Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2019

Stock-Based Compensation

Summary of stock option activity

		Weighted		Weighted
		Average		Average
		Exercise		Remaining
		Price		Contractual
	Shares	Per Share		Term (In Years)
Options Outstanding at December 31, 2018	866,132	$	93.70	7.1
Granted	863,290		2.78
Exercised	—		—
Canceled	(39,348)		131.86
Options Outstanding at June 30, 2019	1,690,074		46.37	8.4
Options Vested and Expected to Vest at June 30, 2019	1,538,046		50.45	8.3
Options Exercisable at June 30, 2019	529,136		132.85	5.7
Shares Available for Grant Under the 2008 Plan	433,391

Schedule of stock-based compensation expense

	Three months ended June 30,				Six months ended June 30,
	2019		2018		2019		2018
	(In thousands)				(In thousands)
Research and development	$	654	$	978	$	1,410	$	2,289
General and administrative		810		1,070		1,747		2,247
Total stock-based compensation expense	$	1,464	$	2,048	$	3,157	$	4,536

Schedule of assumptions used for the fair value of employee stock options granted

	Three months ended June 30,		Six months ended June 30,
	2019	2018	2019	2018
Expected stock price volatility	91%	85%	91%	73 - 85%
Expected option term	6.0 Years	6.0 Years	6.0 Years	6.0 Years
Risk-free interest rate	1.9 – 2.4%	2.9%	1.9 – 2.5%	2.8 – 3.0%
Expected dividend yield	None	None	None	None