Combinations of Mesna with Cyclophosphamide or Adriamycin in the Treatment of Mice with Tumors1

Following therapeutic administration, cyclophosphamide and Adria mycin are biotransformed to reactive metabolites, some of which are responsible for undesirable systemic toxicities of these chemicals, whereas others are responsible for their chemotherapeutic effectiveness. Microsomal mixed function oxidases activate cyclophosphamide to pro duce phosphoramide mustard and acrolein, while cytochrome reducÃ-ase and xanthine oxidase are capable of transforming Adriamycin and form ing free radicals. These reactive metabolites produce unwantedtoxic side effects; however, their action may be partially ameliorated by the con comitant administration of thiols. In this study we evaluated the thera peutic activity of combinations of mesna (2-mercaptoethanesulfonate) with cyclophosphamide or Adriamycin in mice with a variety of transplantable tumors (LI 210 and P-388 leukemia, Lewis lung and colon 26 carcinoma, B16 melanoma, and M5076 sarcoma). In all cases the admin istration of mesna prior to cyclophosphamide or Adriamycin treatment did not reduce the antitumor effectiveness of these agents and in some instances (C57BL/6 mice with B16 melanoma or M5076 sarcoma) small improvements were observed. Therefore, the addition of thiols, to reduce effectively the buildup of toxic metabolites of cyclophosphamide or Adriamycin may result in the improved therapeutic effectiveness for these agents in the treatment of cancer.