Patent ID: 7514067

Claim:
A method of in-vivo localizing a water-insoluble drug within the extracellular space of solid tumor tissue in an animal, the method comprising administering a water-soluble prodrug to the animal, wherein the prodrug comprises the drug substituted with a prosthetic group that is cleavable by an enzyme, which is present in the extracellular space of the tumor and which is produced naturally by cells of the tumor, wherein the enzyme is only produced by tumor cells or is produced at concentrations that are higher than that in normal tissues, whereby cleavage of the prosthetic group from the prodrug yields the substantially water-insoluble drug entrapped in the extracellular space, wherein the prodrug has the structure wherein R 1 is selected from the group consisting of a hydrogen radical, a radionuclide, a molecule labeled with one or more radionuclides, a boron atom, a molecule labeled with one or more boron atoms, and a boron cage; R 2 is selected from the group consisting of a hydrogen radical, a radionuclide, and a boron cage; at least one of R 1 and R 2 is not a hydrogen radical; and R 3 is a prosthetic group that can be cleaved from the prodrug by the enzyme.