A study has shown that a single dose of temoporfin (Foscan), a photosensitiser, followed by minimal exposure to light, can lead to partial thickness burns. Researchers from the regional burns centre (Chelsea and Westminster hospital, London) and the Charterhouse clinical research unit (London) report the results of the study of 14 healthy men in the British Medical Journal (2000;320:1245).
The volunteers were given a single dose of temoporfin and after two weeks were exposed to a test dose of sunlight. Twelve men showed no photosensitivity and were discharged. However, within 48 hours, six of the 12 men developed partial thickness burns on the forearm after transient exposure to daylight. Healing took longer than for conventional thermal injury and scarring occurred.
Temoporfin is a second generation photosensitiser. Photosensitising agents are used in the treatment of various malignancies. The agent accumulates in malignant tissue and is activated by a light source which causes it to generate highly reactive oxygen species that destroy malignant cells.
Responding to the study, the manufacturer of temoporfin, Scotia Pharmaceuticals, said that the incidence of burns was significantly higher than had been reported from its overall safety database where mild to moderate photosensitivity reactions had been reported in 10 per cent of over 800 patients. Dr Chris Blackwell (director of development, Scotia) said: "The data are at odds with the results of Foscan trials on several hundred other patients. We do not believe that it will have any effect on the likelihood of our receiving approval for this product from the regulatory authorities."