Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 24,516	$ 13,459
Restricted cash	361	422
Prepaid expenses and other current assets	543	1,072
Total current assets	25,420us-gaap_AssetsCurrent	14,953us-gaap_AssetsCurrent
Property, equipment and leasehold improvements, net	1,431us-gaap_PropertyPlantAndEquipmentNet	1,605us-gaap_PropertyPlantAndEquipmentNet
Other assets	130us-gaap_OtherAssetsNoncurrent	135us-gaap_OtherAssetsNoncurrent
Total assets	26,981us-gaap_Assets	16,693us-gaap_Assets
Current liabilities:
Accounts payable	793us-gaap_AccountsPayableCurrent	569us-gaap_AccountsPayableCurrent
Loan payable-current portion	320us-gaap_LoansPayableCurrent	320us-gaap_LoansPayableCurrent
Note payable-current portion		18us-gaap_NotesPayableCurrent
Derivative warrant liability	12,644us-gaap_DerivativeLiabilitiesCurrent	7,224us-gaap_DerivativeLiabilitiesCurrent
Accrued expenses	1,364us-gaap_AccruedLiabilitiesCurrent	1,044us-gaap_AccruedLiabilitiesCurrent
Total current liabilities	15,121us-gaap_LiabilitiesCurrent	9,175us-gaap_LiabilitiesCurrent
Loan payable	1,600us-gaap_LongTermLoansPayable	1,600us-gaap_LongTermLoansPayable
Total liabilities	16,721us-gaap_Liabilities	10,775us-gaap_Liabilities
Commitments and Contingencies
Stockholders' equity:
Common stock, $0.00001 par value, authorized 50,000,000 shares; issued and outstanding 26,011,852 and 23,453,000 shares at March 31, 2015 and December 31, 2014, respectively.	1us-gaap_CommonStockValue	1us-gaap_CommonStockValue
Additional paid-in capital	126,344	106,172
Accumulated deficit	(116,085)	(100,255)
Total stockholders' equity	10,260us-gaap_StockholdersEquity	5,918us-gaap_StockholdersEquity
Total liabilities and stockholders' equity	$ 26,981	$ 16,693

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