Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 48,371	$ 12,303
Marketable securities	30,650
Prepaid expenses and other current assets	1,797	334
Total current assets	80,818	12,637
Property and equipment, net	70	76
Other assets	242	45
Total assets	81,130	12,758
Current liabilities:
Accounts payable	1,188	300
Accrued expenses and other current liabilities	19,895	22,007
Current portion of note payable, net of discount		13,005
Total current liabilities	21,083	35,312
Note payable, net of current portion and discount	20,299
Warrant liability		1,945
Commitments and contingencies
Stockholders' equity (deficit):
Common stock, $.0001 par value; 200,000,000 shares and 100,000,000 authorized, 29,726,194 shares and 385,664 issued and outstanding at June 30, 2014 and December 31, 2013, respectively	3
Additional paid-in-capital	348,600
Accumulated other comprehensive income	1
Accumulated deficit	(308,856)	(277,301)
Total stockholders' equity (deficit)	39,748	(277,301)
Total liabilities, convertible preferred stock and stockholders' equity (deficit)	81,130	12,758
Series B Convertible Preferred Stock
Current liabilities:
Preferred Stock		43,892
Stockholders' equity (deficit):
Total stockholders' equity (deficit)		43,892
Series A-1 Convertible Preferred Stock
Current liabilities:
Preferred Stock		78,737
Stockholders' equity (deficit):
Total stockholders' equity (deficit)		78,737
Series A-2 Convertible Preferred Stock
Current liabilities:
Preferred Stock		93,977
Stockholders' equity (deficit):
Total stockholders' equity (deficit)		93,977
Series A-3 Convertible Preferred Stock
Current liabilities:
Preferred Stock		12,232
Stockholders' equity (deficit):
Total stockholders' equity (deficit)		12,232
Series A-4 Convertible Preferred Stock
Current liabilities:
Preferred Stock		271
Stockholders' equity (deficit):
Total stockholders' equity (deficit)		271
Series A-5 Convertible Preferred Stock
Current liabilities:
Preferred Stock		525
Stockholders' equity (deficit):
Total stockholders' equity (deficit)		525
Series A-6 Convertible Preferred Stock
Current liabilities:
Preferred Stock		23,168
Stockholders' equity (deficit):
Total stockholders' equity (deficit)		$ 23,168