Condensed Consolidated Statements of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Revenues:
Collaborative research and development revenue from related party		$ 1,927
Operating expenses:
Research and development	8,149	9,255
General and administrative	3,523	2,964
Total operating expenses	11,672	12,219
Loss from operations	(11,672)	(10,292)
Other income (expense):
Interest income	146	116
Interest expense	(11)	(17)
Total other income, net	135	99
Net loss	$ (11,537)	$ (10,193)
Basic and diluted net loss per common share	$ (0.27)	$ (0.28)
Shares used to compute basic and diluted net loss per common share	43,107	36,611