Photoprotection is protection from the damage caused by ultraviolet (UV) and visible light, used here to describe protection of human skin. These wavelengths of light (10-750nm) have a range of damaging effects on skin, including: sunburn, photoaging, carcinogenesis (development of cancer) and a host of symptoms specific to certain medical conditions.
Eumelanin (henceforth referred to simply as melanin) is the brown-black coloured pigment produced by the skin. It acts as a photoprotectant by absorbing part of the incoming UV radiation and dissipating it safely. Its properties of reflectance also make melanin capable of scattering and refracting damaging UV rays away from the skin.
Melanin is produced in the outermost later of the skin, the epidermis, in a specific type of cell known as a melanocyte. When the drug afamelanotide is administered it comes into direct contact with the melanocytes. There it binds to receptors on the outside of the cells called melanocortin 1, or MC1R. This binding activates a series of chemical reactions which lead to an increase in the production of melanin. The process of melanin synthesis is known as melanogenesis.
Melanin is made and stored in a small pouch inside the melanocyte, called a melanosome. The melanosomes are then transported from the melanocyte, via tentacle-like projections called dendrites, to another type of cell on the surface of the skin – keratinocytes. Once inside the keratinocytes, the melanosomes containing the melanin granules spread out like an umbrella and protect the skin cells and their genetic information from damage caused by UV light exposure.
SCENESSE® (afamelanotide 16mg) has been approved by the European Commission for the prevention of phototoxicity in adult patients with erythropoietic protoporphyria (EPP). The drug is understood to provide photoprotection to EPP patients by activating the production of melanin in the skin.
A phase IIa proof of concept study evaluating SCENESSE® in variegate porphyria (CUV040) is expected to start patient treatment in the northern hemisphere spring of 2019.