August 28, 2015
An emerging optogenetic therapy that holds promise for restoring vision for people completely blind from retinitis pigmentosa (RP), and potentially other retinal diseases, will soon be moving into a clinical trial. RetroSense Therapeutics, developer of the treatment, has received authorization from the U.S. Food and Drug Administration (FDA) to launch the 15-person, Phase I/II human study.
The Foundation Fighting Blindness provided early funding for the development of RetroSense’s treatment and participated in discussions about the clinical trial with the FDA.
The trial, the first ever for an optogenetic retinal treatment, will be conducted at the Retina Foundation of the Southwest, with David Birch, Ph.D., as the principal investigator.
Information on patient participation will be posted at http://www.clinicaltrials.gov when recruitment begins.
Sean Ainsworth, chief executive officer at RetroSense, says the primary goal of the initial phase of the trial is to evaluate safety, but the company hopes to see some efficacy as well. “Like other safety studies for retinal-disease treatments, we’ll start with the most severely affected patients. But these are the patients we expect to benefit most from the treatment,” he explains. “We hope to see some signs of efficacy within a relatively short period of time. In contrast to many other therapies, we’re not trying to slow progression of disease, which can take years to detect.”
People with RP become completely blind if they lose all of their photoreceptors, the cells in the retina that make vision possible. RetroSense’s optogenetic therapy restores vision by bestowing light sensitivity to retinal ganglion cells, which survive after photoreceptors are lost. Retinal ganglion cells normally don’t process light; rather, they perform image-processing functions downstream.
RetroSense’s optogenetic treatment is a gene therapy, which uses a human-engineered adeno-associated virus (AAV) to deliver a gene to retinal ganglion cells that encodes channelrhodpsin-2, a light-sensing protein. AAVs are being widely used as a delivery system in clinical trials of gene-replacement therapies.
Unlike gene replacement, however, the optogenetic approach has the potential to work independent of the patient’s disease-causing gene — that is, the patient may not need to know his or her gene mutation to benefit from the treatment.
RetroSense has achieved encouraging results for vision restoration in animal studies, but those are difficult to translate to humans because a mouse’s vision is much different from a human’s. For example, a mouse can’t read. “It would be a huge win if, in the human study, we get ambulatory vision and the ability to discern shapes and large objects,” says Ainsworth.
We’re delighted about RetroSense’s forthcoming clinical trial because it offers an alternative for people with highly advanced or complete vision loss in addition to options such as the artificial retina,” says Stephen Rose, Ph.D., chief research officer, Foundation Fighting Blindness.