Stock-based Compensation (Tables)

9 Months Ended

Sep. 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   SEPTEMBER 30,				NINE MONTHS ENDED   SEPTEMBER 30,
(in thousands)	2016		2015		2016		2015
Research and development	$	693	$	597	$	2,219	$	1,691
General and administrative	3,406		2,719		9,295		7,842
Total	$	4,099	$	3,316	$	11,514	$	9,533

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	783,936		16.22
Exercised	(134,481	)	3.59
Canceled	(81,017	)	19.22
Options outstanding at September 30, 2016	5,152,024		$	13.51	7.6	$	124,827
Options vested or expected to vest (1)	5,090,131		$	13.44	7.6	$	123,667
Options exercisable at September 30, 2016	2,973,566		$	10.19	7.0	$	81,920

(1) Includes vested options and options that are expected to vest in the future 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	(58,365	)	14.26
Canceled	(2,549	)	17.63
RSAs outstanding at September 30, 2016	171,734		$	19.56