Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2022

Stock-Based Compensation [Abstract]

Stock Option Activity

The following table summarizes stock option activity for the years ended December 31, 2022 and 2021:

	Number of Shares under Option Plan			Weighted- Average Exercise Price per Option		Weighted- Average Remaining Contractual Life (in years)
Outstanding at January 1, 2021		5,292,888		$	1.87
Granted		2,463,714			1.70
Exercised		(1,557,628	)		1.12
Forfeited and expired		(2,260,361	)		2.10
Outstanding at December 31, 2021		3,938,613		$	1.90		7.91
Granted		1,000,000			1.41
Exercised		(15,000	)		1.29
Forfeited and expired		(448,899	)		2.63
Outstanding at December 31, 2022		4,474,714		$	1.72		8.02
Exercisable at December 31, 2022		2,202,792		$	1.88		7.28

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

For the years ended December 31, 2022 and 2021, the grant date fair value of all option grants was estimated at the time of grant using the Black-Scholes option-pricing model using the following weighted average assumptions:

	Year Ended December 31,
	2022			2021
Expected term (in years)		6.10			5.96
Expected volatility		89.57	%		90.03	%
Risk-free rate		2.51	%		1.08	%
Dividend rate		0.00	%		0.00	%

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 Units			Weighted- Average Grant Date Fair Value
Outstanding at January 1, 2021		—		$	—
Granted		290,861			1.44
Vested		(146,364	)		1.42
Forfeited and expired		(53,957	)		1.45
Unvested at December 31, 2021		90,540		$	1.45
Granted		187,464			0.96
Vested		(158,407	)		1.26
Forfeited and expired		—			—
Unvested at December 31, 2022		119,597		$	0.93