CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Income Statement [Abstract]
License revenue	$ 0	$ 0	$ 3,000	$ 0
Operating expenses:
Research and development	9,342	8,854	18,253	14,509
General and administrative	5,316	4,560	9,986	9,343
Total operating expenses	14,658	13,414	28,239	23,852
Loss from operations	(14,658)	(13,414)	(25,239)	(23,852)
Other income (expense):
Interest income	7	394	303	463
Interest expense	(687)	(512)	(1,271)	(911)
Change in fair value of preferred stock warrant liability	0	0	0	(288)
Change in fair value of derivative liability	0	0	0	183
Other income	194	149	235	149
Loss on extinguishment of debt	0	0	(162)	0
Total other income (expense), net	(486)	31	(895)	(404)
Loss before provision for income taxes	(15,144)	(13,383)	(26,134)	(24,256)
Provision for income taxes	0	0	148	0
Net loss	(15,144)	(13,383)	(26,282)	(24,256)
Accruing dividends on Series A convertible preferred stock	0	0	0	(592)
Net loss attributable to common stockholders	$ (15,144)	$ (13,383)	$ (26,282)	$ (24,848)
Net loss per share attributable to common stock holders—basic and diluted (usd per share)	$ (0.76)	$ (1.02)	$ (1.31)	$ (3.32)
Weighted average common shares outstanding—basic and diluted (in shares)	20,032,000	13,177,000	20,016,000	7,479,000
Net loss	$ (15,144)	$ (13,383)	$ (26,282)	$ (24,256)
Currency translation adjustments	0	(65)	0	(42)
Total comprehensive loss	$ (15,144)	$ (13,448)	$ (26,282)	$ (24,298)