Income taxes - Components of Deferred Tax Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets:
Net operating losses	$ 126,798	$ 113,981
R&D capitalization	67,107	40,380
Tax credit carryforwards	28,409	21,429
Stock-based compensation	6,899	6,522
Accrued expenses	3,142	3,340
Lease liabilities	2,274	3,096
Capitalized licenses	2,725	3,077
Deferred revenue	3,688	1,062
Depreciation	353	437
Other	156	116
Total gross deferred tax assets	241,551	193,440
Valuation allowance	(239,468)	(190,588)
Net deferred tax assets less valuation allowance	2,083	2,852
Deferred tax liabilities
Right-of-use assets	(2,083)	(2,852)
Total gross deferred tax liabilities	(2,083)	(2,852)
Net deferred taxes	$ 0	$ 0