The Burden of X-Linked Retinitis Pigmentosa on Patients and Society: A Narrative Literature Review

The Impacts of Caregiving for Patients with X-Linked Retinitis Pigmentosa (XLRP): Findings from the EXPLORE XLRP-2 Study

INTRODUCTION

Informal caregivers play an important part in the healthcare of patients with chronic diseases, including those leading to visual impairment. X-linked retinitis pigmentosa (XLRP) is considered one of the most severe forms of retinitis pigmentosa and causes declines in vision starting in childhood, ultimately progressing to legal blindness in adulthood. Caregivers are expected to play an increasing role in patient care, but real-world impacts of XLRP on caregivers are poorly evaluated.

METHODS

EXPLORE XLRP-2 was an exploratory, multicentre, non-interventional study. Cross-sectional surveys were used to gather experiences directly from caregivers across Europe and Israel by both validated and newly developed caregiver-reported outcome surveys.

RESULTS

Seventy caregivers of patients with XLRP associated with retinitis pigmentosa GTPase regulator (RPGR) mutations were enrolled, of whom 68 were included in analyses; 87.7% of caregivers were female and mean (standard deviation [SD]) age was 49.4 (11.7) years. They were most commonly either spouses (50.8%) or parents (41.5%) of patients. Caregivers spent a mean (SD) 28.7 (34.5) hours per week caring for patients. Of the 72.3% of caregivers who were employed, 34.8% worked part time; of the 27.7% of caregivers who were unemployed, 33.3% cited caregiving responsibilities as a cause for unemployment; 23.1% and 46.2% of caregivers reported any level of depression and anxiety, respectively, with few additional impacts captured by the surveys.

CONCLUSIONS

Some caregivers reported employment and mental health impacts in this study. However, despite many hours spent per week caring for patients with XLRP, the surveys did not reflect the expected burden experienced by caregivers, highlighting the need for further research in this field.

Voluntary running partially prevents photoreceptor cell death in retinitis pigmentosa

Retinitis pigmentosa (RP) is a progressive retinal degenerative disorder characterized by photoreceptor cell death, leading to vision loss. Current treatments are limited, and there is a need for non-invasive interventions. This study evaluates the neuroprotective effects of voluntary exercise in an RP mouse model and explores the role of the adiponectin signaling pathway in mediating these effects. Pregnant Pde6b rd10 (rd10) mice, a transgenic model of RP, and wild-type C57BL/6J mice were divided into sedentary or voluntary running groups (n = 4 per group). Offspring were analyzed at 6 weeks for photoreceptor nuclei counts, outer segment lengths, serum and retinal adiponectin levels, and expression of AMPK and PGC-1α proteins using immunohistochemistry, ELISA, and Western blotting. Voluntary exercise significantly preserved photoreceptor nuclei (97 ± 16 vs. 32 ± 5 in sedentary rd10 mice) and outer segment lengths for rods (13.1 ± 1.2 μ vs. 1.1 ± 0.6 μ) and cones (7 ± 0.9 μ vs. 0.2 ± 0.1 μm) compared to sedentary rd10 mice. Serum adiponectin levels increased significantly in exercised rd10 mice (p < 0.05), while retinal adiponectin levels were elevated in both sedentary and exercised rd10 mice relative to wild-type controls (p < 0.005). No significant changes in AMPK (p = 0.724) and PGC-1α (p = 0.794) protein levels were observed between exercised and sedentary rd10 mice. These findings suggest that voluntary exercise enhances photoreceptor survival in RP by increasing serum adiponectin levels, potentially contributing to neuroprotection. Elevated retinal adiponectin appears linked to RP pathology rather than exercise-induced changes. This study highlights the therapeutic potential of exercise in RP and identifies adiponectin as a promising target for further investigation into neuroprotective mechanisms and treatments.

Health state utilities associated with X-linked retinitis pigmentosa (XLRP)

BACKGROUND

X-linked retinitis pigmentosa (XLRP) is a rare, inherited retinal disease characterized by impairment in visual field and visual acuity with continuous progression leading to blindness. Gene therapies for XLRP are under investigation, and health state utilities are needed for use in cost-utility analyses examining the value of these treatments.

OBJECTIVE

This study aimed to estimate utilities associated with XLRP severity.

METHODS

Eleven health state vignettes depicting combinations of impairment in visual field and visual acuity associated with XLRP were developed based on literature review and input from clinicians, patients, and a caregiver. Vignettes included text describing visual acuity impairment, visual field impairment, night blindness, impact on quality of life, and two images representing the combination of visual field and visual acuity impairment for each health state. Health states were valued in time trade-off interviews with general population respondents in the UK.

RESULTS

A total of 245 participants completed interviews (51.0% female; mean age = 41.4 years; Newcastle, n = 80; London, n = 85; Edinburgh, n = 80). In a ranking task, participants preferred health states with less severe visual impairment, and this preference was reflected in the utilities. Mean (standard deviation) utilities ranged from 0.900 (0.121) for the health state with no visual acuity impairment and mild visual field impairment to 0.271 (0.478) for the health state describing blindness.

CONCLUSION

Results highlight the substantial impact of visual impairment on health state preference and quality of life. The health state utilities estimated in this study may be appropriate for use in cost-effectiveness models evaluating treatments for XLRP.

JEL CLASSIFICATION CODES

I1; I12; I19.

The Uneven Effect of Rare Diseases on Functional Status and Work Capacity

Background: Rare diseases are defined as clinical conditions that affect only a small number of persons in a population, considered fewer than 1 per 2000 in the European Union or fewer than 1 per 1600 in the United States They are serious, often chronic and progressive conditions, characterized by a pronounced clinical polymorphism that crosses all medical specialties. Multiple areas of life beyond just physical health are affected with significant impact on patients, families, and healthcare systems. Objective: To analyze the socio-demographic, medical, and vocational characteristics that correlate with functional status and work disability as a measure of quality of life in rare diseases. Methods: An observational retrospective study of adults with rare diseases evaluated for eligibility for social insurance rights in the National Institute of Medical Assessment and Work Capacity Rehabilitation Bucharest (INEMRCM, the Romanian abbreviation) over a 5-year period was made. Descriptive analysis was used to present sample characteristics. Means and standard deviations (SD) were calculated to describe numerical variables, frequencies were used to describe categorical variables, and logistic regression analysis was conducted to evaluate potential predictors of work capacity. All statistical analyses were performed by PSPP.3 software. p < 0.05 was the cut-off for statistical significance with a 95% confidence interval. Results: 90 consecutive persons were included in the survey. The mean age of the group was 44.5 years ± SD 10.61 years, with a female/male ratio of 48/42 persons. The mean disease duration was 10.61 years ± SD 9.76 years. Men had more severe disease (73.81%); p = 0.018 and significantly younger retirement age, M/F = 39.10 ± 12.26/43.06 ± 9.32; p = 0.037. Less disabling diseases were predominant autoimmune conditions (85.71% of cases); genetic conditions had a more severe functional impact in 63.75% of cases; p = 0.037. People with multisystem diseases but with specific or targeted treatment can work more frequently (76.19%); those with visual impairment have more severe impairments (73.77%); p < 0.001. All individuals who received specific therapy had a better functional status, unlike only 37.21% of those who received symptomatic treatment or treatment for complications; p = 0.023. Logistic regression analysis indicated that the type of impairment and the availability of specific treatments could serve as predictors of a reduced likelihood of employment in rare disease cases. Education level and occupation were not correlated with functional impairment and work disability (NS). Conclusions: Several factors, including some that are modifiable, were associated with better outcomes, such as reduced disability and an increased potential for work participation. Sex, disease etiology, type of impairment, and treatment were all significantly linked to functional capacity. Among these, the type of impairment and the availability of specific treatments might be predictors of employment. Addressing these parameters requires a multidisciplinary team, involving specialized care and comprehensive support services to improve the overall quality of life of individuals affected by rare diseases.

Unveiling the Genetic and Phenotypic Landscape of a Chinese Cohort With Retinitis Pigmentosa

INTRODUCTION

Retinitis pigmentosa (RP) is a type of inherited retinal degeneration (IRD) that typically leads to vision loss in individuals of working age. Currently, over 100 genes and loci, as well as over 1000 individual variants, have been identified in relation to RP. The aim of this study was to investigate the genetic distribution and characteristics of Chinese patients with RP, as well as to describe and analyze the genetic features of the high-frequency variant from the RPGR gene.

METHODS

A total of 69 Chinese patients diagnosed with RP from 36 families were included in this study. Blood samples were collected, and DNA was extracted for genetic analysis. A custom panel targeting 822 genes associated with RP was designed for next-generation sequencing (NGS) analysis. The sequenced data were processed and analyzed using bioinformatics tools to identify genetic variants. Variant classification followed the guidelines provided by the American College of Medical Genetics and Genomics (ACMG), taking into consideration functional effects, population frequencies, and previous literature reports. Variant validation was performed using Sanger sequencing to confirm the presence of identified variants. The inheritance pattern of RP-associated variants was determined by analyzing the segregation pattern within families. Pedigrees were constructed based on the clinical and genetic information of the participants. Statistical analysis was conducted to summarize the clinical characteristics of the RP patients using descriptive statistics. Ethical considerations were strictly followed throughout the study, with approval obtained from the ethics committee and informed consent obtained from all participants.

RESULTS

Following this, the identified variants were classified and subjected to statistical analysis. A total of 15 candidate genes associated with RP were identified, along with 39 variants, consisting of 36 reported variants and 3 novel variants. The majority of these variants were classified as pathogenic. The most common changes observed in this study were substitutions, followed by missense variants. Genetic analysis indicated that all variants occurred in the exon region. In the RPGR gene, half the variants are located in the ORF15. Gene, with half of variants located in ORF15. The most frequent variant within this group was RPGR NM_001034853.1: c.2236_2237del, which was identified in a large five-generation pedigree. The three novel variants reported in this study include NM_015629.3: c.1168_1169insGATTCAGCCTGGCC of PRPF31, NM_001034853.1: c.3026_3027insAGAGGGAGAGGAAGAAGG and NM_000328.2: c.611T>G of RPGR.

CONCLUSIONS

The findings of this study offer valuable insights into the genetic variants responsible for RP in affected individuals, which can be utilized for genetic counseling and diagnosis. This underscores the significance of genetic testing in the management and treatment of RP.

The burden of X-linked retinitis pigmentosa (XLRP) on patient experience and patient-reported outcomes (PROs): findings from the EXPLORE XLRP-2 study

BACKGROUND/AIMS

X-linked retinitis pigmentosa (XLRP) is considered one of the most severe forms of retinitis pigmentosa (RP), accounting for 5-15% of all RP cases and primarily affecting males. However, the real-world humanistic impacts of this disease on patients are poorly investigated, especially with respect to burdens faced by patients with varying disease severities.

METHODS

EXPLORE XLRP-2 was an exploratory, multicentre, non-interventional study. A retrospective chart review was conducted to collect clinical/demographic data, including XLRP clinical stage (mild, moderate or severe). Cross-sectional surveys were used to gather experiences directly from patients by validated and modified patient-reported outcomes.

RESULTS

176 patients with XLRP caused by retinitis pigmentosa GTPase regulator (RPGR) gene mutation were enrolled, of whom 169 were included in analyses. 81% of patients were male, mean (SD) age was 39.3 (17.61) years, and 20 adolescents were included. Mean age (SD) at genetic confirmation was 33.4 years (17.98), and the mean duration (SD) from initial symptoms to genetic diagnosis was 16.4 (15.66) years. Compared with patients with mild disease, patients with severe XLRP are more likely to experience difficulties with functioning in low luminance, depression, unemployment, productivity issues, mobility and daily activities.

CONCLUSION

This is the first real-world study to collect data directly from patients on the burden of XLRP and to correlate that burden with disease stage. As a result, several areas of significant burden, especially for patients with severe disease, have been identified that should provide focus for future public policies and therapeutic prospects.

Pre-Clinical and Clinical Advances in Gene Therapy of X-Linked Retinitis Pigmentosa: Hope on the Horizon

X-linked retinitis pigmentosa (XLRP) is a severe inherited retinal degenerative disease characterized by progressive loss of photoreceptors and retinal pigment epithelium, leading to blindness. Predominantly affecting males due to mutations in the RPGR gene, XLRP currently lacks effective treatments beyond supportive care. Gene therapy has emerged as a promising approach to restore photoreceptor function by delivering functional copies of the RPGR gene. Recent clinical trials using AAV vectors, such as AAV5-RPGR and AGTC-501, have demonstrated encouraging results, including improvements in retinal sensitivity and visual function. While early successes like LUXTURNA have set the precedent for gene therapy in retinal diseases, adapting these strategies to XLRP presents unique challenges due to the complexity of RPGR mutations and the need for efficient photoreceptor targeting. Advances in vector design, including the use of optimized AAV serotypes with enhanced tropism for photoreceptors and specific promoters, have significantly improved gene delivery. Despite setbacks in some studies, ongoing research and clinical trials continue to refine these therapies, offering hope for patients affected by XLRP. This review explores the etiology and pathophysiology of XLRP, evaluates current treatment challenges, highlights recent clinical advances in gene therapy, and discusses future perspectives for bringing these therapies into clinical practice.

THREE-DIMENSIONAL HILL OF VISION OF RETINAL SENSITIVITY IN PARTICIPANTS WITH X-LINKED RETINITIS PIGMENTOSA UNDER SCOTOPIC AND MESOPIC CONDITIONS

PURPOSE

To evaluate the utility of three-dimensional hill of vision (HOV) analysis in assessing retinal sensitivity in patients with X-linked retinitis pigmentosa (XLRP) under scotopic cyan, scotopic red, and mesopic microperimetry conditions.

METHODS

Baseline microperimetry data from 31 eyes of 16 patients with XLRP enrolled in the Horizon study were analyzed. HOVs were generated using thin plate spline interpolation. Grid volumes of the central 20° (V 20 ) were compared between lighting conditions using the Wilcoxon signed-rank test with Bonferroni correction. Central and global deficits were evaluated across age groups and genotypes.

RESULTS

The mesopic group showed the highest mean V 20 (1.3 dB-Sr), followed by scotopic red (0.6 dB-Sr) and scotopic cyan (0.5 dB-Sr). Significant differences were found between mesopic and scotopic conditions (P < 0.01), but not between scotopic conditions ( P = 0.26). Central and global deficits were more prevalent under scotopic conditions and increased with age.

CONCLUSION

HOV analysis provides a comprehensive assessment of retinal sensitivity in XLRP, enabling detection of localized changes and quantification of sensitivity gradients. This volumetric approach offers advantages over traditional methods for diagnosis, monitoring progression, and evaluating treatment response.

XOLARIS: A 24-Month, Prospective, Natural History Study of 201 Participants with Retinitis Pigmentosa GTPase Regulator-Associated X-Linked Retinitis Pigmentosa

Objective

To improve the understanding of the natural disease progression of retinitis pigmentosa GTPase regulator (RPGR)-associated X-linked retinitis pigmentosa (XLRP).

Design

A multicenter, prospective, observational natural history study over 24 months.

Participants

Male participants aged ≥7 years with a pathogenic variant in the RPGR gene, a best-corrected visual acuity (BCVA) score of ≥34 ETDRS letters, and a mean 68-loci retinal sensitivity (assessed by microperimetry) of 0.1 to 20 decibels (dB).

Methods

Participants were divided into subgroups based on their BCVA score at baseline: 34 to 73 (lower BCVA) or ≥74 (higher BCVA) ETDRS letters. There were 7 visits over 24 months.

Main Outcome Measures

Change from baseline in BCVA, retinal sensitivity, low luminance visual acuity (LLVA), fixation stability, contrast sensitivity, visual field, anatomical measures, 25-item Visual Function Questionnaire (VFQ-25), intraocular pressure, and adverse events (AEs).

Results

Overall, 201 participants were included. The mean (standard deviation [SD]) age was 30.3 (11.9) years in the lower BCVA subgroup (n = 170) and 27.7 (10.1) years in the higher BCVA subgroup (n = 31). The study eye baseline mean (SD) BCVA scores were 59.4 (10.30) and 77.3 (3.95) in the lower and higher BCVA subgroups, respectively; the lower BCVA subgroup had lower retinal sensitivity in the study eye at baseline than the higher BCVA subgroup. Over 24 months, there were small observed changes in BCVA, retinal sensitivity, LLVA, fixation, contrast sensitivity, and fundus photography findings. There were observed mean (SD) changes at 24 months in the lower and higher BCVA subgroups of -1.01 (4.67) and 0.03 (5.83) dB-steradians in the volume of full-field hill of vision, -330.6 (869.51) and -122.7 (22.01) μm in distance from foveal center to the nearest border of preserved fundus autofluorescence, -104.3 (277.80) and -207.1 (171.01) μm in central ellipsoid width, and -2.8 (9.7) and -0.6 (7.6) in VFQ-25 composite score, respectively. There was 1 death from completed suicide. There were no ocular serious adverse events, and most AEs were mild/moderate.

Conclusions

This study provides evidence of the slow natural progression of XLRP over 24 months in both subgroups and provides important functional, anatomical, and safety data.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Challenges in Value Assessment for One-Time Gene Therapies for Inherited Retinal Diseases: Are We Turning a Blind Eye?

OBJECTIVES

X-linked retinitis pigmentosa (XLRP) is a rare inherited retinal disease with no available treatment. Gene therapies in clinical trials will pose challenges for health technology assessment (HTA) if found to be safe and effective. We evaluated 2 of these challenges, namely acceptability and difficulties in assessing value beyond short-term patient health and healthcare savings and discounting in economic evaluation.

METHODS

We conducted a narrative literature review on the socioeconomic burden of XLRP to identify relevant components of value for a hypothetical gene therapy from a societal perspective and to assess their relative importance. We compared the resulting value profile against the value frameworks of three European HTA agencies. We also reviewed their guidelines on discounting and potential discounting issues specific to XLRP.

RESULTS

Much of the societal value of an XLRP gene therapy is likely to originate from productivity effects, carer spillovers, and value elements related to patient uncertainty. The evidence on these effects, however, is often limited, making it difficult for HTA agencies to assess them. Cost-effectiveness results are likely to be highly sensitive to the discount rate, and discounting will compound the effects of omitting important sources of value.

CONCLUSIONS

We have identified and detailed important components of societal value, key evidence gaps, and potential discounting issues for an XLRP gene therapy, which can inform future value assessments. Many of these may apply to gene therapies in other disease areas. Revisiting existing HTA approaches is recommended to ensure these are fit for purpose for such new classes of treatment.

Phase 1/2 AAV5-hRKp.RPGR (Botaretigene Sparoparvovec) Gene Therapy: Safety and Efficacy in RPGR-Associated X-Linked Retinitis Pigmentosa

PURPOSE

To assess the safety and efficacy of AAV5-hRKp.RPGR in participants with retinitis pigmentosa GTPase regulator (RPGR)-associated X-linked retinitis pigmentosa (XLRP).

DESIGN

Open-label, phase 1/2 dose escalation/expansion study (ClinicalTrials.gov Identifier: NCT03252847).

METHODS

Males (≥5 years old) with XLRP-RPGR were evaluated. In the dose escalation phase, subretinal AAV5-hRKp.RPGR (low: 1.0 × 1011 vg/ml; intermediate: 2.0 × 1011 vg/ml; high: 4.0 × 1011 vg/ml) was administered to the poorer-seeing eye (n = 10). Dose confirmation (intermediate dose) was carried out in 3 pediatric participants. In the dose expansion phase, 36 participants were randomized 1:1:1 to immediate (low or intermediate dose) or deferred (control) treatment. The primary outcome was safety. Secondary efficacy outcomes included static perimetry, microperimetry, vision-guided mobility, best corrected visual acuity, and contrast sensitivity. Safety and efficacy outcomes were assessed for 52 weeks for immediate treatment participants and 26 weeks for control participants.

RESULTS

AAV5-hRKp.RPGR was safe and well tolerated, with no reported dose-limiting events. Most adverse events (AEs) were transient and related to the surgical procedure, resolving without intervention. Two serious AEs were reported with immediate treatment (retinal detachment, uveitis). A third serious AE (increased intraocular pressure) was reported outside the reporting period. All ocular inflammation-related AEs responded to corticosteroids. Treatment with AAV5-hRKp.RPGR resulted in improvements in retinal sensitivity and functional vision compared with the deferred group at Week 26; similar trends were observed at Week 52.

CONCLUSIONS

AAV5-hRKp.RPGR demonstrated an anticipated and manageable AE profile through 52 weeks. Safety and efficacy findings support investigation in a phase 3 trial.

Impacts of X-linked Retinitis Pigmentosa and Patient Pathways in European Countries: Results from the Cross-sectional EXPLORE XLRP-1 Physician Survey

INTRODUCTION

X-linked retinitis pigmentosa (XLRP) is a rare, incurable, vision-threatening, genetic disease. In this study, we aimed to reveal the real-world burden of this disease from the viewpoint of retina specialists and geneticists involved directly in XLRP care and to identify unique insights that may not otherwise be available through typical clinical studies or health economic research.

METHODS

In this exploratory, cross-sectional study (EXPLORE XLRP-1), retina specialists (n = 20) and geneticists (n = 5) in France, Germany, Italy, Spain, and the UK provided anonymized insights on their experiences managing patients with XLRP (n = 80) via an online survey and 60-min telephone interview.

RESULTS

Survey respondents reported that patient independence decreased over time, where 37% of patients were considered "completely autonomous" at diagnosis versus 23% at the last consultation. At their last visit, 45% of patients were active in the workforce; 67% (12/18) of "completely autonomous" patients had active working status compared with 13% (1/8) of "completely dependent" patients. The average time from onset of symptoms to diagnosis was 4 years and varied among countries. In 78% of patients, XLRP was confirmed by genetic testing, the rate of which varied among countries (range, 50-94%), taking up to 6 months to receive results. Specialists identified unmet needs in XLRP management including more standardized assessments of quality of life (QoL) as well as easier and earlier access to specialists, genetic testing, patient support programs, and effective treatment options.

CONCLUSIONS

The diagnosis, genetic testing, and management pathways among patients with XLRP can vary considerably. There is a need for more standardized diagnosis and management pathways, and QoL assessments, due to the major impact that XLRP has on patients' lives.

Exploring self-reported visual function and vision-related anxiety in patients with RPGR-associated retinal degeneration

Variants in the retinitis pigmentosa GTPase regulator (RPGR) gene are responsible for the majority of X-linked retinitis pigmentosa cases, which not only affects male patients but also some heterozygous females. Vision-related disability and anxiety of patients with RPGR-associated retinal degeneration have never been explored before. This study aimed to evaluate self-reported visual function and vision-related anxiety in a Portuguese cohort of male and female patients with RPGR-associated retinal degeneration using two validated patient-reported outcome measures. Cross-sectional data of thirty-two genetically-tested patients was examined, including scores of the Michigan retinal degeneration questionnaire (MRDQ) and Michigan vision-related anxiety questionnaire. Patients were classified according to retinal phenotypes in males (M), females with male phenotype (FM), and females with radial or focal pattern. Both M and FM revealed higher rod-function and cone-function anxiety scores (p < 0.017). Most MRDQ disability scores were higher in M and FM (p < 0.004). Overall, positive correlations (p < 0.004) were found between every MRDQ domain and both anxiety scores. In RPGR-associated retinal degeneration, males and females with male phenotype show similar levels of increased vision-related anxiety and disability. Every MRDQ visual function domain showed a strong correlation with anxiety scores.

Long-read sequencing improves the genetic diagnosis of retinitis pigmentosa by identifying an Alu retrotransposon insertion in the EYS gene

BACKGROUND

Biallelic variants in EYS are the major cause of autosomal recessive retinitis pigmentosa (arRP) in certain populations, a clinically and genetically heterogeneous disease that may lead to legal blindness. EYS is one of the largest genes (~ 2 Mb) expressed in the retina, in which structural variants (SVs) represent a common cause of disease. However, their identification using short-read sequencing (SRS) is not always feasible. Here, we conducted targeted long-read sequencing (T-LRS) using adaptive sampling of EYS on the MinION sequencing platform (Oxford Nanopore Technologies) to definitively diagnose an arRP family, whose affected individuals (n = 3) carried the heterozygous pathogenic deletion of exons 32-33 in the EYS gene. As this was a recurrent variant identified in three additional families in our cohort, we also aimed to characterize the known deletion at the nucleotide level to assess a possible founder effect.

RESULTS

T-LRS in family A unveiled a heterozygous AluYa5 insertion in the coding exon 43 of EYS (chr6(GRCh37):g.64430524_64430525ins352), which segregated with the disease in compound heterozygosity with the previously identified deletion. Visual inspection of previous SRS alignments using IGV revealed several reads containing soft-clipped bases, accompanied by a slight drop in coverage at the Alu insertion site. This prompted us to develop a simplified program using grep command to investigate the recurrence of this variant in our cohort from SRS data. Moreover, LRS also allowed the characterization of the CNV as a ~ 56.4kb deletion spanning exons 32-33 of EYS (chr6(GRCh37):g.64764235_64820592del). The results of further characterization by Sanger sequencing and linkage analysis in the four families were consistent with a founder variant.

CONCLUSIONS

To our knowledge, this is the first report of a mobile element insertion into the coding sequence of EYS, as a likely cause of arRP in a family. Our study highlights the value of LRS technology in characterizing and identifying hidden pathogenic SVs, such as retrotransposon insertions, whose contribution to the etiopathogenesis of rare diseases may be underestimated.

Pluripotent stem cell-derived models of retinal disease: Elucidating pathogenesis, evaluating novel treatments, and estimating toxicity

Blindness poses a growing global challenge, with approximately 26% of cases attributed to degenerative retinal diseases. While gene therapy, optogenetic tools, photosensitive switches, and retinal prostheses offer hope for vision restoration, these high-cost therapies will benefit few patients. Understanding retinal diseases is therefore key to advance effective treatments, requiring in vitro models replicating pathology and allowing quantitative assessments for drug discovery. Pluripotent stem cells (PSCs) provide a unique solution given their limitless supply and ability to differentiate into light-responsive retinal tissues encompassing all cell types. This review focuses on the history and current state of photoreceptor and retinal pigment epithelium (RPE) cell generation from PSCs. We explore the applications of this technology in disease modelling, experimental therapy testing, biomarker identification, and toxicity studies. We consider challenges in scalability, standardisation, and reproducibility, and stress the importance of incorporating vasculature and immune cells into retinal organoids. We advocate for high-throughput automation in data acquisition and analyses and underscore the value of advanced micro-physiological systems that fully capture the interactions between the neural retina, RPE, and choriocapillaris.

PREVALENCE AND CLINICAL FEATURES OF RADIAL FUNDUS AUTOFLUORESCENCE IN HIGH MYOPIC WOMEN

PURPOSE

To determine the prevalence and characteristics of radial fundus autofluorescence (FAF) in highly myopic women.

METHODS

This was a retrospective, observational case study to determine the prevalence of radial FAF in the ultra-widefield FAF images in women. The clinical characteristics of these patients were evaluated.

RESULTS

Fifteen of 1,935 (0.78%) highly myopic women were found to have radial FAF. Their mean age was 36.6 ± 25.6 years, and their mean best-corrected visual acuity was 0.3 ± 0.42 logMAR units. The mean axial length (AL) was 28.8 ± 2.8 mm. Among the 15 cases, eight did not have pigmentary changes and seven had pigmentary changes in the ultra-widefield FAF images. The women with the pigmentary changes were significantly older ( P = 0.021), had poorer BCVA ( P = 0.001), and had longer ALs ( P = 0.002). The visual fields and electroretinograms were worse in the eyes with pigmentary changes.

CONCLUSION

The prevalence of radial FAF was 0.78% in women with high myopia. These patients might have mutations in the RPGR or RP2 genes and can develop high myopia and retinitis pigmentosa. Ultra-widefield FAF images should be examined in all highly myopic patients for early detection of radial FAF, and myopia prevention and genetic counseling for possible genetic therapy are recommended.

Novel hemizygous single-nucleotide duplication in RPGR in a patient with retinal dystrophy and sensorineural hearing loss

BACKGROUND

The RPGR gene has been associated with X-linked cone-rod dystrophy. This report describes a variant in RPGR detected with exome sequencing (ES). Genes like RPGR have not always been included in panel-based testing and thus genome-wide tests such as ES may be required for accurate diagnosis.

METHODS

The Texome Project is studying the impact of ES in medically underserved patients who are in need of genomic testing to guide diagnosis and medical management. The hypothesis is that ES could uncover diagnoses not made by standard medical care.

RESULTS

A 58-year-old male presented with retinitis pigmentosa, sensorineural hearing loss, and a family history of retinal diseases. A previous targeted gene panel for retinal disorders had not identified a molecular cause. ES through the Texome Project identified a novel, hemizygous variant in RPGR (NM_000328.3: c.1302dup, p.L435Sfs*18) that explained the ocular phenotype.

CONCLUSIONS

Continued genetics evaluation can help to end diagnostic odysseys of patients. Careful consideration of genes represented when utilizing gene panels is crucial to ensure an accurate diagnosis. Medically underserved populations are less likely to receive comprehensive genetic testing in their diagnostic workup. Our report is an example of the medical impact of genomic medicine implementation.

A SYSTEMATIC LITERATURE REVIEW OF DISEASE PROGRESSION REPORTED IN RPGR -ASSOCIATED X-LINKED RETINITIS PIGMENTOSA

PURPOSE

Retinitis pigmentosa GTPase regulator-associated X-linked retinitis pigmentosa ( RPGR -associated XLRP) is a rare and severe form of retinitis pigmentosa, resulting in progressive visual impairment; however, disease progression data are limited. A systematic literature review was conducted to assess available data on disease progression in RPGR -associated XLRP.

METHODS

PubMed, Embase, and select congress abstracts were evaluated through June 2022. Eligible studies included results specific to RPGR -associated XLRP or populations with ≥80% of patients with retinitis pigmentosa carrying disease-causing RPGR variants. End points of interest included visual acuity, visual field, ellipsoid zone width, progression to blindness, and patient-reported outcomes.

RESULTS

Fourteen studies met ≥1 end point of interest. Progressive declines in visual acuity, visual field, and ellipsoid zone width were reported across studies. Nearly all publications reported annual declines in visual acuity (3.5%-8.2%). Annual visual field declines ranged from 4.2% to 13.3%. Changes in retinal structure were also observed (ellipsoid zone width changes: -177 to -830 µ m/year). Most studies measured blindness using visual acuity; visual field-based definitions resulted in blindness by age ∼25 years. Patient-reported outcome data were limited.

CONCLUSION

Published evidence shows that patients with RPGR -associated XLRP experience progressive decline in visual acuity, visual field, and ellipsoid zone width, eventually resulting in blindness. Additional longitudinal data with standardized end points and expanded collection of patient-reported outcomes are needed to assess visual decline in RPGR -associated XLRP.

Deep Learning-Facilitated Study of the Rate of Change in Photoreceptor Outer Segment Metrics in RPGR-Related X-Linked Retinitis Pigmentosa

Purpose

The aim of this retrospective cohort study was to obtain three-dimensional (3D) photoreceptor outer segment (OS) metrics measurements with the assistance of a deep learning model (DLM) and to evaluate the longitudinal change in OS metrics and associated factors in retinitis pigmentosa GTPase regulator (RPGR) X-linked retinitis pigmentosa (XLRP).

Methods

The study included 34 male patients with RPGR-associated XLRP who had preserved ellipsoid zone (EZ) within their spectral-domain optical coherence tomography volume scans and an approximate 2-year or longer follow-up. Volume scans were segmented using a DLM with manual correction for EZ and apical retinal pigment epithelium (RPE). OS metrics were measured from 3D EZ-RPE layers of volume scans. Linear mixed-effects models were used to calculate the rate of change in OS metrics and the associated factors, including baseline age, baseline OS metrics, and follow-up duration.

Results

The mean (standard deviation) of progression rates were -0.28 (0.43) µm/y, -0.73 (0.61) mm2/y, and -0.014 (0.012) mm3/y for OS thickness, EZ area, and OS volume, respectively. In multivariable analysis, the progression rates of EZ area and OS volume were strongly associated with their baseline values, with faster decline in eyes with larger baseline values (P ≤ 0.003), and nonlinearly associated with the baseline age (P ≤ 0.003). OS thickness decline was not associated with its baseline value (P = 0.32).

Conclusions

These results provide evidence to support using OS metrics as biomarkers to assess the progression of XLRP and as the outcome measures of clinical trials. Given that their progression rates are dependent on their baseline values, the baseline EZ area and OS volume should be considered in the design and statistical analysis of future clinical trials. Deep learning may provide a useful tool to reduce the burden of human graders to analyze OCT scan images and to facilitate the assessment of disease progression and treatment trials for retinitis pigmentosa.

Overcoming the Challenges to Clinical Development of X-Linked Retinitis Pigmentosa Therapies: Proceedings of an Expert Panel

X-linked retinitis pigmentosa (XLRP) is a rare inherited retinal disease manifesting as impaired night vision and peripheral vision loss that progresses to legal blindness. Although several trials of ocular gene therapy for XLRP have been conducted or are in progress, there is currently no approved treatment. In July 2022, the Foundation Fighting Blindness convened an expert panel to examine relevant research and make recommendations for overcoming the challenges and capitalizing on the opportunities in conducting clinical trials of RPGR-targeted therapy for XLRP. Data presented concerned RPGR structure and mutation types known to cause XLRP, RPGR mutation-associated retinal phenotype diversity, patterns in genotype/phenotype relationships, disease onset and progression from natural history studies, and the various functional and structural tests used to monitor disease progression. Panel recommendations include considerations, such as genetic screening and other factors that can impact clinical trial inclusion criteria, the influence of age on defining and stratifying participant cohorts, the importance of conducting natural history studies early in clinical development programs, and the merits and drawbacks of available tests for measuring treatment outcomes. We recognize the need to work with regulators to adopt clinically meaningful end points that would best determine the efficacy of a trial. Given the promise of RPGR-targeted gene therapy for XLRP and the difficulties encountered in phase III clinical trials to date, we hope these recommendations will help speed progress to finding a cure.

Translational Relevance

Examination of relevant data and recommendations for the successful clinical development of gene therapies for RPGR-associated XLRP.

Quality of Life and Economic Impacts of Retinitis Pigmentosa on Japanese Patients: A Non-interventional Cross-sectional Study

INTRODUCTION

Retinitis pigmentosa (RP) is an inherited progressive disease, characterized by a loss of photoreceptors, and is the second leading cause of visual impairment in Japan. RP is currently incurable and can result in complete blindness, with affected patients typically experiencing a gradual loss of light sensitivity, visual field, and visual acuity. Identification of any unmet medical needs of patients with this condition requires an understanding of the impacts of RP; in this study, we surveyed Japanese patients with RP to investigate the quality of life and economic impacts of visual impairment.

METHODS

This non-interventional, cross-sectional study surveyed Japanese patients with RP. Economic impact was measured using an original questionnaire that assessed out-of-pocket cost (e.g., vision aids and medical services), salary gap with the general public, and the cost of depression and anxiety. Worker productivity was assessed using the Work Productivity and Activity Impairment Questionnaire (WPAI). Quality of life was evaluated using the Health Utilities Index Mark 3 (HUI3), the National Eye Institute Visual Function Questionnaire-25 (VFQ-25), and the 5-level EQ-5D version (EQ-5D-5L). The primary outcome was direct and indirect costs of visual impairment or blindness during the lifetime of patients with RP.

RESULTS

Among 122 surveyed patients with RP, the estimated annual cost per patient was 218,520 yen (2176 USD), and the estimated lifetime cost per patient was 18,523,909 yen (184,501 USD). Additional robustness testing increased the estimated annual cost and lifetime cost per patient to 783,176 yen (7801 USD) and 66,389,827 yen (661,253 USD), respectively. In working patients, work productivity loss was 26.2% per person and impairment of daily activities was 31.6% per person. The mean VFQ-25, HUI3, and EQ-5D-5L scores were 42.0, 0.393, and 0.833, respectively.

CONCLUSION

RP imposed a heavy economic burden and negative quality of life impacts in Japanese patients.

Retinitis Pigmentosa: Current Clinical Management and Emerging Therapies

Retinitis pigmentosa (RP) comprises a group of inherited retinal dystrophies characterized by the degeneration of rod photoreceptors, followed by the degeneration of cone photoreceptors. As a result of photoreceptor degeneration, affected individuals experience gradual loss of visual function, with primary symptoms of progressive nyctalopia, constricted visual fields and, ultimately, central vision loss. The onset, severity and clinical course of RP shows great variability and unpredictability, with most patients already experiencing some degree of visual disability in childhood. While RP is currently untreatable for the majority of patients, significant efforts have been made in the development of genetic therapies, which offer new hope for treatment for patients affected by inherited retinal dystrophies. In this exciting era of emerging gene therapies, it remains imperative to continue supporting patients with RP using all available options to manage their condition. Patients with RP experience a wide variety of physical, mental and social-emotional difficulties during their lifetime, of which some require timely intervention. This review aims to familiarize readers with clinical management options that are currently available for patients with RP.

Economic Impacts and Quality of Life for Caregivers of Patients with Retinitis Pigmentosa: A Cross-Sectional Japanese Study

Retinitis pigmentosa (RP) is the second leading cause of visual impairment in Japan and causes progressive vision loss in affected patients. Caregiving for patients with RP is associated with socioeconomic impacts; however, data on the magnitude and scope of these impacts are lacking. This cross-sectional study surveyed informal caregivers of patients with RP in Japan. The questionnaire assessed the socioeconomic status of participants; work impacts through the Work Productivity and Activity Impairment Questionnaire adapted for caregivers; and quality of life impacts through the Japanese version of the Caregiver Reaction Assessment (CRA) and the 5-level EQ-5D version (EQ-5D-5L). Of the 37 participating caregivers, 28 (75.7%) were employed. Among those, the average annual income was 2,722,080 yen (n = 20) and the mean loss of work productivity was 6.6%. The mean EQ-5D-5L index score was 0.882, and the mean CRA total score was 2.1. A mild to very severe impact on family life, leisure and hobbies, social life, and mental health was experienced by 83.8%, 78.4%, 75.7%, and 70.3%, respectively. These results suggest that caregivers of patients with RP may be disadvantaged in terms of employment and income and may experience wide-ranging impacts on their quality of daily life.

Longitudinal analysis of health care costs in patients with childhood onset inherited retinal dystrophies compared to healthy controls

BACKGROUND

We evaluated health care costs in patients with childhood onset visual impairment caused by inherited retinal dystrophies (IRD).

METHODS

The IRD cohort, identified from the Danish Registry of Blind and Partially Sighted Children, was compared to age- and sex-matched controls from the national, Danish population registry. Information on health care expenditures for somatic and psychiatric in- and outpatient services, purchase of prescription medications and paid assistance at home were obtained from national registries for the years 2002-2017.

RESULTS

We included 412 in the IRD cohort (6,290 person years) and 1656 (25,088 person years) in the control cohort. Average, annual health care expenditures from age 0-48 years of age were €1,488 (SD 4,711) in the IRD cohort and €1,030 (4,639) in the control cohort. The largest difference was for out-patient eye care (13.26 times greater, 95% confidence interval 12.90-13.64). Psychiatric in-patient expenditures were 1.71 times greater (95% CI 1.66-1.76) in the IRD cohort but psychiatric out-patient health care costs were comparable between groups.

CONCLUSIONS

Health care costs were approximately 40% greater in the IRD cohort compared to an age- and sex-matched sample from the general Danish population. This is relevant in the current situation with a number of trials aimed at treating IRDs using genetically based therapies. Although eye care expenditures were many times greater, they made up < 10% of the total health care expenditures even in the IRD cohort. The reduced costs related to injuries in the visually impaired cohort was a surprising finding but may reflect a reduced propensity to seek medical care rather than a reduced risk of injuries.

Retinitis Pigmentosa: Burden of Disease and Current Unmet Needs

Retinitis Pigmentosa (RP), a group of inherited retinal dystrophies characterised by progressive vision loss, is the leading cause of visual disability and blindness in subjects less than 60 years old. Currently incurable, therapy is aimed at restricting degeneration of vision, treating complications, and helping patients to cope with the psychosocial impact of their disease. Hence, RP is associated with a high burden of disease. This paper describes the current therapeutic landscape for RP and the disease burden for patients, caregivers, and society. A review of available data was conducted in three stages: (1) a literature search of publicly available information on all domains of RP; (2) a systematic literature review using Medline, Embase, the Cochrane Library and grey literature (GlobalData) on epidemiology and cost of RP; and (3) qualitative research with senior physicians treating RP patients in the EU4 and the UK to validate research findings from secondary sources. RP severely impacts the daily lives of over a million people worldwide. Progressive vision loss significantly affects the ability to perform basic daily tasks, to maintain employment, and maintain independence. Consequently, most patients will experience reduced quality of life, with a greater emotional and psychological impact than other conditions related to vision loss such as diabetic retinopathy or age-related macular degeneration. RP is also associated with a high level of carer burden, arising from psychological and financial stress. The therapeutic landscape for RP is limited, with few treatment options and minimal guidance for the diagnosis, treatment, and care of patients. A curative intervention, voretigene neparvovec (Luxturna®), only exists for 1-6% of patients. Although disease management can be successful in developing coping strategies, most patients live with this chronic, progressive condition without interventions to change the disease course. Innovative new therapies can transform the therapeutic landscape, provided appropriate clinical guidance is forthcoming.