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:
Licensing revenue	$ 4,500us-gaap_LicensesRevenue	$ 729us-gaap_LicensesRevenue	$ 876us-gaap_LicensesRevenue
Product sales	881us-gaap_SalesRevenueGoodsNet	870us-gaap_SalesRevenueGoodsNet	1,877us-gaap_SalesRevenueGoodsNet
Other, net	1,052us-gaap_OtherSalesRevenueNet	0us-gaap_OtherSalesRevenueNet	207us-gaap_OtherSalesRevenueNet
Total revenues	6,433us-gaap_Revenues	1,599us-gaap_Revenues	2,960us-gaap_Revenues
Operating expenses:
Cost of product sales	638us-gaap_CostOfGoodsSold	669us-gaap_CostOfGoodsSold	1,518us-gaap_CostOfGoodsSold
Research and development	22,746us-gaap_ResearchAndDevelopmentExpense	11,554us-gaap_ResearchAndDevelopmentExpense	8,604us-gaap_ResearchAndDevelopmentExpense
General and administrative	12,927us-gaap_GeneralAndAdministrativeExpense	4,433us-gaap_GeneralAndAdministrativeExpense	3,713us-gaap_GeneralAndAdministrativeExpense
Total operating expenses	36,311us-gaap_OperatingExpenses	16,656us-gaap_OperatingExpenses	13,835us-gaap_OperatingExpenses
Loss from operations	(29,878)us-gaap_OperatingIncomeLoss	(15,057)us-gaap_OperatingIncomeLoss	(10,875)us-gaap_OperatingIncomeLoss
Interest and other income	4us-gaap_OtherNonoperatingIncomeExpense	37us-gaap_OtherNonoperatingIncomeExpense	35us-gaap_OtherNonoperatingIncomeExpense
Change in fair value of convertible preferred stock warrant liability	(4,277)us-gaap_FairValueAdjustmentOfWarrants	(955)us-gaap_FairValueAdjustmentOfWarrants	0us-gaap_FairValueAdjustmentOfWarrants
Net loss attributable to common stockholders	$ (34,151)	$ (15,975)	$ (10,840)
Earnings Per Share
Basic and diluted net loss per share attributable to common stockholders (in USD per share)	$ (4.56)us-gaap_EarningsPerShareBasicAndDiluted	$ (43.48)us-gaap_EarningsPerShareBasicAndDiluted	$ (30.43)us-gaap_EarningsPerShareBasicAndDiluted
Weighted Average Number of Shares Outstanding, Diluted
Weighted-average shares used to compute basic and diluted net loss per share attributable to common stockholders (in shares)	7,494,790	367,437	356,215

Total costs related to goods produced and sold during the reporting period.

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