Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 145,460	$ 168,517
Marketable securities	197,104	228,962
Prepaid expenses and other current assets	6,480	5,100
Total current assets	349,044	402,579
Property and equipment, net	1,560	1,388
Restricted cash	564	564
Total assets	351,168	404,531
Current liabilities:
Accounts payable	8,230	12,817
Accrued expenses	23,652	22,352
Total current liabilities	31,882	35,169
Other liabilities	840	845
Total liabilities	32,722	36,014
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized at March 31, 2017 and December 31, 2016; no shares issued or outstanding at March 31, 2017 and December 31, 2016
Common stock, $0.0001 par value per share; 120,000,000 shares authorized at March 31, 2017 and December 31, 2016; 37,307,047 and 37,222,518 shares issued at March 31, 2017 and December 31, 2016, respectively; 37,306,701 and 37,222,172 shares outstanding at March 31, 2017 and December 31, 2016, respectively	4	4
Treasury stock, at cost; 346 shares at March 31, 2017 and December 31, 2016	(17)	(17)
Additional paid-in capital	695,645	688,959
Accumulated deficit	(377,105)	(320,327)
Accumulated other comprehensive income (loss)	(81)	(102)
Total stockholders’ equity	318,446	368,517
Total liabilities and stockholders’ equity	$ 351,168	$ 404,531