Short-Term Outcomes of the First in Vivo Gene Therapy for RPE65-Mediated Retinitis Pigmentosa

Improvements induced by retinal gene therapy with voretigene neparvovec depend on visual cortical hemispheric dominance mechanisms

BACKGROUND

RPE65-associated retinal degeneration (RPE65-RD) causes severe visual deficits. Gene therapy with AAV2-hRPE65v2 is a breakthrough but it is currently unknown which visual pathways benefit from treatment and if cortical mechanisms can amplify retinal improvements.

METHODS

In this within-subject design, ten patients with biallelic RPE65-RD underwent sub-retinal injection of AAV2-hRPE65v2. Psychophysical full-field stimulus threshold determination and functional magnetic resonance imaging were performed before and 12 months after treatment. Population receptive fields (pRF) were computed in V1 and visual responses assessed using contrast-reversed checkerboards (3 contrast levels).

RESULTS

Here we show significant improvement in light sensitivity at low-luminance and neural response enhancements under low-luminance conditions specifically in the right hemisphere, which is known to show dominance in attentional and visual pooling of spatial information. Changes in pRF size also reflect known hemispheric spatial asymmetries (left/right biased for local/global analysis, respectively).

CONCLUSIONS

Our findings show a contribution of known early and high-level cortical dominance mechanisms on improvement, which constrain the effects of therapy and are therefore a target for neurorehabilitation. These findings provide insight into the limits of clinical benefits of gene therapy and suggest that neurorehabilitation approaches may be needed to enhance improvements, similarly to cochlear implants.

Longitudinal changes in optoretinography provide an early and sensitive biomarker of outer retinal disease

Objective

To examine whether optoretinography (ORG) can provide greater sensitivity for assessing the time-course of disease progression in Retinitis Pigmentosa compared to standard clinical imaging in a longitudinal study.

Design

Cohort, longitudinal study.

Participants

Five non-syndromic RP patients and eight control subjects participated in the study.

Methods

Clinical examination, imaging sessions and data analysis were all conducted at the University of Washington. Five eyes of 5 patients diagnosed with RP, comparing standard clinical imaging to ORG, were collected over a 21-month span between August 2022 and May 2024.

Main outcome and measures

ORG response to visual stimuli, ellipsoid zone (EZ) width and outer segment length (OS length) were evaluated for longitudinal changes as markers of disease progression.

Results

The reduction in cone function with ORG over time exceeds that observed in standard clinical markers of photoreceptor structure - EZ width and OS length. EZ width and OSL decreased by 4.5% ± 5.9% and 6.5% ± 1.4%, respectively, approximately 9.9 and 6.9 times less than the reduction noted in ORG, respectively. The most notable degradation was noted at the borders of the transition zone, where ORG showed progressive and sub-clinical losses in photoreceptor function whereas standard OCT showed healthy, unaffected outer retinal structure.

Conclusions

Optoretinography detects sub-clinical disease and reliably identifies longitudinal markers of progression with greater sensitivity compared to standard clinical imaging. The ability to detect functional changes in the outer retina prior to standard clinical measures underscores its potential as a sensitive, accelerated and clinically-relevant outcome measure to guide patient selection and their therapeutic response in future clinical trials.

Voretigene neparvovec for inherited retinal dystrophy due to RPE65 mutations: a scoping review of eligibility and treatment challenges from clinical trials to real practice

Biallelic mutations in the RPE65 gene affect nearly 8% of Leber Congenital Amaurosis and 2% of Retinitis Pigmentosa cases. Voretigene neparvovec (VN) is the first gene therapy approach approved for their treatment. To date, real life experience has demonstrated functional improvements following VN treatment, which are consistent with the clinical trials outcomes. However, there is currently no consensus on the characteristics for eligibility for VN treatment. We reviewed relevant literature to explore whether recommendations on patient eligibility can be extrapolated following VN marketing. We screened 166 papers through six research questions, following scoping reviews methodology, to investigate: (1) the clinical and genetic features considered in VN treatment eligibility; (2) the psychophysical tests and imaging modalities used in the pre-treatment and follow-up; (3) the potential correlations between visual function and retinal structure that can be used to define treatment impact on disease progression; (4) retinal degeneration; (5) the most advanced testing modalities; and (6) the impact of surgical procedure on treatment outcomes. Current gaps concerning patients' eligibility in clinical settings, such as pre-treatment characteristics and outcomes are not consistently reported across the studies. No upper limit of retinal degeneration can be defined as the univocal factor in patient eligibility, although evidence suggested that the potential for function rescue is related to the preservation of photoreceptors before treatment. In general, paediatric patients retain more viable cells, present a less severe disease stage and show the highest potential for improvements, making them the most suitable candidates for treatment.

Preclinical dose response study shows NR2E3 can attenuate retinal degeneration in the retinitis pigmentosa mouse model RhoP23H+/. Gene Ther 2024;31:255-262. [PMID: 38273095 PMCID: PMC11090815 DOI: 10.1038/s41434-024-00440-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Retinitis pigmentosa (RP) is a heterogeneous disease and the main cause of vision loss within the group of inherited retinal diseases (IRDs). IRDs are a group of rare disorders caused by mutations in one or more of over 280 genes which ultimately result in blindness. Modifier genes play a key role in modulating disease phenotypes, and mutations in them can affect disease outcomes, rate of progression, and severity. Our previous studies have demonstrated that the nuclear hormone receptor 2 family e, member 3 (Nr2e3) gene reduced disease progression and loss of photoreceptor cell layers in RhoP23H-/- mice. This follow up, pharmacology study evaluates a longitudinal NR2E3 dose response in the clinically relevant heterozygous RhoP23H mouse. Reduced retinal degeneration and improved retinal morphology was observed 6 months following treatment evaluating three different NR2E3 doses. Histological and immunohistochemical analysis revealed regions of photoreceptor rescue in the treated retinas of RhoP23H+/- mice. Functional assessment by electroretinogram (ERG) showed attenuated photoreceptor degeneration with all doses. This study demonstrates the effectiveness of different doses of NR2E3 at reducing retinal degeneration and informs dose selection for clinical trials of RhoP23H-associated RP.

Full-field stimulus threshold testing: a scoping review of current practice

The full-field stimulus threshold (FST) is a psychophysical measure of whole-field retinal light sensitivity. It can assess residual visual function in patients with severe retinal disease and is increasingly being adopted as an endpoint in clinical trials. FST applications in routine ophthalmology clinics are also growing, but as yet there is no formalised standard guidance for measuring FST. This scoping review explored current variability in FST conduct and reporting, with an aim to inform further evidence synthesis and consensus guidance. A comprehensive electronic search and review of the literature was carried out according to the Preferred Reporting Items for Systematic Reviews and Meta-analysis Extension for Scoping Reviews (PRISMA-ScR) checklist. Key source, participant, methodology and outcomes data from 85 included sources were qualitatively and quantitatively compared and summarised. Data from 85 sources highlight how the variability and insufficient reporting of FST methodology, including parameters such as units of flash luminance, colour, duration, test strategy and dark adaptation, can hinder comparison and interpretation of clinical significance across centres. The review also highlights an unmet need for paediatric-specific considerations for test optimisation. Further evidence synthesis, empirical research or structured panel consultation may be required to establish coherent standardised guidance on FST methodology and context or condition dependent modifications. Consistent reporting of core elements, most crucially the flash luminance equivalence to 0 dB reference level is a first step. The development of criteria for quality assurance, calibration and age-appropriate reference data generation may further strengthen rigour of measurement.

Development of experimental treatments for patients with retinitis pigmentosa

Retinitis pigmentosa (RP) is a group of inherited diseases that lead to degeneration of the retina and decreased vision. The World Health Organization reports around 1,300 million people affected by some type of visual impairment worldwide. The prevalence is 1 in every 4000 inhabitants and it is the first cause of blindness of genetic origin, frequent in men with a percentage of 60% and 40% in women. There is a lack of information on this pathology in the world, mainly on the existing treatments for this disease, so this bibliographic review aims to update the existing or under-study treatments and inform the limitations of each of these therapies. This review of scientific literature was carried out by consulting databases such as PubMed and Web of science, the search will be limited to articles from the years 2018-2022. There are several types of therapy in studies: gene therapy, transcorneal electrical stimulation, use of neuroprotectors, optogenic therapy, stem cell transplants and oligonucleotide therapy, which will be discussed in this article, both their benefits and the existing barriers in each treatment experimental. In conclusion, each of these therapies promises a viable treatment in the future for selective groups of people with retinitis pigmentosa, however, some therapies have shown benefit at the beginning of the disease, losing their efficacy in the long term.

Lessons Learned from the Development of the First FDA-Approved Gene Therapy Drug, Voretigene Neparvovec-rzyl

In the 5 years following U.S. Food and Drug Administration (FDA) approval of the first gene therapy reagent approved to treat a genetic disease, voretigene neparvovec-rzyl (Luxturna), retinal disease clinics, hospital pharmacies, operating rooms, and even health insurance entities around the world have incorporated gene therapy as a standard procedure. The success of Luxturna has helped pave the way to establish a template for developing other gene therapy reagents that promise to restore sight or halt the progression of photoreceptor cell loss in both inherited and acquired retinal diseases. Here we review lessons learned from development of a gene therapy drug for RPE65 disease and how these lessons may expedite the development of additional treatments for previously untreatable blinding conditions.

Voretigene Neparvovec for the Treatment of RPE65-associated Retinal Dystrophy: Consensus and Recommendations from the Korea RPE65-IRD Consensus Paper Committee

Mutations in the RPE65 gene, associated with Leber congenital amaurosis, early-onset severe retinal dystrophy, and retinitis pigmentosa, gained growing attention since gene therapy for patients with RPE65-associated retinal dystrophy is available in clinical practice. RPE65 gene accounts for a very small proportion of patients with inherited retinal degeneration, especially Asian patients. Because RPE65-associated retinal dystrophy shares common clinical characteristics, such as early-onset severe nyctalopia, nystagmus, low vision, and progressive visual field constriction, with retinitis pigmentosa by other genetic mutations, appropriate genetic testing is essential to make a correct diagnosis. Also, fundus abnormalities can be minimal in early childhood, and the phenotype is highly variable depending on the type of mutations in RPE65-associated retinal dystrophy, which makes a diagnostic difficulty. The aim of this paper is to review the epidemiology of RPE65-associated retinal dystrophy, mutation spectrum, genetic diagnosis, clinical characteristics, and voretigene neparvovec, a gene therapy product for the treatment of RPE65-related retinal dystrophy.

Estimation of Visual Function Using Deep Learning From Ultra-Widefield Fundus Images of Eyes With Retinitis Pigmentosa

Importance

There is no widespread effective treatment to halt the progression of retinitis pigmentosa. Consequently, adequate assessment and estimation of residual visual function are important clinically.

Objective

To examine whether deep learning can accurately estimate the visual function of patients with retinitis pigmentosa by using ultra-widefield fundus images obtained on concurrent visits.

Design, Setting, and Participants

Data for this multicenter, retrospective, cross-sectional study were collected between January 1, 2012, and December 31, 2018. This study included 695 consecutive patients with retinitis pigmentosa who were examined at 5 institutions. Each of the 3 types of input images-ultra-widefield pseudocolor images, ultra-widefield fundus autofluorescence images, and both ultra-widefield pseudocolor and fundus autofluorescence images-was paired with 1 of the 31 types of ensemble models constructed from 5 deep learning models (Visual Geometry Group-16, Residual Network-50, InceptionV3, DenseNet121, and EfficientNetB0). We used 848, 212, and 214 images for the training, validation, and testing data, respectively. All data from 1 institution were used for the independent testing data. Data analysis was performed from June 7, 2021, to December 5, 2022.

Main Outcomes and Measures

The mean deviation on the Humphrey field analyzer, central retinal sensitivity, and best-corrected visual acuity were estimated. The image type-ensemble model combination that yielded the smallest mean absolute error was defined as the model with the best estimation accuracy. After removal of the bias of including both eyes with the generalized linear mixed model, correlations between the actual values of the testing data and the estimated values by the best accuracy model were examined by calculating standardized regression coefficients and P values.

Results

The study included 1274 eyes of 695 patients. A total of 385 patients were female (55.4%), and the mean (SD) age was 53.9 (17.2) years. Among the 3 types of images, the model using ultra-widefield fundus autofluorescence images alone provided the best estimation accuracy for mean deviation, central sensitivity, and visual acuity. Standardized regression coefficients were 0.684 (95% CI, 0.567-0.802) for the mean deviation estimation, 0.697 (95% CI, 0.590-0.804) for the central sensitivity estimation, and 0.309 (95% CI, 0.187-0.430) for the visual acuity estimation (all P < .001).

Conclusions and Relevance

Results of this study suggest that the visual function estimation in patients with retinitis pigmentosa from ultra-widefield fundus autofluorescence images using deep learning might help assess disease progression objectively. Findings also suggest that deep learning models might monitor the progression of retinitis pigmentosa efficiently during follow-up.