Biochemical and biological activity of the anthracycline analog, 4-demethyl-6-O-methyl-doxorubicin.

The chromophore-modified derivative of doxorubicin, 4-demethyl-6-O-methyl-doxorubicin, has been tested for antitumor activity in a range of experimental murine tumor systems. In contrast to the inactive 6-O-methyl derivative of daunorubicin, 4-demethyl-6-O-methyl-doxorubicin provided antitumor effects comparable to that of the parent compound. In addition, detailed DNA-interaction studies showed that the doxorubicin derivative retains the ability to bind DNA by the intercalation mechanism. However, the binding affinity was appreciably reduced following structural modification in the anthraquinone chromophore. On the basis of the proposed models of intercalation, these results could be rationalized in terms of steric influence of the bulky methoxy group. The results of this study are in agreement with the correlation already observed between DNA binding and relative antitumor activity of anthracyclines.