Accounting for Shared-Based Payments (Tables)

9 Months Ended

Sep. 30, 2014

Accounting for Shared-Based Payments

Schedule of stock-based compensation expense

	Three Months Ended September 30,				Nine Months Ended September 30
($ in thousands)	2014		2013		2014		2013
Research and development	$	522	$	391	$	1,391	$	1,082
General and administrative	400		699		1,796		2,176
Total stock-based compensation expense	$	922	$	1,090	$	3,187	$	3,258

Schedule of weighted-average assumptions used to estimate fair value of stock option awards using the Black-Scholes option valuation model

	Nine Months Ended September 30,  2014	Nine Months Ended September 30,  2013
Risk-free interest rate	1.78%-2.30%	0.41% — 2.64%
Dividend yield	—	—
Expected volatility	52%-60%	60%
Expected term (in years)	6 years	6 years

Summary of stock option activity and of changes in stock options outstanding under the Plan

	Number of Options		Exercise Price Per Share		Weighted Average Exercise Price Per Share		Intrinsic Value (in thousands)		Weighted Average Remaining Contractual Term
Balance outstanding, December 31, 2013(1)	11,324,049		$	0.44-20.01	$	3.31	$	37,521	6.94 years
Granted	1,664,000		$	3.70-5.97	$	4.63
Exercised	(9,999	)	$	3.40-3.95	$	3.58	$	23
Forfeited	(110,190	)	$	8.34-20.01	$	17.51
Balance outstanding, September 30, 2014(1)	12,867,860		$	0.44-13.90	$	3.36	$	7,555	6.69 years
Exercisable, at September 30, 2014	5,880,483		$	0.44-13.90	$	2.96	$	4,552	5.91 years

(1) Number of options represented above includes 4,364,000 options vesting upon change of control, granted during the years ended December 31, 2009 and 2010, at an exercise price of $0.70 per share. Because the probability of a change of control transaction is not predictable no stock based compensation expense associated with these options has been recognized since the grant date.