X-Linked Retinitis Pigmentosa

Retinitis pigmentosa (RP) is the most common inherited form of blindness; it is characterized by progressive vision loss due to gradual loss of the light-sensitive retinal cells called rods and cones. RP is a group of diseases caused by mutations in one of multiple genes that lead to similar phenotypes, and can be inherited in an autosomal dominant, autosomal recessive or X-linked fashion. Most cases of X-linked RP are due to a mutation in RPGR (retinitis pigmentosa GTPase regulator), a protein primarily expressed in photoreceptors in the retina. Mutations in RPGR are associated with a more severe form of the disease, causing early onset of disease, and a relatively fast progression.

Status

The proposed therapeutic would use ReGenX’s AAV Vector Technology to deliver a normal copy of the RPGR gene to the photoreceptors to restore photoreceptor function and to prevent further vision loss. AAV8 has been shown to be the most efficient AAV serotype to deliver genes to the target cell type (photoreceptors). Given the limited volumes that can be injected in the subretinal space, a more efficient vector is expected to deliver higher efficacy at a given dose. The proposed therapeutic is in the research stage of development.

Market

Over one million people world-wide (100,000 in the U.S.) are affected with retinitis pigmentosa, with up to 10% of those having the form of X-linked RP. The lifetime cost of a person afflicted with X-linked RP is $400,000 (undiscounted, $1.6 million)¹. No treatment is currently available.