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Amount of cost to be recognized for option under share-based payment arrangement.

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Share-based compensation - Costs (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2020	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0	$ 1,155	$ 117	$ 2,229	$ 302
Unrecognized compensation cost		13,500		$ 13,500
Recognition period				3 years 4 months 24 days
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		402	39	$ 924	94
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 753	$ 78	$ 1,305	$ 208