Reconstitution of CXCR3(+) CCR6(+) Th17.1-Like T Cells in Response to Ofatumumab Therapy in Patients With Multiple Sclerosis.

BACKGROUND AND OBJECTIVES: Ofatumumab, a fully human anti-CD20 monoclonal antibody, is effective in reducing relapses and disability progression in patients with multiple sclerosis. This study aimed to examine immune profile changes associated with ofatumumab in a prospective cohort of Chinese patients with relapsing-remitting multiple sclerosis (RRMS). METHODS: Seventeen RRMS patients were enrolled in this uncontrolled, prospective, observational cohort study (OMNISCIENCE study) and received regular subcutaneous ofatumumab treatments. Immune cell subsets were analyzed by single-cell mass cytometry at baseline and 6 months post-treatment. Peripheral blood monoclonal cells (PBMCs) from a separate cohort of treatment-naive RRMS patients were used for cytokine analysis through ex vivo flow cytometry. RESULTS: Following ofatumumab treatment, B cells in peripheral blood remained depleted, with surviving cells predominantly consisting of antibody-secreting cells and transitional B cells. Increased proportions of NK cells and myeloid cells, particularly HLA-DR(hi) intermediate monocytes, were observed, and FOXP3 and CTLA-4 expression on CD4(+) T cells was upregulated. Notably, prior to the subsequent dose of ofatumumab, Th17.1-like CXCR3(+)CCR6(+) memory CD4(+) and CD8(+) T cell clusters increased significantly, with a transient CD20 expression rebound. In vitro experiments further confirmed that ofatumumab reduced these Th17.1 cell subsets and related pro-inflammatory cytokines. DISCUSSION: These findings suggest that ofatumumab impacts interactions among pathogenic B cells, T cells, and myeloid cells, with Th17.1 cells emerging as a potential direct target within T cells. Persistent and regular infusions of ofatumumab appear necessary to sustain clinical efficacy. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT05414487.