rituximab + methotrexate + ifosfamide + cytarabine + dexamethasone

This is an investigational multi-agent chemoimmunotherapy combination comprising rituximab, methotrexate, ifosfamide, cytarabine, and dexamethasone, designed for the treatment of aggressive B‑cell lymphomas and related hematologic malignancies. Rituximab is a chimeric monoclonal antibody targeting CD20 on B cells, inducing complement-dependent cytotoxicity, antibody‑dependent cellular cytotoxicity, and direct apoptosis of malignant B lymphocytes. Methotrexate is an antimetabolite that inhibits dihydrofolate reductase, depleting reduced folates and blocking thymidylate and purine synthesis, thereby impairing DNA replication in rapidly dividing cells. Ifosfamide is an alkylating agent of the oxazaphosphorine class that produces DNA crosslinks and strand breaks, leading to apoptosis, while cytarabine is a pyrimidine antimetabolite that is phosphorylated intracellularly and incorporated into DNA to inhibit DNA polymerase and chain elongation. Dexamethasone is a synthetic glucocorticoid that exerts lympholytic and anti‑inflammatory effects, contributing to cytotoxicity against lymphoid cells and symptom control. Together, this regimen combines CD20‑directed immunotherapy with multiple non‑overlapping cytotoxic mechanisms to achieve deep tumor debulking in relapsed or high‑risk lymphoma settings; however, this exact five‑drug combination is not a standard named regimen and is typically considered an extrapolation or intensification of established rituximab‑platinum/ifosfamide and methotrexate–cytarabine–steroid–rituximab protocols.[1][2][4][9]