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Gene trial ‘restores sight’

pharmafile | January 17, 2014 | News story | Research and Development, Sales and Marketing NHS, Oxford University Hospitals NHS Trust, choroideremia, eyes 

A UK Phase I trial of a gene therapy designed to restore sight in patients suffering from an inherited form of blindness has gone better than anticipated, say researchers.

Nine patients with choroideremia – which is caused by a defective gene that affects light sensing cells in the eye and currently has no cure – have had one eye treated at the Oxford Eye Hospital, part of Oxford University Hospitals NHS Trust.

Patients’ vision in dim light improved and two patients were able to read more lines on an eye chart – and because the results were promising in the first six patients, the next three were tested at a higher dose.

The operation is similar in some ways to cataract surgery: however, doctors have been at pains to point out, despite the encouraging results reported in The Lancet, that there is uncertainty.

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“It is still too early to know if the gene therapy treatment will last indefinitely,” admitted Professor Robert MacLaren of the Nuffield Laboratory of Ophthalmology at the University of Oxford, who led the trial.

But he added: “We can say that vision improvements have been maintained for as long as we have been following up the patients, which is two years in one case. We are now trying higher doses of the gene therapy in the next part of the clinical trial to find what level is needed to stop the degeneration.”

The trial, funded by the Health Innovation Challenge Fund, a partnership between the Wellcome Trust and the Department of Health, initially had a more modest aim: to ensure that replacing the defective CHM gene by injecting a virus under the retina could be achieved without causing damage.

“The difficult bits are done,” MacLaren suggested. “We know the virus carrying the gene therapy gets into the cells and the retina recovers after the surgery. Now it’s just waiting to see how the patients progress.”

The idea is that the CHM gene, once within the cells of the retina, starts producing protein to stop the cells dying off: only one eye is treated in the trial in order to allow comparison with progression of the disease in the other eye.

Despite the caveats, MacLaren is “incredibly excited to see what will happen” and says if the treatment works it might be possible to prevent the condition from taking hold.

Choroideremia affects around one in 50,000 people, with the signs appearing in boys – since it is caused by defects in the CHM gene on the X chromosome – in late childhood and the disease progressing until vision is lost.

The National Institute for Health Research (NIHR) Oxford Biomedical Research Centre and the charity Fight for Sight have also supported the research.

Adam Hill

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