CONDENSED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS
Alliance revenue	$ 255	$ 378
Operating expenses:
Research and development	13,556	11,485
General and administrative	6,979	4,081
Total operating expenses	20,535	15,566
Loss from operations	(20,280)	(15,188)
Other income (expense):
Interest income	211	153
Interest expense	(7)	(16)
Foreign currency exchange loss	(19)	(6)
Net loss	$ (20,095)	$ (15,057)
Net loss per share applicable to common stockholders - basic and diluted (Note 12)	$ (0.10)	$ (0.10)
Weighted-average number of common shares used in computing net loss per share applicable to common stockholders - basic and diluted	199,037	149,100
Net loss	$ (20,095)	$ (15,057)
Other comprehensive income (loss):
Unrealized gain on available-for-sale securities		16
Total other comprehensive income		16
Comprehensive loss	$ (20,095)	$ (15,041)