CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue:
Total revenue	$ 828	$ 372
Operating expenses:
Research and development	6,103	8,751
General and administrative	2,723	3,357
Total operating expenses	8,826	12,108
Loss from operations	(7,998)	(11,736)
Other income (expense):
Interest and other income	95	339
Interest and other expense	(141)	(232)
Net loss	(8,044)	(11,629)
Change in unrealized gain on investments	0	5
Comprehensive loss	(8,044)	(11,624)
Net loss	$ (8,044)	$ (11,629)
Net loss per share, basic and diluted (in dollars per share)	$ (0.18)	$ (0.38)
Weighted-average shares used to compute basic and diluted net loss per share (in shares)	45,476,338	30,886,085
Collaboration revenue
Revenue:
Total revenue	$ 681	$ 348
Grant revenue
Revenue:
Total revenue	$ 147	$ 24