Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue:
Total revenues	$ 30		$ 2,350
Cost of revenue			464
Gross profit	30		1,886
Operating expenses:
Research and development	16,046	$ 20,572	29,396	$ 42,960
General and administrative	6,138	5,846	12,329	11,892
Total operating expenses	22,184	26,418	41,725	54,852
Loss from operations	(22,154)	(26,418)	(39,839)	(54,852)
Other income (expense), net	(135)	697	535	1,123
Loss before provision for income taxes	(22,289)	(25,721)	(39,304)	(53,729)
Provision for income taxes	2		6
Net loss	$ (22,291)	$ (25,721)	$ (39,310)	$ (53,729)
Net loss per common share, basic and diluted	$ (0.42)	$ (0.54)	$ (0.78)	$ (1.13)
Shares used in computing net loss per share - basic and diluted	52,824,483	47,403,243	50,206,470	47,373,404
Comprehensive loss:
Net loss	$ (22,291)	$ (25,721)	$ (39,310)	$ (53,729)
Unrealized (loss) gain on available-for-sale securities, net of tax	55	9	11	31
Comprehensive loss	(22,236)	$ (25,712)	(39,299)	$ (53,698)
Licensing
Revenue:
Total revenues			2,320
Other
Revenue:
Total revenues	$ 30		$ 30