Condensed Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 38,749	$ 10,096
Restricted cash	311
Prepaid expenses and other current assets	397	198
Total current assets	39,457	10,294
Property and equipment, net	116	218
Restricted cash		311
Total assets	39,573	10,823
Current liabilities:
Accounts payable	254	1,129
Accrued expenses	2,204	3,002
Total current liabilities	2,458	4,131
Other liabilities	6	65
Total liabilities	2,464	4,196
Commitments and contingencies
Series D Redeemable Convertible Preferred Stock, $0.01 par value, Designated, issued and outstanding - 1,124 shares at December 31, 2012		5,921
Non-redeemable preferred stock, common stock, and other stockholders' equity:
Preferred stock, $0.01 par value
Common stock, $0.001 par value, Authorized - 280,000 and 140,000 shares at September 30, 2013 and December 31, 2012, respectively; Issued and outstanding - 62,682 and 27,643 shares at September 30, 2013 and December 31, 2012, respectively	63	28
Additional paid-in capital	432,848	391,635
Accumulated deficit	(406,794)	(394,658)
Total stockholders' equity	37,109	706
Total liabilities, redeemable preferred stock and stockholders' equity	39,573	10,823
Series E Preferred Stock [Member]
Non-redeemable preferred stock, common stock, and other stockholders' equity:
Preferred stock, $0.01 par value	5,528	3,701
Series D Preferred Stock [Member]
Non-redeemable preferred stock, common stock, and other stockholders' equity:
Preferred stock, $0.01 par value	5,464
Series A Preferred Stock [Member]
Non-redeemable preferred stock, common stock, and other stockholders' equity:
Preferred stock, $0.01 par value