Stock-based Compensation (Tables)

3 Months Ended

Mar. 31, 2022

Stock-based Compensation [Abstract]

Stock Option Activity

The following table summarizes stock option activity for the three months ended March 31, 2022:

	Number of shares			Weighted average exercise price per share		Weighted average remaining contractual term (years)
Outstanding at January 1, 2022		3,938,613		$	1.90
Granted		860,000		$	1.45
Exercised		(15,000	)	$	1.29
Forfeited and expired		(348,899	)	$	2.97
Outstanding at March 31, 2022		4,434,714		$	1.73		8.8
Exercisable at March 31, 2022		1,396,863		$	1.94		7.5

Weighted Average Assumption Used for Grant Date Fair Value of Option Grants

For the three months ended March 31, 2022, the fair value of each option was estimated on the date of grant using the weighted average assumptions in the table below:

Expected volatility	89.6	%
Risk‑free interest rate	2.4	%
Expected life (in years)	6.1
Expected dividend yield	0.0	%

Summary of Restricted Stock Unit Unvested

Restricted stock units have been issued to certain board members. Restricted stock units unvested are summarized in the following table:

	Number of shares			Weighted average grant date fair value
Unvested at January 1, 2022		90,540		$	1.45
Granted		9,141		$	1.47
Vested		(10,000	)	$	1.45
Unvested at March 31, 2022		89,681		$	1.45