Accrued expenses and other current liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Accrued expenses and other current liabilities
Accrued employee compensation and benefits	$ 9,760	$ 9,928
Accrued external research and development expenses	18,010	10,859
Accrued professional fees	1,319	1,068
Current portion of operating lease liabilities	$ 4,661	$ 3,125
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities
Other	$ 303	$ 1,472
Accrued expenses and other current liabilities	$ 34,053	$ 26,452