Summary of significant accounting policies - Narrative (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2021 USD ($) segment	Dec. 31, 2020 USD ($)	Jan. 01, 2022 USD ($)
Summary of significant accounting policies
Impairment losses	$ 0	$ 0
Deferred offering costs	300	0
Restricted cash	100	100
Change in fair value of warrant liability		5,538
Research and development expense	$ 0	$ 0
Number of operating segments | segment	1
Expected dividend yield	0.00%
ASU 2016-02
Summary of significant accounting policies
Operating lease right-of-use asset			$ 200
Operating lease liability			$ 200