Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2015

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-Based Compensation Expense for Options Granted, Restricted Stock and Stock Purchase Rights as Reflected in Statement of Operations

Stock-based compensation expense for options granted and restricted stock awards (“RSAs”) is reflected in the consolidated statement of operations as follows:

	THREE MONTHS ENDED   JUNE 30,				SIX MONTHS ENDED   JUNE 30,
(in thousands)	2015		2014		2015		2014
Research and development	$	583	$	237	$	1,094	$	852
General and administrative	2,893		2,145		5,123		3,452
Total	$	3,476	$	2,382	$	6,217	$	4,304

Schedule of Stock Options Activity

The following table summarizes the stock option activity under the Plans:

	NUMBER OF SHARES		WEIGHTED AVERAGE EXERCISE PRICE		AGGREGATE INTRINSIC VALUE
					(000’s)
Options outstanding at December 31, 2014	3,826,459		$	8.39	$	79,792
Granted	921,400		27.09		—
Exercised	(83,270	)	1.46		—
Canceled	(62,758	)	13.66		—
Options outstanding at June 30, 2015	4,601,831		$	12.14	$	25,356
Options exercisable at June 30, 2015	1,962,997		$	6.45	$	21,986

Restricted Stock and Restricted Stock Units Activity

The following table summarizes the RSA activity under the Plans:

	NUMBER OF SHARES		WEIGHTED AVERAGE FAIR VALUE PER SHARE
RSAs outstanding at December 31, 2014	103,064		$	2.47
Granted	99,027		28.00
Vested	(46,539	)	2.74
Canceled	(1,538	)	32.30
RSAs outstanding at June 30, 2015	154,014		$	18.50