Condensed Consolidated Statements of Operations (USD $) In Thousands, except Share data	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Collaboration revenues:
License and milestone revenue	$ 1,143	$ 1,143	$ 2,286	$ 2,286
Cost sharing reimbursements, net		2,217		5,097
Total collaboration revenues	1,143	3,360	2,286	7,383
Grant revenues	211		211
Total revenues	1,354	3,360	2,497	7,383
Operating expenses:
Research and development	10,417	9,688	19,854	19,883
General and administrative	2,946	2,716	5,618	5,802
Total operating expenses	13,363	12,404	25,472	25,685
Loss from operations	(12,009)	(9,044)	(22,975)	(18,302)
Interest expense, net	(493)	(30)	(928)	(80)
Net loss	$ (12,502)	$ (9,074)	$ (23,903)	$ (18,382)
Net loss per common share:
Basic and diluted net loss per common share (in dollars per share)	$ (0.30)	$ (0.22)	$ (0.57)	$ (0.46)
Weighted-average common shares outstanding:
Basic weighted average number of common shares outstanding (in shares)	42,166,739	40,342,671	42,088,215	39,899,593
Diluted weighted average number of common shares outstanding (in shares)	42,166,739	40,342,671	42,088,215	39,899,593