Stockholders' Equity (Deficit) (Tables)

12 Months Ended

Dec. 31, 2022

Equity [Abstract]

Summary of Stock Based Compensation Expense

Stock compensation expense was allocated between departments as follows (in thousands):

	Year ended
	December 31, 2022		December 31, 2021
Research and development	$	692	$	734
General and administrative		1,838		2,542
Total	$	2,530	$	3,276

Schedule of Fair Value of Award Granted Using Black-Scholes Option Pricing Model

The fair value of each award granted was estimated on the date of grant using the Black-Scholes option pricing model with the following assumptions:

	Year Ended
	December 31, 2022	December 31, 2021
Expected life (years)	5.5-6.0	5.5-6.0
Risk-free interest rate	1.7%-3.1%	0.6%-1.4%
Volatility	88%-95%	89%-108%
Dividend rate	—  %	—  %

Summary of Stock Option and Restricted Stock Unit Transactions

The following table summarizes stock option and restricted stock unit transactions for the years ended December 31, 2022 and 2021 as issued under the 2014 Plan and the Inducement Plan:

	Number of Options			Weighted- Average Exercise Price per		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value
	Outstanding			Share		(in years)		(in thousands)
Balance at December 31, 2020		189,142		$	62.63		7.62
Options granted		230,854			31.95
Options canceled/forfeited		(11,667	)		28.65
Balance at December 31, 2021		408,329		$	46.28		7.94
Options granted		283,919			3.56
Options canceled/forfeited		(5,674	)		19.31
Balance at December 31, 2022		686,574		$	28.83		7.93	$	—
Options exercisable at December 31, 2022		357,573		$	39.54		7.21	$	—
Options vested and expected to vest at    December 31, 2022		663,616		$	28.67		7.93	$	—

Summary of Restricted Stock Unit Transactions

The following table summarizes restricted stock unit transactions for the years ended December 31, 2022 and 2021 as issued under the 2014 Plan:

	Number of Restricted Stock Units			Weighted- Average Grant-Date Fair Value per Share
Outstanding at December 31, 2020		38,733		$	57.75
Restricted stock units granted		11,863			15.75
Restricted stock units vested		(21,546	)		34.65
Outstanding at December 31, 2021		29,050		$	57.75
Restricted stock units granted		8,965			5.33
Restricted stock units vested		(18,646	)		32.55
Restricted stock units cancelled/forfeited		(301	)		57.85
Outstanding at December 31, 2022		19,068		$	57.75