The road to commercializing gene therapies has been anything but smooth. The concept of using viruses (or “vectors”) to deliver a new gene to targeted cells in the body that can help to fight off disease took a bit of a hiatus after the surprising and tragic death of the first gene therapy patient in 1999.
In 2018, however, gene therapy is expected to make its comeback with expected FDA approvals for a variety of inherited retinal diseases (“IRDs”). Due to the rareness of these conditions, the lack of any known treatment, and the growing knowledge surrounding the specific genetic etiology causing vision loss, researchers maintained their hope that the delivery of a new gene could reverse the loss of vision in some patients.
The gene therapy that expects FDA approval uses a recombinant AAV2 vector encoding a functional copy of the RPE65 gene is predicted to be approved to treat inherited retinal diseases (“IRDs”) caused by biallelic RPE65 mutations. Examples of the RPE65-mediated inherited retinal diseases include some forms of Leber congenital amaurosis and retinitis pigmentosa. Leber congenital amaurosis is an inherited, early-onset retinal dystrophy, and causes severe vision loss in children. Retinitis pigmentosa is more common and affects adults. This condition causes the rod photoreceptor cells to die first, resulting in night blindness and a loss of visual field. Eventually, the cones are also lost, making vision severely limited. Progressive vision loss and blindness are inevitable.
In 2017, the FDA awarded orphan drug status to RPE65 gene therapy, and in October, a panel of U.S. health advisers recommended approval for these innovative approaches to IRDs. Experts believe an approval could lead to more gene therapies getting orphan drug and breakthrough status.
The road is now clearer than it has ever been for restoring vision for patients with IRDs, and for bringing gene therapy into the mainstream.
Where Are They Now
In December 2017, the aforementioned RPE65 gene therapy received its long-awaited FDA approval. The approval makes this gene therapy the first to target a disease caused by mutations in a specific gene. In July 2018, the FDA released a new framework for the development, review, and approval of gene therapies. In the framework, guidance and recommendations related to preclinical testing, clinical trial design, and product development for gene therapies designed for inherited retinal diseases is given. It is the hope that this updated framework with increased emphasis on IRDs will expedite the integration of these therapies into care.