Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 6,414	$ 18,078
Short-term investments	53,817us-gaap_ShortTermInvestments	26,349us-gaap_ShortTermInvestments
Prepaid expenses and other current assets	1,647	650
Total current assets	61,878us-gaap_AssetsCurrent	45,077us-gaap_AssetsCurrent
Property and equipment, net	3,367us-gaap_PropertyPlantAndEquipmentNet	880us-gaap_PropertyPlantAndEquipmentNet
Investment in joint venture		1,500us-gaap_EquityMethodInvestments
Restricted cash	197	88
Other long-term assets	130us-gaap_OtherAssetsNoncurrent
Total assets	65,572us-gaap_Assets	47,545us-gaap_Assets
Current liabilities:
Accounts payable	2,520us-gaap_AccountsPayableCurrent	1,654us-gaap_AccountsPayableCurrent
Accrued expenses	7,654us-gaap_AccruedLiabilitiesCurrent	4,120us-gaap_AccruedLiabilitiesCurrent
Total current liabilities	10,174us-gaap_LiabilitiesCurrent	5,774us-gaap_LiabilitiesCurrent
Other non-current liabilities	73us-gaap_OtherLiabilitiesNoncurrent	70us-gaap_OtherLiabilitiesNoncurrent
Total liabilities	10,247us-gaap_Liabilities	5,844us-gaap_Liabilities
Commitments and contingencies (Note 11)
Stockholders' equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized, no shares issued and outstanding
Common stock, $0.001 par value; 100,000,000 shares authorized; 24,413,666, and 18,528,215 shares issued at December 31, 2014 and 2013, respectively; 24,084,637 and 17,541,126 shares outstanding at December 31, 2014 and 2013, respectively	24us-gaap_CommonStockValue	18us-gaap_CommonStockValue
Additional paid-in capital	150,025us-gaap_AdditionalPaidInCapital	86,851us-gaap_AdditionalPaidInCapital
Accumulated other comprehensive (loss) income	(26)	10
Accumulated deficit	(94,698)	(45,178)
Total stockholders' equity	55,325us-gaap_StockholdersEquity	41,701us-gaap_StockholdersEquity
Total liabilities and stockholders' equity	$ 65,572	$ 47,545

Carrying value as of the balance sheet date of liabilities incurred (and for which invoices have typically been received) and payable to vendors for goods and services received that are used in an entity's business. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 19

-Subparagraph a

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.19(a))

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682