busulfan + melphalan + fludarabine + anti-thymocyte globulin + palifermin

This is a **combination myeloablative conditioning regimen** used prior to allogeneic hematopoietic stem cell transplantation (allo-HSCT), especially for patients with hematologic malignancies such as acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS)[3][7]. The regimen includes the following agents: - **Busulfan:** An alkylating agent that cross-links DNA, leading to inhibition of DNA replication and cell death. - **Melphalan:** Another alkylating agent that also cross-links DNA, providing potent anti-tumor activity. - **Fludarabine:** A purine analog antimetabolite inhibiting DNA synthesis, leading to immunosuppression and anti-leukemic effects[9]. - **Anti-thymocyte globulin (ATG):** A polyclonal antibody preparation that depletes T lymphocytes, providing additional immunosuppression to prevent graft rejection. - **Palifermin:** A recombinant human keratinocyte growth factor (KGF) used to reduce oral mucositis by stimulating epithelial cell proliferation and healing in the oral mucosa[2][10]. This combination is used to maximize anti-leukemic effect, ensure immunosuppression for graft acceptance, and reduce regimen-related toxicity such as severe oral mucositis. Palifermin is included specifically for its protective effects against mucositis, which can be a significant side effect of high-dose chemotherapy[2][6][7].