Equity Incentive Plans (Tables)

3 Months Ended

Mar. 31, 2022

Equity Incentive Plans

Summary of stock option activity under the Equity Plans

		Weighted
		Average		Weighted		Aggregate
		Exercise Price		Average Remaining		Intrinsic
	Options	Per Share		Life in Years		Value
Outstanding at December 31, 2021	8,525,618	$	4.48	7.58	$	7,673
Granted	650,000	$	1.97
Forfeited	(74,111)	$	2.11
Outstanding at March 31, 2022	9,101,507	$	4.32	7.45	$	697
Options exercisable at March 31, 2022	5,983,001	$	5.48	6.73	$	514
Options vested and expected to vest at March 31, 2022	9,101,507	$	4.32	7.45	$	697

Schedule of assumptions used to determine grant-date fair value of stock options

	Three Months		Three Months
	Ended March 31,		Ended March 31,
	2022		2021
Expected volatility	82.70	%	66.94	%
Weighted average risk-free interest rate	1.67	%	0.66	%
Expected dividend yield	0.00	%	0.00	%
Expected term (in years)	6.01		6.86

Summary of RSU activity under the 2016 Plan

		Weighted
		Average Grant
	Number of Shares	Date Fair Value
Outstanding at December 31, 2020	753,106	$	1.52
Awarded	275,000	$	2.57
Settled in cash	(92,500)	$	1.97
Outstanding at December 31, 2021	935,606	$	1.76
Awarded	2,575,000	$	1.94
Outstanding at March 31, 2022	3,510,606	$	1.89

Schedule of recognized stock-based compensation expense related to the issuance of stock option awards and RSUs to employees and non-employees in the condensed consolidated statements of operations

	Three Months Ended March 31,
	2022		2021
Research and development	$	554	$	345
General and administrative		650		488
Total	$	1,204	$	833