Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 221,861	$ 39,814
Available for sale securities	74,731	423,746
Due from Novartis Pharma AG	4,389	960
Prepaid expenses and other current assets	5,504	8,812
Total current assets	306,485	473,332
Available for sale securities	95,298
Property and equipment, net	3,466	1,555
Deferred tax assets	23,113	4,517
Other assets	489	382
Total assets	428,851	479,786
Current liabilities
Accrued research and development expenses	18,820	7,918
Accounts payable and accrued expenses	12,018	8,707
Deferred revenue	6,667	3,206
Total current liabilities	37,505	19,831
Deferred revenue, long-term	206,399	206,418
Royalty purchase liability	125,000	125,000
Total liabilities	$ 368,904	$ 351,249
Stockholders' equity
Preferred stock - $0.001 par value, 5,000,000 shares authorized, no shares issued or outstanding
Common stock - $0.001 par value, 200,000,000 shares authorized, 35,196,567 and 33,994,520 shares issued and outstanding at December 31, 2015 and December 31, 2014, respectively	$ 35	$ 34
Additional paid-in capital	465,924	428,390
Accumulated deficit	(405,539)	(299,822)
Accumulated other comprehensive loss	(473)	(65)
Total stockholders' equity	59,947	128,537
Total liabilities and stockholders' equity	$ 428,851	$ 479,786