Evaluation of succinyl neocarzinostatin in vivo.

The toxicity of the bis-succinyl derivative of the protein antibiotic, neocarzinostatin, was compared with the parent compound, neocarzinostatin (NCS), in rats. The derivative was found to be about two to five fold more active than NCS in vivo. The antitumor activity in rats bearing eleven distinct Yoshida hepatoma ascitic cell lines was tested under four possible combinations with regard to sites of drug and tumor cell administration. The results indicate that the antitumor spectrum of the derivative had changed slightly. Antitumor activity in mice was also tested with L1210 and P388 lymphatic leukemia, and with B16 melanocarcinoma. When the effect of the derivative was compared with parental NCS at the molecular level with respect to the inhibition of DNA synthesis in vitro, the specific activities of the two were found to be almost identical. These results were interpreted to indicate that the succinyl derivative of NCS was more stable to inactivation and proteolytic break-down in vivo than NCS as observed previously in in vitro studies.