A synthetic light-activated chlorin with photodynamic activity. Upon systemic administration, temoporfin distributes throughout the body and is taken up by tumor cells. Upon stimulation of temoporfin by non-thermal laser light (at 652 nm), and in the presence of oxygen, this agent produces highly reactive short-lived singlet oxygen and other reactive oxygen radicals, resulting in local damage to tumor cells. This may kill tumor cells and may reduce the tumor size. or An anticancer drug that is also used in cancer prevention. It belongs to the family of drugs called photosensitizing agents.