CONDENSED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 13,419	$ 36,079
Prepaid expenses and other current assets	387	232
Total current assets	13,806	36,311
Property and equipment, net	353	407
Restricted cash	174	94
Other assets	0	13
Total assets	14,333	36,825
Current liabilities:
Accounts payable	1,588	1,246
Accrued expenses	491	1,794
Notes payable, current portion	0	4,134
Deferred revenue	203	406
Total current liabilities	2,282	7,580
Other liabilities	81	423
Notes payable, net of current portion	0	9,763
Warrant liability	$ 0	$ 115
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.001 par value per share; 5,000,000 shares authorized at March 31, 2016 and December 31, 2015 and no shares issued and outstanding at March 31, 2016 and December 31, 2015	$ 0	$ 0
Common stock, $0.001 par value per share; 200,000,000 shares authorized at March 31, 2016 and December 31, 2015 and 19,767,545 and 19,619,124 shares issued and outstanding at March 31, 2016 and December 31, 2015, respectively	20	20
Additional paid-in capital	144,726	144,126
Accumulated deficit	(132,776)	(125,202)
Total stockholders’ equity	11,970	18,944
Total liabilities and stockholders’ equity	$ 14,333	$ 36,825