One of the top causes for vision loss in people over 60 is Age-related Macular Degeneration (AMD). In more severe cases of wet AMD, a protein called VEGF is over-active. This protein stimulates new blood vessels to grow, leaking blood and fluid into the eye. This fluid build-up damages light-sensing cells, leaving the owner of the eye with progressively larger blind spots.

Current treatments involve injecting a VEGF-binding protein (sFLT01) directly into the eye, thus taking VEGF out of play and preventing the root cause of wet AMD. However, the body does not produce sFLT01 on its own, so treatments must be repeated monthly, leaving the patient open to eye infections and other side effects.

Scientists at Johns Hopkins genetically engineered a common cold virus (AAV2 strain) to deposit a new gene that codes for sFLT01. The virus was chosen because previous studies have shown it was safe to use in the eye. In a small clinical study, four patients showed significant improvement after only one injection and two patients experienced partial improvement. Five patients had AAV2 antibodies present in their system before the study, meaning their immune system was all too happy to destroy the virus before it could be effective. Scientists measured the expression of the gene in patients for 12 months and concluded that higher doses could safely be used to produce more long-lasting results.

While these preliminary results are promising, the scientists admit that a larger and more thorough study is required before proceeding. This study is the first to show that pre-existing antibodies will significantly affect the outcome. Because most people have experienced the common cold, the antibodies for AAV2 and related virus strains are probably widespread. Scientists might have to use less common, and potentially less safe, virus strains to produce an effective treatment for a significant portion of the population.

Managing Correspondent: Zane Wolf

Image Credit: Gary Meek, Georgia Tech

Article: Intravitreous injection of AAV2-sFLT01 in patients with advanced neovascular age-related macular degeneration: a phase 1, -open-label trial – The Lancet

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