Pheophorbide a (Pba) has been pegylated to methoxypolyethylene glycol (mPE G-Pba) to produce a soluble photosensitizer that exhibits a higher tissue distribution than free Pba. In vitro studies have shown that mPE G-Pba promotes a fairly strong photosensitizing effect in cancer cells, as previously observed for the unpegylated molecule. mPE G-Pba targets the mitochondria where, following photoactivation, ROS are produced which cause a cellular injury by lipid peroxidation. The results indicate that although pegylation somewhat decreases the phototoxicity, it significantly increases the drug solubility and tissue distribution and tumor uptake of mPE G-Pba, making the conjugate an interesting photosensitizer for PDT.
