Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2018

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, 2017	723,747	$	141.00	6.1
Granted	338,517	$	9.11
Exercised	(6,967)	$	42.00
Canceled	(189,165)	$	125.38
Options Outstanding at December 31, 2018	866,132	$	93.70	7.1
Options Vested and Expected to Vest at December 31, 2018	846,352	$	95.47	7.0
Options Exercisable at December 31, 2018	426,612	$	162.83	5.1
Shares Available for Grant Under the 2008 Plan	356,913

Summary of restricted stock activity

		Weighted
		Average
		Grant Date
		Fair Value
	Shares	(per share)
Outstanding and unvested at December 31, 2017	6,445	$	44.70
Granted	—	$	—
Vested	(2,449)	$	47.94
Canceled	(444)	$	34.83
Outstanding and unvested at December 31, 2018	3,552	$	43.84

Schedule of stock-based compensation expense

	2018		2017		2016
	(In thousands)
Research and development	$	3,874	$	6,693	$	7,821
General and administrative		4,207		5,619		7,496
Total stock-based compensation expense	$	8,081	$	12,312	$	15,317

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

	2018	2017	2016
Expected stock price volatility	73 - 85%	75 - 77%	70 - 77%
Expected option term	6.0 Years	6.0 Years	6.0 Years
Risk-free interest rate	2.8 - 3.1%	2.0 - 2.3%	1.4 - 2.3%
Expected dividend yield	None	None	None