Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 264,861	$ 148,627
Marketable securities	225,444	42,900
Prepaid expenses and other current assets	968	485
Total current assets	491,273	192,012
Property and equipment, net	255	301
Total assets	491,528	192,313
Current liabilities:
Accounts payable	588	1,929
Accrued expenses	4,848	8,125
Total current liabilities	5,436	10,054
Total liabilities	5,436	10,054
Stockholders' equity:
Preferred stock, par value $0.0001 per share authorized: 5,000,000 shares at June 30, 2018 and December 31, 2017; 1,969,797 shares issued and outstanding at June 30, 2018 and December 31, 2017
Common stock, par value $0.0001 per share authorized: 200,000,000 at June 30, 2018 and December 31, 2017; 15,365,384 and 14,227,634 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	2	1
Additional paid-in-capital	605,418	288,750
Accumulated other comprehensive loss	(43)	(31)
Accumulated deficit	(119,285)	(106,461)
Total stockholders' equity	486,092	182,259
Total liabilities and stockholders' equity	$ 491,528	$ 192,313