belimumab + ocrelizumab

Belimumab + ocrelizumab is a combination of two monoclonal antibody drugs, each targeting B cells through distinct mechanisms. Belimumab is a fully human IgG1λ monoclonal antibody that inhibits B lymphocyte stimulator protein (BLyS), reducing the survival and differentiation of autoreactive B cells. It is approved for systemic lupus erythematosus (SLE) and lupus nephritis, where it helps decrease disease activity by limiting autoantibody production[3][8]. Ocrelizumab is a humanized anti-CD20 monoclonal antibody that binds to CD20 on the surface of pre-B, naïve, and memory B cells (but not plasma cells or stem/progenitor B cells), leading to their depletion via antibody-dependent cellular cytotoxicity and complement-mediated lysis. Ocrelizumab is approved for multiple sclerosis (MS), including relapsing-remitting and primary progressive forms[2][6]. The rationale for combining these agents would be to achieve more comprehensive suppression of pathogenic B cell populations in autoimmune diseases; however, there are no known clinical trials or regulatory approvals specifically for this combination as of June 2025.