STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
REVENUE:
Product Development and Licensing Agreements	$ 2,174	$ 1,442	$ 838
Contracts and Grants	4,612	4,038	2,748
Total Revenue	6,786	5,480	3,586
OPERATING EXPENSE:
Research and Development	102,726	100,171	104,381
General and Administrative	35,979	33,837	20,622
Amortization of Acquired Intangible Assets	997	1,013	1,013
Total Operating Expense	139,702	135,021	126,016
Operating Loss	(132,916)	(129,541)	(122,430)
Investment and Other Income, Net	4,386	2,344	4,350
Net Loss	$ (128,530)	$ (127,197)	$ (118,080)
Basic and Diluted Net Loss Per Common Share (in dollars per share)	$ (1.27)	$ (1.31)	$ (1.32)
Shares Used in Calculating Basic and Diluted Net Loss per Share (in shares)	101,529	97,051	89,399
COMPREHENSIVE LOSS:
Net Loss	$ (128,530)	$ (127,197)	$ (118,080)
Other Comprehensive Income (Loss):
Foreign Currency Translation Adjustments		15	(5)
Unrealized Gain (Loss) on Marketable Securities	234	(298)	(73)
Comprehensive Loss	$ (128,296)	$ (127,480)	$ (118,158)