Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 56,901	$ 59,991
Other current assets and prepaid expenses	1,220	1,472
Total current assets	58,121	61,463
Property and equipment, net	2,155	2,505
Other assets	108	58
Total assets	60,384	64,026
Current liabilities:
Accounts payable	1,049	780
Accrued expenses	9,141	4,656
Other current liabilities	91	44
Total current liabilities	10,281	5,480
Long-term liabilities	59	100
Commitments and contingencies (note 4)
Stockholders’ equity:
Preferred stock, $0.0001 par value; 20,000,000 authorized and no shares issued or outstanding at December 31, 2017 and 2016	0	0
Common stock, $0.0001 par value; 130,000,000 shares authorized at December 31, 2017 and 2016; 42,368,864 and 32,143,475 shares issued and outstanding at December 31, 2017 and 2016, respectively	4	3
Additional paid-in capital	345,915	302,185
Accumulated other comprehensive income	78	83
Accumulated deficit	(295,953)	(243,825)
Total stockholders’ equity	50,044	58,446
Total liabilities and stockholders’ equity	$ 60,384	$ 64,026