Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 46,177	$ 49,778
Available for sale securities	142,472	88,676
Prepaid expenses and other current assets	3,873	2,563
Total current assets	192,522	141,017
Property and equipment, net	1,832	540
Deferred offering costs		102
Other assets	1,281	1,281
Total assets	195,635	142,940
Current liabilities:
Accounts payable	5,143	2,313
Accrued expenses	15,789	9,555
Total current liabilities	20,932	11,868
Deferred rent	1,406	69
Deferred revenue	40,000
Other non-current liabilities	9	5
Total liabilities	62,347	11,942
Commitments and contingencies (Note 8)
Stockholders' equity:
Preferred stock $0.00001 par value, 25,000,000 shares authorized at June 30, 2016 and December 31, 2015; 0 shares issued and outstanding at June 30, 2016 and December 31, 2015
Common stock: $0.00001 par value; 175,000,000 shares authorized at June 30, 2016 and December 31, 2015; 38,008,933 and 30,662,218 shares issued and outstanding at June 30, 2016 and December 31, 2015, respectively	0	0
Additional paid-in capital	356,217	292,783
Treasury stock, at cost, 0 shares in 2016, 8,643 shares in 2015		(162)
Accumulated other comprehensive income (loss)	37	(234)
Accumulated deficit	(222,966)	(161,389)
Total stockholders' equity	133,288	130,998
Total liabilities and stockholders' equity	$ 195,635	$ 142,940