A New Gene Therapy Vision

Vertebrates see by converting photons into electrical signals in the retina, which, in turn are interpreted by the brain into visual depictions of the environment.  Part of this phototransduction system relies on an enzyme called retinoid isomerohydrolase (or retinal pigment epithelium-specific 65 kDa protein ("RPE65")) to convert all-trans-retinyl esters into 11-cis-retinol in the smooth endoplasmic reticulum.  Healthy functioning of retinal pigment epithelium ("RPE"), a thin layer of cells that nurtures the retina, can become impaired when both RPE65 genes contain mutations that prevent normal enzymatic function.  In patients with Confirmed Biallelic RPE65 Mutation-associated Retinal Dystrophy, this can lead to poor vision or even blindness.

The Food and Drug Adminstration ("FDA") announced, on December 19, 2017, its approval of a gene therapy method developed to improve, or even restore, healthy RPE65 enzyme function by introducing wild-type copies of RPE65 genes directly into RPE tissue.  The method involves surgical delivery of RPE65 genes incorporated into adeno-associated viruses.  Spark Therapeutics, the company marketing this gene therapy, calls its "drug" voretigene neparvovec-rzyl (brand-named LUXTURNA).

As the FDA announced, LUXTURNA "is the first directly administered gene therapy approved in the U.S. that targets a disease caused by mutations in a specific gene."  In the FDA press release, FDA Commissioner, Scott Gottlieb, waxed enthusiastic, suggesting that

this milestone reinforces the potential of this breakthrough approach in treating a wide-range of challenging diseases. The culmination of decades of research has resulted in three gene therapy approvals this year for patients with serious and rare diseases. I believe gene therapy will become a mainstay in treating, and maybe curing, many of our most devastating and intractable illnesses[.]

After previous fatal missteps (e.g., see here), gene therapy is finally seeing the light of day.