Stock-Based Compensation (Tables)

9 Months Ended

Sep. 30, 2013

	Shares		Weighted average exercise price
Outstanding at January 1	5,521,584		$	6.40
Options granted	1,801,079		9.53
Options exercised	(132,991	)	8.14
Options cancelled	(453,463	)	9.88
Outstanding at September 30	6,736,209		$	6.97
Exercisable at September 30	3,662,767		$	6.61

	Shares		Weighted average grant date fair value
Outstanding at January 1	35,122		$	5.04
Vested	(32,622	)	5.33
Granted	115,000		7.99
Forfeited	(75,000	)	9.59
Outstanding at September 30	42,500		$	4.78

	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Risk-free interest rate	1.74	%	0.92	%	1.12	%	1.11	%
Expected life in years	6.25		6.23		6.25		6.24
Volatility	103	%	102	%	102	%	101	%
Expected dividend yield	—		—		—		—

Stock-based compensation expense during the three months and nine months ended September 30, 2013 and 2012 was as follows (in thousands):

	Three Months Ended September 30,				Nine Months Ended September 30,
	2013		2012		2013		2012
Stock-based compensation expense by type of award:
Employee stock options	$	1,620	$	765	$	4,276	$	2,222
Restricted stock	63		36		214		137
Total stock-based compensation expense	$	1,683	$	801	$	4,490	$	2,359

Effect of stock-based compensation expense by line item:
Research and development	$	902	$	612	$	2,363	$	1,797
General and administrative	781		189		2,127		562
Total stock-based compensation expense included in net loss	$	1,683	$	801	$	4,490	$	2,359

Unrecognized stock-based compensation expense as of September 30, 2013 was as follows (dollars in thousands):

	Unrecognized stock compensation expense as of September 30, 2013		Weighted average remaining period (in years)
Employee stock options	$	14,125	2.85
Restricted stock	159		.72
Total	$	14,284	2.83