Accounting for Shared-Based Payments (Tables)

3 Months Ended

Mar. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of stock-based compensation expense

Stock-based compensation has been recognized in operating results as follows:

	Three Months Ended March 31,
($ in thousands)	2016		2015
Employees—included in research and development	810		530
Employees—included in general and administrative	392		1,875
Total stock-based compensation expense	$	1,202	$	2,405

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

The estimated fair value of stock option awards was determined on the date of grant using the Black-Scholes option valuation model with the following weighted-average assumptions during the periods indicated.

	Three Months Ended March 31, 2016		Three Months Ended March 31, 2015
Risk-free interest rate	1.47%-1.74%		1.46%-2.02%
Dividend yield	—		—
Expected volatility	60	%	57	%
Expected term (in years)	6 years		6-9.3 years

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

A summary of stock option activity and of changes in stock options outstanding under the Plan is presented below:

	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, 2015 (1)	20,953,375		$0.44-9.12	$	3.86	$	42,438	7.15 years
Granted	405,000		$3.12-4.14	4.00		—
Exercised	—		0	—		—
Forfeited	(130,427	)	$6-9.12	6.65		—
Balance outstanding, March 31, 2016 (1)	21,227,948		0.44-9.12	$	3.83	$	—	7.00 years
Exercisable, at March 31, 2016	9,991,733		0.44-9.12	$	3.30	$	4,347	5.82 years

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(1)   Number of options represented above includes 2,159,500 options vesting upon a change of control, granted between November 20, 2009 and June 22, 2010. The fair value at the date of grant was approximately $28.6 million. 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.