Current and Upcoming Clinical Trials Now, let’s consider 2 treatments where few or no photoreceptor cells remain alive. Possible treatments here would include: • Donor Photoreceptor Cell and Stem Cell Transplantation • The use of Electronic Prosthetic Devices Photoreceptor Cell Transplantation Clinical Trial • The idea of replacing dead photoreceptor cells with new, donor photoreceptors by transplantation has long been worked on. • There is a small human Clinical Trial on transplantation of photoreceptor cells being conducted by Dr. Norman Radtke in the USA. • It has proven the relatively safety of the technique. BUT, unfortunately, there has not been much good news from the study as to improvement in vision in the patients. Thus, with only very modest positive results from both animal and human studies, it is difficult to see how this will be a viable treatment in the future. Transplantation: Stem Cells An exciting new area of research is in the study of Stem Cell transplantation. • Stem cells are cells that have the potential of multiplying and developing into almost any type of cell in the body. • Thus, theoretically, stem cells could be transplanted into the retinal space where photoreceptor cells have died and could develop and replace them. • However, proper and complex biological signals have to be given to the stem cells such that they develop into mature, functional photoreceptor cells – instead of other cell types. A Stem Cell Clinical Trial? • There are some reports that a clinical trial using stem cells on RP patients has been stopped in the USA. However, the company has not confirmed that stem cells were actually being used. • There are also reports of commercial stem cell therapy in some other countries but these are not well documented as to scientific safety and efficacy. • Much more work needs to be done on stem cells before they can be used as an RD treatment. Electronic Prosthetic Devices for Sight Restoration These fall into 2 categories: 1) Brain (cortical) electronic implants 2) Retinal implants – in front or behind the retina For the retinal implants, there are many different designs and surgical approaches from groups around the world. Brain Prosthetic Devices Three main groups of investigators have worked or are working on brain prosthetic devices that will have the potential to bypass the eye completely. • One group has prematurely done human implants with poor results. • A second group continues to do mainly basic lab work. • The third group is doing excellent work in monkey and is planning a human clinical trial. How Does the Retinal Prosthesis Work? • The device uses electrical signals to bypass defective or dead photoreceptors and stimulate remaining viable, non- photoreceptor cells of the retina. • Images comes from an external video camera worn behind the patient’s glasses. • The images are transmitted through a computer to electrodes (called an array) attached to the retina to reproduce the visual image in the brain. Retinal Prosthesis Trials Groups in many countries are developing retinal prostheses. There are 4 groups around the world that have implanted human subjects with retinal prosthetic devices of different design. • Optobionics Co. (Chicago, IL) – poor design such that it does not function well or at all. • 2 excellent German companies – early stages of human testing – e.g., Retina Implant AG. • Second Sight (Sylmar, CA) – with Dr. Humayun, has already implanted 6 subjects in a Phase 1 study and now over 10 subjects in a Phase 2 Clinical Trial that recently started. Phase 1 Patient Update Chronic studies on human implants have been done on an early electrode device with 16 electrodes -- from 2/02. Six patients were implanted. There were NO device failures. All subjects saw discrete visual images (called phosphenes) and could perform visual spatial and motion tasks. Mobility (walking and navigation) has been improved. The remaining 5 patients use the device at home. Retinal Prostheses – The Future • Several clinical trials have been started. If successful, commercial models should soon become available for implant. • Designs are improving to increase the number of electrodes touching the retina. • Theoretically, a design with about 1,000 electrodes is needed to give reading ability and face recognition. • The prosthetic device may be the best hope for restoring sight to severely affected RP and dry AMD patients. In Conclusion for RP…. Several Clinical Trials are in progress. Proof of Principle for several other types of therapies has been established. • For example, Gene Therapy work on a dog model of RP-LCA shows not only sight restoration but a long term, positive effect. • Other basic work in the fields of gene therapy, stem cell research, pharmaceutical therapy, nutrition and electronic implants show promise in current and future Clinical Trials.
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