Consolidated Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Revenues:
Product sales	$ 76us-gaap_SalesRevenueGoodsNet
Product royalty revenues	3,407us-gaap_RoyaltyRevenue	1,773us-gaap_RoyaltyRevenue	1,083us-gaap_RoyaltyRevenue
Research revenue			13
Research and development reimbursements	12,712	2,783
Contract revenue	22,749us-gaap_ContractsRevenue	6,800us-gaap_ContractsRevenue	53,446us-gaap_ContractsRevenue
Total revenues	38,944us-gaap_Revenues	11,356us-gaap_Revenues	54,542us-gaap_Revenues
Cost of sales	4,939us-gaap_CostOfRevenue	2,082us-gaap_CostOfRevenue	1,910us-gaap_CostOfRevenue
Expenses:
Research and development	34,285us-gaap_ResearchAndDevelopmentExpense	53,327us-gaap_ResearchAndDevelopmentExpense	35,366us-gaap_ResearchAndDevelopmentExpense
Selling, general and administrative	38,460	12,349	10,205
Total expenses	72,745us-gaap_OperatingExpenses	65,676us-gaap_OperatingExpenses	45,571us-gaap_OperatingExpenses
(Loss) income from operations	(38,740)us-gaap_OperatingIncomeLoss	(56,402)us-gaap_OperatingIncomeLoss	7,061us-gaap_OperatingIncomeLoss
Interest (expense) income, net	(2,016)us-gaap_InterestIncomeExpenseNet	(903)us-gaap_InterestIncomeExpenseNet	281us-gaap_InterestIncomeExpenseNet
Derivative (loss) gain	(13,167)	121	(5,594)
Other (expenses) income, net	(295)us-gaap_OtherNonoperatingIncomeExpense	(210)us-gaap_OtherNonoperatingIncomeExpense	33us-gaap_OtherNonoperatingIncomeExpense
Total nonoperating Income (Expense)	(15,478)us-gaap_NonoperatingIncomeExpense	(992)us-gaap_NonoperatingIncomeExpense	(5,280)us-gaap_NonoperatingIncomeExpense
(Loss) income before taxes	(54,218)	(57,394)	1,781
Income tax expense			(129)us-gaap_IncomeTaxExpenseBenefit
Net (loss) income attributable to common stockholders	$ (54,218)	$ (57,394)	$ 1,652
Basic:
Weighted average common stock shares outstanding	48,355,200	37,941,044	30,546,581
Basic earnings per share	$ (1.12)us-gaap_EarningsPerShareBasic	$ (1.51)us-gaap_EarningsPerShareBasic	$ 0.05us-gaap_EarningsPerShareBasic
Diluted:
Diluted weighted average common stock shares outstanding	48,355,200	37,941,044	30,689,235
Diluted earnings per share	$ (1.12)us-gaap_EarningsPerShareDiluted	$ (1.51)us-gaap_EarningsPerShareDiluted	$ 0.05us-gaap_EarningsPerShareDiluted

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