Why is the eye good for testing new therapy approaches?

GENE AND cell therapies offer the potential to treat an array of diseases. Problematic genes could be silenced or overridden, or crucial cell types could be replaced or protected in diseases where they tend to die too early.

But before such therapies get into mainstream use, they have to be trialled in humans to make sure they are safe and that they work.

The eye is one place where new gene and cell therapies are being tested out. But why is the eye such a good spot for it?

“It is an isolated system, so we can inject substances into the eye without risk of systemic [body-wide] side effects,” explains Prof Robin Ali, professor of human molecular genetics at University College London’s Institute of Ophthalmology and Moorfields Eye Hospital. He is leading a trial of gene therapy for a rare inherited form of degenerative blindness called Leber’s congenital amaurosis.

The eye is also a sensitive system for testing how effective therapies are, he adds, and saving even a small number of light-receptive cells called photoreceptors could have a big impact.

“You only need very few functioning photoreceptors to mediate vision,” says Prof Ali, who is associate director of research at Irish charity Fighting Blindness. “So if you preserve a few photoreceptors, you will preserve vision for longer.”

This spring, Prof Ali and colleagues will start an early clinical trial using retinal cells derived from embryonic stem cells. The trial is to involve 12 patients with a different type of degenerative blindness, Stargardt’s disease, and the study will be assessing the safety of introducing the cell therapy into the eye.