Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 16,434	$ 21,464
Restricted cash	361	361
Marketable securities	734	11,577
Prepaid expenses and other current assets	475	451
Total current assets	18,004	33,853
Property, equipment and leasehold improvements, net	190	510
Other assets	402	421
Total assets	18,596	34,784
Current liabilities:
Accounts payable	1,270	1,011
Loan payable, current portion	444	423
Derivative warrant liability	41	1,314
Deferred rent, current portion	30	141
Accrued expenses	1,784	1,959
Total current liabilities	3,569	4,848
Loan payable, net of current portion	516	852
Deferred rent, net of current portion	208	135
Other liabilities	52
Total liabilities	4,345	5,835
Commitments and contingencies (Note 6)
Stockholders' equity:
Common stock, $0.00001 par value, authorized 100,000,000 shares; 34,234,580 shares issued and outstanding at September 30, 2017; 32,044,087 shares issued and outstanding at December 31, 2016	1	1
Additional paid-in capital	193,493	185,955
Accumulated deficit	(179,243)	(157,007)
Total stockholders' equity	14,251	28,949
Total liabilities and stockholders' equity	$ 18,596	$ 34,784