Stock Options, Restricted Stock and Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2022

Share-Based Payment Arrangement [Abstract]

Schedule of Stock Option Activity

On July 14, 2021, the Company’s 2021 Equity Incentive Plan, or the 2021 Plan, was approved by the Company’s stockholders, and became effective upon completion of the IPO and serves as the successor to the 2015 Plan. There are 2,054,000 shares of common stock reserved for issuance under the 2021 Plan and 1,854,464 shares remained available for grants as of June 30, 2022. Stock option activity is summarized as follows:

	NUMBER OF STOCK OPTIONS			WEIGHTED- AVERAGE EXERCISE PRICE
Outstanding as of December 31, 2021		4,783,333		$	2.34
Granted		1,222,400			4.23
Cancelled, forfeited or expired		(30,273	)		4.19
Exercised		(324,675	)		1.46
Outstanding as of June 30, 2022		5,650,785		$	2.79
Exercisable as of June 30, 2022		2,410,505		$	2.11
Unvested as of June 30, 2022		3,240,280		$	3.30

Schedule of Fair Value of Stock Options Granted Was Estimated on Black-Scholes Options

The fair value of stock options granted was estimated on the grant date using the Black-Scholes option pricing model based on the following weighted-average assumptions:

	SIX MONTHS ENDED JUNE 30,
	2022			2021
Expected option life (years)	6.02 - 6.08			5.00 - 6.25
Risk-free interest rate	1.69% - 3.03%			0.89% - 1.12%
Expected volatility	85.09% - 86.09%			85.87% - 89.02%
Expected dividend yield		0	%		0	%
Exercise price	$3.24 - $5.19			$4.97 - $6.64
Fair value of common stock	$3.24 - $5.19			$4.97 - $6.64

Schedule of Stock-based Compensation Expense

Stock-based compensation expense for the three and six months ended June 30, 2022 and 2021 was classified in the condensed consolidated statements of operations as follows:

	THREE MONTHS ENDED June 30,				SIX MONTHS ENDED JUNE 30,
	2022		2021		2022		2021
Research and development	$	57	$	400	$	199	$	516
General and administrative	381		669		730		984
Total stock-based compensation expense	$	438	$	1,069	$	929	$	1,500