Stock-based Compensation (Tables)

6 Months Ended

Jun. 30, 2016

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 statements of operations as follows:

	THREE MONTHS ENDED   JUNE 30,				SIX MONTHS ENDED   JUNE 30,
(in thousands)	2016		2015		2016		2015
Research and development	$	814	$	583	$	1,526	$	1,094
General and administrative	3,067		2,893		5,889		5,123
Total	$	3,881	$	3,476	$	7,415	$	6,217

Schedule of Stock Options Activity

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

	NUMBER OF SHARES		WEIGHTED AVERAGE EXERCISE PRICE		WEIGHTED AVERAGE REMAINING CONTRACTUAL LIFE (YEARS)	AGGREGATE INTRINSIC VALUE (000’s)
Options outstanding at December 31, 2015	4,583,586		$	12.86
Granted	758,736		16.18
Exercised	(30,403	)	2.44
Canceled	(40,640	)	21.96
Options outstanding at June 30, 2016	5,271,279		$	11.04	7.8	$	35,051
Options vested and expected to vest at June 30, 2016(1)	5,194,864		$	13.25	7.8	$	34,896
Options exercisable at June 30, 2016	2,760,266		$	9.48	7.0	$	27,204

(1) Includes vested options and options that are expected to vest as of the balance sheet date after applying an estimated annual forfeiture rate.

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, 2015	119,993		$	20.31
Granted	112,655		15.98
Vested	(47,538	)	16.90
Canceled	(477	)	19.23
RSAs outstanding at June 30, 2016	184,633		$	18.55