Consolidated Balance Sheets - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 168,517,000	$ 186,753,000
Marketable securities	228,962,000	0
Prepaid expenses and other current assets	5,100,000	1,738,000
Total current assets	402,579,000	188,491,000
Property and equipment, net	1,388,000	286,000
Restricted cash	564,000	39,000
Deferred offering costs		200,000
Total assets	404,531,000	189,016,000
Current liabilities:
Accounts payable	12,817,000	5,159,000
Accrued expenses	22,352,000	10,148,000
Total current liabilities	35,169,000	15,307,000
Other liabilities	845,000	14,000
Total liabilities	36,014,000	15,321,000
Commitments and contingencies (Note 5)
Stockholders’ equity:
Preferred stock, $0.0001 par value per share; 5,000,000 shares authorized at December 31, 2016 and 2015; no shares issued or outstanding at December 31, 2016 and 2015
Common stock, $0.0001 par value per share; 120,000,000 shares authorized at December 31, 2016 and 2015; 37,222,518 and 28,823,549 shares issued at December 31, 2016 and 2015, respectively; 37,222,172 and 28,823,549 shares outstanding at December 31, 2016 and 2015, respectively	4,000	3,000
Treasury stock, at cost; 346 shares at December 31, 2016 and none at December 31, 2015	(17,000)
Additional paid-in capital	688,959,000	335,032,000
Accumulated deficit	(320,327,000)	(161,340,000)
Accumulated other comprehensive income (loss)	(102,000)
Total stockholders’ equity	368,517,000	173,695,000
Total liabilities and stockholders’ equity	$ 404,531,000	$ 189,016,000