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Choroideremia gene therapy gives long-lasting improvements to vision

Patients who took part in the world’s first gene therapy clinical trial for choroideremia have had a real and long-lasting improvement in vision. A follow-up report is published in the current issue of The New England Journal of Medicine by Professor Robert MacLaren, who led the study at the University of Oxford. The clinical trial was made possible due to research by Professor Miguel Seabra at Imperial College London supported via the Tommy Salisbury Choroideremia Fund at Fight for Sight.

Choroideremia is a rare inherited cause of severe sight loss that affects the male population. Symptoms start in childhood with difficulty seeing at night and eventually lead to complete blindness by around the age of 40.

Tommy Salisbury, from Welling in Kent, was just four-years-old when he was diagnosed in 2005. Following diagnosis his family established the Tommy Salisbury Choroideremia Fund at Fight for Sight, the UK’s main eye research charity. To date, the family has raised over £460,000, led by Tommy’s mother Emma and grandmother Dot Grindley. The funds have directly supported Professor Seabra’s work to identify the function of the CHM protein, which is faulty in choroideremia.

Emma Salisbury said: “It’s a mother’s worst fear to know that your child has an eye condition that’s currently incurable and will cause them to lose their sight. We’ve put our hearts and souls into fundraising and are delighted to have been able to support the initial steps to help make the clinical trial possible. We’ll continue to do everything we can to support Fight for Sight until a cure is found.”

Initial results from the Phase I clinical trial were published in The Lancet in 2014. They showed that two of six patients treated with gene therapy for choroideremia had significant improvements in their vision, in the treated eye.

The follow-up report shows that the benefits have lasted for 3.5 years since treatment, even though vision has become worse in the untreated eye during this time. Two other patients in the study have seen no further loss of vision in their treated eye, while the youngest participant showed no change in either eye. One participant has had a steady decline in vision.

Dolores Conroy, Director of Research at Fight for Sight said: “We’re delighted, to have supported Professor Seabra’s work through the Tommy Salisbury Choroideremia Fund, which has allowed Professor MacLaren and his team to produce some incredible findings. Maintaining these positive results is very encouraging as similar mechanisms for other conditions have not shown improvement lasting over time.”

Professor MacLaren said “This clinical trial marked a major step in developing gene therapy treatments for retinal diseases. It would not have been possible without the scientific funding provided by Fight for Sight through the Tommy Salisbury Choroideremia Fund. In my opinion, this is the single most significant factor that has enabled us to lead the world in starting the first clinical trial for this disease. We shouldn’t under-estimate the power that individuals can have in influencing the course of research through their fundraising activities.”

Article: Visual Acuity after Retinal Gene Therapy for Choroideremia, The New England Journal of Medicine, doi: 10.1056/NEJMc1509501, published 27 April 2016.