Share-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2019

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Summary of Stock Option Activity

The following table summarizes stock option activity for the year ended December 31, 2019:

	Number of Options			Weighted- Average Exercise Price		Weighted- Average Remaining Contractual Term (Years)		Aggregate Intrinsic Value
Outstanding — January 1, 2019		972,569		$	23.85		8.46	$	—
Granted		651,600		$	1.06
Exercised		—			—
Forfeited or expired		(724,166	)	$	18.54
Outstanding — December 31, 2019		900,003		$	11.63		8.52	$	—
Exercisable — December 31, 2019		401,453		$	23.14		7.71	$	—

Calculation of Fair Value Assumptions Using Black Scholes Option Model

The estimated fair values of employee stock options granted during the year ended December 31, 2019 and 2018, were determined on the date of grant using the Black-Scholes option-pricing model with the following assumptions:

	For the year ended December 31,
	2019	2018
Expected option life (years)	6.02		5.58	%
Risk-free interest rate	2.22%		2.77	%
Expected volatility	74.14%		79.67	%
Expected dividend yield	0%		0	%

Stock-Based Compensation Expense

The following table presents total stock-based compensation expense for the years ended December 31, 2019 and 2018, respectively:

	For the years ended December 31,
	2019		2018
Research and development	$	156	$	970
General and administrative		1,910		2,003
Total stock-based compensation expense	$	2,066	$	2,973