Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 180,991	$ 119,456
Short-term marketable securities	264,957
Accounts receivable	3,147	3,153
Prepaid expenses and other current assets	3,494	2,612
Total current assets	452,589	125,221
Long-term marketable securities	2,464
Property and equipment, net	2,454	1,053
Other assets	347	188
Total assets	457,854	126,462
Current liabilities:
Accounts payable	4,413	5,030
Accrued clinical trial and manufacturing expenses	4,886	3,350
Accrued expenses and other liabilities	4,069	2,408
Deferred revenue	19,732	33,427
Total current liabilities	33,100	44,215
Deferred revenue	181,481	2,592
Deferred rent	56
Convertible preferred stock warrant liability		100
Common stock warrant liability		889
Total liabilities	$ 214,637	$ 47,796
Commitments and contingencies (Note 6)
Convertible preferred stock; $0.0001 par value, 0 and 69,716,345 shares authorized at September 30, 2015 and December 31, 2014; 0 and 69,608,339 shares issued and outstanding at September 30, 2015 and December 31, 2014, respectively		$ 139,963
Stockholders’ equity (deficit):
Preferred stock, $0.0001 par value; 10,000,000 and 0 shares authorized at September 30, 2015 and December 31, 2014; 0 shares issued and outstanding at September 30, 2015 and December 31, 2014, respectively
Common stock, $0.0001 par value; 300,000,000 and 85,000,000 shares authorized at September 30, 2015 and December 31, 2014; 62,290,683 and 361,997 shares issued and outstanding at September 30, 2015 and December 31, 2014, respectively	$ 6
Additional paid-in capital	347,088	$ 346
Accumulated other comprehensive income	75
Accumulated deficit	(103,952)	(61,643)
Total stockholders’ equity (deficit)	243,217	(61,297)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 457,854	$ 126,462