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Xencor Presents Initial Plamotamab Data in Rheumatoid Arthritis at ACR Convergence 2026 and Updates Progress in First-in-Human Study of XmAb657

XNCR
  • Subcutaneous plamotamab (CD20 x CD3) demonstrated deep B-cell depletion (>99%) and dose-dependent reductions in disease activity at Week 12 in a Phase 1b study of rheumatoid arthritis patients.
  • In higher-dose cohorts (DL3 & DL4) of the plamotamab study, patients experienced clinically meaningful decreases in CDAI scores, improvements in DAS28-ESR, & reduced tender/swollen joint counts.
  • Plamotamab showed a well-tolerated safety profile with one Grade 1 cytokine release syndrome event, no neurotoxicity, & common adverse events including pyrexia & injection site erythema.
  • XmAb657 (CD19 x CD3) demonstrated dose-dependent B-cell reductions in 30 healthy participants in its first-in-human Phase 1 study, with one Grade 1 cytokine release syndrome event reported.
  • Xencor plans to complete one additional single-dose cohort of XmAb657 in healthy participants by year-end 2026 & begin enrolling patients with severe autoimmune diseases in Q1 2027.
  • The plamotamab data is being presented at the ACR Convergence 2026 conference, while the company continues multiple-dose escalation for plamotamab & prepares for patient enrollment in the XmAb657 study.