GADOLINIUM(III) TEXAPHYRIN - A TUMOR SELECTIVE RADIATION SENSITIZER THAT IS DETECTABLE BY MRI

Gadolinium(III) texaphyrin (Gd-tex(2+)) is representative of a new cla ss of radiation sensitizers detectable by magnetic resonance imaging ( MRI). This porphyrin-like complex has a high electron affinity [E(1/2) (red.) approximate to 0.08 V versus normal hydrogen electrode] and fo rms a long-lived pi-radical cation upon exposure to hydrated electrons , reducing ketyl radicals, or superoxide ions. Consistent with these c hemical findings, Gd-tex(2+) was found to be an efficient radiation se nsitizer in studies carried out with HT29 cells in in vitro as well as in vivo single and multifraction irradiation studies with a murine ma mmary carcinoma model, Selective localization of Gd-tex(2+) in tumors was confirmed by MRI scanning.