Segment Information - Schedule of Segment expenses reviewed by the CDMO (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Segment Reporting Information [Line Items]
Research and development expense	$ 13,684	$ 16,198	$ 26,039	$ 35,050
General and administrative expense	4,963	5,774	10,222	11,379
Net loss and comprehensive loss	(18,711)	(21,072)	(34,045)	(44,306)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Research and development expense	13,684	16,198	26,039	35,050
General and administrative expense	4,963	5,774	10,222	11,379
Interest and other income (loss)	(64)	900	2,216	2,123
Net loss and comprehensive loss	(18,711)	(21,072)	(34,045)	(44,306)
Operating Segments [Member] | Total program expenses
Segment Reporting Information [Line Items]
Research and development expense	10,168	10,805	17,376	24,087
Operating Segments [Member] | Personnel and related
Segment Reporting Information [Line Items]
Research and development expense	2,145	3,347	5,603	6,770
General and administrative expense	1,577	1,938	3,680	3,906
Operating Segments [Member] | Equity-based compensation
Segment Reporting Information [Line Items]
Research and development expense	567	1,164	1,342	2,244
General and administrative expense	810	1,332	1,680	2,553
Operating Segments [Member] | Facilities and other
Segment Reporting Information [Line Items]
Research and development expense	804	882	1,718	1,949
General and administrative expense	2,576	2,504	4,862	4,920
Operating Segments [Member] | Mecbotamab vedotin, BA3011 | Total program expenses
Segment Reporting Information [Line Items]
Research and development expense	3,051	3,500	5,992	8,833
Operating Segments [Member] | Ozuriftamab vedotin, BA3021 | Total program expenses
Segment Reporting Information [Line Items]
Research and development expense	1,208	2,023	3,285	4,564
Operating Segments [Member] | Evalstotug, BA3071 | Total program expenses
Segment Reporting Information [Line Items]
Research and development expense	3,045	2,447	3,224	5,055
Operating Segments [Member] | BA3182 | Total program expenses
Segment Reporting Information [Line Items]
Research and development expense	2,136	1,206	3,076	2,377
Operating Segments [Member] | Other CAB Programs | Total program expenses
Segment Reporting Information [Line Items]
Research and development expense	$ 728	$ 1,629	$ 1,799	$ 3,258