Income Taxes - Deferred tax assets (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Deferred tax assets
Net operating loss carryforwards	$ 85,734	$ 80,136
Tax credit carryforwards	14,576	12,073
Capitalized research and development	16,927	8,094
Capitalized licenses	4,041
Capitalized legal expenses	918	964
Lease liability	90	257
Other differences	2,587	2,365
Total gross deferred tax assets	124,873	103,889
Less valuation allowance	(124,774)	(103,630)
Net deferred tax assets	99	259
Deferred tax liabilities
ROU asset	(99)	(259)
Net deferred taxes	0	0
Deferred tax assets research and development	16,900	8,100
Increase in valuation allowance	$ 21,100	$ 14,600