Stock-Based Compensation Plan (Tables)

6 Months Ended

Jun. 30, 2019

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The Company utilized the Black-Scholes valuation model for estimating the fair value of the stock options granted, with the following weighted-average assumptions for options granted in the six months ended June 30, 2019 and 2018, respectively:

	2019		2018
Risk-free interest rate	2.23	%	2.69	%
Expected volatility	126	%	90	%
Expected term in years	6.0		6.1
Dividend yield	—	%	—	%

Warrant [Member]

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The following summary represents option activity under the Company’s stock-based compensation plans for the six months ended June 30, 2019:

		Weighted-
		Average
		Exercise
	Options	Price
	(in thousands)
Outstanding at December 31, 2018	37	$	112.60
Granted	35		18.40
Cancelled	(1)		41.33
Outstanding at June 30, 2019	71		67.18
Exercisable at June 30, 2019	22	$	145.97