CONDENSED BALANCE SHEETS (Unaudited) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 28,052,543	$ 32,218,905
Short-term investments	37,101,506	45,621,593
Receivables	5,153,127us-gaap_ReceivablesNetCurrent	2,019,293us-gaap_ReceivablesNetCurrent
Interest receivable	76,254us-gaap_InterestReceivable	104,627us-gaap_InterestReceivable
Prepaid expenses and other current assets	930,277	3,250,355
Total current assets	71,313,707us-gaap_AssetsCurrent	83,214,773us-gaap_AssetsCurrent
Equipment and furnishings, net	949,305us-gaap_PropertyPlantAndEquipmentNet	970,873us-gaap_PropertyPlantAndEquipmentNet
Goodwill	183,780us-gaap_Goodwill	183,780us-gaap_Goodwill
Other assets	1,319,505us-gaap_OtherAssetsNoncurrent	1,323,156us-gaap_OtherAssetsNoncurrent
Total assets	73,766,297us-gaap_Assets	85,692,582us-gaap_Assets
Current liabilities:
Accounts payable	4,637,623us-gaap_AccountsPayableCurrent	6,655,962us-gaap_AccountsPayableCurrent
Accrued expenses and other current liabilities	10,354,489	5,994,072
Warrant liability	7,002,379us-gaap_DerivativeLiabilitiesCurrent	5,131,085us-gaap_DerivativeLiabilitiesCurrent
Total current liabilities	21,994,491us-gaap_LiabilitiesCurrent	17,781,119us-gaap_LiabilitiesCurrent
Commitments and contingencies
Stockholders' equity
Preferred Stock, $0.01 par value, 5,000,000 shares authorized, including 25,000 shares of Series A Junior Participating Preferred Stock; no shares issued and outstanding	0us-gaap_PreferredStockValue	0us-gaap_PreferredStockValue
Common stock, $0.001 par value, 250,000,000 shares authorized; 55,921,986 shares issued and outstanding at March 31, 2015 and December 31, 2014	55,924us-gaap_CommonStockValue	55,924us-gaap_CommonStockValue
Additional paid-in capital	378,360,877us-gaap_AdditionalPaidInCapital	376,975,984us-gaap_AdditionalPaidInCapital
Treasury stock, at cost (199,275 shares at March 31, 2015 and December 31, 2014)	(2,612,861)us-gaap_TreasuryStockValue	(2,612,861)us-gaap_TreasuryStockValue
Accumulated deficit	(324,032,134)	(306,507,584)
Total stockholders' equity	51,771,806us-gaap_StockholdersEquity	67,911,463us-gaap_StockholdersEquity
Total liabilities and stockholders' equity	$ 73,766,297	$ 85,692,582

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.