Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue:
Product royalty fees		$ 20	$ 26
License fees	4,144	4,143	5,318
Total revenue	4,144	4,163	5,344
Cost of revenue:
Product royalty fees		24	24
Gross profit	4,144	4,139	5,320
Operating expenses:
Research and development	42,131	21,968	9,023
General and administrative	9,900	8,137	6,330
Sales and marketing	4,755	2,857	1,793
Total operating expenses	56,786	32,962	17,146
Loss from operations	(52,642)	(28,823)	(11,826)
Investment income	262	169	46
Interest expense	(41)	(21)	(20)
Other income			244
Net loss	$ (52,421)	$ (28,675)	$ (11,556)
Net loss per share-basic and diluted (in dollars per share)	$ (0.88)	$ (0.54)	$ (0.29)
Weighted average common shares outstanding-basic and diluted (in shares)	59,481	52,512	40,455