Investigators from the University of Florida College of Medicine have created a gene therapy to target retinitis pigmentosa (RP) using three animal models.
Give me some background first.
Autosomal-dominant RP (adRP) has been found to be caused by mutations in the gene for rhodopsin (RHO).
Previous research of these mutations involving canines found that an adeno-associated viral (AAV) vector involving mRNA prevented retinal degeneration for more than 8 months post-injection.
The question remained, however, if the RNA replacement vector is able to perform independently of the types of mutations and or species.
Talk about this study.
Researchers used this gene therapy to break down and replace malfunctioning genetic material that affects light-sensing photoreceptors within the retina of mice via intravitreally injecting an engineered virus that delivered a functional copy of the gene to one infected eye each.
Spectral-domain optical coherence tomography (SD-OCT) was used to monitor retinal structure and electroretinopathy (ERG) for retinal function for the duration of the 9-month study.
Findings?
Investigators observed improvements in both retinal structure and function of the injected mice throughout the study period, with their eyes retaining 50% of their retinal thickness after 9 months.
Eyes not treated with the gene therapy exhibited a 40% decrease in retinal thickness after Month 1 and a 50% decrease in photoreceptors after 3 months.
Anything else?
An unexpected by-product of the unilateral therapeutic virus injection included delivering a small amount of beneficial DNA to the untreated eye; however, the levels were much lower than the injected eyes.
Further, photoreceptor survival in mice with a treated eye was found to be improved in both eyes at all ages.
Significance?
With positive data supporting the use of the gene therapy for treating RP in animals, researchers see the potential for advancing its use in human clinical trials.
What’s next?
Researchers plan to investigate a small dose size of the therapeutic virus in preclinical models that might allow them to estimate the optimal dosage for human use.