Investigations on the mechanism of action of the novel antitumor agents 2-benzothiazolyl, 2-benzoxazolyl, and 2-benzimidazolyl hydrazones derived from 2-acetylpyridine.

2-Acetylpyridine hydrazone derivatives of benzothiazole, benzoxazole, and benzimidazole were found to exhibit potent cytotoxic activity against the growth of suspended leukemia and lymphomas. They were also active in a number of solid tumor screens, e.g. HeLa uterine carcinoma, SOS bone osteosarcoma, lung MB9812, lung A549, Mcf-7 breast growth. In L1210 lymphoid leukemia cells the compounds preferentially inhibited RNA synthesis followed by DNA synthesis at 100 microM after 60 min. The reduction of de novo purine synthesis by the compounds at the regulatory sites PRPP-amido transferase, IMP dehydrogenase and dihydrofolate reductase was responsible for the suppression of nucleic synthesis. Other minor sites where the agents have metabolic effects were thymidylate synthetase and thymidine kinase which would be additive with the overall inhibition of cell growth. The ct-DNA studies suggest that the compounds also interacted with the DNA molecule itself, probably affecting template activity.