Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revenues:
Collaboration agreements	$ 3,592	$ 7,801	$ 7,303	$ 20,472
Research grants	110	557	341	1,377
Total revenues	3,702	8,358	7,644	21,849
Operating expenses:
Research and development	19,454	15,618	34,720	30,598
General and administrative	11,090	5,017	16,447	9,749
Total operating expenses	30,544	20,635	51,167	40,347
Loss from operations	(26,842)	(12,277)	(43,523)	(18,498)
Interest and other income, net	243	151	430	305
Loss before income taxes	(26,599)	(12,126)	(43,093)	(18,193)
Benefit from income taxes	24		24	748
Net loss	$ (26,575)	$ (12,126)	$ (43,069)	$ (17,445)
Basic and diluted net loss per share	$ (0.38)	$ (0.17)	$ (0.61)	$ (0.25)
Shares used in computing basic and diluted net loss per share	70,487	69,684	70,430	69,485