Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2021

Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]

Summary of All Option Activity Under 2007 Plan, 2014 Plan, 2020 Plan and Inducement Grants

The following table summarizes all option activity under the 2007 Plan, 2014 Plan, 2020 Plan and inducement grants:

	Shares Issuable Under Options			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)
Outstanding as of January 1, 2020		91,403		$	139.96		8.2	$	—
Granted		2,191,462			9.15
Options Assumed		1,346,398			7.58
Forfeited / Canceled		(7,784	)		586.16
Outstanding as of December 31, 2020		3,621,479			10.63		8.9	$	—
Granted		702,836			10.69
Exercised		(174	)		4.73
Forfeited / Canceled		(110,164	)		19.50
Outstanding as of December 31, 2021		4,213,977		$	10.33		8.4	$	—
Options vested and expected to vest as of December 31, 2021		4,132,506		$	10.18		8.2	$	—
Options exercisable as of December 31, 2021		1,871,327		$	11.64		7.8	$	—

Schedule of Assumptions Used in Black-Scholes Option Pricing Model to Determine the Fair Value of Stock Options Granted

The following table presents the assumptions used in the Black-Scholes option pricing model to determine the fair value of stock options granted in the periods presented, as follows:

	Year Ended December 31,
	2021	2020
Expected stock price volatility	105% - 110%	74% - 87%
Risk-free interest rate	1%	1% - 3%
Expected life of option (in years)	6.25 - 6.75	6
Estimated dividend yield	0%	0%

Summary of RSU Activity

The following table shows the RSU activity, as follows:

	Shares Issuable Under RSUs			Weighted Average Exercise Price		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
						(In years)
Outstanding as of January 1, 2020		3,056		$	66.96		9.2	$	—
Granted		—			—
RSUs Vested		(3,056	)		66.96		9.2
Forfeited / Canceled		—			—
Outstanding as of December 31, 2020		—			—		—		—
Granted		20,000			5.07		9.8
RSUs Vested		—			—
Forfeited / Canceled		—			—
Outstanding as of December 31, 2021		20,000		$	5.07		9.8	$	—
RSUs vested and expected to vest as of December 31, 2021		20,000		$	5.07		9.8	$	—
RSUs exercisable as of December 31, 2021		—		$	—			$	—

Schedule of Stock-Based Compensation Expense Related to Stock-Based Awards

Total compensation expense related to all of the Company’s stock-based awards for the years ended December 31, 2021 and 2020 was comprised of the following (in thousands):

	Year Ended December 31,
	2021		2020
Stock-based compensation classified as:
Research and development expense	$	3,166	$	1,254
General and administrative expense		4,738		1,917
Total stock-based compensation expense	$	7,904	$	3,171