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First Patient Treated in Choroideremia Gene Therapy Clinical Trial in U.K.

Dr. MacLaren speaks to Jonathan Wyatt, the first patient to be treated, just before the gene therapy operation.”
Dr. MacLaren speaks to Jonathan Wyatt,
the first patient to be treated, just before
the gene therapy operation.
October, 28, 2011 – The first-ever choroideremia gene therapy clinical trial is now underway at the John Radcliffe Hospital in Oxford, United Kingdom. Researchers there have treated their first patient, a 63-year-old man with only a few degrees of central vision.

Choroideremia is an inherited retinal disease that causes progressive vision loss
and affects approximately 6,000 people in the United States and 100,000 around the world. There are currently no treatments for the condition.

“This is a big moment for people with choroideremia,” says Dr. Stephen Rose, chief research officer, Foundation Fighting Blindness. “We have had a number of challenges in developing this therapy, but the persistence and ingenuity of the researchers has paid off well. We now have the opportunity to halt the disease and save vision in people.”

The Foundation Fighting Blindness supported years of preclinical work that made the study possible, and is providing some funding for the clinical trial through its support of the Moorfields Eye Hospital at the University College London, which is also involved in the trial.

Dr. Robert MacLaren of the University of Oxford, who is leading the trial, co-developed the treatment with Dr. Miguel Seabra of the Imperial College, London. Dr. MacLaren says that the initial goal of the 12-person study is to evaluate safety, which will become increasingly evident in the coming months. He hopes to know about the therapy’s effectiveness in about 24 months.

Choideremia is caused by defects in the gene CHM, which affects the choroid, a network of blood vessels underneath the retina that provides critical proteins, blood supply and nutrients to other cells in the retina including photoreceptors and retinal pigment epithelial cells.

The gene therapy delivers copies of the corrective CHM gene into the cells of the retina using a genetically engineered virus known as an adeno-associated virus (AAV). Scientists believe a single treatment may halt the disease for several years or even a lifetime.

The AAV gene delivery technology is similar to that used in clinical trials of gene therapy that restored vision for people with Leber congenital amaurosis, a retinal disease that causes severe vision loss and blindness in children.

As an X-linked condition, choroideremia usually affects men, leading to severe vision loss or blindness in middle age. While women are usually unaffected by choroideremia, they sometimes experience vision loss from the disease, as well.

The Foundation is also funding a choroideremia research project at the University of Pennsylvania. Led by Dr. Jean Bennett, the goal of that effort is to launch a choroideremia gene therapy clinical trial in the U.S. within the next three years.

“We are excited to see results from both the U.K. choroideremia study and the forthcoming U.S. trial,” says Dr. Rose. “It will be of great benefit to have two choroideremia studies underway, because there will likely be significant differences to each approach and we will learn different things from each effort. Ultimately, having two studies greatly increases our chances for success and saving vision.”



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