Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 133,450	$ 168,517
Marketable securities	152,478	228,962
Prepaid expenses and other current assets	5,192	5,100
Total current assets	291,120	402,579
Property and equipment, net	1,443	1,388
Restricted cash	849	564
Total assets	293,412	404,531
Current liabilities:
Accounts payable	6,042	12,817
Accrued expenses	26,239	22,352
Total current liabilities	32,281	35,169
Other liabilities	827	845
Total liabilities	33,108	36,014
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized at June 30, 2017 and December 31, 2016; no shares issued or outstanding at June 30, 2017 and December 31, 2016
Common stock, $0.0001 par value per share; 120,000,000 shares authorized at June 30, 2017 and December 31, 2016; 37,423,464 and 37,222,518 shares issued at June 30, 2017 and December 31, 2016, respectively; 37,423,118 and 37,222,172 shares outstanding at June 30, 2017 and December 31, 2016, respectively	4	4
Treasury stock, at cost, 346 shares at June 30, 2017 and December 31, 2016	(17)	(17)
Additional paid-in capital	707,690	688,959
Accumulated deficit	(447,306)	(320,327)
Accumulated other comprehensive loss	(67)	(102)
Total stockholders’ equity	260,304	368,517
Total liabilities and stockholders’ equity	$ 293,412	$ 404,531