Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 13,459	$ 13,980
Restricted cash	422	602
Prepaid expenses and other current assets	1,072	20
Total current assets	14,953	14,602
Property and equipment, net	1,605	2,337
Other assets	135	157
Total assets	16,693	17,096
Current liabilities:
Accounts payable	569	899
Loan payable-current portion	320
Note payable-current portion	18	74
Capital lease payable		3
Derivative warrant liability	7,224	0
Accrued expenses	1,044	1,292
Total current liabilities	9,175	2,268
Loan payable-less current portion	1,600	1,920
Note payable-less current portion		18
Total liabilities	10,775	4,206
Commitments and contingencies
Stockholders' equity:
Common stock, $0.00001 par value, authorized 200,000,000 shares; issued and outstanding 93,812,000 and 78,773,736 shares at December 31, 2014 and 2013, respectively	1	1
Additional paid-in capital	106,172	94,798
Accumulated deficit	(100,255)	(81,909)
Total stockholders' equity	5,918	12,890
Total liabilities and stockholders' equity	$ 16,693	$ 17,096