Consolidated Balance Sheets (Unaudited) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current Assets:
Cash and cash equivalents	$ 75,942	$ 86,283
Accounts receivable	0	67
Inventory, net	173	112
Prepaid expenses and other current assets	702	777
Total current assets	76,817	87,239
Property and equipment, net	2,007	1,656
Restricted cash	325	325
Other assets	349	97
Total assets	79,498	89,317
Current Liabilities:
Accounts payable	2,578	1,433
Accrued expenses	3,726	4,785
Deferred revenue	85	139
Common stock warrant liability	4,672	5,425
Equipment loans, current portion	74	73
Total current liabilities	11,135	11,855
Long-term debt, $30,000 net of discount of $11,207 at March 31, 2014 and $11,646 at December 31, 2013	18,793	18,354
Equipment loans, non-current portion	49	69
Other liabilities	714	538
Total liabilities	30,691	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; 150,000,000 shares authorized; 85,073,173 and 84,659,111 shares issued at March 31, 2014 and December 31, 2013, respectively; 85,052,281 and 84,638,219 shares outstanding at March 31, 2014 and December 31, 2013, respectively	85	85
Additional paid-in capital	543,202	541,420
Accumulated deficit	(491,426)	(479,950)
Treasury stock (at cost); 20,892 shares	(3,054)	(3,054)
Total stockholders' equity	48,807	58,501
Total liabilities & stockholders' equity	$ 79,498	$ 89,317