Antitumor activity of a new antibiotic, kazusamycin.

The antitumor activity of a new antibiotic, kazusamycin, against various murine tumors was studied by various treatment schedules. Single, intermittent, and successive injections of the antibiotic were almost equally effective against Ehrlich carcinoma, IMC carcinoma and sarcoma 180 tumor, but successive injections showed more efficacy than the other schedules against Meth A fibrosarcoma and Lewis lung carcinoma. Interestingly, there was no clear dose response for the efficacy of kazusamycin on murine tumors. When HeLa cells were exposed to kazusamycin for 72 hours in vitro, the IC50 value was about 1 ng/ml, however the cytotoxicity of the antibiotic depended on the incubation time.