Treatment with a single dose of Ocrevus (ocrelizumab) depleted a subset of immune T-cells within two weeks in patients with relapsing multiple sclerosis (MS) or primary progressive MS (PPMS), according to a study.
The study, “Ocrelizumab Depletes CD20+ T Cells in Multiple Sclerosis Patients,” was published in the journal Cells.
Autoreactive immune T-cells, which attack the body’s own tissues, have been regarded as the primary mediator of MS; however, this view has been challenged by the effectiveness of therapies targeting immune B-cells that contain the CD20 cell surface protein in reducing disease activity.
Because CD20 is mainly expressed by B-cell precursors and mature B-cells, Ocrevus is often considered to selectively deplete CD20-containing B-cells. However, CD20 is also expressed by highly activated T-cells with the CD3 protein marker, characterized by the increased production of proinflammatory molecules, or cytokines.
These T-cells are found in the blood, cerebrospinal fluid — the liquid surrounding the brain and spinal cord — and chronic brain lesions of MS patients, and show an elevated expression of the CD8 and CD45 markers.
Off-label use of rituximab (marketed as Rituxan in the U.S. and MabThera in Europe), a lymphoma and rheumatoid arthritis treatment that also targets CD20, has been associated with the depletion of CD20-containing T-cells in MS patients. Therefore, targeting this T-cell subtype has been hypothesized as an additional mechanism for rituximab’s clinical effectiveness.
However, scientists did not know whether Ocrevus, which is different from rituximab in terms of CD20 binding and cell toxicity, also depletes CD20-positive T-cells.
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