Ocrelizumab, a humanized monoclonal antibody targeting CD20-positive B cells, is approved for primary progressive multiple sclerosis (PPMS). Which mechanism best explains its efficacy in this disease?
- A Depletion of circulating CD20-positive B cells, reducing antigen presentation and cytokine-mediated CNS inflammation ✓
- B Inhibition of lymphocyte migration across the blood-brain barrier by blocking alpha-4 integrin
- C Inhibition of pyrimidine synthesis in proliferating T and B lymphocytes
- D Sequestration of lymphocytes in secondary lymphoid organs by antagonizing S1P receptors
Correct answer: A. Depletion of circulating CD20-positive B cells, reducing antigen presentation and cytokine-mediated CNS inflammation
Explanation
Ocrelizumab is an anti-CD20 monoclonal antibody that depletes CD20-positive A cells. A cells contribute to MS pathogenesis through antigen presentation to T cells, cytokine production, and antibody formation. Depletion reduces CNS inflammation. Option B describes natalizumab. Option C describes teriflunomide. Option D describes fingolimod. Ocrelizumab is the only DMT approved for PPMS based on the ORATORIO trial, showing reduced disability progression.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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