Photodynamic Therapy for Psoriasis

Originally prepared for the Canadian Psoriasis Foundation by:

, MD, FRCPC
Assistant Professor, Division of Dermatology
University of British Columbia

A NEW FORM OF TREATMENT called "Photodynamic Therapy" has recently been approved in Canada, Japan, Holland, and the United States for patients with certain types of cancer involving the lung, bladder, and esophagus. Like PUVA therapy, photodynamic therapy (also known as "PDT") involves the administration of a drug followed by light exposure. In PDT, drugs known as porphyrins are administered intravenously into the body to sensitize diseased tissue to visible light. The affected tissue is then exposed to laser light in order to activate the porphyrin drug and cause chemical reactions in the tissue. The net result is selective tumor destruction. Several different drugs have been developed for PDT, but porfimer sodium (Photofrin^®) is the only drug that has received official approval for routine use in patients, and only then for the treatment of certain cancers. Porfimer sodium has been developed by QLT Phototherapeutics Inc., which is a Canadian pharmaceutical company. Pilot research studies in patients have shown that porfimer sodium and light can also be useful for psoriasis, but there is a significant side effect-patients who receive porfimer sodium become profoundly sensitive to outdoor light for a six to eight week period. This limits the practical use of intravenous porfimer sodium as a photosensitizer for psoriasis.
Since 1991, we have been investigating the use of laser light and a new drug known as "BPD verteporfin" at UBC for PDT of skin cancer and psoriasis. BPD does not appear to cause prolonged photosensitivity as does porfimer sodium and thus is of potential practical use for psoriasis. BPD is also being developed by QLT Phototherapeutics. To date, BPD and red laser light appear to possess significant anti-psoriasis activity. Our studies have been restricted to treating only small patches of psoriasis on a given patient, and it will be important to confirm our preliminary results by treating wider areas of psoriasis in a larger number of patients. Patients have undergone PDT on an outpatient basis at the Lions Laser Skin Centre of the Vancouver Hospital & Health Sciences Centre. It has recently been discovered using animal models that BPD and light may possess immune suppressive effects that can lead to improvement of inflammatory arthritis. This has not yet been tested for arthritis in humans, but this finding suggests that one day it may be possible for PDT to treat both psoriasis and arthritis in the same patient.
Lasers are expensive medical devices that require significant maintenance and training in order to operate. To get around this limitation in PDT, we have been evaluating a new type of light source known as a "light-emitting diode array," or LED array for short, in our studies of psoriasis. LED arrays are compact, simple to operate, and can be plugged directly into a standard wall socket. LED arrays alone are not effective for psoriasis and must be used in combination with PDT drugs. PDT drugs and light sources are used only on an experimental basis at the present time for psoriasis. We are probably at least 2 to 3 years away from offering routine treatment of psoriasis using PDT. Waiting around for new therapies can be frustrating for patients, but it is important that both the safety and efficacy of any treatment be tested scientifically before it is approved by the Canadian Health Protection Branch. Although we are encouraged by the results achieved thus far, it is important to emphasize that we are not yet able to predictably clear any patient's psoriasis with PDT at the present time.
Our research team in Vancouver includes , , (Research Nurse), and . We are grateful to the patients from the Vancouver area who have helped us by volunteering for our research program. For further information on our PDT studies, please browse our Internet web server at:
http://www.derm.ubc.ca/
For information on the use of PDT for cancer, please contact QLT Phototherapeutics Inc. at 1-800-663-5486.

Disclaimer: Neither the above investigators nor the UBC Division of Dermatology
own any financial interest in QLT Phototherapeutics Inc.

Created: 18Feb96.

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