Balance Sheets (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Current assets
Cash and cash equivalents	$ 39,568	$ 39,814
Due from Novartis Pharma, AG	50,249	960
Available for sale securities	393,718	423,746
Prepaid expenses and other current assets	8,900	8,812
Deferred tax assets	469	293
Total current assets	492,904	473,625
Property and equipment, net	1,563	1,555
Deferred tax assets, non-current	22,597	22,808
Security deposits	282	282
Other Assets	79	100
Total assets	517,425	498,370
Current liabilities
Accounts payable and accrued expenses	4,783	8,707
Accrued research and development expenses	8,103	7,918
Deferred revenue	6,637	3,206
Total current liabilities	19,523	19,831
Deferred revenue, long-term	211,309	206,418
Royalty purchase liability	125,000	125,000
Total liabilities	355,832	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, 34,245,730 and 33,994,520 shares issued and outstanding at March 31, 2015 and December 31, 2014, respectively	34	34
Additional paid-in capital	435,204	428,390
Accumulated deficit	(273,628)	(281,238)
Accumulated other comprehensive loss	(17)	(65)
Total stockholders' equity	161,593	147,121
Total liabilities and stockholders' equity	$ 517,425	$ 498,370