Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Share-based Payment Arrangement [Abstract]

Summary of Stock Option and Award Activity Excluding Inducement Grants

The following table summarizes option and award activity under the 2012 Plan and the 2014 Plan for the fiscal years ended December 31, 2018 and 2019:

	Shares Available for Grant		Outstanding Number of Shares		Weighted- Average Exercise Price per Share		Weighted- Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value
Balance at January 1, 2018	29,571		99,029		$	25.33	8.46
Additional shares reserved	1,225,223		—		$	—
Options granted	(1,212,200	)	1,212,200		$	4.24
Options canceled/forfeited	15,072		(15,072	)	$	12.38
Shares expired under 2012 Plan	(1,867	)	—		$	—
Balance at December 31, 2018	55,799		1,296,157		$	5.75	9.23	$	—
Additional shares reserved	419,056		—		$	—
Options granted	(503,950	)	503,950		$	3.27
Options canceled/forfeited/expired	93,914		(93,914	)	$	6.03
Shares expired under 2012 Plan	(1,415	)	—		$	—
Balance at December 31, 2019	63,404		1,706,193		$	5.00	7.59	$	—
Exercisable at December 31, 2019			571,852		$	6.86	7.41	$	—

Summary of Company's Inducement Grant Stock Option Activities

The following table summarizes the Company’s inducement grant stock option activities:

	Outstanding Number of Shares		Weighted- Average Exercise Price per Share		Weighted-Average Remaining Contractual Term (In Years)	Aggregate Intrinsic Value
Balance at January 1, 2018	19,350		$	19.12	8.91	$	—
Options granted	—		$	—
Options canceled/forfeited	(5,513	)	$	15.40
Balance at December 31, 2018	13,837		$	20.60	4.52	$	—
Options granted	550,000		$	1.89
Options canceled/forfeited/expired	(9,723	)	$	17.81
Balance at December 31, 2019	554,114		$	2.08	9.76	$	—
Exercisable at December 31, 2019	3,228		$	27.20	3.77	$	—

Summary of Stock-Based Compensation Expense

Total stock-based compensation expense recognized was as follows:

	Year Ended December 31, 2019		Year Ended December 31, 2018
	(in thousands)
Research and development	$	742	$	529
General and administrative	870		649
Total	$	1,612	$	1,178

Schedule of Weighted-Average Assumptions for the Black-Scholes Option-Pricing Model Used in Determining the Fair Value of Options Granted to Employees

The following table presents the weighted-average assumptions for the Black-Scholes option-pricing model used in determining the fair value of options granted to employees:

	Year Ended December 31, 2019	Year Ended December 31, 2018
Dividend yield	—%	—%
Risk-free interest rate	1.60% - 2.66%	2.46% - 3.11%
Expected volatility	106.33%-107.76%	89%
Expected term (years)	5.96 - 6.08	6.08