Poster Presentation 18th International Congress on Photobiology 2024

Chlorin e6 (1) also known as Phytochlorin e6 has over 3,200 literature references. Recently a number of publications have indicated that Chlorin e6 is a U.S. FDA approved photosensitiser. While Chlorin e6 appears on the FDA database, and has a Unique Ingredient Identifier (UNII), it is not an FDA approved photosensitiser.

Chlorin e6 itself has low solubility in aqueous systems and is generally used as one of its more water-soluble salt forms (2), (3) and (4). The chlorin e6 trisodium salt (2) administered with polyvinyl pyrrolidone (PVP) is known as Photolon is approved in the Russian Federation and the Republic of Belarus for the treatment of a number of cancers. Photodithiazine (3) is the dimeglumine salt of Chlorin e6, also approved in the Russian Federation. The trimeglumine salt (4) known as KAE is currently under evaluation in China as an alternative photosensitiser for cancer indications. All three salts are considered 2^nd generation photodynamic agents.

Although these salts have provided valuable learnings, and are no doubt active as photodynamic agents, they are to our knowledge not approved, at this stage, in western countries as photosensitisers.

We have found that all three salts of chlorin e6 are not stable in solution, producing the same major degradation product which we have identified. This degradation product has been tested using in-vitro anticancer screens and has been found to be a more powerful photosensitiser than any of the three chlorin e6 salts. A patent application has been filed (RMWC Limited) covering this invention for application in cancer treatments.