STUDIES ON ANTITUMOUR DRUGS Ⅳ. A COMPARATIVE EVALUATION OF N-FORMYLSARCOLYSINE AND SARCOLYSINE IN EXPERIMENTAL TUMOURS

The anti-tumour effects of N-formylsarcolysine (N-F) on rat Yoshida sarcoma (ascitic and solid forms) were compared with those of sarcolysine. The single oral LD₅₀ and LD₁₀ of N-F in rats were 700 and 400 mg/kg, and those of sarcolysine were 75 and 43 mg/kg respectively.The CD₅₀ and CD₉₀ of N-F on the Yoshida sarcoma ascitic form were 32 and 68 mg/kg, and those of sarcolysine were 6 and 7 mg/kg respectively.The therapeutic indices (T.I.) of N-F and sarcolysine were respectively 22 and 13; the safety margin (S.M.) of N-F was found to be 6, being equal to that of sarcolysine.The single intravenous LD₅₀ and LD₁₀) of N-F in rats were res- pectively 74 and 49 mg/kg, and those of sarcolysine were 20 and 16 mg/kg.The CD₅₀ and CD₉₀ of N-F on the Yoshida sarcoma solid form were respectively 3.8 and 15 mg/kg, and those of sarcolysine were 0.9 and 4 mg/kg. The T.I. of N-F and sarcolysine were respectively 20 and 21; the S.M. of N-F and sarcolysine were 3.3 and 4 respectively. The results indicate that no significant difference between N-F and sarcolysine in T.I. and S.M. on the Yoshida sarcoma (ascitic and solid forms) was observed. The single intravenous LD₅₀ and LD₁₀ of N-F in mice were 150 and 118 mg/kg, and those of sarcolysine were 18 and 14 mg/kg respectively. The ID₅₀ and ID₉₀ of N-F on mouse reticulosarcoma L₂ were 8.8 and 22 mg/kg, and those of sarcolysine were 17 and 5 respectively; the S.M. of N-F and sarcolysine were 5 and 1.6. It appears that N-F showed a higher antitumour effect and lower toxicity on reticulosarcoma L₂ than sarcoly- sine.