Significant agreements - Ionis (Details) $ in Thousands		1 Months Ended	3 Months Ended		12 Months Ended
	Jul. 09, 2021 USD ($) item	Dec. 31, 2021 USD ($)	Mar. 31, 2022 USD ($) item	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaboration revenues			$ 3,860	$ 1,808
Deferred revenue		$ 71,340	$ 65,578		$ 35,156
Ionis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of collaboration programs | item			4
Number of collaboration targets | item	4
Total transaction price initially determined	$ 38,000		$ 38,000
Upfront payment	31,000
Total share premium	3,400
Estimated amount payable to CROs			$ 600
Expected period for satisfaction of performance obligations			3 years
Material rights exercise period			4 years
Collaboration revenues			$ 2,314	$ 0
Deferred revenue		34,115	30,895
Ionis | Combined licenses and research and discovery performance obligation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total transaction price initially determined			34,100
Ionis | Four material rights associated with credits for IND Acceptance fees
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total transaction price initially determined			3,900
Ionis Evaluation and Option Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment	$ 3,000		$ 3,000		3,000
Collaboration revenues					3,000
Deferred revenue		34,115			$ 3,000
Amended Ionis
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment		1,600
Collaboration revenues		800
Amended Ionis | Service for initial six month
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment		800
Amended Ionis | Service for additional six month
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment		$ 800