Consolidated Statements of Convertible Preferred Shares and Shareholders' Equity (Deficit) - USD ($) $ in Thousands	Ordinary Shares Ionis Share Purchase Agreement	Ordinary Shares	Additional Paid-in Capital Ionis Share Purchase Agreement	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Convertible Preferred Shares	Ionis Share Purchase Agreement	Total
Beginning balance at Dec. 31, 2018							$ 122,197
Beginning balance (in shares) at Dec. 31, 2018							8,070,447
Increase (decrease) in convertible preferred shares
Issuance of convertible preferred shares							$ 1,583
Issuance of convertible preferred shares (in shares)							80,385
Conversion of convertible preferred shares to ordinary shares							$ (123,780)
Conversion of convertible preferred shares to ordinary shares (in shares)							(8,150,832)
Beginning balance at Dec. 31, 2018		$ 10		$ 1,857	$ (1,751)	$ (69,942)			$ (69,826)
Beginning balance (in shares) at Dec. 31, 2018		814,728
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 1		142					143
Issuance of ADSs upon exercise of share options (in shares)		85,839
Issuance of ADSs, net of commissions and offering expenses		$ 59		56,322					56,381
Issuance of ADSs, net of commissions and offering expenses (in shares)		4,637,666
Share-based compensation expense				2,688					2,688
Foreign currency translation adjustment					216				216
Net loss						(30,608)			(30,608)
Conversion of convertible preferred shares to ordinary shares		$ 146		123,634					123,780
Conversion of convertible preferred shares to ordinary shares (in shares)		11,647,529
Reclassification of warrant liability to additional paid-in capital and exercise of warrants		$ 9		10,018					10,027
Reclassification of warrant liability to additional paid-in capital and exercise of warrants (in shares)		723,992
Issuance of restricted share awards		$ 2		395					397
Issuance of restricted share awards (in shares)		83,947
Ending balance at Dec. 31, 2019		$ 227		195,056	(1,535)	(100,550)			93,198
Ending balance (in shares) at Dec. 31, 2019		17,993,701
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 1		270					271
Issuance of ADSs upon exercise of share options (in shares)		79,158
Issuance of ADSs, net of commissions and offering expenses		$ 37		48,107					48,144
Issuance of ADSs, net of commissions and offering expenses (in shares)		2,928,813
Issuance of ordinary shares upon exercise of warrants		$ 1							1
Issuance of ordinary shares upon exercise of warrants (in shares)		92,885
Share-based compensation expense				6,514					6,514
Foreign currency translation adjustment					(1,658)				(1,658)
Net loss						(51,010)			(51,010)
Ending balance at Dec. 31, 2020		$ 266		249,947	(3,193)	(151,560)			$ 95,460
Ending balance (in shares) at Dec. 31, 2020		21,094,557							21,094,557
Increase (decrease) in shareholders' equity (deficit)
Issuance of ADSs upon exercise of share options		$ 10		7,173					$ 7,183
Issuance of ADSs upon exercise of share options (in shares)		703,786
Issuance of ADSs, net of commissions and offering expenses	$ 4	$ 104	$ 7,554	290,880				$ 7,558	290,984
Issuance of ADSs, net of commissions and offering expenses (in shares)	282,485	7,498,536
Share-based compensation expense				12,083					12,083
Foreign currency translation adjustment					(195)				(195)
Net loss						(66,819)			(66,819)
Ending balance at Dec. 31, 2021		$ 384		$ 567,637	$ (3,388)	$ (218,379)			$ 346,254
Ending balance (in shares) at Dec. 31, 2021		29,579,364							29,579,364