Consolidated Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 9,846	$ 13,980
Restricted cash	371	602
Prepaid expenses	445	20
Total current assets	10,662	14,602
Property, equipment and leasehold improvements, net	2,182	2,337
Other assets	152	157
Total assets	12,996	17,096
Current liabilities:
Accounts payable	704	899
Note payable-current portion	74	74
Capital lease payable		3
Accrued expenses	1,236	1,292
Total current liabilities	2,014	2,268
Loan payable	1,920	1,920
Note payable-less current portion		18
Total liabilities	3,934	4,206
Commitments and Contingencies
Stockholders' equity:
Common stock, $0.00001 par value, authorized 200,000,000 shares at March 31, 2014 and December 31, 2013; issued and outstanding 79,021,039 and 78,773,736 shares at March 31, 2014 and December 31, 2013, respectively	1	1
Additional paid-in capital	96,073	94,798
Deficit accumulated during the development stage	(87,012)	(81,909)
Total stockholders' equity	9,062	12,890
Total liabilities and stockholders' equity	$ 12,996	$ 17,096