Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 465,867	$ 119,456
Accounts receivable	1,214	3,153
Prepaid expenses and other current assets	2,515	2,612
Total current assets	469,596	125,221
Property and equipment, net	2,122	1,053
Other assets	833	188
Total assets	472,551	126,462
Current liabilities:
Accounts payable	3,961	5,030
Accrued clinical trial and manufacturing expenses	4,181	3,350
Accrued expenses and other liabilities	5,967	2,408
Deferred revenue	17,754	33,427
Total current liabilities	31,863	44,215
Deferred consideration from Novartis collaboration (Note 5)	200,000
Deferred revenue		2,592
Convertible preferred stock warrant liability		100
Common stock warrant liability		889
Total liabilities	$ 231,863	$ 47,796
Commitments and contingencies (Note 6)
Convertible preferred stock; $0.0001 par value, 0 and 69,716,345 shares authorized at June 30, 2015 and December 31, 2014; 0 and 69,608,339 shares issued and outstanding at June 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 June 30, 2015 and December 31, 2014; 0 shares issued and outstanding at June 30, 2015 and December 31, 2014, respectively
Common stock, $0.0001 par value; 300,000,000 and 85,000,000 shares authorized at June 30, 2015 and December 31, 2014; 62,262,615 and 361,997 shares issued and outstanding at June 30, 2015 and December 31, 2014, respectively	$ 6
Additional paid-in capital	345,201	$ 346
Accumulated deficit	(104,519)	(61,643)
Total stockholders’ equity (deficit)	240,688	(61,297)
Total liabilities, convertible preferred stock and stockholders’ equity (deficit)	$ 472,551	$ 126,462