General Information

Visudyne was approved by the FDA to treat wet age-related macular degeneration sufferers (wet AMD). The drug is a blood-vessel-blocking photoreactive dye that gets injected into the arm of the patient. The dye moves to the blood vessels that are responsible for the loss of sight and is then activated by shining a non-burning beam of light into the eye. The treatment prevents the growth of the destructive blood vessels without hurting the surrounding tissues.

The one other current treatment, laser photocoagulation, is a powerful laser treatment which does carry the risk of hurting the eye. Furthermore, the other treatment only applies to 15% of patients, while Visudyne may be a viable treatment option for 30% of patients.

Although Visudyne is not a cure for wet AMD, it may slow the loss of vision in patients who otherwise may lose much more sight, even to the point of blindness.

Wet AMD is the rarer of the two forms of macular degeneration (accounting for only 10% of patients), however it is the more destructive form. In cases of wet AMD, blood vessels leak into the macula, the light-sensitive layer of tissue in the center of the retina, quickly destroying it. The progression from blurriness of detail to blindness may occur in less than two years.

The other form of AMD is called "dry" AMD, and is less severe, in that vision loss occurs very slowly and may only progress to the point of the patient experiencing a blind spot. Visudyne is not indicated for dry AMD. Furthermore, of the wet AMD patient population, only 2% would qualify to receive this treatment.

AMD is the leading cause of blindness in Americans over 50-years-old. It causes visual impairment in approximately 1.7 million Americans. There is neither a known cause, nor a known cure at this time.

Clinical Results

Two placebo-controlled studies were conducted for 609 patients with age-related macular degeneration. At the end of the one-year treatment period, the group treated with Visudyne had statistically better visual acuity than did those who had placebo treatment. 60% of Visudyne-treated patients had stable vision over the year, versus the 45% of placebo-treated patients who had stable vision.

Side Effects

The most common side effect of the Visudyne treatment is skin photosensitivity or sun sensitivity.

There were also reports of irritations at the injection site in the arm, and mild to moderate transient visual disturbances.

Finally, about 3% of patients experienced increased sensitivity to light, usually within the fist 24-hours following treatment.

Mechanism of Action

Visudyne therapy is a two-stage process requiring administration of both verteporfin for injection and nonthermal red light.

Verteporfin is transported in the plasma primarily by lipoproteins. Once verteporfin is activated by light in the presence of oxygen, highly reactive, short-lived singlet oxygen and reactive oxygen radicals are generated. Light activation of verteporfin results in local damage to neovascular endothelium, resulting in vessel occlusion. Damaged endothelium is known to release procoagulant and vasoactive factors through the lipo-oxygenase (leukotriene) and cyclo-oxygenase (eicosanoids such as thromboxane) pathways, resulting in platelet aggregation, fibrin clot formation and vasoconstriction. Verteporfin appears to somewhat preferentially accumulate in neovasculature, including choroidal neocovasculature. However, animal models indicate that the drug is also present in the retina. Therefore, there may be collateral damage to retinal structures following photoactivation including the retinal pigmented epithelium and outer nuclear layer of the retina. The temporary occlusion of choroidal neovascularization (CNV) following Visudyne therapy has been confirmed in humans by flourescein angiography.
(From FDA Label)

Additional Information

Visudyne will cost $2,000 per treatment. On average, patients will receive five treatments over a two-year period.

Visit the QLT PhotoTherapeutics, Inc. web site to learn more about Visudyne and about other products, research, and services provided by the company that developed this drug.

For more information about Macular Degeneration and research being done in this field, visit the web sites of
the National Eye Institute (NEI)
and
the Macular Degeneration Foundation.