Condensed Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Collaboration and license revenue	$ 2,601	$ 66,865	$ 5,709	$ 69,346
Operating expenses:
Research and development	20,833	13,088	38,556	26,049
General and administrative	3,708	3,059	6,747	5,865
Total operating expenses	24,541	16,147	45,303	31,914
Income (loss) from operations	(21,940)	50,718	(39,594)	37,432
Interest and other income (expense), net	342	(956)	(147)	(796)
Net income (loss)	(21,598)	49,762	(39,741)	36,636
Net income (loss) attributable to common stockholders:
Basic	(21,598)	2,319	(39,741)	1,257
Diluted	$ (21,598)	$ 3,314	$ (39,741)	$ 1,816
Shares used to compute net income (loss) per share attributable to common stockholders:
Basic	14,681,570	1,355,934	8,078,308	1,329,133
Diluted	14,681,570	1,985,644	8,078,308	1,968,821
Net income (loss) per share attributable to common stockholders:
Basic	$ (1.47)	$ 1.71	$ (4.92)	$ 0.95
Diluted	$ (1.47)	$ 1.67	$ (4.92)	$ 0.92