Stock-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2014

	Shares		Weighted average exercise price
Outstanding at January 1, 2014	6,814,417		$	6.90
Options granted	1,751,327		6.14
Options exercised	(203,125	)	4.16
Options cancelled	(756,353	)	7.19
Outstanding at June 30, 2014	7,606,266		$	6.76
Exercisable at June 30, 2014	4,696,388		$	6.72

	Shares		Weighted average grant date fair value
Outstanding at January 1	45,000		$	4.63
Vested	(20,000	)	5.00
Forfeited	(25,000	)	4.34
Outstanding at June 30	—		$	—

Stock-based compensation expense during the three months and six months ended June 30, 2014 and 2013 was as follows (in thousands):

	Three Months Ended June 30,				Six Months Ended June 30,
	2014		2013		2014		2013
Stock-based compensation expense by type of award:
Employee stock options	$	1,471	$	1,526	$	4,000	$	2,657
Restricted stock	42		65		99		150
Total stock-based compensation expense	$	1,513	$	1,591	$	4,099	$	2,807

Effect of stock-based compensation expense by line item:
Research and development	$	1,132	$	832	$	2,263	$	1,461
General and administrative	381		759		1,836		1,346
Total stock-based compensation expense included in net loss	$	1,513	$	1,591	$	4,099	$	2,807

Unrecognized stock-based compensation expense as of June 30, 2014 was as follows (dollars in thousands):

	Unrecognized stock compensation expense as of June 30, 2014		Weighted average remaining period (in years)
Employee stock options	$	13,188	2.85
Restricted stock	—		—
Total	$	13,188	2.85