Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 60,680	$ 30,688
Restricted cash	1,082	82
Prepaid expenses	1,247	2,147
Other assets	5,517	6,211
Total current assets	68,526	39,128
Property and equipment, net	316	108
Intangible assets, net	1,350	1,823
Other non-current assets		4,694
Total assets	70,192	45,753
Current liabilities:
Accounts payable	4,105	1,557
Accrued expenses	8,259	5,524
Warrant liability	1	19
Current portion of long-term debt	4,089	2,000
Total current liabilities	16,454	9,100
Long-term debt		2,452
Total liabilities	16,454	11,552
Commitments and contingencies
Stockholders' equity:
Common stock, $0.001 par value; 500,000,000 shares authorized; 33,609,212 and 21,310,614 shares issued and outstanding at September 30, 2014 and December 31, 2013, respectively	34	21
Additional paid-in-capital	232,190	179,159
Accumulated deficit	(203,318)	(144,979)
Total stockholders' equity	53,738	34,201
Total liabilities and stockholders' equity	70,192	45,753
Series F Convertible Preferred Stock [Member]
Stockholders' equity:
Convertible preferred stock	$ 24,832