| Contingencies and commitments - Universal Cells Research, Collaboration and License Agreement and Co-development and Co-commercialization agreement (Details) - Collaboration and license agreement - Universal Cells, Inc. | Dec. 31, 2022  USD ($) | 
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| Contingencies and commitments | |
| First milestone payment | $ 500,000 | 
| Second milestone payment | 600,000 | 
| Third milestone payment | $ 400,000 | 
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- Definition The amount of milestone payment three. No definition available. 
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- Definition The amount of milestone payment two. No definition available. 
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. Reference 1: http://www.xbrl.org/2003/role/disclosureRef 
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