Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 3,545	$ 15,101
Marketable securities	81,219	91,640
Income tax receivable	608	384
Other receivables	373	80
Prepaid expenses	3,398	1,729
Total current assets	89,143	108,934
Property and equipment, net	1,433	1,263
Restricted cash	1,469	700
Total assets	92,045	110,897
Current liabilities:
Accounts payable and accrued expenses	8,168	5,268
Total current liabilities	8,168	5,268
Deferred lease obligation	1,289	585
Commitments and contingencies (Note 12)
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at June 30, 2016 and December 31, 2015, zero shares issued and outstanding at June 30, 2016 and December 31, 2015.
Common stock; $0.001 par value; 100,000,000 shares authorized at June 30, 2016 and December 31, 2015, 27,282,863 shares and 27,254,863 shares issued and outstanding at June 30, 2016 and December 31, 2015, respectively	27	27
Additional paid-in capital	211,177	209,943
Accumulated deficit	(128,657)	(104,891)
Accumulated other comprehensive income (loss)	41	(35)
Total stockholders' equity	82,588	105,044
Total liabilities and stockholders' equity	$ 92,045	$ 110,897