Stock-Based Compensation (Tables)

3 Months Ended

Mar. 31, 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 March 31,
(in thousands)	2022		2021
Research and development		315		733
General and administrative		538		1,464
Stock-based compensation expense	$	853	$	2,197

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

For the three months ended March 31, 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 March 31,
	2022	2021
Risk-free interest rate	1.63 – 2.43%	0.09 – 1.05%
Expected life in years	6.25	5.50 - 6.25
Expected volatility	74.49 - 76.27%	72.92 - 74.20%
Expected dividend yield	—%	—%

2.

Stock Option Activity under Stock Option Plan

Stock option activity under the Company’s stock option plans for the three months ended March 31, 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		2,690,000			0.69
Cancelled		(2,386,216	)		3.68
Outstanding, March 31, 2022		10,969,653		$	2.16		9.02	$	—
Options exercisable, March 31, 2022		3,394,055		$	3.35		7.86	$	—
Options exercisable, December 31, 2021		4,410,312		$	3.85		7.53	$	—
Options available for future grant		15,242,103

Summary of Unvested Restricted Stock

A summary of the status of unvested restricted stock for the three months ended March 31, 2022 is as follows:

	Number of Shares			Weighted-Average Grant Date Fair Value
Unvested, December 31, 2021		1,198,580		$	2.10
Vested		(27,819	)		3.16
Cancelled		(176,882	)		2.79
Unvested, March 31, 2022		993,879		$	1.95