The era of gene therapy is coming – there’s no doubt about that. And the eye is a promising candidate, as it provides easy surgical access, good visualization of the treated tissue, and has a (relatively) immune privileged status. Over a dozen gene therapies for retinal disease are currently in clinical trials, and many more are in the pipeline.

Adeno-associated virus (AAV) serotype 2 (AAV2) is the vector that, for the most part, has been used safely and successfully in the vast majority of these trials. But there’s a problem. Mouse studies have shown that intravitreal injection (IVI) of AAV2 results in the transduction of the innermost retinal ganglion cells, but not the photoreceptors in the outer retina. Subretinal injection transduces both, but this approach is considerably more challenging, invasive, costlier and riskier to perform than an IVI. In an ideal world, you’d have a vector and genetic payload that can be injected by IVI, and penetrate and target the cell types of interest – even those in the outer retina.