Stockholders' Equity (Tables)

3 Months Ended

Mar. 31, 2022

Equity [Abstract]

Summary of Stock Option Activity

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

	Shares Subject to Options			Weighted- Average Exercise Price Per Share		Weighted Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value (in thousands)
Options outstanding at December 31, 2021		3,947,025		$	4.58
Granted		1,749,800		$	3.86
Exercised		-		$	-
Forfeitures and cancellations		(482,063	)	$	4.85
Options outstanding at March 31, 2022		5,214,762		$	4.32		8.27	$	742
Options exercisable at March 31, 2022		1,868,381		$	4.22		7.13	$	497

(a)Aggregate intrinsic value in this table was calculated as the positive difference, if any, between the closing price per share of the Company’s common stock on March 31, 2022 of $3.15 and the price of the underlying options.

Summary of Non-cash Stock-based Compensation Expense

The non-cash stock-based compensation expense for all stock awards, net of forfeitures recognized as they occur, that was recognized in the condensed consolidated statements of operations is as follows (in thousands):

	Three Months Ended March 31,
	2022		2021
Research and development	$	544	$	474
General and administrative		754		570
Total	$	1,298	$	1,044

Summary of Reserved Shares of Common Stock for Future Issuance

Common stock reserved for future issuance at March 31, 2022 is as follows:

	March 31,		December 31,
	2022		2021
Stock options issued and outstanding		5,214,762		3,947,025
Warrants for common stock		1,366,141		1,366,141
Awards available under the 2018 Equity Incentive Plan		672,070		467,024
Employee stock purchase plan		1,064,214		769,658
Total		8,317,187		6,549,848