Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Collaboration agreements	$ 37,844	$ 43,880	$ 21,678
Research grants	1,695	1,990	2,455
Total revenues	39,539	45,870	24,133
Operating expenses:
Research and development	67,198	56,974	37,039
General and administrative	19,197	15,677	13,800
Total operating expenses	86,395	72,651	50,839
Loss from operations	(46,856)	(26,781)	(26,706)
Other income, net	431	364	82
Loss before taxes	(46,425)	(26,417)	(26,624)
Benefit from income taxes	5,722
Net loss	$ (40,703)	$ (26,417)	$ (26,624)
Basic and diluted net loss per share	$ (0.58)	$ (0.39)	$ (0.48)
Shares used in computing basic and diluted net loss per share	69,757	67,022	55,974