Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Revenue:
Total revenue	$ 2,757	$ 860
Operating expenses:
Research and development	23,000	17,438
General and administrative	3,874	3,160
Total operating expenses	26,874	20,598
Loss from operations	(24,117)	(19,738)
Other expense:
Interest and other income, net	420	234
Change in fair value of preferred stock warrants	1,632	(5,152)
Equity in net loss of equity method investment	(40)
Net loss	(22,105)	(24,656)
Preferred dividends	(1,357)	(2,793)
Net loss available to common stockholders	$ (23,462)	$ (27,449)
Weighted-average shares outstanding used in computing net loss available to common stockholders:
Basic (in shares)	3,146,632	166,373
Diluted (in shares)	3,146,632	166,373
Net loss per common share:
Basic (in dollars per share)	$ (7.02)	$ (148.20)
Diluted (in dollars per share)	(7.02)	(148.20)
Preferred dividends:
Basic (in dollars per share)	(0.43)	(16.78)
Diluted (in dollars per share)	(0.43)	(16.78)
Net loss per share available to common stockholders:
Basic (in dollars per share)	(7.45)	(164.98)
Diluted (in dollars per share)	$ (7.45)	$ (164.98)
Collaboration revenue
Revenue:
Total revenue	$ 1,168	$ 771
Grant
Revenue:
Total revenue	$ 1,589	$ 89