	$	3.69
Restricted stock units vested	(24,750)	$	12.20
Restricted stock units forfeited	(353,000)	$	4.86
Non-vested at September 30, 2022	454,250	$	4.14