How Do Retinal Gene Therapies Work?

Reviewed on 6/24/2021

What are retinal gene therapies and how do they work?

Retinal gene therapy is a treatment for a rare disease that causes retinal degeneration (dystrophy) due to inherited mutations in a gene known as RPE65. RPE65 encodes retinal pigment epithelial 65-kDa (RPE65), a protein that plays an essential role in the visual cycle. Retinal gene therapy delivers a healthy copy of RPE65 to the retinal cells.

Visual or retinoid cycle is the biological conversion of a light particle (photon) into an electrical signal by the retinal cells. The retina sends the electrical signal to the brain through the optic nerve, enabling vision. Mutations in the RPE65 gene can cause reduced levels or lack of RPE65 protein, leading to retinal dystrophy, progressive vision loss and ultimately, complete blindness.

Retinal gene therapy is a treatment in which a normal copy of the RPE65 gene is injected into the retinal cells. The RPE65 gene is delivered in an adeno-associated virus whose DNA is modified to carry the gene. The normal RPE65 copy enables the production of functional RPE65 protein and prevents vision loss.

In December 2017, the FDA approved retinal gene therapy for patients with confirmed biallelic (both maternal and paternal copies of the gene) RPE65 mutation-associated retinal dystrophy. The patients must also have viable retinal cells for the therapy to be administered.

Retinal gene therapy is an expensive treatment costing USD 850,000 for both eyes. RPE65 mutation-associated retinal dystrophy affects approximately 1000 to 2000 Americans.

How are retinal gene therapies used?

Retinal gene therapy is a one-time treatment for patients with biallelic RPE65 mutation-associated retinal dystrophy, who have viable retinal cells. Retinal gene therapy is administered as a subretinal injection in one eye at a time, in close intervals but separated at least by six days. Oral corticosteroids are started three days before treatment of each eye, and tapered in 10 days.

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What are side effects of retinal gene therapies?

Side effects of retinal gene therapy may include:

Ocular side effects

Systemic side effects

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor.

What are names of some retinal gene therapy drugs?

Generic and brand name of FDA-approved retinal gene therapy drug is:

References
https://reference.medscape.com/drugs/retinal-gene-therapies

https://www.fda.gov/news-events/press-announcements/fda-approves-novel-gene-therapy-treat-patients-rare-form-inherited-vision-loss

https://pubmed.ncbi.nlm.nih.gov/30711576/

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