May 21, 2007
U-M Kellogg Eye Center to offer treatment trial that could slow progress of RP
ANN ARBOR, MI - The University of Michigan Kellogg Eye Center is one of several sites across the nation to evaluate a new treatment for individuals who have lost vision from retinitis pigmentosa, a progressive eye disease that can lead to blindness over time. Participants whose condition meets specific criteria will have surgery to implant a sustained-release capsule in one eye. The capsule releases a naturally occurring protein that is known to retard retinal degeneration.
Ophthalmologists have very few options in treating patients with retinitis pigmentosa (RP). Antioxidant vitamins may help, but are not curative. Currently, there are no proven or known effective treatments for these degenerative eye diseases that affect at least 100,000 Americans.
The symptoms and severity of RP can vary, but the disease often begins with the loss of peripheral or side vision and difficulty seeing at night. As the disease progresses, an individual will have a narrower range of vision, resulting in tunnel vision. The remaining vision may or may not be clear and sharp.
John R. Heckenlively, M.D., an internationally-known expert on inherited retinal disease, will lead the study for the U-M Kellogg Eye Center. He is cautiously optimistic about the prospects for the new treatment because earlier research has demonstrated that the protein, ciliary neurotrophic factor (CNTF), had the ability to slow the degeneration of photoreceptors, the light-sensing cells essential for sight. Dr. Heckenlively explains that after a promising start in the early 1990s, the research on CNTF stalled for lack of a practical method to deliver the therapeutic protein to the eye. With the development of encapsulated cell technology (ECT) by Neurotech USA, Inc., the delivery problem appears to have been solved.
“In light of the preliminary work on CNTF, there are high expectations for this new therapeutic technology,” says Dr. Heckenlively. “This is the first non-specific therapy to emerge with promising experimental results.” He adds that RP is difficult to treat, in part, because there are so many genetic forms. “Rather than targeting a particular type of RP,” says Dr. Heckenlively, “this new therapy focuses on the endpoint of all RP types: vision loss due to degeneration of photoreceptors.”
Dr. Heckenlively, who also has a translational research program, is the principle investigator on a project that has developed over 100 mouse models of inherited ocular diseases that also occur in humans. The natural history and mechanisms of these diseases can be studied closely in mice and the information can then be used to develop treatments for humans. These models have also helped scientists identify disease-causing retinal genes and their effect on vision. To date, scientists have identified over 100 different genes that cause RP.
A Phase I Clinical Trial concluded in 2005 that the CNTF implant using encapsulated cell technology exhibited a safe profile for humans. Currently, there are two Phase II/III clinical trials that will enroll 60 patients each for early- and late-onset forms of RP as well as the related conditions Usher Syndrome (Type II) and Choroideremia. In the current trials, two different doses of CNTF will be used: a high dose or a low dose in one eye, as well as a sham surgery in the other eye so participants will not know which eye has been treated with CNTF.
More information, including requirements for participating in the study, is online at www.clinicaltrials.gov and at the U-M Kellogg Eye Center site at www.kellogg.umich.edu/research/open_clinicaltrials.html.
Written by Betsy Nisbet