In synthetic studies on the chemical modification of the nucleoside antibiotic bredinin, two new derivatives, 5-carbamoyl-1H-imidazol-4-yl 1-adamantanecarboxylate and 5-carbamoyl-1H-imidazol-4-yl piperonylate, were found to possess a potent antitumor activity in several experimental tumor systems, even though bredinin itself shows only in vitro cytotoxicity and thus lacks therapeutic effectiveness.

These two derivatives of bredinin exhibited antitumor activity against a wide variety of tumors, including leukemias L1210 and P388, Lewis lung carcinoma, B16 melanoma, Colon 26 and 38 adenocarcinomas, Ehrlich carcinoma, and Sarcoma 180. It is noteworthy that these agents showed good therapeutic effects not only against ascitic types of tumors but also against a number of slow-growing solid tumor lines, particularly the ascitic and solid forms of Ehrlich carcinoma. At their optimal doses, both compounds effected a complete cure of all or most of the mice treated.

Although the mechanisms of action of these compounds remain unknown, they are able to suppress in vivo tumor growth, presumably by being slowly anabolized in vivo to an active form and inhibiting purine de novo synthesis as bredinin does.

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