Condensed Consolidated Statements of Operations (Unaudited) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues:
Collaborative research and development revenue from related party	$ 1,128	$ 1,441	$ 3,274	$ 5,621
Operating expenses:
Research and development	8,746	8,321	25,349	22,914
General and administrative	2,619	1,772	7,654	5,721
Total operating expenses	11,365	10,093	33,003	28,635
Loss from operations	(10,237)	(8,652)	(29,729)	(23,014)
Other income (expense):
Interest income	141	95	411	319
Interest expense	(20)	(117)	(776)	(170)
Other income		16		16
Total interest income (expense), net	121	(6)	(365)	165
Net loss	$ (10,116)	$ (8,658)	$ (30,094)	$ (22,849)
Net loss per share, basic and diluted	$ 0.28	$ (2.06)	$ (0.86)	$ (5.49)
Shares used in computing basic and diluted loss per share amounts	36,180	4,201	35,117	4,162