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
Condensed Consolidated Statements of Operations and Comprehensive Loss
Collaboration revenues	$ 1,571	$ 1,522	$ 2,700	$ 7,906
Operating expenses:
Research and development	7,958	6,537	15,728	12,813
General and administrative	6,196	2,973	11,197	6,375
Total operating expenses	14,154	9,510	26,925	19,188
Loss from operations	(12,583)	(7,988)	(24,225)	(11,282)
Other income (expense):
Interest and other income, net	371	90	583	154
Other expense, net		(2,184)		(5,377)
Total other income (expense), net	371	(2,094)	583	(5,223)
Net loss before income tax provision	(12,212)	(10,082)	(23,642)	(16,505)
(Benefit from) provision for income taxes	(97)	135	(204)	215
Net loss	(12,115)	(10,217)	(23,438)	(16,720)
Net loss attributable to ordinary shareholders	$ (12,115)	$ (10,217)	$ (23,438)	$ (16,720)
Net loss per share attributable to ordinary shareholders, basic and diluted	$ (0.67)	$ (1.40)	$ (1.30)	$ (4.08)
Weighted average ordinary shares outstanding, basic and diluted	18,077,770	7,298,139	18,024,314	4,101,564
Comprehensives Loss:
Net loss	$ (12,115)	$ (10,217)	$ (23,438)	$ (16,720)
Other comprehensive income (loss):
Foreign currency translation adjustment	(1)	(1,512)	(2,185)	(432)
Total comprehensive loss	$ (12,116)	$ (11,729)	$ (25,623)	$ (17,152)