Equity (Tables)

6 Months Ended

Jun. 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 June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Research and development expenses	$	1,051	$	1,409	$	2,315	$	2,427
General and administrative expenses	1,261		1,509		2,443		2,911
Total stock-based compensation expense	$	2,312	$	2,918	$	4,758	$	5,338

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 June 30,				Six Months Ended June 30,
	2022		2021		2022		2021
Expected volatility	82.68	%	89.12	%	83.01	%	89.19	%
Expected dividends	0	%	0	%	0	%	0	%
Expected terms (years)	5.73		5.94		5.96		5.95
Risk free rate	2.77	%	1.07	%	2.22	%	1.00	%

Schedule of Stock Option Activity

A summary of the Company’s stock option activity and related information for the six months ended June 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	1,079,700	$	2.06
Options exercised	(36,500)	$	3.67
Options cancelled/forfeited	(2,368,752)	$	7.87
Outstanding at June 30, 2022	7,638,393	$	6.29	8.11	$	4
Exercisable as of June 30, 2022	3,189,117	$	6.08	7.20	$	—

Summary of RSU Activity

A summary of the Company’s RSU activity and related information for the six months ended June 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	(10,000)	$	12.49
Restricted stock units forfeited	(219,000)	$	5.13
Non-vested at June 30, 2022	603,000	$	4.39