Padeliporfin

Vascular-targeted photodynamic therapy (VTP), or vascular targeted photochemotherapy, is a focal treatment for localized prostate cancer. VTP involves the process of light activation of photosensitizer localized in the target tissue, which produces reactive oxygen species that work to destroy target cells.

Padeliporfin is retained within the vascular system. When activated with 753 nm wavelength laser light, padeliporfin triggers a photochemical reaction that generates oxygen radicals (hydroxyl radical, superoxide radical), thereby causing local hypoxia of the target tissue. Nitric oxide radicals are also released, resulting in transient arterial vasodilatation that triggers the release of the vasoconstrictor, endothelin-1. Rapid consumption of the nitric oxide radicals by oxygen radicals leads to the formation of reactive nitrogen species (RNS) including peroxynitrite, in parallel to arterial constriction.

Impaired deformability enhances erythrocyte aggregability and formation of blood clots at the interface of the arterial supply of the target tissue, leading to occlusion of the tumour vasculature, or "vascular shutdown." This effect is enhanced by RNS-induced endothelial cell apoptosis and initiation of self-propagated tumour cells necrosis through peroxidation of their membrane.