Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2018

Schedule of stock-based compensation expense attributable to share-based payments made to employees and directors and included in operating expenses


	Three Months Ended				Six Months Ended
	June 30,				June 30,
(in thousands)	2018		2017		2018		2017
Stock-based compensation:
Research and development
Employee Stock Purchase Plans	$	29	$	20	$	51	$	42
Equity Incentive Plans		520		4,627		1,076		5,341
	$	549	$	4,647	$	1,127	$	5,383
General and administrative
Employee Stock Purchase Plans	$	18	$	11	$	32	$	30
Equity Incentive Plans		971		1,100		1,968		2,129
	$	989	$	1,111	$	2,000	$	2,159
Total stock-based compensation expense	$	1,538	$	5,758	$	3,127	$	7,542

Schedule of weighted average assumptions applied to options


	Six Months Ended
	June 30,
	2018		2017
Average risk free interest rate		2.2%		1.7%
Expected dividend yield		—		—
Expected lives (years)		3.9		4.0
Expected volatility		75.6%		86.9%
Weighted average exercise price (per share)	$	17.42	$	12.80

Schedule of information related to outstanding and exercisable options


($ in thousands, except per share data)	Stock Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Life (in years)	Aggregate Intrinsic Value
Outstanding at December 31, 2017	2,675,184	$	23.52	6.5	$	5,805
Granted	569,199		17.42
Exercised	(858)		12.77
Forfeited	(162,420)		19.04
Expired	(126,030)		55.07
Outstanding at June 30, 2018 (1)	2,955,075	$	21.25	6.6	$	1,191
Exercisable at June 30, 2018	1,901,703	$	22.98	5.4	$	1,190

(1)

Includes both vested stock options as well as unvested stock options for which the requisite service period has not been rendered but that are expected to vest based on achievement of a service condition.