Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 20,194	$ 13,459
Restricted cash	361	422
Prepaid expenses and other current assets	184	1,072
Total current assets	20,739	14,953
Property and equipment, net	938	1,605
Other assets	115	135
Total assets	21,792	16,693
Current liabilities:
Accounts payable	521	569
Loan payable, current portion	395	320
Note payable, current portion		18
Derivative warrant liability	1,907	7,224
Deferred rent payable, current portion	115	114
Accrued expenses	374	539
Total current liabilities	3,312	8,784
Loan payable, net of current portion	1,275	1,600
Deferred rent payable, net current portion	276	391
Total liabilities	$ 4,863	$ 10,775
Commitments and Contingencies
Stockholders' equity:
Common stock, $0.00001 par value, authorized - 50,000,000 shares; issued and outstanding - 27,555,948 and 23,453,000 shares at December 31, 2015 and 2014, respectively	$ 1	$ 1
Additional paid-in capital	150,497	106,172
Accumulated deficit	(133,569)	(100,255)
Total stockholders' equity	16,929	5,918
Total liabilities and stockholders' equity	$ 21,792	$ 16,693