STATEMENTS OF COMPREHENSIVE LOSS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Revenues:
Collaboration revenue	$ 379	$ 10,379
Royalty revenue	80
Total revenues	459	10,379
Operating expenses:
Research and development	13,353	12,178
Selling, general and administrative	10,735	7,400
Total operating expenses	24,088	19,578
Loss from operations	(23,629)	(9,199)
Interest income	81	55
Net loss	(23,548)	(9,144)
Other comprehensive (loss) income:
Unrealized (loss) gain on available-for sale securities	(19)	12
Comprehensive loss	$ (23,567)	$ (9,132)
Basic and diluted net loss per share	$ (0.50)	$ (0.26)
Shares used to compute basic and diluted net loss per share	47,249	35,629