Accounting for Shared-Based Payments (Tables)

3 Months Ended

Mar. 31, 2013

Accounting for Shared-Based Payments

Schedule of stock-based compensation expense

	Three Months Ended March 31,				November 15, 2005 (inception) to
($ in thousands)	2013		2012		March 31, 2012
Employees—included in research and development	$	276	$	116	$	1,877
Employees—included in general and administrative	450		94		1,859
Subtotal employee stock based compensation	726		210		3,736
Non-employees—included in research and development	135		0		432
Non-employees—included in general and administrative	396		228		2,573
Subtotal non-employee stock based compensation	531		228		3,005
Total stock-based compensation expense	$	1,257	$	438	$	6,741

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

	Three Months Ended March 31, 2013	Three Months Ended March 31, 2012
Risk-free interest rate	0.04%-1.87%	1.05%-1.50%
Dividend yield	—	—
Expected volatility	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, 2012	9,734,268		$	0.50 -5.20	$	2.75	$	24,482	6.45 years
Granted	1,249,316	(a)	$	0.44-20.01	$	8.29
Exercised	(34,352	)	$	0.50 — 4.28	$	3.04
Forfeited	(500,000	)	$	4.42	$	4.42
Balance outstanding, March 31, 2013	10,449,232	(a)	$	0.44-20.01	$	3.33	$	32,466	7.1 years
Exercisable at March 31, 2013	3,917,662	(a)	$	0.44-20.01	$	3.09	$	14,136	5.3 years

(a) Includes 1,221,316 stock options issued to former Callisto option holders under the terms of Callisto Synergy Merger Agreement dated January 17, 2013, of which 1,010,026 stock options are vested as of March 31, 2013. (Note 7)