Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Stock-based Compensation

Assumptions used in the black-Scholes model

	Year ended
	December 31, 2021	December 31, 2020
Risk-free interest rate	0.73% - 1.29%	0.13% - 1.48%
Expected volatility	84.07% - 93.37%	90.43% - 94.0%
Expected term (in years)	5.50 - 7.00	5.50 - 7.00
Expected dividend yield	0%	0%

Allocation of Stock-Based Compensation Expenses

	Year Ended December 31,
	2021		2020
Research and development	$	1,505,000	$	1,252,000
General and administrative		1,377,000		2,223,000
Total stock-based compensation	$	2,882,000	$	3,475,000

Summary of Stock Option Activity

	Options Outstanding
				Weighted
				Average
		Weighted		Remaining
		Average		Contractual	Aggregate
		Exercise		Term	Intrinsic
	Shares	Price		(Years)	Value
Outstanding at December 31, 2020	1,668,926	$	6.30	8.32		—
Granted	856,150		4.77			—
Exercised	(99,517)		3.24		$	121,000
Forfeited/Cancelled	(15,877)		42.20			—
Outstanding at December 31, 2021	2,409,682	$	5.64	8.00	$	3,630,000
Vested and expected to vest at December 31, 2021	2,409,682	$	5.64	8.00	$	3,630,000
Exercisable at December 31, 2021	829,624	$	8.67	6.90	$	1,564,000

Schedule of restricted stock awards

		Weighted Avg
		Grant Date
	Shares	Fair Value
Outstanding at December 31, 2020	322,756	$	19.55
Granted	—		—
Forfeited/Cancelled	(1,047)		6.89
Vested and Issued as Common Stock	(167,691)		20.29
Outstanding at December 31, 2021	154,018	$	27.49

Shares Reserved for Future Issuance

	Shares Reserved
Stock options outstanding	2,409,682
Unvested restricted stock units	30,000
Employee stock purchase plan	9,748
Available for future grants under the 2016 Plan	228,797
Warrants outstanding	16,647,219
Total shares reserved	19,325,446