v3.26.1
Segment Reporting - Segment Reporting Information, by Segment (Details) - USD ($)
$ in Thousands
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Mar. 31, 2026
Jun. 30, 2025
Mar. 31, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting [Line Items]            
Total revenues $ 51,221   $ 43,608   $ 55,737 $ 76,340
Research and development stock based compensation 9,192   10,737   18,753 22,950
General and administrative 16,384   15,115   34,093 32,452
Other income (expense), net 15,149   2,097   (35,625) (2,985)
Income tax (benefit) expense 190   250   (90) (117)
Net loss including noncontrolling interest (21,729) $ (128,916) (30,825) $ (48,632) (150,645) (79,457)
License            
Segment Reporting [Line Items]            
Total revenues 0   0   100 0
Milestone            
Segment Reporting [Line Items]            
Total revenues 10,000   25,000   10,000 39,500
Royalties            
Segment Reporting [Line Items]            
Total revenues 41,221   18,608   45,637 36,840
Reportable Segment            
Segment Reporting [Line Items]            
Total revenues 51,221   43,608   55,737 76,340
Internal research and development expenses (24,737)   (23,686)   (50,756) (47,741)
Research and development stock based compensation (4,680)   (6,395)   (9,758) (13,677)
General and administrative (16,384)   (15,115)   (34,093) (32,452)
Other income (expense), net 15,149   2,097   (35,625) (2,985)
Income tax (benefit) expense 190   250   (90) (117)
Net loss including noncontrolling interest (21,729)   (30,825)   (150,645) (79,457)
Reportable Segment | XmAb942 (Xtend TL1A)            
Segment Reporting [Line Items]            
External research and development expense (14,395)   (2,963)   (21,806) (5,365)
Reportable Segment | XmAb819 (ENPP3 x CD3)            
Segment Reporting [Line Items]            
External research and development expense (8,090)   (6,338)   (16,946) (11,148)
Reportable Segment | XmAb412 (TL1A x IL-23p19)            
Segment Reporting [Line Items]            
External research and development expense (2,918)   (1,275)   (10,056) (1,275)
Reportable Segment | XmAb541 (CLDN6 x CD3)            
Segment Reporting [Line Items]            
External research and development expense (5,230)   (2,834)   (8,526) (4,975)
Reportable Segment | XmAb657 (CD19 x CD3)            
Segment Reporting [Line Items]            
External research and development expense (1,544)   (5,778)   (2,413) (10,177)
Reportable Segment | Plamotamab (CD20 x CD3)            
Segment Reporting [Line Items]            
External research and development expense (712)   (2,095)   (1,029) (3,641)
Reportable Segment | XmAb808 (B7-H3 x CD28)            
Segment Reporting [Line Items]            
External research and development expense (199)   (1,679)   347 (3,875)
Reportable Segment | Other programs including research and early stage            
Segment Reporting [Line Items]            
External research and development expense (8,930)   (5,509)   (14,016) (7,601)
Reportable Segment | Wind down costs of terminated programs            
Segment Reporting [Line Items]            
External research and development expense (470)   (3,113)   (1,615) (10,768)
Reportable Segment | License            
Segment Reporting [Line Items]            
Total revenues 0   0   100 0
Reportable Segment | Milestone            
Segment Reporting [Line Items]            
Total revenues 10,000   25,000   10,000 39,500
Reportable Segment | Royalties            
Segment Reporting [Line Items]            
Total revenues $ 41,221   $ 18,608   $ 45,637 $ 36,840