Tumor coils which have both saccharidase and tyrosinase activity are selectively treated by administration of a conjugate of a cytotoxic compound which is a substrate for tyrosinase and at least one saccharide or a pharmaceutically acceptable salt or ester thereof. Among the cytotoxic phenolic compounds which are substrates for tyrosinase which can be used are 4-hydroxyanisole, butylated hydroxyanisole, L-3,4-dihydrophenylalanine, dopamine, tertbutylcatechol, hydroquinone, resorcinol, 6-hydroxydopa, and methyl gallate. The efficacy of the treatment is enhanced by also administering a compound that inhibits the action of glutathione reductase.

The metabolism of tumor cells which have .beta.-glucuronidase activity is inhibited by administering to a patient a conjugate of glucuronic acid and a thiocarbamate compound of the formula: ##STR1## wherein R.sup.1 and R.sup.2 are selected from the group consisting of C.sub.1 -C.sub.6 alkyl and C.sub.1 -C.sub.6 cycloaliphatic, and M is selected from the group consisting of hydrogen, an electropositive, ionically bonded metal, and the radical ##STR2## and R.sup.3 and R.sup.4 are selected from the group consisting of C.sub.1 -C.sub.6 alkyl and C.sub.1 -C.sub.6 cycloaliphatic groups.

According to the present invention, a substrate for cytochrome p450 which, after oxidation by cytochrome p450, reacts with thiol groups is conjugated to a saccharide to provide a tumor-specific compound which has low toxicity to normal cells. In one embodiment of the present invention, the saccharide conjugate of the cytochrome p450 substrate is administered in conjunction with a saccharide conjugate of a cytotoxic phenol, which provides a synergistic effect in destroying tumors.