Enhancement of the antitumor effect of 1,3-bis(2-chloroethyl)-l-nitrosourea (BCNU) by phenylethylbiguanide (phenformin).

Phenlethylbiguanide (phenformin) a commonly used antidiabetic medication has been found to enhance the antitumor effect of 1,3-bis(2-chloroethyl)-l-nitrosourea (BCNU) in advanced subcutaneously implanted murine L1210 leukemia. Enhancement required two doses of phenformin given twelve to 18 hours apart, the treatment starting either before or after BCNU administration. With BCNU alone median survival (MS) was 18 days with 5% cures. BCNU plus phenformin, in optimal dose and schedule, gave a MS of 25 days with 29% cures. Th mechanism of action of phenformin is unknown but may involve several established metabolic effects of this drug.