Photodynamic therapy (PDT) is a combination treatment that combines light energy with a drug (photosensitizer) to destroy cancerous and precancerous cells. The process begins with the topical application of the photosensitizer. This photosensitizer is then absorbed by both abnormal and healthy cells, undergoing a six-step biosynthesis to transform into the active pharmaceutical ingredient, protoporphyrin XI. Upon exposure to light, protoporphyrin XI converts oxygen into reactive oxygen species, which are cytotoxic to cells.

The current standard for photodynamic therapy in dermatology is based on 5-aminolevulinic acid (5-ALA), a non-natural amino acid that serves as a prodrug for protoporphyrin XI. However, 5-ALA-based PDT has two primary drawbacks: its non-selective cytotoxicity, which can harm healthy cells, and the inconvenience of use due to the necessity of a six-step biosynthesis process.