[Effect of some N-alkyl-N-NO-carbamyl esters on leukemia L 5222].

Contrary to N-methyl-N-NO-carbamyl esters, two N-ethyl-N-NO-urethanes have shown, at s.c. application, good chemotherapeutic effectiveness on the monocytic-myelogeneous rat leukaemia L 5222. It was possible to achieve definite healing. Single doses of N-ethyl-N-NO-n-butyl-urethane were equally effective as repeatedly applied smaller doses, the rate of curing amounting in both cases to 80 percent. N-Ethyl-N-NO-ethyl-urethane, however, can be compared to N-ethyl-N-NO-n-butyl-urethane only at repeated application. As suggested by orientative experiments, N-ethyl-N-NO-n-butyl urethane acts directly upon leukaemic cells and does not need any activation in the organism. Whether or not splitting by esterases, which are present in the cells of L 5222, should be decisive for the chemotherapeutic effectiveness of these substances can only be elucidated by further investigation. It is yet too early to form a definite opinion on the carcinogenicity of s.c. applied N-ethyl-N-NO-n-butyl-urethane.