Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 83,416	$ 102,238
Restricted cash	533	1,592
Other current assets and prepaid expenses	1,139	986
Total current assets	85,088	104,816
Property and equipment, net	3,809	3,068
Other assets	184	198
Total assets	89,081	108,082
Current liabilities:
Accounts payable	1,221	1,153
Accrued expenses	5,271	8,875
Other current liabilities	163	250
Total current liabilities	6,655	10,278
Other long-term liabilities	$ 101	$ 241
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.0001 par value; 20,000,000 authorized and no shares issued or outstanding at December 31, 2015 and 2014	$ 0	$ 0
Common stock, $0.0001 par value; 130,000,000 shares authorized at December 31, 2015 and 2014; 30,473,083 and 23,982,786 shares issued and outstanding at December 31, 2015 and 2014, respectively	3	2
Additional paid-in capital	285,098	248,305
Accumulated other comprehensive income	80	89
Accumulated deficit	(202,856)	(150,833)
Total stockholders’ equity	82,325	97,563
Total liabilities and stockholders’ equity	$ 89,081	$ 108,082