Stockholders' Equity (Tables)

6 Months Ended

Jun. 30, 2022

Summary of Warrant Activity and Changes in Warrants Outstanding

A summary of warrant activity and changes in warrants outstanding is presented below:

	Number of Shares Underlying Warrants		Weighted-Average Exercise Price Per Share		Weighted-Average Remaining Contractual Term (in years)
Balance at December 31, 2021		4,234,910	$	10.50		3.31
Issued		—	$	—		—
Forfeited		—	$	—		—
Exercised		—	$	—		—
Balance at June 30, 2022		4,234,910	$	10.50		2.82

Summary of Stock Option Activity

	Number of Options			Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)		Aggregate Intrinsic Value
Outstanding at December 31, 2021		6,444,744		$	5.28			$	613,190
Granted		2,139,718		$	1.80
Forfeited		(380,184	)	$	4.52
Exercised		—		$	—
Outstanding at June 30, 2022		8,204,278		$	4.40		8.5	$	148,560
Options vested and expected to vest as of June 30, 2022		8,204,278		$	4.40		8.5	$	148,560
Options vested and exercisable as of June 30, 2022		2,617,257		$	4.91		7.1	$	117,365

Summary of Restricted Stock Unit Activity

Restricted stock unit activity under Equity Incentive Plans is summarized as follows:

	Number of Restricted Stock Units			Weighted-Average Grant Date Fair Value
Outstanding at December 31, 2021		—		$	—
Granted		464,007		$	2.43
Forfeited		(13,610	)	$	2.43
Exercised		—		$	—
Outstanding at June 30, 2022		450,397		$	2.43
Units expected to vest as of June 30, 2022		450,397		$	2.43
Units vested as of June 30, 2022		—		$	—

Schedule of Assumptions Used to Determine Fair Value

The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of stock option grants, were as follows:

	Three Months Ended						Six Months Ended
	June 30,						June 30,
	2022			2021			2022			2021
Risk-free interest rate		3.2	%		1.1	%		2.0	%		0.8	%
Expected volatility		97.0	%		89.1	%		99.8	%		89.6	%
Expected term (in years)		5.9			6.0			6.1			6.2
Expected dividend yield		—	%		—	%		—	%		—	%

Summary of Share-Based Compensation Expense

Stock-based compensation expense recognized for all equity awards has been reported in the condensed consolidated statements of operations as follows (in thousands):

	Three Months Ended				Six Months Ended
	June 30,				June 30,
	2022		2021		2022		2021
Research and development	$	820	$	703	$	1,883	$	1,177
General and administrative		857		1,133		1,772		1,497
	$	1,677	$	1,836	$	3,655	$	2,674

Common Stock Reserved for Future Issuance

Common stock reserved for future issuance is as follows (in thousands):

	June 30, 2022
Common stock warrants		4,235
Common stock options issued and outstanding		8,204
Restricted stock unit awards		450
Common stock available for issuance under the Inducement Plan and 2019 Plan		2,104
		14,993