BALANCE SHEETS (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 129,684	$ 42,803
Receivables	62us-gaap_ReceivablesNetCurrent	145us-gaap_ReceivablesNetCurrent
Prepaid expenses and other current assets	857	1,139
Total current assets	130,603us-gaap_AssetsCurrent	44,087us-gaap_AssetsCurrent
Property and equipment, net	426us-gaap_PropertyPlantAndEquipmentNet	531us-gaap_PropertyPlantAndEquipmentNet
Deposits	128us-gaap_DepositsAssetsNoncurrent	128us-gaap_DepositsAssetsNoncurrent
Other non-current assets	491us-gaap_OtherAssetsNoncurrent	491us-gaap_OtherAssetsNoncurrent
Total assets	131,648us-gaap_Assets	45,237us-gaap_Assets
Current liabilities:
Accounts payable	779us-gaap_AccountsPayableCurrent	2,004us-gaap_AccountsPayableCurrent
Accrued expenses	8,220us-gaap_AccruedLiabilitiesCurrent	7,182us-gaap_AccruedLiabilitiesCurrent
Deferred revenue-current portion	1,088us-gaap_DeferredRevenueCurrent	1,360us-gaap_DeferredRevenueCurrent
Deferred rent-current portion	405us-gaap_DeferredRentCreditCurrent	280us-gaap_DeferredRentCreditCurrent
Total current liabilities	10,492us-gaap_LiabilitiesCurrent	10,826us-gaap_LiabilitiesCurrent
Deferred rent	553us-gaap_DeferredRentCreditNoncurrent	570us-gaap_DeferredRentCreditNoncurrent
Total liabilities	11,045us-gaap_Liabilities	11,396us-gaap_Liabilities
Commitments and contingencies (note 6)
Stockholders' equity:
Common stock, $0.001 par value; 250,000,000 shares authorized; 128,232,537 and 104,452,105 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	128us-gaap_CommonStockValue	104us-gaap_CommonStockValue
Additional paid-in capital-common stock	571,318	406,349
Accumulated deficit	(450,843)	(372,612)
Total stockholders' equity	120,603us-gaap_StockholdersEquity	33,841us-gaap_StockholdersEquity
Total liabilities and stockholders' equity	$ 131,648	$ 45,237

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