cyclophosphamide + hydroxychloroquine + methylprednisolone + rituximab

This is a combination therapy consisting of cyclophosphamide (an alkylating agent), hydroxychloroquine (an antimalarial), methylprednisolone (a corticosteroid), and rituximab (a monoclonal antibody). The combination has been studied for treatment of intractable rheumatoid arthritis. Cyclophosphamide works through DNA cross-linking/alkylation, while hydroxychloroquine raises pH in endosomes, inhibits antigen processing, and reduces inflammatory cytokine release. Methylprednisolone provides anti-inflammatory effects, and rituximab targets CD20-positive B cells. This specific four-drug combination builds upon earlier research that showed efficacy with cyclophosphamide, hydroxychloroquine, and azathioprine in treating refractory rheumatoid arthritis.