Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 113,450	$ 85,586
Short-term investments	56,286us-gaap_ShortTermInvestments	54,339us-gaap_ShortTermInvestments
Prepaid expenses and other current assets	1,219	1,122
Total current assets	170,955us-gaap_AssetsCurrent	141,047us-gaap_AssetsCurrent
Long-term investments	9,574us-gaap_LongTermInvestments	18,275us-gaap_LongTermInvestments
Furniture, fixtures and equipment, net	796us-gaap_PropertyPlantAndEquipmentNet	240us-gaap_PropertyPlantAndEquipmentNet
Other assets, net	13,872us-gaap_OtherAssetsNoncurrent	1,523us-gaap_OtherAssetsNoncurrent
Total assets	195,197us-gaap_Assets	161,085us-gaap_Assets
Current liabilities
Accounts payable and other current liabilities	21,852	8,336
Interest payable	539	551
Total current liabilities	22,391us-gaap_LiabilitiesCurrent	8,887us-gaap_LiabilitiesCurrent
Convertible notes, net of discounts	124,187us-gaap_ConvertibleLongTermNotesPayable	124,156us-gaap_ConvertibleLongTermNotesPayable
Total liabilities	146,578us-gaap_Liabilities	133,043us-gaap_Liabilities
Commitments and contingencies (Note 12)
Stockholders’ equity
Preferred stock, $0.001 par value; 15,000,000 shares authorized as of March 31, 2015 and December 31, 2014; None issued and outstanding	0us-gaap_PreferredStockValue	0us-gaap_PreferredStockValue
Common stock, $0.001 par value; 150,000,000 shares authorized as of March 31, 2015 and December 31, 2014; 25,275,672 and 24,018,577 shares issued and outstanding as of March 31, 2015 and December 31, 2014, respectively	25us-gaap_CommonStockValue	24us-gaap_CommonStockValue
Additional paid-in capital	209,092us-gaap_AdditionalPaidInCapital	171,326us-gaap_AdditionalPaidInCapital
Accumulated other comprehensive loss	(58)	(107)
Accumulated deficit	(160,440)	(143,201)
Total stockholders’ equity	48,619us-gaap_StockholdersEquity	28,042us-gaap_StockholdersEquity
Total liabilities and stockholders’ equity	$ 195,197	$ 161,085

Sum of the carrying values as of the balance sheet date of obligations incurred through that date and due within one year (or the operating cycle, if longer), including liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received, and other costs not separately disclosed in the balance sheet that are statutory in nature, are incurred on contractual obligations, or accumulate over time and for which invoices have not yet been received or will not be rendered.

No definition available.