Macular degeneration is the leading cause of blindness in people over 50. Researchers at Trinity College in Dublin, Ireland announced that they have made a major breakthrough in the treatment for age-related macular degeneration. They published their findings online on April 2 in the journal Science Translational Medicine.
The investigators discovered that interleukin-18 (IL-18), which is a component of the immune system, can protect macular degeneration patients from vision loss; in addition, it can be administered in a non-invasive manner. The administration route is in itself a major breakthrough because current treatments for macular degeneration entails monthly injection of medication directly into the eyeball. IL-18 is administered intravenously and the substance has already been subjected to clinical trials, which have found that it has an excellent safety profile when administered intravenously.
Two forms of age-related macular degeneration exist: the “wet” and “dry” forms. The wet form is by far the most common; it accounts for 90% of the severe cases. The wet form is due to blood vessels growing into the retina, the layer of tissue lining the inner surface of the eye, which collects images to be sent to the brain. These blood vessels leak blood or fluid, which causes immediate retinal blindness. Retinal blindness can be devastating to patients because the retina provides sharp, central vision for reading, driving, and perceiving small details. IL-18 was found to be effective for treating wet macular degeneration.
The researchers note that IL-18 completely prevents the development of a molecule called VEGF, which is responsible for stimulating the overgrowth of blood vessels into the retina. They evaluated IL-18 in a mouse model. They reproduced the damage that wet AMD patients experience by aiming a very fine laser beam to damage the backs of the mice’s eyes. They then administered a form of IL-18 that the pharmaceutical company GlaxoSmithKline had been developing as a potential cancer therapy. They found that IL-18 was able to prevent the leakage from the blood vessels into the retina, as well as stop their overgrowth. Because IL-18 is pro-inflammatory agent (an agent that promotes inflammation), the investigators were concerned about patient tolerance; however, preliminary human trials have shown that low doses have no adverse side effects, other than a very low-grade fever.
The research team is hopeful that IL-18 may be used as an adjunct (additional) therapy to anti-VEGF therapies until further studies can confirm it as a feasible replacement. Because the cells produced by IL-18 tend to remain in the body for six to eight weeks, this treatment could potentially lessen, if not eliminate, the number of injections wet AMD patients must receive each year.