Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Consolidated Statements of Operations and Comprehensive Loss
Collaboration revenues	$ 13,801	$ 7,136	$ 2,060
Operating expenses:
Research and development	25,540	20,761	11,866
General and administrative	14,560	8,121	6,407
Total operating expenses	40,100	28,882	18,273
Loss from operations	(26,299)	(21,746)	(16,213)
Other income (expense):
Interest and other income	814	169	50
Other expense, net	(5,377)	(665)	(119)
Total other expense, net	(4,563)	(496)	(69)
Net loss before income tax provision	(30,862)	(22,242)	(16,282)
Benefit from income taxes	(254)	(396)	(23)
Net loss	(30,608)	(21,846)	(16,259)
Net loss attributable to ordinary shareholders	$ (30,608)	$ (21,846)	$ (16,259)
Net loss per share attributable to ordinary shareholders, basic and diluted	$ (2.77)	$ (49.78)	$ (48.81)
Weighted average ordinary shares outstanding, basic and diluted	11,045,370	438,862	333,125
Comprehensives Loss:
Net loss	$ (30,608)	$ (21,846)	$ (16,259)
Other comprehensive income (loss):
Foreign currency translation adjustment	216	(1,820)	2,355
Total comprehensive loss	$ (30,392)	$ (23,666)	$ (13,904)