Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 65,557	$ 86,283
Accounts receivable	41	67
Inventory, net	443	112
Prepaid expenses and other current assets	443	777
Total current assets	66,484	87,239
Property and equipment, net	2,178	1,656
Restricted cash	325	325
Other assets	487	97
Total assets	69,474	89,317
Current Liabilities:
Accounts payable	1,507	1,433
Accrued expenses	5,951	4,785
Deferred revenue	105	139
Common stock warrant liability	3,224	5,425
Equipment loans, current portion	75	73
Total current liabilities	10,862	11,855
Long-term debt, $30,000 net of discount of $10,736 at June 30, 2014 and $11,646 at December 31, 2013	19,264	18,354
Equipment loans, non-current portion	28	69
Other liabilities	114	538
Total liabilities	30,268	30,816
Stockholders' Equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized; no shares issued or outstanding	0	0
Common stock, $0.001 par value; 250,000,000 and 150,000,000 shares authorized at June 30, 2014 and December 31, 2013, respectively; 85,227,508 and 84,659,111 shares issued at June 30, 2014 and December 31, 2013, respectively; 85,206,616 and 84,638,219 shares outstanding at June 30, 2014 and December 31, 2013, respectively	85	85
Additional paid-in capital	544,224	541,420
Accumulated deficit	(502,049)	(479,950)
Treasury stock (at cost); 20,892 shares	(3,054)	(3,054)
Total stockholders' equity	39,206	58,501
Total liabilities & stockholders' equity	$ 69,474	$ 89,317