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Gene therapy success in age-related macular degeneration trial

22 May 2017
Appeared in BioNews 901

A small, preliminary clinical trial has demonstrated safe and well-tolerated gene therapy to treat wet age-related macular degeneration (AMD).

This condition is a leading cause of progressive blindness in adults, and is caused by the abnormal growth and leakage of blood vessels in the region of the eye known as the retina.

'Even at the highest dose, the treatment was quite safe. We found there were almost no adverse reactions in our patients,' said senior author Peter Campochiaro, professor of ophthalmology at Johns Hopkins University School of Medicine.

The abnormal blood vessel growth of wet AMD is caused by increased production of a protein called vascular endothelial growth factor (VEGF). The blood vessels leak fluid into the central region of the retina, known as the macula, causing progressive loss of vision.

The phase one clinical trial used a modified common cold virus to insert a gene into the retinal cells. The gene caused the cells to produce a protein called sFLT01, which blocks production of VEGF.

Nineteen men and women aged 50 or older with advanced wet AMD were enrolled in the study. Due to its experimental nature, only patients who were unlikely to regain vision following standard treatment were included, and so only eleven of the 19 patients were likely to show fluid reduction.

Four of the eleven patients showed a dramatic reduction in fluid in their eyes, at an equivalent level to optimal standard treatment. Two additional patients showed some reduction of fluid. However, five patients did not show any change in fluid levels. The researchers found these five patients had pre-existing antibodies to the virus used in the trial, and suggest these may have destroyed the virus before the gene could be inserted into the retinal cells. Further research is needed to investigate this.

Current treatments for wet AMD require regular injections directly into the eye every six to eight weeks, the burden and discomfort of which can dissuade patients from maintaining a regular treatment regime.

'This preliminary study is a small but promising step towards a new approach that will not only reduce doctor visits and the anxiety and discomfort associated with repeated injections in the eye, but may improve long-term outcomes because prolonged suppression of VEGF is needed to preserve vision, and that is difficult to achieve with repeated injections because life often gets in the way,' said Professor Campochiaro.

The study was published in The Lancet.

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