Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

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Stock-Based Compensation Expense on All Employee and Non-Employee Awards

The Company recognized stock-based compensation expense on all employee and non-employee awards as follows:

	For the Three Months Ended June 30,				For the Six Months Ended June 30,
(in thousands)	2022		2021		2022		2021
Research and development		214		847		528		1,580
General and administrative		776		4,443		1,315		5,906
Stock-based compensation expense	$	990	$	5,290	$	1,844	$	7,486

Fair Value of Stock Options Assumptions Using Black-Scholes Option Valuation Model

For the three and six months ended June 30, 2022 and 2021, the fair value of stock options was estimated on the date of grant using a Black-Scholes option valuation model with the following assumptions:

	For the Three Months Ended June 30,				For the Six Months Ended June 30,
	2022	2021			2022	2021
Risk-free interest rate	2.83 – 3.54%		1.15	%	1.63 – 3.54%	0.09 – 1.15%
Expected life in years	5.27 - 6.25	6.25			5.27 - 6.25	5.50 - 6.25
Expected volatility	78.58 - 82.97%		74.08	%	74.49 - 82.97%	72.92 - 74.80%
Expected dividend yield	—%	—%			—%	—%

Stock Option Activity under Stock Option Plan

Stock option activity under the Company’s stock option plans for the six months ended June 30, 2022 is as follows:

(in thousands, except share and per share data)	Number of Shares			Weighted- Average Exercise Price		Weighted- Average Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding, December 31, 2021		10,665,869		$	2.87
Granted		3,382,500			0.71
Cancelled		(3,961,735	)		3.33
Outstanding, June 30, 2022		10,086,635		$	1.97		8.95	$	1,611
Options exercisable, June 30, 2022		2,955,111		$	3.28		7.87	$	89
Options exercisable, December 31, 2021		4,410,312		$	3.85		7.53	$	—
Options available for future grant		15,780,200

Summary of Unvested Restricted Stock

A summary of the status of unvested restricted stock for the six months ended June 30, 2022 is as follows:

	Number of Shares			Weighted-Average Grant Date Fair Value
Unvested, December 31, 2021		1,198,580		$	2.10
Granted		280,000			0.82
Vested		(85,991	)		3.87
Cancelled		(232,901	)		3.15
Unvested, June 30, 2022		1,159,688		$	1.45

At June 30, 2022, total unrecognized compensation costs related to unvested restricted stock outstanding amounted to $1.4 million. The cost is expected to be recognized over a weighted-average period of 1.92 years.