EYECARESCIENCE

Gene Therapy in Ophthalmology

Gene therapy describes the introduction of normal genes into cells in place of missing or defective ones in order to correct genetic disorders. Gene therapy in ophthalmology has made significant advances in recent years, with numerous clinical trials showing promising results. The eye is considered a good candidate for gene therapy; it is small and compartmentalised, requires relatively small numbers of vectors/gene copies, and has special immune response features that can be favourable for gene therapy (1). Some of the key advancements in this field include:

1. Treatment for corneal dystrophies: Corneal dystrophies are a group of inherited disorders that cause progressive clouding of the cornea, leading to vision loss. Gene therapy approaches aim to replace or repair the defective gene responsible for the disease. 
2. Treatment for Retinal Diseases: Gene therapy has shown promising results in the treatment of retinal diseases such as age-related macular degeneration, retinitis pigmentosa, and Leber congenital amaurosis. Gene therapy has shown to restore vision and improve visual acuity in patients with these conditions.
3. CRISPR-Cas9 Technology: CRISPR-Cas9 technology has allowed for precise and efficient editing of specific genes, making it a powerful tool for gene therapy in ophthalmology. This technology has been used to correct mutations that cause retinal diseases, leading to improved visual function.
4. Viral Vectors: Lentiviral and adeno-associated virus (AAV) vectors have also become a popular tool in gene therapy for ocular diseases due to their ability to efficiently deliver therapeutic genes to the retina. AAV vectors in particular have been used to deliver genes to treat conditions such as retinitis pigmentosa, choroideremia, and Stargardt disease.
5. Improved Delivery Methods: Advances in delivery methods, such as the use of subretinal injections and intravitreal injections, have improved the delivery of therapeutic genes to the retina, resulting in more effective treatment of retinal diseases.

One type of gene therapy for ophthalmology has already been approved by the United States Food and Drug Administration (FDA) to treat paediatric patients with a retinal condition called Leber congenital amaurosis who have a deficiency in the RPE65 gene (2). The RPE65 gene provides instructions for making a protein called RPE65, which is involved in the production of a molecule called 11-cis-retinal, an essential component of the visual cycle that allows people to process light.

References:

1. Bennett J. Immune response following intraocular delivery of recombinant viral vectors. Gene Ther. 2003;10(11):977-82.
2. Russell S, Bennett J, Wellman JA, Chung DC, Yu ZF, Tillman A, et al. Efficacy and safety of voretigene neparvovec (AAV2-hRPE65v2) in patients with RPE65-mediated inherited retinal dystrophy: a randomised, controlled, open-label, phase 3 trial. Lancet. 2017;390(10097):849-60.