Simple explanation
The retina is a thin sheet of light-sensing cells at the back of the eye, and dozens of inherited faults can destroy it. The eye is the easiest place in the body to try gene editing: it is tiny, so you need very little of anything; it is sealed off, so what you inject stays put; the immune system leaves it relatively alone; and you can watch the result directly and measure whether vision improved.
Go deeper
Inherited retinal dystrophies are caused by variants in over 280 genes. EDIT-101 (Brilliance) delivered CRISPR-Cas9 by subretinal AAV injection to excise the intronic CEP290 c.2991+1655A>G variant causing Leber congenital amaurosis type 10 — the first in vivo CRISPR administration to a human organ. The trial reported meaningful vision improvement in a subset of participants but was discontinued for strategic reasons given the very small eligible population, not for safety.
What the Brilliance trial showed and did not show
Published results showed clinically meaningful improvement in a minority of participants with an acceptable safety profile — genuine proof that in vivo editing can produce functional benefit in a human organ. It was then discontinued because the eligible population for that specific variant was too small to support a commercial programme.
That ending is worth sitting with. It was not a scientific failure; it was an economic one. For ultra-rare variants the science can work and the medicine still not get made, which is exactly the problem the FDA's 2026 draft framework for individualised therapies is trying to address.
Sources
- New England Journal of Medicine (Pierce et al.) · 2024
Gene editing for CEP290-associated retinal degeneration ↗