Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2020

Stock-Based Compensation

Schedule of compensation expense

	Nine Months Ended September 30,
(In thousands)	2020		2019
Research and development	$	123	$	359
General and administrative		5,562		4,961
Share-based compensation expense	$	5,685	$	5,320

Schedule of weighted-average assumptions used in valuing the stock options

	Nine Months Ended September 30,
	2020		2019
Expected volatility	77.71	%	77.36	%
Range of expected volatility	75.84% to 81.63	%	75.50% to 84.48	%
Range of risk free interest rate	0.31% to 1.77	%	1.62% to 2.59	%
Expected term of option	6.03	years	6.05	years
Expected dividend yield	0.00	%	0.00	%

Schedule of stock option plans and of changes in options outstanding under the plans

		Weighted Average
	Number of Options	Exercise Price
Outstanding at January 1, 2020	18,268,372	$	2.58
Exercised	(2,789,473)	$	1.39
Granted	1,245,686	$	2.92
Expired	(110,430)	$	4.96
Forfeited	(658,125)	$	3.89
Outstanding at September 30, 2020	15,956,030	$	2.75
Vested and expected to vest at September 30, 2020	15,956,030	$	2.75
Exercisable at September 30, 2020	9,153,348	$	2.35