Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 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	940,040	$	2.77
Exercised	—	$	—
Canceled	(106,970)	$	70.22
Options Outstanding at December 31, 2019	1,699,202	$	44.87	8.0
Options Vested and Expected to Vest at December 31, 2019	1,580,780	$	47.90	7.9
Options Exercisable at December 31, 2019	573,996	$	121.76	5.5
Shares Available for Grant Under the 2008 Plan	424,263

Summary of restricted stock activity

		Weighted
		Average
		Grant Date
		Fair Value
	Shares	(per share)
Outstanding and unvested at December 31, 2018	3,552	$	43.84
Granted	—	$	—
Vested	(2,220)	$	49.25
Canceled	(222)	$	34.83
Outstanding and unvested at December 31, 2019	1,110	$	34.83

Schedule of stock-based compensation expense

	2019		2018		2017
	(In thousands)
Research and development	$	2,053	$	3,874	$	6,693
General and administrative		2,498		4,207		5,619
Total stock-based compensation expense	$	4,551	$	8,081	$	12,312

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

	2019	2018	2017
Expected stock price volatility	90 - 91%	73 - 85%	75 - 77%
Expected option term	6.0 Years	6.0 Years	6.0 Years
Risk-free interest rate	1.6 - 2.5%	2.8 - 3.1%	2.0 - 2.3%
Expected dividend yield	None	None	None