Share-based compensation - Costs (Details) - USD ($)	1 Months Ended	12 Months Ended
Aug. 31, 2020	Dec. 31, 2020	Dec. 31, 2019
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense	$ 0	$ 621,000	$ 14,000
Unrecognized compensation cost		$ 3,600,000
Recognition period		3 years 10 months 17 days
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 441,000	5,000
Research and development
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense		$ 180,000	$ 9,000

Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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-Topic 718
-SubTopic 10
-Section S99
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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-Topic 718
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Amount of cost to be recognized for option under share-based payment arrangement.

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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.

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No definition available.

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