Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 9,416	$ 12,092
Marketable securities	103,020	46,184
Income tax receivable	560	852
Other receivables	175	87
Prepaid expenses	1,934	1,530
Restricted cash, current	700	700
Total current assets	115,805	61,445
Property and equipment, net	1,399	1,614
Restricted cash	769	769
Total assets	117,973	63,828
Current liabilities:
Accounts payable and accrued expenses	7,190	11,533
Total current liabilities	7,190	11,533
Deferred lease obligation	1,563	1,570
Commitments and contingencies (Note 14)
Stockholders' equity:
Preferred stock; $0.001 par value; 5,000,000 shares authorized at June 30, 2017 and December 31, 2016, zero shares issued and outstanding at June 30, 2017 and December 31, 2016
Common stock; $0.001 par value; 100,000,000 shares authorized at June 30, 2017 and December 31, 2016, 32,567,485 shares and 27,296,863 shares issued and outstanding at June 30, 2017 and December 31, 2016, respectively	33	27
Additional paid-in capital	302,920	212,866
Accumulated deficit	(193,720)	(162,171)
Accumulated other comprehensive (loss) income	(13)	3
Total stockholders' equity	109,220	50,725
Total liabilities and stockholders' equity	$ 117,973	$ 63,828