fludarabine + cyclophosphamide + mesna

This is a combination chemotherapy regimen consisting of fludarabine, cyclophosphamide, and mesna. Fludarabine is a purine analog that inhibits DNA synthesis by interfering with DNA polymerase and ribonucleotide reductase, leading to cell death in rapidly dividing cells. Cyclophosphamide is an alkylating agent that crosslinks DNA strands, preventing cell division and causing apoptosis. Mesna (sodium 2-mercaptoethanesulfonate) is not an antineoplastic agent but serves as a uroprotective adjuvant; it binds toxic metabolites of cyclophosphamide in the urinary tract to prevent hemorrhagic cystitis without affecting the anticancer efficacy of cyclophosphamide[4][3]. This combination is primarily used as part of conditioning regimens for hematopoietic stem cell transplantation (HSCT), especially reduced-intensity or non-myeloablative protocols for diseases such as acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), chronic lymphocytic leukemia (CLL), and other hematologic malignancies[2][3]. The addition of mesna specifically addresses the risk of bladder toxicity from cyclophosphamide.