|Development of Cell-Based Therapies for Usher syndrome||$52,000|
|Building a Foundation for Clinical Trials in Usher syndrome||$60,000|
|Visual Field Modeling, Analysis, and Development of
Outcome Measures for Treatment Trials in Usher syndrome
Development of Improved Visual Field Testing as an Outcome Measure for Treatment Trials in Usher Syndrome (funded January 2007)
Usher syndrome is a genetic condition causing both hearing loss and vision loss, and is the most common cause of deafblindness in the Western world. Some individuals with Usher syndrome have moderate hearing loss, where others are born totally deaf. With the advent and increasing availability of the cochlear implant, the hearing loss in Usher syndrome can be managed and even, in many cases, cured. The vision loss in Usher syndrome, however, results from retinitis pigmentosa (RP), a progressive disorder of the retina for which there is no known cure or effective treatment. The progressive vision loss resulting from RP is therefore the most disabling aspect of this condition. Finding and delivering effective treatment for RP is the urgent mission of our research.
Accurate monitoring of retinal function in retinitis pigmentosa requires the use of several test methods, including assessment of the visual field and the electroretinogram (ERG). The visual field test quantifies visual field loss, while the ERG measures the electrical impulses of the retina to quantify retinal cell function. Over the last 30 years, the Oregon Retinal Degeneration Center (ORDC), under the direction of Dr. Richard Weleber, has become one of the premier centers in the world for the measurement and standardization of retinal function in RP. As a direct result of Dr. Weleber’s passion and expertise, the ERG has evolved into a highly accurate, sensitive, and reproducible test method. The visual field, however, while extremely informative, has a high degree of test-retest variability. This variability decreases the utility of the visual field test in clinical treatment trials, where accurate, sensitive, and reproducible test measures are vital for monitoring treatment effectiveness. In fact, the lack of acceptable visual field testing for retinal dysfunction is now a limiting factor in initiating clinical trials for RP and Usher syndrome. Dr. Weleber has joined with Dr. Chris Johnson, an internationally known visual field expert with over 20 years of experience in glaucoma research and test development, to refine and develop visual field testing techniques specific to field loss in RP.
This study will assess and optimize computerized visual field test methods for patients with RP by addressing the following three specific aims: to ascertain the test-retest variability of visual field measurements in RP, to spatially characterize visual field losses specific to particular subtypes of RP (including Usher syndrome), and to develop novel testing algorithms that will enable us to move forward with clinical treatment trials. At the conclusion of this study, we will publish our results and make recommendations to the scientific community regarding the best test strategy to use in multi-center clinical treatment trials.
Development of Methods of Usher Syndrome Gene Therapy (funded January 2007)
Usher syndrome is the commonest inherited cause of combined blindness and deafness. The progressive vision loss is currently untreatable, although some hearing may be restored with cochlear implants. Several gene mutations have been identified as causes of the disease, including mutations in the usherin, harmonin and myosin VIIa genes. Gene therapy is a promising experimental treatment that has the potential to prevent the loss of hearing and sight in this devastating condition, but it needs to be developed and tested before it can be attempted in human patients.
The purpose of this application is to develop safe and effective gene therapy methods for Usher syndrome. The long-term goal of this project is to facilitate human clinical trials of this therapy. In this proposal, we have brought together a team of clinical and basic science researchers to accomplish the following goals:
(1) To design and produce a delivery system, using a harmless virus, to deliver the normal usherin, harmonin and myosin VIIa genes to the eye and the inner ear.
(2) To determine the best surgical techniques for safe and efficient delivery of this gene therapy vector to the eye and inner ear. These studies will use a nonhuman primate, the rhesus monkey, because the structure of its eyes and ears are most similar to humans, and different in critical ways from other animals such as rodents.
(3) To test the safety of this gene therapy in monkeys by examining them for any possible side effects of the treatment.
There are no animal models that have Usher syndrome, and therefore it is not possible to test the ability of gene therapy to treat or prevent the disease. However, these studies will be able to test the safety of this treatment in healthy animals. Given the very serious nature of the disease and the potential benefit, clear evidence of safety would make it ethically acceptable to conduct a clinical study in human patients.
Through this project, we aim to provide the foundation for use of gene therapy for Usher syndrome.
We plan that this project will lead to the next steps required to initiate a gene therapy clinical trial: manufacture of a safe vector suitable for a human patients, and, based on demonstration of the treatment’s safety, submission of the necessary regulatory documents to the FDA and other federal agencies. With the experience and information derived from the proposed project, our team at the Casey Eye Institute can then build on its extensive patient base and experience with human clinical trials to bring this new therapy to patients with Usher Syndrome.
Pilot Project of Population Genetic Studies of Usher Syndrome (funded January 2006)
The research is being conducted at the Oregon School of the Deaf in Salem, Oregon by Dr. William Kimberling from Boystown University. The goal of this study is to determine the frequencies of known Usher syndrome subtypes and their mutations in a deaf school population and in students with varied hearing losses in special education classes. This project is nearing completion and we received a synopsis of the study from the researchers at the First Annual Usher Syndrome Symposium in Omaha, Nebraska in October 2006.Ultimately, this information is important for many reasons, including increasing awareness of Usher syndrome, improving genetic testing strategies, providing earlier diagnosis, and identifying individuals as potential treatment candidates for future clinical trials. There is an opportunity that if the pilot project is successful, the National Institute of Health will award a 2.5 million dollar grant for the full screening project. This type of research gives us great hope for a cure.
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