Condensed Balance Sheets (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 19,493	$ 18,653
Marketable securities	10,250	4,000
Prepaid expenses and other current assets	242	2,463
Total current assets	29,985	25,116
Property and equipment, net	91	139
Other assets	45	45
Total assets	30,121	25,300
Current liabilities:
Accounts payable	2,684	550
Accrued expenses and other current liabilities	22,943	8,740
Current portion of note payable, net of discount	10,837	7,800
Total current liabilities	36,464	17,090
Note payable, net of current portion and discount	4,369	13,005
Warrant liability	2,499	830
Other liabilities	22,186	24,387
Commitments and contingencies
Stockholders' deficit:
Common stock, $.0001 par value; 100,000,000 shares authorized, 879,370 and 867,204 shares issued and outstanding at September 30, 2013 and December 31, 2012, respectively
Accumulated deficit	(260,258)	(200,661)
Total stockholders' deficit	(260,258)	(200,661)
Total liabilities, convertible preferred stock and stockholders' deficit	30,121	25,300
Series B Convertible Preferred Stock
Current liabilities:
Preferred Stock	43,024
Stockholders' deficit:
Total stockholders' deficit	43,024
Series A-1 Convertible Preferred Stock
Current liabilities:
Preferred Stock	76,987	71,957
Stockholders' deficit:
Total stockholders' deficit	76,987	71,957
Series A-2 Convertible Preferred Stock
Current liabilities:
Preferred Stock	92,094	86,714
Stockholders' deficit:
Total stockholders' deficit	92,094	86,714
Series A-3 Convertible Preferred Stock
Current liabilities:
Preferred Stock	11,960	11,182
Stockholders' deficit:
Total stockholders' deficit	11,960	11,182
Series A-4 Convertible Preferred Stock
Current liabilities:
Preferred Stock	271	271
Stockholders' deficit:
Total stockholders' deficit	271	271
Series A-5 Convertible Preferred Stock
Current liabilities:
Preferred Stock	525	525
Stockholders' deficit:
Total stockholders' deficit	$ 525	$ 525