Condensed Consolidated Statements of Operations and Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Operating expenses:
Research and development	$ 6,418	$ 7,252	$ 12,102	$ 14,841
General and administrative	2,957	3,153	5,311	5,931
Depreciation and amortization	8	47	16	94
Total operating expenses	9,383	10,452	17,429	20,866
Loss from operations	(9,383)	(10,452)	(17,429)	(20,866)
Other income (expense)
Interest expense, net	(284)	(558)	(854)	(1,150)
Foreign currency exchange gain (loss)	42	43	29	(15)
Tax credit income	461	26	790	873
Total other income (expense), net	219	(489)	(35)	(292)
Net loss	$ (9,164)	$ (10,941)	$ (17,464)	$ (21,158)
Net loss per share:
Basic	$ (0.06)	$ (0.07)	$ (0.11)	$ (0.18)
Diluted	$ (0.06)	$ (0.07)	$ (0.11)	$ (0.18)
Weighted-average common shares outstanding:
Basic	152,771,103	152,460,531	152,770,434	114,934,938
Diluted	152,771,103	152,460,531	152,770,434	114,934,938
Other comprehensive loss:
(Loss) gain on foreign currency translation	$ (745)	$ 83	$ (953)	$ (348)
Unrealized gain (loss) on short-term investments	20	24	(68)	(2)
Total comprehensive loss	$ (9,889)	$ (10,834)	$ (18,485)	$ (21,508)