Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Revenues:
Total revenues	$ 489	$ 4,200
Operating expenses:
Research and development	16,764	13,427
General and administrative	5,103	3,644
Total operating expenses	21,867	17,071
Loss from operations	(21,378)	(12,871)
Other income (expense):
Interest and other income	190	199
Interest and other expense	(24)	(8)
Loss from valuation of convertible note payable	0	(1,811)
Loss before income taxes	(21,212)	(14,491)
Income tax benefit	5	4
Net loss	(21,207)	(14,487)
Other comprehensive loss:
Unrealized gain on short-term investments, net	40	58
Comprehensive loss	$ (21,167)	$ (14,429)
Net loss per share, basic and diluted (in dollars per share)	$ (0.40)	$ (0.29)
Weighted average shares used to compute basic and diluted net loss per share (in shares)	52,710,672	50,071,165
Strategic Alliances and Collaborations
Revenues:
Total revenues	$ 489	$ 4,200