Initial results from a first-in-human gene therapy trial on X-linked retinitis pigmentosa caused by mutations in RPGR

Prevalence of Molecular Diagnoses for Usher Syndrome and the Need for Coordinated Care

INTRODUCTION

Usher syndrome (USH) is a rare, autosomal-recessive genetic disorder and a leading cause of early onset deaf-blindness. A clinical diagnosis is made by the presence of retinitis pigmentosa (RP) with sensorineural hearing loss (SNHL). Subtype (USH1, USH2, USH3) is determined by severity and age of onset. Molecular testing is able to further distinguish USH subtypes by causative gene. As gene therapy strategies continue to be explored for USH, it is important to know the underlying genetic cause and to coordinate care among an interdisciplinary team.

METHODS

We reviewed charts of 198 individuals presenting to the RP clinic at Bascom Palmer Eye Institute (BPEI) for suspected USH. Demographic information, USH clinical diagnosis, molecular testing, molecular diagnosis, and audiological data were collected.

RESULTS

Of the 198 patients reviewed, 190 (96%) met clinical criteria for USH and received a clinical diagnosis. There were 67 (35%) that had a genetic test with a pathogenic molecular diagnosis. The average ages at molecular diagnosis were USH1B, 20 years old; USH2A, 37 years old; USH2C, 50 years old. Of the 67 with a molecular diagnosis, 23 (34%) established ophthalmic care and 8 of these (11%) established audiological care.

DISCUSSION/CONCLUSION

Molecular testing and diagnosis should be part of the routine care of USH individuals to facilitate earlier interventions and coordinated care between ophthalmology and audiology.

LEVEL OF EVIDENCE

4 Laryngoscope, 135:1777-1780, 2025.

Test-retest variability of mesopic microperimetry-associated parameters in patients with retinitis pigmentosa: REPEAT Study Report No. 2

PURPOSE

Understanding test-retest variability (TRV) of mesopic microperimetry is critical for defining meaningful treatment effects in retinitis pigmentosa (RP) trials. This study uniquely evaluates intra- and intervisit TRV and coefficients of repeatability (CoRs) for microperimetry parameters in RP patients with varying best-corrected visual acuity (BCVA) levels.

METHODS

In this single-centre prospective cohort study, RP patients were assessed on two visits, 14.0 days apart. Patients were grouped by BCVA: low (≤20/50 Snellen; ≥0.4 logMAR) or moderate (>20/50 Snellen; <0.4 logMAR). Using Bland-Altman analyses, the CoRs for intra- and intervisit variability were determined for pointwise (dB), mean (dB), and volume sensitivity (dB*deg2) on mesopic microperimetry.

RESULTS

Intravisit CoRs for mean, volume, and pointwise sensitivity were 1.7 dB, 353.2 dB*deg2, and 8.6 dB, respectively, in the low-BCVA group (n = 32), and 0.9 dB, 254.5 dB*deg2, and 7.3 dB in the moderate-BCVA group (n = 15). Intervisit CoRs for mean, volume, and pointwise sensitivity were 2.4 dB, 355.2 dB*deg2, and 10.2 dB in the low-BCVA group (n = 31). The moderate-BCVA group (n = 16) showed smaller CoRs of 1.6 dB, 386.8 dB*deg2, and 7.7 dB for mean, volume, and pointwise sensitivity. BCVA and mean sensitivity, but not fixation stability, are predictors of TRV for volume sensitivity.

CONCLUSIONS

Due to significant TRV, pointwise sensitivity is an unreliable endpoint for RP patients, irrespective of BCVA. Mean sensitivity is suitable as an endpoint when BCVA is relatively preserved. Volume sensitivity provides additional spatial information, and shows promise as a clinical endpoint for assessing macular sensitivity changes on mesopic microperimetry in patients with RP.

The clinical safety landscape for ocular AAV gene therapies: A systematic review and meta-analysis

Adeno-associated virus (AAV) gene therapy is a promising approach for treating ocular monogenic or acquired diseases, though immunogenicity and safety remain critical considerations. We conducted a systematic review of 120 trials and 32 publications to assess immune responses across different delivery routes. Intravitreal administration was associated with higher rates of anterior uveitis (43.06% vs. 10.22%) and intermediate/posterior uveitis (40.36% vs. 6.18%) compared to subretinal delivery. Engineered AAV capsids, used exclusively in intravitreal studies, showed no significant difference in either type of uveitis incidence compared to natural serotypes. Prophylactic immunosuppression (PI) did not affect ocular or systemic immune responses in subretinal delivery, but significantly reduced systemic immune responses in intravitreal administration. These findings underscore the potential of PI to mitigate systemic immune responses in intravitreal AAV therapy. This review should help guide the choice of routes of administration and immunosuppression strategies, and highlights current trends in ocular AAV gene therapy.

Systematic empirical evaluation of individual base editing targets: Validating therapeutic targets in USH2A and comparison of methods

Base editing shows promise for the correction of human mutations at a higher efficiency than other repair methods and is especially attractive for mutations in large genes that are not amenable to gene augmentation therapy. Here, we demonstrate a comprehensive workflow for in vitro screening of potential therapeutic base editing targets for the USH2A gene and empirically validate the efficiency of adenine and cytosine base editor/guide combinations for correcting 35 USH2A mutations. Editing efficiency and bystander edits are compared between different target templates (plasmids vs. transgenes) and assays (next-generation sequencing vs. Sanger), as well as comparisons between unbiased empirical results and computational predictions. Based on these observations, practical assay recommendations are discussed. Finally, a humanized knockin mouse model was created with the best-performing target, the nonsense mutation c.11864G>A p.(Trp3955∗). Split-intein AAV9 delivery of editing reagents resulted in the restoration of USH2A protein and a correction rate of 65% ± 3% at the mutant base pair and of 52% ± 3% excluding bystander amino acid changes. This efficiency is higher than that seen in a retinal gene editing program testing in a clinical trial. These results demonstrate the effectiveness of this overall strategy to identify and test base editing reagents with the potential for human therapeutic applications.

Recombinant adeno-associated virus with anti-tumor necrosis factor-alpha in an experimental autoimmune uveitis model

Uveitis treatment is associated with side effects and inconsistent outcomes. Existing treatments often fail to provide targeted and sustained relief; thus, novel therapeutic approaches are needed. Among these, gene therapy using adeno-associated virus (AAV) vectors target specific retinal cells, show low immunogenicity, and demonstrate sustained gene expression, making it a potential advancement in uveitis treatment. Therefore, we utilized a AAV2 system encapsulating encoded anti-tumor necrosis factor-alpha (TNF-α) antibody to assess its efficacy in the treatment of experimental autoimmune uveitis (EAU) in mice. Compared with the AAV2-GFP group, AAV2-ADA-injected mice showed significantly reduced clinical, OCT, and histopathological scores in EAU with lower percentages of Th1 and Th17 cells in the eyes and higher percentages of Treg cells in the draining lymph nodes (LN). This study demonstrated the safety and effects of AAV2-ADA in EAU treatment, providing a promising therapeutic strategy for uveitis.

The Exponential Constriction Model of the Ellipsoid Zone in Taiwanese Individuals With RPGR-Related X-Linked Retinitis Pigmentosa

Purpose

This study documents the natural disease progression and genotype-phenotype correlation in RPGR-related retinitis pigmentosa (RP) in the Taiwanese population.

Methods

A retrospective analysis was conducted on individuals with molecularly confirmed RPGR-related disease-causing variant(s). Demographics, best-corrected visual acuity (BCVA), spherical equivalent (SE), fundus autofluorescence, and optical coherence tomography were assessed.

Results

Fifty-two individuals from 31 families were diagnosed with RPGR-related disease-causing variant(s). Mean follow-up time was 4.2 years. Among 21 genetic variants, 67% involved the open reading frame 15 region (ORF15) variant, and 33% were Exon 1-14 variants. Male patients (69%) had a mean BCVA of 0.9 logMAR and SE of -3.8 D in the right eye and -3.0 D in the left eye, with high myopia in 19% to 20%. BCVA progression was 0.031 logMAR/year in the ORF15 group (P < 0.001) and 0.011 logMAR/year (P = 0.457) in the Exon 1-14 group. An exponential decay model revealed rapid ellipsoid zone (EZ) constriction during childhood in the ORF15 group. Female patients/carriers (31%) had a mean BCVA of 0.3 logMAR and SE of -4.3D, with high myopia of 31% in the right eye and 46% in the left eye. Among symptomatic females, 73% exhibited clinically significant disease. The most common mutation was the c.2592dup variant (15%).

Conclusions

This first longitudinal analysis of RPGR-related RP in Taiwan presents a predictive model of EZ constriction. Findings suggest earlier onset in Exon 1-14 variants and a tendency for faster progression in the ORF15 group, informing insights for genetic therapy development and disease management.

Identification of IDH3G, encoding the gamma subunit of mitochondrial isocitrate dehydrogenase, as a novel candidate gene for X-linked retinitis pigmentosa

PURPOSE

Retinitis pigmentosa (RP) is a genetically heterogeneous group of retinal degenerative disorders characterized by the loss of rod and cone photoreceptors, leading to visual impairment and blindness. To date, to our knowledge, X-linked RP has been associated with variants in 3 genes (RPGR, RP2, and OFD1), whereas genetic defects at 3 loci (RP6, RP24, and RP34) are yet unidentified. The aim of this study was to identify a novel candidate gene underlying X-linked RP.

METHODS

Participants were identified from cohorts of genetically unsolved male individuals affected by RP, who underwent genome sequencing, exome sequencing, or candidate gene screening via direct Sanger sequencing at 3 referral centers. Specifically, 2 probands were identified at the National Reference Centre for Rare Retinal Diseases (Paris, France), 2 at the Massachusetts Eye and Ear Hospital (Boston, MA), and 1 at the National Reference Centre for Inherited Sensory Diseases (Montpellier, France). The pathogenicity of the identified variants was assessed using bioinformatic predictions, protein expression analyses, and mitochondrial function assays.

RESULTS

We identified 4 rare single-nucleotide variants in IDH3G (HGNC:5386), located at the RP34 locus on the X chromosome, and a complete gene deletion, in 5 unrelated male individuals affected with nonsyndromic RP. The variants segregated with the phenotype in all available family members. In all cases, the disease severity was intermediate. None had high myopia. IDH3G encodes the γ subunit of mitochondrial isocitrate dehydrogenase (IDH3), an enzyme involved in the citric acid cycle, which is expressed in the inner segments of photoreceptors. Variants in IDH3A and IDH3B, encoding the other subunits of IDH3, have already been associated with nonsyndromic autosomal recessive RP. Bioinformatic predictions and functional assays support a pathogenic role for the variants identified in this study, possibly through partial loss of enzymatic activity and mitochondrial function.

CONCLUSION

Our findings suggest that variants in IDH3G are a novel cause of X-linked RP.

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.

Gene Therapy-Associated Uveitis (GTAU): Understanding and mitigating the adverse immune response in retinal gene therapy

Retinal gene therapy using adeno-associated viral (AAV) vectors has been a groundbreaking step-change in the treatment of inherited retinal diseases (IRDs) and could also be used to treat more common retinal diseases such as age-related macular degeneration and diabetic retinopathy. The delivery and expression of therapeutic transgenes in the eye is limited by innate and adaptive immune responses against components of the vector product, which has been termed gene therapy-associated uveitis (GTAU). This is clinically important as intraocular inflammation could lead to irreversible loss of retinal cells, deterioration of visual function and reduced durability of treatment effect associated with a costly one-off treatment. For retinal gene therapy to achieve an improved efficacy and safety profile for treating additional IRDs and more common diseases, the risk of GTAU must be minimised. We have collated insights from pre-clinical research, clinical trials, and the real-world implementation of AAV-mediated retinal gene therapy to help understand the risk factors for GTAU. We draw attention to an emerging framework, which includes patient demographics, vector construct, vector dose, route of administration, and choice of immunosuppression regime. Importantly, we consider efforts to date and potential future strategies to mitigate the adverse immune response across each of these domains. We advocate for more targeted immunomodulatory approaches to the prevention and treatment of GTAU based on better understanding of the underlying immune response.

PNPLA6 regulates retinal homeostasis by choline through phospholipid turnover

Although mutations in human patatin-like phospholipase PNPLA6 are associated with hereditary retinal degenerative diseases, its mechanistic action in the retina is poorly understood. Here, we uncover the molecular mechanism by which PNPLA6 dysfunction disturbs retinal homeostasis and visual function. PNPLA6, by acting as a phospholipase B, regulates choline mobilization from phosphatidylcholine and subsequent choline turnover for phosphatidylcholine regeneration in retinal pigment epithelial cells. PNPLA6-driven choline is supplied from retinal pigment epithelial cells to adjacent photoreceptor cells to support their survival. Inhibition of this pathway results in abnormal morphology, proliferation, metabolism, and functions of retinal pigment epithelial and photoreceptor cells, and mice with retina-specific PNPLA6 deletion exhibit retinitis pigmentosa-like retinal degeneration. Notably, these abnormalities are entirely rescued by choline supplementation. Thus, PNPLA6 plays an essential role in retinal homeostasis by controlling choline availability for phospholipid recycling and provide a framework for the development of an ophthalmic drug target for retinal degeneration.

Efficacy and safety of mesenchymal stem cell therapies in retinitis pigmentosa: a systematic review and meta-analysis

BACKGROUND

Retinitis pigmentosa (RP) is a retinal dystrophy and genetically heterogeneous group that causes vision loss and necessitates innovative therapeutic strategies, and mesenchymal stem cell (MSC) therapy has shown potential due to its regenerative and immunomodulatory properties. This meta-analysis aims to evaluate the efficacy and safety of MSC therapies in improving visual outcomes, focusing on the impact of various MSC types, administration methods, and duration of benefits.

METHODS

A systematic search of peer-reviewed studies was conducted to identify clinical trials and observational studies investigating MSC therapies for retinal conditions. Outcomes of interest included best-corrected visual acuity (BCVA), central macular thickness, retinal sensitivity, quality of life, and safety profiles. Data were synthesized and analyzed using random-effects meta-analysis to calculate pooled effect sizes and heterogeneity.

PROSPERO

CRD42024618158.

RESULTS

Eleven studies involving 355 RP patients were included. Umbilical cord-derived MSCs and bone marrow-derived MSCs demonstrated significant short-term improvements in BCVA and retinal function. Subretinal and suprachoroidal delivery methods were associated with better outcomes compared to systemic infusion. Adverse effects were minimal, with transient inflammation being the most reported. The duration of benefits varied, with most studies reporting sustained improvements up to 12 months, while long-term efficacy beyond this period was less conclusive.

CONCLUSIONS

MSC therapies show promise in improving visual function and retinal health, with safety profiles supporting their clinical feasibility. However, differences in administration methods and MSC types influence outcomes. Further large-scale, long-term randomized controlled trials are needed to optimize treatment protocols and validate sustained benefits.

Retinitis Pigmentosa GTPase Regulator-Associated X-Linked Retinitis Pigmentosa: Molecular Genetics and Clinical Characteristics

PURPOSE

To describe in detail the genetic profile, clinical features, and genotype-phenotype correlation of retinitis pigmentosa GTPase regulator (RPGR)-associated X-linked retinitis pigmentosa (RP) in Koreans.

DESIGN

A retrospective multicenter case series.

METHODS

This study recruited genetically confirmed RPGR-associated X-linked RP patients from nine tertiary hospitals and clinics across Korea. Genetic profiles, age at night blindness onset, visual acuity (VA), visual field radius, ellipsoid zone (EZ) bandwidth, bone spicule pigmentation, fundus autofluorescence (AF) pattern, and genotype-phenotype correlation were analyzed.

RESULTS

A total of 133 patients (104 males and 29 females from 107 families) with pathogenic or likely pathogenic RPGR variants were included. The majority of patients (86.5%) had truncating mutations and 72.9% of variants located in the open reading frame 15 regions. In male patients, night blindness onset occurred before the age of 20 in most patients (85%). Worse VA was associated with older age, with the estimated mean best-corrected VA reaching 20/200 by the age of 40 in male. More than half of the male patients in their 30s had the widest visual field diameter of less than 20°, and more than three-quarters of patients over 40 were classified in this category. Complete loss of the EZ band was rare before the age of 30; however, more than half of the patients in their 30s exhibited complete EZ band loss. Bone spicule pigmentation was uncommon before the age of 20 (10% of those under 10 and 35% in their teens), whereas peripheral hypoAF pattern was commonly observed after the age of 10 (22% of those under 10 and 81% in their teens). Female carriers generally exhibited a milder phenotype and showed significantly greater interocular asymmetry compared to males (all P < .001). Truncating variants were associated with worse VA and a higher risk of complete EZ band loss compared to nontruncating variants (P < .001 and P = .031, respectively).

CONCLUSIONS

This study provides a detailed genetic and age-specific clinical profile of RPGR-related X-linked RP, demonstrating significant differences in phenotypic severity based on the genotype. Our findings provide insights for estimating potential RPGR gene therapy candidate populations, supporting future clinical applications.

Latest trends & strategies in ocular drug delivery

Ocular drug delivery is one of the most challenging routes of administration, and this may be attributed to the complex interplay of ocular barriers and clearance mechanisms that restrict therapeutic payload residence. Most of the currently approved products that ameliorate ocular disease conditions are topical, i.e., delivering therapeutics to the outside anterior segment of the eye. This site of administration works well for certain conditions such as local infections but due to the presence of numerous ocular barriers, the permeation of therapeutics to the posterior segment of the eye is limited. Conditions such as age-related macular degeneration and diabetic retinopathy that contribute to an extreme deterioration of vision acuity require therapeutic interventions at the posterior segment of the eye. This necessitates development of intraocular delivery systems such as intravitreal injections, implants, and specialized devices that deliver therapeutics to the posterior segment of the eye. Frequent dosing regimens and high concentration formulations have been strategized and developed to achieve desired therapeutic outcomes by overcoming some of the challenges of drug clearance and efficacy. Correspondingly, development of suitable delivery platforms such as biodegradable and non-biodegradable implants, nano delivery systems, and implantable devices have been explored. This article provides an overview of the current trends in the development of suitable formulations & delivery systems for ocular drug delivery with an emphasis on late-stage clinical and approved product. Moreover, this work aims to summarize current challenges and highlights exciting pre-clinical developments, and future opportunities in cell and gene therapies that may be explored for effective ocular therapeutic outcomes.

Robotising vitreoretinal surgeries

The use of robotic surgery in ophthalmology has been shown to offer many potential advantages to current surgical techniques. Vitreoretinal surgery requires complex manoeuvres and high precision, and this is an area that exceeds manual human dexterity in certain surgical situations. With the advent of advanced therapeutics such as subretinal gene therapy, precise delivery and minimising trauma is imperative to optimize outcomes. There are multiple robotic systems in place for ophthalmology in pre-clinical and clinical use, and the Preceyes Robotic Surgical System (Preceyes BV) has also gained the CE mark and is commercially available for use. Recent in-vivo and in-human surgeries have been performed successfully with robotics systems. This includes membrane peeling, subretinal injections of therapeutics, and retinal vein cannulation. There is huge potential to integrate robotic surgery into mainstream clinical practice. In this review, we summarize the existing systems, and clinical implementation so far, and highlight the future clinical applications for robotic surgery in vitreo-retina.

A previously unreported RPGR gene variant in a female patient with X-linked retinitis pigmentosa

We present the case of a 40-year-old woman with a history of high myopia and nyctalopia. Her best-corrected visual acuity was 20/80 in the right eye and 20/100 in the left eye. Fundus examination revealed generalized vascular attenuation, optic nerve pallor, and bone spicule pigmentation. Fundus autofluorescence in both eyes showed a Robson-Holder ring in the macula and multiple hypoautofluorescent lesions in the peripheral retina. Macular optical coherence tomography scans revealed a generalized thinning of retinal layers, with atrophy of the outer retinal layers. 10-2 visual fields revealed a small island of central vision in both eyes, and full field electroretinogram showed absence of scotopic and photopic responses. Genetic studies documented a rare variant in the RPGR gene (c.1991C>G p.(Ser664*)). Findings compatible with retinitis pigmentosa in our patient suggests that this mutation is pathogenic. Further study is required to confirm this hypothesis.

Evaluating ocular health in retinal gene therapies

Inherited retinal disease (IRD) refers to a heterogeneous group of genetic eye disease that causes progressive vision loss and was once regarded untreatable. However, regulatory approval for Luxturna (voretigene neparvovec-rzyl) for patients with biallelic mutation in the RPE65 gene has heralded new optimism for patients with the disease. One critical question in designing clinical trial in patients with IRD is choosing appropriate outcome measures to assess the retina, taking into consideration the slow disease progression and the inherent low vision associated with the disease. In this review, the functional and structural endpoints that have been utilised in human retinal gene therapy clinical trials in patient selection as well as measures of safety and efficacy are described. For clinicians, an appreciation of these specialised measures of eye health in a patient with IRD will enhance understanding of retinal health assessments, disease prognosis as well as facilitating discussions with patients potentially eligible for retinal gene therapy clinical trial.

Comparison of CRISPR-Cas13b RNA base editing approaches for USH2A-associated inherited retinal degeneration

CRISPR-Cas13 systems have therapeutic promise for the precise correction of point mutations in RNA. Using adenosine deaminase acting on RNA (ADAR) effectors, A-I base conversions can be targeted using guide RNAs (gRNAs). We compare the Cas13 effectors PspCas13b and Cas13bt3 for the repair of the gene USH2A, a common cause of inherited retinal disease and Usher syndrome. In cultured cells, we demonstrate up to 80% efficiency for the repair of the common c.11864 G > A and its murine equivalent c.11840 G > A, across different gRNAs and promoters. We develop and characterize a mouse model of Usher syndrome carrying the c.11840 G > A mutation designed for the evaluation of base editors for inherited retinal disease. Finally, we compare Cas13 effectors delivered via AAV for the repair of Ush2a in photoreceptors. Mean RNA editing rates in photoreceptors across different constructs ranged from 0.32% to 2.04%, with greater efficiency in those injected with PspCas13b compared to Cas13bt3 constructs. In mice injected with PspCas13b constructs, usherin protein was successfully restored and correctly localized to the connecting cilium following RNA editing. These results support the development of transcriptome targeting gene editing therapies for retinal disease.

Looking to the Future of Viral Vectors in Ocular Gene Therapy: Clinical Review

Eye diseases can significantly affect the quality of life of patients due to decreased visual acuity. Although modern ophthalmological diagnostic methods exist, some diseases of the visual system are asymptomatic in the early stages. Most patients seek advice from an ophthalmologist as a result of rapidly progressive manifestation of symptoms. A number of inherited and acquired eye diseases have only supportive treatment without eliminating the etiologic factor. A promising solution to this problem may be gene therapy, which has proven efficacy and safety shown in a number of clinical studies. By directly altering or replacing defective genes, this therapeutic approach will stop as well as reverse the progression of eye diseases. This review examines the concept of gene therapy and its application in the field of ocular pathologies, emphasizing the most recent scientific advances and their potential impacts on visual function status.

Insights into eye genetics and recent advances in ocular gene therapy

The rapid advancements in the field of genetics have significantly propelled the development of gene therapies, paving the way for innovative treatments of various hereditary disorders. This review focuses on the genetics of ophthalmologic conditions, highlighting the currently approved ophthalmic gene therapy and exploring emerging therapeutic strategies under development. Inherited retinal dystrophies represent a heterogeneous group of genetic disorders that manifest across a broad spectrum from infancy to late middle age. Key clinical features include nyctalopia (night blindness), constriction of the visual field, impairments in color perception, reduced central visual acuity, and rapid eye movements. Recent technological advancements, such as multimodal imaging, psychophysical assessments, and electrophysiological testing, have greatly enhanced our ability to understand disease progression and establish genotype-phenotype correlations. Additionally, the integration of molecular diagnostics into clinical practice is revolutionizing patient stratification and the design of targeted interventions, underscoring the transformative potential of personalized medicine in ophthalmology. The review also covers the challenges and opportunities in developing gene therapies for other ophthalmic conditions, such as age-related macular degeneration and optic neuropathies. We discuss the viral and non-viral vector systems used in ocular gene therapy, highlighting their advantages and limitations. Additionally, we explore the potential of emerging technologies like CRISPR/Cas9 in treating genetic eye diseases. We briefly address the regulatory landscape, concerns, challenges, and future directions of gene therapy in ophthalmology. We emphasize the need for long-term safety and efficacy data as these innovative treatments move from bench to bedside.

Safety and Vision Outcomes Following Gene Therapy for Bietti Crystalline Dystrophy: A Nonrandomized Clinical Trial

Importance

Bietti crystalline dystrophy (BCD) is a severe genetic retinopathy caused by variants in the CYP4V2 gene. Currently, there is no approved treatment for BCD.

Objective

To evaluate safety and vision outcomes following gene therapy with adeno-associated virus (AAV) encoding CYP4V2 (rAAV-hCYP4V2, NGGT001 [Next Generation Gene Therapeutics]).

Design, Setting, and Participants

This open-label, dose-escalation nonrandomized clinical trial was conducted from February 2023 to May 2024 at 2 study sites in China. Patients with genetically confirmed biallelic disease-linked CYP4V2 variants received subretinal injections of rAAV2-hCYP4V2 at 1 of 2 dosage levels and were followed up for 12 months.

Intervention

A single unilateral injection of 1.5 × 1011 or 3.0 × 1011 total vector genomes of recombinant AAV-hCYP4V2 in the worse eye, based on visual acuity letter score.

Main Outcomes and Measures

The primary outcome was safety, assessed by clinical examination of ocular inflammation and evaluated by routine clinical chemistry and immunogenicity testing. Secondary outcomes were changes in visual function from baseline in best-corrected visual acuity (BCVA), microperimetry, and contrast sensitivity 12 months after treatment.

Results

Among 12 patients with BCD (6 patients per dose group), mean (SD) patient age was 40.5 (7.1) years, and 5 patients (42%) were female. No severe adverse events related to the treatment were observed. However, mild intraocular inflammation was noted in 1 participant. The median (IQR) baseline BCVA letter score for the study eye was 34 (10-53), equivalent to 20/200 Snellen, while the nonstudy eye had a median (IQR) BCVA of 60 (40-67), equivalent to approximately 20/63 Snellen. At 12 months, the study eye improved by a mean (SD) letter score of 13.9 (13.1) compared with 6.3 (7.4) in the nonstudy eye. The 12-month median (IQR) BCVA for the study eye was 53 (37-64) (equivalent to approximately 20/80 Snellen) and 62 (42-70) (approximately 20/50 Snellen) for the nonstudy eye.

Conclusions and Relevance

This open-label, exploratory nonrandomized clinical trial identified no serious safety concerns related to gene therapy over 12 months' follow-up among patients with BCD. While improvement in BCVA was noted, the magnitude was within test-retest values typically noted in eyes with very low levels of visual acuity, and BCVA improvement in both the study and nonstudy eyes could be related to a learning effect, with greater improvement in the study eye possibly related to study eyes' being the worse-seeing eye.

Trial Registration

ClinicalTrials.gov Identifier: NCT06302608.

Edridge Green Lecture 2022-demystifying clinical trials and regulatory approvals in drug development

This article provides a comprehensive overview of clinical trial design and regulatory pathways essential for drug development, specifically in the context of retinal diseases. Key concepts include trial structure, efficacy and safety endpoints, and regulatory expectations from agencies like the FDA. It delves into recent regulatory advancements, such as the inclusion of low-luminance vision as a secondary endpoint and analyses case studies from age-related macular degeneration (AMD) trials. Approvals for key retinal drugs, such as ranibizumab and aflibercept, treatments for AMD and diabetic macular oedema, are discussed highlighting criteria like the 15-letter gain/loss in visual acuity as approvable/clinical meaningful efficacy endpoints. Insights into geographic atrophy (GA) and diabetic retinopathy trials showcase the evolving landscape, where anatomical endpoints and new drugs bring fresh challenges and opportunities. It also emphasizes the importance of academic-industry collaboration, citing instances of gene therapy development and innovative endpoint measures like the Multi-Luminance Mobility Test for retinal dystrophies. The overarching aim of this lecture was to demystify the process that spans the design of clinical trials to regulatory approval of drugs so that clinicians understand these complexities. In particular, it is important to understand the reasons behind selection of trial design, inclusion and exclusion criteria, primary and secondary efficacy endpoints and safety endpoints. Since this lecture, there have been important changes in this field including new guidance from the Food and Drug Administration (FDA) as well as lessons learnt from recent drug approvals that are included in this manuscript.

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.

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.

Diseases caused by altered specificity of a protein kinase for its allosteric activators

Protein kinases regulate many intracellular processes, and their dysregulation causes cancers and other diseases. This review focuses on the atypical alpha-kinase 1 (ALPK1), which is activated in mammalian cells by nucleoside diphosphate heptoses (ADP-heptose, UDP-heptose, and CDP-heptose) produced by microbial pathogens but not by mammalian cells. Mutations in human ALPK1 cause ROSAH syndrome and spiradenoma, which result from an alteration in its specificity for nucleoside diphosphate heptoses, causing aberrant activation by mammalian nucleoside diphosphate sugars without microbial infection. These may be the first diseases caused by altered specificity of an enzyme for its allosteric activators and has suggested ways in which selective drugs could be developed to treat them without compromising the innate immune system.

Canine models of inherited retinal diseases: from neglect to well-recognized translational value

Large animal models of inherited retinal diseases, particularly dogs, have been extensively used over the past decades to study disease natural history and evaluate therapeutic interventions. Our group of investigators at the University of Pennsylvania, School of Veterinary Medicine, has played a pivotal role in characterizing several of these animal models, documenting the natural history of their diseases, developing gene therapies, and conducting proof-of-concept studies. Additionally, we have assessed the potential toxicity of these therapies for human clinical trials, contributing to the regulatory approval of voretigene neparvovec-rzyl (Luxturna®) by the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of patients with confirmed biallelic mutation-associated retinal dystrophy. In this review, we aim to summarize the clinical features of a subset of these diseases and reflect on the challenges encountered in integrating canine models into the translational pipeline.

Syndromic Retinitis Pigmentosa

Retinitis pigmentosa (RP) is a progressive inherited retinal dystrophy, characterized by the degeneration of photoreceptors, presenting as a rod-cone dystrophy. Approximately 20-30% of patients with RP also exhibit extra-ocular manifestations in the context of a syndrome. This manuscript discusses the broad spectrum of syndromes associated with RP, pathogenic mechanisms, clinical manifestations, differential diagnoses, clinical management approaches, and future perspectives. Given the diverse clinical and genetic landscape of syndromic RP, the diagnosis may be challenging. However, an accurate and timely diagnosis is essential for optimal clinical management, prognostication, and potential treatment. Broadly, the syndromes associated with RP can be categorized into ciliopathies, inherited metabolic disorders, mitochondrial disorders, and miscellaneous syndromes. Among the ciliopathies associated with RP, Usher syndrome and Bardet-Biedl syndrome are the most well-known. Less common ciliopathies include Cohen syndrome, Joubert syndrome, cranioectodermal dysplasia, asphyxiating thoracic dystrophy, Mainzer-Saldino syndrome, and RHYNS syndrome. Several inherited metabolic disorders can present with RP including Zellweger spectrum disorders, adult Refsum disease, α-methylacyl-CoA racemase deficiency, certain mucopolysaccharidoses, ataxia with vitamin E deficiency, abetalipoproteinemia, several neuronal ceroid lipofuscinoses, mevalonic aciduria, PKAN/HARP syndrome, PHARC syndrome, and methylmalonic acidaemia with homocystinuria type cobalamin (cbl) C disease. Due to the mitochondria's essential role in supplying continuous energy to the retina, disruption of mitochondrial function can lead to RP, as seen in Kearns-Sayre syndrome, NARP syndrome, primary coenzyme Q10 deficiency, SSBP1-associated disease, and long chain 3-hydroxyacyl-CoA dehydrogenase deficiency. Lastly, Cockayne syndrome and PERCHING syndrome can present with RP, but they do not fit the abovementioned hierarchy and are thus categorized as 'Miscellaneous'. Several first-in-human clinical trials are underway or in preparation for some of these syndromic forms of RP.

Nanomedicine in Ophthalmology: From Bench to Bedside

Ocular diseases such as cataract, refractive error, age-related macular degeneration, glaucoma, and diabetic retinopathy significantly impact vision and quality of life worldwide. Despite advances in conventional treatments, challenges like limited bioavailability, poor patient compliance, and invasive administration methods hinder their effectiveness. Nanomedicine offers a promising solution by enhancing drug delivery to targeted ocular tissues, enabling sustained release, and improving therapeutic outcomes. This review explores the journey of nanomedicine from bench to bedside, focusing on key nanotechnology platforms, preclinical models, and case studies of successful clinical translation. It addresses critical challenges, including pharmacokinetics, regulatory hurdles, and manufacturing scalability, which must be overcome for successful market entry. Additionally, this review highlights safety considerations, current marketed and FDA-approved nanomedicine products, and emerging trends such as gene therapy and personalized approaches. By providing a comprehensive overview of the current landscape and future directions, this article aims to guide researchers, clinicians, and industry stakeholders in advancing the clinical application of nanomedicine in ophthalmology.

Recombinant adeno-associated virus as a delivery platform for ocular gene therapy: A comprehensive review

Adeno-associated virus (AAV) has emerged as a leading platform for in vivo gene therapy, particularly in ocular diseases. AAV-based therapies are characterized by low pathogenicity and broad tissue tropism and have demonstrated clinical success, as exemplified by voretigene neparvovec-rzyl (Luxturna) being the first gene therapy to be approved by the U.S. Food and Drug Administration to treat RPE65-associated Leber congenital amaurosis (LCA). However, several challenges remain in the development of AAV-based gene therapies, including immune responses, limited cargo capacity, and the need for enhanced transduction efficiency, especially for intravitreal delivery to photoreceptors and retinal pigment epithelium cells. This review explores the biology of AAVs in the context of gene therapy, innovations in capsid engineering, and clinical advancements in AAV-based ocular gene therapy. We highlight ongoing clinical trials targeting inherited retinal diseases and acquired conditions, discuss immune-related limitations, and examine novel strategies for enhancing AAV vector performance to address current barriers.

When do patients with retinitis pigmentosa present to ophthalmologists? A multi-centre retrospective study

BACKGROUND

Planned gene therapies for retinitis pigmentosa (RP) depend on viable photoreceptors for efficacy. Understanding disease severity at presentation, and drivers that influence time to presentation is important when planning interventions. We examined features that influence RP severity at initial presentation.

METHODS

Multi-centre retrospective cohort study of RP patients at initial presentation. Disease severity was scored using ellipsoid zone (EZ) width on SD-OCT and logistic regression used to determine risk factors for advanced disease at presentation.

RESULTS

A total of 146 unrelated RP patients were included. Median age at onset and presentation was 40.5 (range 1-74) and 50.1 (range 3.9-81.8), respectively. Severe disease (<5° of remaining EZ width) was present in 28.1% of cases at presentation. Patients with family history of RP had greater odds of severe disease (OR 3.29, 95% CI 1.56, 6.95; p = 0.002), while male gender, race, age, syndromic features, and socioeconomic status did not. Patients with affected siblings (median EZ width 6.2°; p = 0.01), but not affected parents (median EZ width 9.4°; p = 0.99), presented with severe EZ loss compared to patients without family history (median EZ width 13.1°). Patients with affected siblings had delayed presentation (≥5 years; OR 5.76, 95% CI 1.817, 18.262; p = 0.003) compared to patients without family history.

CONCLUSIONS

Family history influences the stage of disease at which RP patients initially seek ophthalmology review. This has implications for patient counselling and the number of patients who may benefit from future therapies.

Expanding the genotypic and phenotypic spectra with a novel variant in the ciliopathy gene, CFAP410, associated with selective cone degeneration

BACKGROUND

CFAP410 (Cilia and Flagella Associated Protein 410) encodes a protein that has an important role in the development and function of cilia. In ophthalmology, pathogenic variants in CFAP410 have been described in association with cone rod dystrophy, retinitis pigmentosa, with or without macular staphyloma, or with systemic abnormalities such as skeletal dysplasia and amyotrophic lateral sclerosis. Herein, we report a consanguineous family with a novel homozygous CFAP410 c.335_346del variant with cone only degeneration and no systemic features.

METHODS

A retrospective analysis of ophthalmic history, examination, retinal imaging, electrophysiology and microperimetry was performed as well as genetic testing with in silico pathogenicity predictions and a literature review.

RESULTS

A systemically well 28-year-old female of Pakistani ethnicity with parental consanguinity and no relevant family history, presented with childhood-onset poor central vision and photophobia. Best-corrected visual acuity and colour vision were reduced (0.5 LogMAR, 6/17 Ishihara plates (right) and 0.6 LogMAR, 3/17 Ishihara plates (left). Fundus examination showed no pigmentary retinopathy, no macular staphyloma and autofluorescence was unremarkable. Optical coherence tomography showed subtle signs of intermittent disruption of the ellipsoid zone. Microperimetry demonstrated a reduction in central retinal sensitivity. Electrodiagnostic testing confirmed a reduction in cone-driven responses. Whole-genome sequencing identified an in-frame homozygous deletion of 12 base pairs at c.335_346del in CFAP410.

CONCLUSIONS

The non-syndromic cone dystrophy phenotype reported herein expands the genotypic and phenotypic spectra of CFAP410-associated ciliopathies and highlights the need for light of potential future genetic therapies.

Measuring X-Chromosome inactivation skew for X-linked diseases with adaptive nanopore sequencing

X-linked genetic disorders typically affect females less severely than males owing to the presence of a second X Chromosome not carrying the deleterious variant. However, the phenotypic expression in females is highly variable, which may be explained by an allelic skew in X-Chromosome inactivation. Accurate measurement of X inactivation skew is crucial to understand and predict disease phenotype in carrier females, with prediction especially relevant for degenerative conditions. We propose a novel approach using nanopore sequencing to quantify skewed X inactivation accurately. By phasing sequence variants and methylation patterns, this single assay reveals the disease variant, X inactivation skew, and its directionality and is applicable to all patients and X-linked variants. Enrichment of X Chromosome reads through adaptive sampling enhances cost-efficiency. Our study includes a cohort of 16 X-linked variant carrier females affected by two X-linked inherited retinal diseases: choroideremia and RPGR-associated retinitis pigmentosa. As retinal DNA cannot be readily obtained, we instead determine the skew from peripheral samples (blood, saliva, and buccal mucosa) and correlate it to phenotypic outcomes. This reveals a strong correlation between X inactivation skew and disease presentation, confirming the value in performing this assay and its potential as a way to prioritize patients for early intervention, such as gene therapy currently in clinical trials for these conditions. Our method of assessing skewed X inactivation is applicable to all long-read genomic data sets, providing insights into disease risk and severity and aiding in the development of individualized strategies for X-linked variant carrier females.

Phenotypic and Genetic Spectrum in 309 Consecutive Pediatric Patients with Inherited Retinal Disease

Inherited retinal dystrophies (IRDs) are a common cause of blindness or severe visual impairment in children and may occur with or without systemic associations. The aim of the present study is to describe the phenotypic and genotypic spectrum of IRDs in a pediatric patient cohort in Retrospective single-center cross-sectional analysis. Presenting symptoms, clinical phenotype, and molecular genetic diagnosis were assessed in 309 pediatric patients with suspected IRD. Patients were grouped by age at genetic diagnosis (preschool: 0-6 years, n = 127; schoolchildren: 7-17 years, n = 182). Preschool children most frequently presented with nystagmus (34.5% isolated, 16.4% syndromic), no visual interest (20.9%; 14.5%), or nyctalopia (22.4%; 3.6%; p < 0.05); schoolchildren most frequently presented with declining visual acuity (31% isolated, 21.1% syndromic), nyctalopia (10.6%; 13.5%), or high myopia (5.3%; 13.2%). Pathogenic variants were identified in 96 different genes (n = 69 preschool, n = 73 schoolchildren). In the preschool group, 57.4% had isolated and 42.6% had syndromic IRDs, compared to 70.9% and 29.1% in schoolchildren. In the preschool group, 32.4% of the isolated IRDs were related to forms of Leber's congenital amaurosis (most frequent were RPE65 (11%) and CEP290 (8.2%)), 31.5% were related to stationary IRDs, 15.1% were related to macular dystrophies (ABCA4, BEST1, PRPH2, PROM1), and 8.2% to rod-cone dystrophies (RPGR, RPB3, RP2, PDE6A). All rod-cone dystrophies (RCDs) were subjectively asymptomatic at the time of genetic diagnosis. At schoolage, 41% were attributed to cone-dominated disease (34% ABCA4), 10.3% to BEST1, and 10.3% to RCDs (RP2, PRPF3, RPGR; IMPG2, PDE6B, CNGA1, MFRP, RP1). Ciliopathies were the most common syndromic IRDs (preschool 37%; schoolchildren 45.1%), with variants in USH2A, CEP290 (5.6% each), CDH23, BBS1, and BBS10 (3.7% each) being the most frequent in preschoolers, and USH2A (11.7%), BBS10 (7.8%), CEP290, CDHR23, CLRN1, and ICQB1 (3.9% each) being the most frequent in syndromic schoolkids. Vitreoretinal syndromic IRDs accounted for 29.6% (preschool: COL2A1, COL11A1, NDP (5.6% each)) and 23.5% (schoolage: COL2A1, KIF11 (9.8% each)), metabolic IRDs for 9.4% (OAT, HADHA, MMACHD, PMM2) and 3.9% (OAT, HADHA), mitochondriopathies for 3.7% and 7.8%, and syndromic albinism accounted for 5.6% and 3.9%, respectively. In conclusion we show here that the genotypic spectrum of IRDs and its quantitative distribution not only differs between children and adults but also between children of different age groups, with an almost equal proportion of syndromic and non-syndromic IRDs in early childhood. Ophthalmic screening visits at the preschool and school ages may aid even presymptomatic diagnosis and treatment of potential sight and life-threatening systemic sequelae.

Investigating Microperimetric Features in Bietti Crystalline Dystrophy Patients: A Cross-Sectional Longitudinal Study in a Large Cohort

Purpose

To assess the clinical and genetic characteristics of patients with Bietti crystalline dystrophy (BCD) with a focus on potential of microperimetry in monitoring macular function.

Methods

A total of 208 genetically-confirmed BCD patients were enrolled in this retrospective study. The patients were categorized into subgroups based on their fundus characteristics (fovea sparing and fovea involved), optical coherence tomography (OCT) findings (presence/absence of retinal pigment epithelium [RPE] or ellipsoid zone [EZ] line at the fovea/parafovea), and genetic profiles (Mis/Mis, Tru/Mis, Tru/Tru). Fixation patterns were analyzed, and macular sensitivity (MS) parameters were compared among different groups. Longitudinal analysis was performed to calculate the annual changes in MS parameters. Correlation between genotype and phenotype were further investigated by analyzing cumulative incidence of vision impairment among different genotypic groups.

Results

Patients with well-preserved RPE or EZ at the foveal/parafoveal region exhibited higher MS. Notably, there was a decline in sensitivity parameters, with a decrease of -2.193 dB/year (95% confidence interval [CI] -4.292 to -0.095, P = 0.041) at the fovea and -1.353 dB/year (95% CI -2.047 to -0.659, P < 0.001) in average sensitivity. An age-adjusted comparison of sensitivity among genotypic groups and cumulative incidence analyses showed no association between genotypic groups and vision loss.

Conclusions

Microperimetry proves to be one of a credible tool for detecting macular functional changes in BCD patients. BCD patients with different genotypes may have similar disease progression.

Comparison of Microperimetry and Static Perimetry for Evaluating Macular Function and Progression in Retinitis Pigmentosa

Purpose

To compare the usefulness of microperimetry and static automated perimetry in patients with retinitis pigmentosa (RP), using macular anatomical metrics as a reference.

Design

Prospective observational study.

Participants

Forty-eight eyes of 48 patients with RP in Kyushu University Hospital who underwent microperimetry-3 (MP-3) and Humphrey Field Analyzer (HFA) 10-2 testing ≥3 times during ≥2 years were included.

Methods

Macular anatomy (ellipsoid zone [EZ] length) was assessed by OCT, and macular function was assessed by MP-3 (mean retinal sensitivity at radii 2°, 4°, and 8°) and HFA10-2 program (mean retinal sensitivity at radii 2°, 4°, and 8°). Correlations between functional and anatomical parameters were analyzed cross sectionally at baseline and longitudinally by comparing the rate of progression.

Main Outcome Measures

Correlation coefficients between anatomical and functional metrics.

Results

The mean age at baseline was 50.1 ± 12.3 years, and the mean follow-up period was 2.8 ± 0.7 years. At baseline, EZ length was significantly correlated with MP-3 mean retinal sensitivity at radii 2°, 4°, and 8° (Spearman's ρ = 0.65, 0.84, 0.89; all P < 0.005) and HFA10-2 mean retinal sensitivity at radii 2°, 4°, and 8° (Spearman's ρ = 0.61, 0.73, 0.78; all P < 0.005). Longitudinal analysis showed that the slope of EZ length (-88.92 μm/year) was significantly correlated with the slope of MP-3 retinal sensitivity at 8° radius (-0.62 decibels [dB]/year; Spearman's ρ = 0.31, P=0.03) and the slope of HFA retinal sensitivity at 8° radius (-0.60 dB/year; Spearman's ρ = 0.43, P < 0.005).

Conclusions

Both MP-3 and HFA values were cross sectionally well-correlated with EZ length in patients with patients; however, these associations became weaker in the longitudinal analysis. This highlights the need for researchers to explore additional or more sensitive parameters to better monitor RP progression.

Financial Disclosures

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

Optimal transcorneal electrical stimulation parameters for preserving photoreceptors in a mouse model of retinitis pigmentosa

JOURNAL/nrgr/04.03/01300535-202419110-00034/figure1/v/2024-03-08T184507Z/r/image-tiff Retinitis pigmentosa is a hereditary retinal disease that affects rod and cone photoreceptors, leading to progressive photoreceptor loss. Previous research supports the beneficial effect of electrical stimulation on photoreceptor survival. This study aims to identify the most effective electrical stimulation parameters and functional advantages of transcorneal electrical stimulation (tcES) in mice affected by inherited retinal degeneration. Additionally, the study seeked to analyze the electric field that reaches the retina in both eyes in mice and post-mortem humans. In this study, we recorded waveforms and voltages directed to the retina during transcorneal electrical stimulation in C57BL/6J mice using an intraocular needle probe with rectangular, sine, and ramp waveforms. To investigate the functional effects of electrical stimulation on photoreceptors, we used human retinal explant cultures and rhodopsin knockout (Rho-/-) mice, demonstrating progressive photoreceptor degeneration with age. Human retinal explants isolated from the donors' eyes were then subjected to electrical stimulation and cultured for 48 hours to simulate the neurodegenerative environment in vitro. Photoreceptor density was evaluated by rhodopsin immunolabeling. In vivo Rho-/- mice were subjected to two 5-day series of daily transcorneal electrical stimulation using rectangular and ramp waveforms. Retinal function and visual perception of mice were evaluated by electroretinography and optomotor response (OMR), respectively. Immunolabeling was used to assess the morphological and biochemical changes of the photoreceptor and bipolar cells in mouse retinas. Oscilloscope recordings indicated effective delivery of rectangular, sine, and ramp waveforms to the retina by transcorneal electrical stimulation, of which the ramp waveform required the lowest voltage. Evaluation of the total conductive resistance of the post-mortem human compared to the mouse eyes indicated higher cornea-to-retina resistance in human eyes. The temperature recordings during and after electrical stimulation indicated no significant temperature change in vivo and only a subtle temperature increase in vitro (~0.5-1.5°C). Electrical stimulation increased photoreceptor survival in human retinal explant cultures, particularly at the ramp waveform. Transcorneal electrical stimulation (rectangular + ramp) waveforms significantly improved the survival and function of S and M-cones and enhanced visual acuity based on the optomotor response results. Histology and immunolabeling demonstrated increased photoreceptor survival, improved outer nuclear layer thickness, and increased bipolar cell sprouting in Rho-/- mice. These results indicate that transcorneal electrical stimulation effectively delivers the electrical field to the retina, improves photoreceptor survival in both human and mouse retinas, and increases visual function in Rho-/- mice. Combined rectangular and ramp waveform stimulation can promote photoreceptor survival in a minimally invasive fashion.

Infantile Nystagmus Syndrome-Associated Inherited Retinal Diseases: Perspectives from Gene Therapy Clinical Trials

Inherited retinal diseases (IRDs) are a clinically and genetically diverse group of progressive degenerative disorders that can result in severe visual impairment or complete blindness. Despite their predominantly monogenic inheritance patterns, the genetic complexity of over 300 identified disease-causing genes presents a significant challenge in correlating clinical phenotypes with genotypes. Achieving a molecular diagnosis is crucial for providing patients with definitive diagnostic clarity and facilitating access to emerging gene-based therapies and ongoing clinical trials. Recent advances in next-generation sequencing technologies have markedly enhanced our ability to identify genes and genetic defects leading to IRDs, thereby propelling the development of gene-based therapies. The clinical success of voretigene neparvovec (Luxturna), the first approved retinal gene therapy for RPE65-associated Leber congenital amaurosis (LCA), has spurred considerable research and development in gene-based therapies, highlighting the importance of reviewing the current status of gene therapy for IRDs, particularly those utilizing adeno-associated virus (AAV)-based therapies. As novel disease-causing mutations continue to be discovered and more targeted gene therapies are developed, integrating these treatment opportunities into the standard care for IRD patients becomes increasingly critical. This review provides an update on the diverse phenotypic-genotypic landscape of IRDs, with a specific focus on recent advances in the understanding of IRDs in children with infantile nystagmus syndrome (INS). We highlight the complexities of the genotypic-phenotypic landscape of INS-associated IRDs, including conditions such as achromatopsia, LCA, congenital stationary night blindness, and subtypes of retinitis pigmentosa. Additionally, we provide an updated overview of AAV-based gene therapies for these diseases and discuss the potential of gene-based therapies for underlying IRDs that lead to INS, offering a valuable resource for pediatric patients potentially eligible for ongoing clinical trials.

A systematic review of immunosuppressive protocols used in AAV gene therapy for monogenic disorders

The emergence of adeno-associated virus (AAV)-based gene therapy has brought hope to patients with severe monogenic disorders. However, immune responses to AAV vectors and transgene products present challenges that require effective immunosuppressive strategies. This systematic review focuses on the immunosuppressive protocols used in 38 clinical trials and 35 real-world studies, considering a range of monogenic diseases, AAV serotypes, and administration routes. The review underscores the need for a deeper understanding of immunosuppressive regimens to enhance the safety and effectiveness of AAV-based gene therapy. Characterizing the immunological responses associated with various gene therapy treatments is crucial for optimizing treatment protocols and ensuring the safety and efficacy of forthcoming gene therapy interventions. Further research and understanding of the impact of immunosuppression on disease, therapy, and route of administration will contribute to the development of more effective and safer gene therapy approaches in the future.

Multicenter Normative Data for Mesopic Microperimetry

Purpose

The purpose of this study was to provide a large, multi-center normative dataset for the Macular Integrity Assessment (MAIA) microperimeter and compare the goodness-of-fit and prediction interval calibration-error for a panel of hill-of-vision models.

Methods

Microperimetry examinations of healthy eyes from five independent study groups and one previously available dataset were included (1137 tests from 531 eyes of 432 participants [223 women and 209 men]). Linear mixed models (LMMs) were fitted to the data to obtain interpretable hill-of-vision models. A panel of regression models to predict normative data was compared using cross-validation with site-wise splits. The mean absolute error (MAE) and miscalibration area (area between the calibration curve and the ideal diagonal) were evaluated as the performance measures.

Results

Based on the parameters "participant age," "eccentricity from the fovea," "overlap with the central fixation target," and "eccentricity along the four principal meridians," a Bayesian mixed model had the lowest MAE (2.13 decibel [dB]; 95% confidence interval [CI] = 1.9-2.36 dB) and miscalibration area (0.13; 95% CI = 0.07-0.19). However, a parsimonious linear model provided a comparable MAE (2.17 dB; 95% CI = 1.93-2.4 dB) and a similar miscalibration area (0.14; 95% CI = 0.08-0.2).

Conclusions

Normal variations in visual sensitivity on mesopic microperimetry can be effectively explained by a linear model that includes age and eccentricity. The dataset and a code vignette are provided for estimating normative values across a large range of retinal locations, applicable to customized testing patterns.

From onset to blindness: a comprehensive analysis of RPGR-associated X-linked retinopathy in a large cohort in China

BACKGROUND

Variants in the RPGR are the leading cause of X-linked retinopathies (XLRPs). Further in-depth investigation is needed to understand the natural history.

METHODS

Review of all case records, molecular genetic testing results, best-corrected visual acuity (BCVA), retinal imaging data (including fundus autofluorescence imaging and optical coherence tomography (OCT)), static visual field (VF) assessments and full-field electroretinogram.

RESULTS

Genetic testing was conducted on 104 male patients from 89 family pedigrees, identifying 22 novel variants and 1 de novo variant. The initial symptoms appeared in 78.2% of patients at a median age of 5 years. BCVA declined at a mean rate of 0.02 (IQR, 0-0.04) logarithm of the minimum angle of resolution per year, with a gradual, non-linear decrease over the first 40 years. Autofluorescence imaging revealed macular atrophy at a median age of 36.1 (IQR, 29.9-43.2) years. Patients experienced blindness at a median age of 42.5 (IQR, 32.9-45.2) years according to WHO visual impairment categories. OCT analysis showed a mean ellipsoid zone narrowing rate of 23.3 (IQR, -1.04-22.29) µm/month, with an accelerated reduction in the first 40 years (p<0.01). The median age at which ERG no longer detected a waveform was 26.5 (IQR, 20.5-32.8) years. Comparison by variant location indicated faster progression in patients with exon 1-14 variants during the initial two decades, while those with ORF15 variants showed accelerated progression from the third decade.

CONCLUSIONS

We provide a foundation for determining the treatment window and an objective basis for evaluating the therapeutic efficacy of gene therapy for XLRP.

Update on Clinical Trial Endpoints in Gene Therapy Trials for Inherited Retinal Diseases

Inherited retinal diseases (IRDs) encompass a wide spectrum of rare conditions characterized by diverse phenotypes associated with hundreds of genetic variations, often leading to progressive visual impairment and profound vision loss. Multiple natural history studies and clinical trials exploring gene therapy for various IRDs are ongoing. Outcomes for ophthalmic trials measure visual changes in three main categories-structural, functional, and patient-focused outcomes. Since IRDs may range from congenital with poor central vision from birth to affecting the peripheral retina initially and progressing insidiously with visual acuity affected late in the disease course, typical outcome measures such as central visual acuity and ocular coherence tomography (OCT) imaging of the macula may not provide adequate representation of therapeutic outcomes including alterations in disease course. Thus, alternative unique outcome measures are necessary to assess loss of peripheral vision, color vision, night vision, and contrast sensitivity in IRDs. These differences have complicated the assessment of clinical outcomes for IRD therapies, and the clinical trials for IRDs have had to design novel specialized endpoints to demonstrate treatment efficacy. As genetic engineering and gene therapy techniques continue to advance with growing investment from industry and accelerated approval tracks for orphan conditions, the clinical trials must continue to improve their assessments to demonstrate safety and efficacy of new gene therapies that aim to come to market. Here, we will provide an overview of the current gene therapy approaches, review various endpoints for measuring visual function, highlight those that are utilized in recent gene therapy trials, and provide an overview of stage 2 and 3 IRD trials through the second quarter of 2024.

Targeted long-read sequencing enriches disease-relevant genomic regions of interest to provide complete Mendelian disease diagnostics

Despite advances in sequencing technologies, a molecular diagnosis remains elusive in many patients with Mendelian disease. Current short-read clinical sequencing approaches cannot provide chromosomal phase information or epigenetic information without further sample processing, which is not routinely done and can result in an incomplete molecular diagnosis in patients. The ability to provide phased genetic and epigenetic information from a single sequencing run would improve the diagnostic rate of Mendelian conditions. Here, we describe targeted long-read sequencing of Mendelian disease genes (TaLon-SeqMD) using a real-time adaptive sequencing approach. Optimization of bioinformatic targeting enabled selective enrichment of multiple disease-causing regions of the human genome. Haplotype-resolved variant calling and simultaneous resolution of epigenetic base modification could be achieved in a single sequencing run. The TaLon-SeqMD approach was validated in a cohort of 18 individuals with previous genetic testing targeting 373 inherited retinal disease (IRD) genes, yielding the complete molecular diagnosis in each case. This approach was then applied in 2 IRD cases with inconclusive testing, which uncovered noncoding and structural variants that were difficult to characterize by standard short-read sequencing. Overall, these results demonstrate TaLon-SeqMD as an approach to provide rapid phased-variant calling to provide the molecular basis of Mendelian diseases.

Interim safety and efficacy of gene therapy for RLBP1-associated retinal dystrophy: a phase 1/2 trial

Gene therapy holds promise for treatment of inherited retinal dystrophies, a group of rare genetic disorders characterized by severe loss of vision. Here, we report up to 3-year pre-specified interim safety and efficacy results of an open-label first-in-human dose-escalation phase 1/2 gene therapy clinical trial in 12 patients with retinal dystrophy caused by biallelic mutations in the retinaldehyde-binding protein 1 (RLBP1) gene of the visual cycle. The primary endpoints were systemic and ocular safety and recovery of dark adaptation. Secondary endpoints included microperimetry, visual field sensitivity, dominant eye test and patient-reported outcomes. Subretinal delivery of an adeno-associated viral vector (AAV8-RLBP1) was well tolerated with dose-dependent intraocular inflammation which responded to corticosteroid treatment, and focal atrophy of the retinal pigment epithelium as the dose limiting toxicity. Dark adaptation kinetics, the primary efficacy endpoint, improved significantly in all dose-cohorts. Treatment with AAV8-RLBP1 resulted in the resolution of disease-related retinal deposits, suggestive of successful restoration of the visual cycle. In conclusion, to date, AAV8-RLBP1 has shown preliminary safety and efficacy in patients with RLBP1-associated retinal dystrophy. Trial number: NCT03374657.

Safety and efficacy of ATSN-101 in patients with Leber congenital amaurosis caused by biallelic mutations in GUCY2D: a phase 1/2, multicentre, open-label, unilateral dose escalation study

BACKGROUND

Leber congenital amaurosis 1 (LCA1), caused by mutations in GUCY2D, is a rare inherited retinal disease that typically causes blindness in early childhood. The aim of this study was to evaluate the safety and preliminary efficacy of ascending doses of ATSN-101, a subretinal AAV5 gene therapy for LCA1.

METHODS

15 patients with genetically confirmed biallelic mutations in GUCY2D were included in this phase 1/2 study. All patients received unilateral subretinal injections of ATSN-101. In the dose-escalation phase, three adult cohorts (n=3 each) were treated with three ascending doses: 1·0 × 1010 vg/eye (low dose), 3·0 × 1010 vg/eye (middle dose), and 1·0 × 1011 vg/eye (high dose). In the dose-expansion phase, one adult cohort (n=3) and one paediatric cohort (n=3) were treated at the high dose. The primary endpoint was the incidence of treatment-emergent adverse events (TEAEs), and secondary endpoints included full-field stimulus test (FST) and best-corrected visual acuity (BCVA). A multi-luminance mobility test (MLMT) was also done. Data through the 12-month main study period are reported.

FINDINGS

Patients were enrolled between Sept 12, 2019, and May 5, 2022. A total of 68 TEAEs were observed, 56 of which were related to the surgical procedure. No serious TEAE was related to the study drug. Ocular inflammation was mild and reversible with steroid treatment. For patients who received the high dose, mean change in dark-adapted FST was 20·3 decibels (dB; 95% CI 6·6 to 34·0) for treated eyes and 1·1 dB (-3·7 to 5·9) for untreated eyes at month 12 (white stimulus); improvements were first observed at day 28 and persisted over 12 months (p=0·012). Modest improvements in BCVA were also observed (p=0·10). Three of six patients who received the high dose and did the MLMT achieved the maximum score in the treated eye.

INTERPRETATION

ATSN-101 is well tolerated 12 months after treatment, with no drug-related serious adverse events. Clinically significant improvements in retinal sensitivity were sustained in patients receiving the high dose.

FUNDING

Atsena Therapeutics.

Establishing Clinical Trial Endpoints in Selecting Patients for RPGR Retinal Gene Therapy

Purpose

Clinical trials for X-linked retinitis pigmentosa (RP) often assess retinal structure using optical coherence tomography (OCT) and function using microperimetry to evaluate initial eligibility and endpoints. Therefore, we seek to determine which parameters might be most sensitive in screening new patients for enrollment.

Methods

Thirty-one patients (62 eyes) with confirmed retinitis pigmentosa GTPase regulator (RPGR) mutations attending Oxford Eye Hospital were included in this retrospective analysis. Outer retinal structure was investigated by measuring the remaining ellipsoid zone (EZ) and external limiting membrane (ELM) on OCT. Visual function was evaluated by using 10-2 microperimetry mean sensitivity.

Results

The median age of patients with RPGR was 31 years (interquartile range [IQR] = 22-39 years). For the right and left eyes, respectively, the median EZ length through the foveal section was 921 µm (IQR = 607-1570) and 865 µm (IQR = 508-1442) and median ELM length was 2056 µm (IQR = 1336-2764) and 1860 µm (IQR = 1152-2680). Similarly, the median microperimetry sensitivity (MS) was 2.0 decibel (dB; IQR = 0.4-5.4) and 1.1 dB (IQR = 0.1-5.4). Linear mixed model regression analysis showed that EZ was significantly positively correlated to ELM (P < 0.001, R² = 0.931). EZ and ELM were significantly correlated with the microperimetry sensitivity with exponential relationship (P < 0.001, R² = 0.71 and 0.72, respectively). Using the exponential equation of regression line, EZ below approximately 600 µm (RE = 637 µm, 95% confidence interval [CI] = 397-877, LE = 586 µm, 95% CI = 356-817) results in microperimetry sensitivity of approximately 0 dB. There was high degree of inter-eye symmetry for progression of EZ, ELM, and microperimetry sensitivity. Age was significantly correlated with the analyzed parameters (P < 0.001), although with low R² for each of them.

Discussion

EZ may comprise a surrogate biomarker for prediction of visual function in X-linked RP caused by mutations in RPGR and, in turn, identification of appropriate patients for enrollment in clinical trials. As expected, age plays a role in predicting potential biomarkers and visual function, however, it should not be used to preclude patients for gene therapy due to the poor correlation and heterogeneity of disease onset.

Translational Relevance

Biomarkers of visual function in RPGR-associated RP may lead to identification of appropriate patients for enrollment in clinical trials.

Current developments of gene therapy in human diseases

Gene therapy has witnessed substantial advancements in recent years, becoming a constructive tactic for treating various human diseases. This review presents a comprehensive overview of these developments, with a focus on their diverse applications in different disease contexts. It explores the evolution of gene delivery systems, encompassing viral (like adeno-associated virus; AAV) and nonviral approaches, and evaluates their inherent strengths and limitations. Moreover, the review delves into the progress made in targeting specific tissues and cell types, spanning the eye, liver, muscles, and central nervous system, among others, using these gene technologies. This targeted approach is crucial in addressing a broad spectrum of genetic disorders, such as inherited lysosomal storage diseases, neurodegenerative disorders, and cardiovascular diseases. Recent clinical trials and successful outcomes in gene therapy, particularly those involving AAV and the clustered regularly interspaced short palindromic repeats (CRISPR)-CRISPR-associated proteins, are highlighted, illuminating the transformative potentials of this approach in disease treatment. The review summarizes the current status of gene therapy, its prospects, and its capacity to significantly ameliorate patient outcomes and quality of life. By offering comprehensive analysis, this review provides invaluable insights for researchers, clinicians, and stakeholders, enriching the ongoing discourse on the trajectory of disease treatment.

Genetic therapies and potential therapeutic applications of CRISPR activators in the eye

Conventional gene therapy involving supplementation only treats loss-of-function diseases and is limited by viral packaging sizes, precluding therapy of large genes. The discovery of CRISPR/Cas has led to a paradigm shift in the field of genetic therapy, with the promise of precise gene editing, thus broadening the range of diseases that can be treated. The initial uses of CRISPR/Cas have focused mainly on gene editing or silencing of abnormal variants via utilising Cas endonuclease to trigger the target cell endogenous non-homologous end joining. Subsequently, the technology has evolved to modify the Cas enzyme and even its guide RNA, leading to more efficient editing tools in the form of base and prime editing. Further advancements of this CRISPR/Cas technology itself have expanded its functional repertoire from targeted editing to programmable transactivation, shifting the therapeutic focus to precise endogenous gene activation or upregulation with the potential for epigenetic modifications. In vivo experiments using this platform have demonstrated the potential of CRISPR-activators (CRISPRa) to treat various loss-of-function diseases, as well as in regenerative medicine, highlighting their versatility to overcome limitations associated with conventional strategies. This review summarises the molecular mechanisms of CRISPRa platforms, the current applications of this technology in vivo, and discusses potential solutions to translational hurdles for this therapy, with a focus on ophthalmic diseases.

Gene Therapies in Clinical Development to Treat Retinal Disorders

Gene therapies have emerged as promising treatments in clinical development for various retinal disorders, offering hope to patients with inherited degenerative eye conditions. Several gene therapies have already shown remarkable success in clinical trials, with significant improvements observed in visual acuity and the preservation of retinal function. A multitude of gene therapies have now been delivered safely in human clinical trials for a wide range of inherited retinal disorders but there are some gaps in the reported trial data. Some of the most exciting treatment options are not under peer review and information is only available in press release form. Whilst many trials appear to have delivered good outcomes of safety, others have failed to meet primary endpoints and therefore not proceeded to phase III. Despite this, such trials have enabled researchers to learn how best to assess and monitor patient outcomes, which will guide future trials to greater success. In this review, we consider recent and ongoing clinical trials for a variety of potential retinal gene therapy treatments and discuss the positive and negative issues related to these trials. We discuss the treatment potential following clinical trials as well as the potential risks of some treatments under investigation. As these therapies continue to advance through rigorous testing and regulatory approval processes, they hold the potential to revolutionise the landscape of retinal disorder treatments, providing renewed vision and enhancing the quality of life for countless individuals worldwide.

HSF5 Deficiency Causes Male Infertility Involving Spermatogenic Arrest at Meiotic Prophase I in Humans and Mice

Meiosis is a specialized cell division process that generates gametes for sexual reproduction. However, the factors and underlying mechanisms involving meiotic progression remain largely unknown, especially in humans. Here, it is first showed that HSF5 is associated with human spermatogenesis. Patients with a pathogenic variant of HSF5 are completely infertile. Testicular histologic findings in the patients reveal rare postmeiotic germ cells resulting from meiotic prophase I arrest. Hsf5 knockout (KO) mice confirms that the loss of HSF5 causes defects in meiotic recombination, crossover formation, sex chromosome synapsis, and sex chromosome inactivation (MSCI), which may contribute to spermatocyte arrest at the late pachytene stage. Importantly, spermatogenic arrest can be rescued by compensatory HSF5 adeno-associated virus injection into KO mouse testes. Mechanistically, integrated analysis of RNA sequencing and chromatin immunoprecipitation sequencing data revealed that HSF5 predominantly binds to promoters of key genes involved in crossover formation (e.g., HFM1, MSH5 and MLH3), synapsis (e.g., SYCP1, SYCP2 and SYCE3), recombination (TEX15), and MSCI (MDC1) and further regulates their transcription during meiotic progression. Taken together, the study demonstrates that HSF5 modulates the transcriptome to ensure meiotic progression in humans and mice. These findings will aid in genetic diagnosis of and potential treatments for male infertility.

The menace of severe adverse events and deaths associated with viral gene therapy and its potential solution

Over the past decade, in vivo gene replacement therapy has significantly advanced, resulting in market approval of numerous therapeutics predominantly relying on adeno-associated viral vectors (AAV). While viral vectors have undeniably addressed several critical healthcare challenges, their clinical application has unveiled a range of limitations and safety concerns. This review highlights the emerging challenges in the field of gene therapy. At first, we discuss both the role of biological barriers in viral gene therapy with a focus on AAVs, and review current landscape of in vivo human gene therapy. We delineate advantages and disadvantages of AAVs as gene delivery vehicles, mostly from the safety perspective (hepatotoxicity, cardiotoxicity, neurotoxicity, inflammatory responses etc.), and outline the mechanisms of adverse events in response to AAV. Contribution of every aspect of AAV vectors (genomic structure, capsid proteins) and host responses to injected AAV is considered and substantiated by basic, translational and clinical studies. The updated evaluation of recent AAV clinical trials and current medical experience clearly shows the risks of AAVs that sometimes overshadow the hopes for curing a hereditary disease. At last, a set of established and new molecular and nanotechnology tools and approaches are provided as potential solutions for mitigating or eliminating side effects. The increasing number of severe adverse reactions and, sadly deaths, demands decisive actions to resolve the issue of immune responses and extremely high doses of viral vectors used for gene therapy. In response to these challenges, various strategies are under development, including approaches aimed at augmenting characteristics of viral vectors and others focused on creating secure and efficacious non-viral vectors. This comprehensive review offers an overarching perspective on the present state of gene therapy utilizing both viral and non-viral vectors.