Emerging Therapeutic Approaches and Genetic Insights in Stargardt Disease: A Comprehensive Review.

Stargardt disease, one of the most common forms of inherited retinal diseases, affects individuals worldwide. The primary cause is mutations in the ABCA4 gene, leading to the accumulation of toxic byproducts in the retinal pigment epithelium (RPE) and subsequent photoreceptor cell degeneration. Over the past few years, research on Stargardt disease has advanced significantly, focusing on clinical and molecular genetics. Recent studies have explored various innovative therapeutic approaches, including gene therapy, stem cell therapy, and pharmacological interventions. Gene therapy has shown promise, particularly with adeno-associated viral (AAV) vectors capable of delivering the ABCA4 gene to retinal cells. However, challenges remain due to the gene's large size. Stem cell therapy aims to replace degenerated RPE and photoreceptor cells, with several clinical trials demonstrating safety and preliminary efficacy. Pharmacological approaches focus on reducing toxic byproduct accumulation and modulating the visual cycle. Precision medicine, targeting specific genetic mutations and pathways, is becoming increasingly important. Novel techniques such as clustered regularly interspaced palindromic repeats (CRISPR)/Cas9 offer potential for directly correcting genetic defects. This review aims to synthesize recent advancements in understanding and treating Stargardt disease. By highlighting breakthroughs in genetic therapies, stem cell treatments, and novel pharmacological strategies, it provides a comprehensive overview of emerging therapeutic options.

The CFTR Corrector, VX-809 (Lumacaftor), Rescues ABCA4 Trafficking Mutants: a Potential Treatment for Stargardt Disease.

BACKGROUND/AIMS: Mutations in ABCA4 cause Stargardt macular degeneration, which invariably ends in legal blindness. We studied two common mutants, A1038V (in NBD1) and G1961E (in NBD2), with the purpose of exploring how they interact with the cell's quality control mechanism. The study was designed to determine how these mutants can be rescued. METHODS: We expressed wt and mutant ABCA4 in HEK293 cells and studied the effect of the mutations on trafficking and processing and the ability of correctors to rescue them. We used a combination of western blotting, confocal microscopy and surface biotinylation coupled with pulldown of plasma membrane proteins. RESULTS: G1961E is sensitive to inhibitors of the aggresome, tubacin and the lysosome, bafilomycin A. Both mutants cause a reduction in heat shock protein, Hsp27. Incubation of HEK293 cells expressing the mutants with VX-809, an FDA approved drug for the treatment of cystic fibrosis, increased the levels of A1038V and G1961E by 2- to 3-fold. Importantly, VX-809 increased the levels of both mutants at the plasma membrane suggesting that trafficking had been restored. Transfecting additional Hsp27 to the cells also increased the steady state levels of both mutants. However, in combination with VX-809 the addition of Hsp27 caused a dramatic increase in the protein expression particularly in the G1961 mutant which increased approximately 5-fold. CONCLUSION: Our results provide a new mechanism for the rescue of ABCA4 trafficking mutants based on the restoration of Hsp27. Our results provide a pathway for the treatment of Stargardt disease.

Targeted next generation sequencing reveals genetic defects underlying inherited retinal disease in Iranian families.

Purpose: Inherited retinal diseases (IRDs) are clinically and genetically heterogeneous showing progressive retinal cell death which results in vision loss. IRDs include a wide spectrum of disorders, such as retinitis pigmentosa (RP), Leber congenital amaurosis (LCA), cone-rod dystrophy (CRD), and Stargardt disease (STGD1). Methods: In this study, we performed targeted next-generation sequencing based on molecular inversion probes (MIPs) that allowed the sequence analysis of 108 IRD-associated genes in 50 Iranian IRD probands. Results: The sequencing and variant filtering led to the identification of putative pathogenic variants in 36 out of 50 (72%) probands. Among 36 unique variants, we identified 20 novel variants in 15 genes. Four out of 36 probands carry compound heterozygous variants, and 32 probands carry homozygous variants. Conclusions: Employing a cost-effective targeted next-generation sequencing procedure, we identified the genetic causes of different retinal disorders in the majority of Iranian families in this study.

Clinical and Genetic Characteristics Analysis of Korean Patients with Stargardt Disease Using Targeted Exome Sequencing.

PURPOSE: To investigate genetic mutations in Korean patients with Stargardt disease (STGD) using exome sequencing, and to analyze the correlations between genetic mutations and clinical phenotypes. METHODS: Peripheral venous blood was obtained from 24 clinically diagnosed Korean STGD patients, followed by extraction of genomic DNAs. Using exome sequencing we investigated gene mutations for the adenosine triphosphate-binding cassette, subfamily A, member 4 (ABCA4) elongation of very-long-chain fatty acids 4 (ELOVL4), and prominin 1 (PROM1), and confirmed gene mutations by the direct sequencing of polymerase chain reaction products. RESULTS: ABCA4 mutations were confirmed in 17 of 24 patients, and 12 novel mutations were identified. ELOVL4 and PROM1 gene mutations were not identified in this study. We also identified 16 previously reported mutations related to STGD1. In patients whose disease symptoms occurred before 20 years of age, visual acuity was poorer and atrophic flecks were more frequently found. In addition, more ABCA4 mutations were found in patients who had choroidal silence or atrophic flecks. CONCLUSIONS: Novel ABCA4 gene mutations were found in Korean patients with STGD1. This study will facilitate better understanding of the relationships between ABCA4 gene mutations and clinical symptoms in Korean patients.

Expression of ABCA4 in the retinal pigment epithelium and its implications for Stargardt macular degeneration.

Recessive Stargardt disease (STGD1) is an inherited blinding disorder caused by mutations in the Abca4 gene. ABCA4 is a flippase in photoreceptor outer segments (OS) that translocates retinaldehyde conjugated to phosphatidylethanolamine across OS disc membranes. Loss of ABCA4 in Abca4-/- mice and STGD1 patients causes buildup of lipofuscin in the retinal pigment epithelium (RPE) and degeneration of photoreceptors, leading to blindness. No effective treatment currently exists for STGD1. Here we show by several approaches that ABCA4 is additionally expressed in RPE cells. (i) By in situ hybridization analysis and by RNA-sequencing analysis, we show the Abca4 mRNA is expressed in human and mouse RPE cells. (ii) By quantitative immunoblotting, we show that the level of ABCA4 protein in homogenates of wild-type mouse RPE is about 1% of the level in neural retina homogenates. (iii) ABCA4 immunofluorescence is present in RPE cells of wild-type and Mertk-/- but not Abca4-/- mouse retina sections, where it colocalizes with endolysosomal proteins. To elucidate the role of ABCA4 in RPE cells, we generated a line of genetically modified mice that express ABCA4 in RPE cells but not in photoreceptors. Mice from this line on the Abca4-/- background showed partial rescue of photoreceptor degeneration and decreased lipofuscin accumulation compared with nontransgenic Abca4-/- mice. We propose that ABCA4 functions to recycle retinaldehyde released during proteolysis of rhodopsin in RPE endolysosomes following daily phagocytosis of distal photoreceptor OS. ABCA4 deficiency in the RPE may play a role in the pathogenesis of STGD1.

Relative frequency of inherited retinal dystrophies in Brazil.

Among the Brazilian population, the frequency rates of inherited retinal dystrophies and their causative genes are underreported. To increase the knowledge about these dystrophies in our population, we retrospectively studied the medical records of 1,246 Brazilian patients with hereditary retinopathies during 20 years of specialized outpatient clinic care. Of these patients, 559 had undergone at least one genetic test. In this cohort, the most prevalent dystrophies were non-syndromic retinitis pigmentosa (35%), Stargardt disease (21%), Leber congenital amaurosis (9%), and syndromic inherited retinal dystrophies (12%). Most patients had never undergone genetic testing (55%), and among the individuals with molecular test results, 28.4% had negative or inconclusive results compared to 71.6% with a conclusive molecular diagnosis. ABCA4 was the most frequent disease-causing gene, accounting for 20% of the positive cases. Pathogenic variants also occurred frequently in the CEP290, USH2A, CRB1, RPGR, and CHM genes. The relative frequency rates of different inherited retinal dystrophies in Brazil are similar to those found globally. Although mutations in more than 250 genes lead to hereditary retinopathies, only 66 genes were responsible for 70% of the cases, which indicated that smaller and cheaper gene panels can be just as effective and provide more affordable solutions for implementation by the Brazilian public health system.

Ophthalmological findings in ectodermal dysplasia, ectrodactyly, and macular dystrophy syndrome: a case report / Achados oftalmológicos na displasia ectodérmica, ectrodactilia e síndrome da distrofia macular: relato de caso

ABSTRACT We report on a case of two sisters, daughters of consanguineous parents, presenting with a similar condition of low visual acuity associated with retinal dystrophy in both eyes associated with alopecia and bone alterations or syndactyly.

RESUMO Relatamos um caso de duas irmãs, filhas de pais consanguíneos, apresentando uma condição semelhante de baixa acuidade visual associado à distrofia retiniana em ambos os olhos associado à alopecia e alterações ósseas ou sindactilia.

Ophthalmological findings in ectodermal dysplasia, ectrodactyly, and macular dystrophy syndrome: a case report.

We report on a case of two sisters, daughters of consanguineous parents, presenting with a similar condition of low visual acuity associated with retinal dystrophy in both eyes associated with alopecia and bone alterations or syndactyly.

Stargardt macular dystrophy and evolving therapies.

INTRODUCTION: Stargardt macular dystrophy (STGD1) is a hereditary retinal degeneration that lacks effective treatment options. Gene therapy, stem cell therapy, and pharmacotherapy with visual cycle modulators (VCMs) and complement inhibitors are discussed as potential treatments. AREAS COVERED: Investigational therapies for STGD1 aim to reduce toxic bisretinoids and lipofuscin in the retina and retinal pigment epithelium (RPE). These agents include C20-D3-vitamin A (ALK-001), isotretinoin, VM200, emixustat, and A1120. Avacincaptad pegol is a C5 complement inhibitor that may reduce inflammation-related RPE damage. Animal models of STGD1 show promising data for these treatments, though proof of efficacy in humans is lacking. Fenretinide and emixustat are VCMs for dry AMD and STGD1 that failed to halt geographic atrophy progression or improve vision in trials for AMD. A1120 prevents retinol transport into RPE and may spare side effects typically seen with VCMs (nyctalopia and chromatopsia). Stem cell transplantation suggests potential biologic plausibility in a phase I/II trial. Gene therapy aims to augment the mutated ABCA4 gene, though results of a phase I/II trial are pending. EXPERT OPINION: Stem cell transplantation, ABCA4 gene therapy, VCMs, and complement inhibitors offer biologically plausible treatment mechanisms for treatment of STGD1. Further trials are warranted to assess efficacy and safety in humans.

Transplantation of Human Embryonic Stem Cell-Derived Retinal Pigment Epithelial Cells in Macular Degeneration.

PURPOSE: Transplantation of human embryonic stem cell (hESC)-derived retinal pigment epithelial (RPE) cells offers the potential for benefit in macular degeneration. Previous trials have reported improved visual acuity (VA), but lacked detailed analysis of retinal structure and function in the treated area. DESIGN: Phase 1/2 open-label dose-escalation trial to evaluate safety and potential efficacy (clinicaltrials.gov identifier, NCT01469832). PARTICIPANTS: Twelve participants with advanced Stargardt disease (STGD1), the most common cause of macular degeneration in children and young adults. METHODS: Subretinal transplantation of up to 200 000 hESC-derived RPE cells with systemic immunosuppressive therapy for 13 weeks. MAIN OUTCOME MEASURES: The primary end points were the safety and tolerability of hESC-derived RPE cell administration. We also investigated evidence of the survival of transplanted cells and measured retinal structure and function using microperimetry and spectral-domain OCT. RESULTS: Focal areas of subretinal hyperpigmentation developed in all participants in a dose-dependent manner in the recipient retina and persisted after withdrawal of systemic immunosuppression. We found no evidence of uncontrolled proliferation or inflammatory responses. Borderline improvements in best-corrected VA in 4 participants either were unsustained or were matched by a similar improvement in the untreated contralateral eye. Microperimetry demonstrated no evidence of benefit at 12 months in the 12 participants. In one instance at the highest dose, localized retinal thinning and reduced sensitivity in the area of hyperpigmentation suggested the potential for harm. Participant-reported quality of life using the 25-item National Eye Institute Visual Function Questionnaire indicated no significant change. CONCLUSIONS: Subretinal hyperpigmentation is consistent with the survival of viable transplanted hESC-derived RPE cells, but may reflect released pigment in their absence. The findings demonstrate the value of detailed analysis of spatial correlation of retinal structure and function in determining with appropriate sensitivity the impact of cell transplantation and suggest that intervention in early stage of disease should be approached with caution. Given the slow rate of progressive degeneration at this advanced stage of disease, any protection against further deterioration may be evident only after a more extended period of observation.

Treatments for dry age-related macular degeneration and Stargardt disease: a systematic review.

BACKGROUND: Age-related macular degeneration (AMD) is the leading cause of visual loss in older people. Advanced AMD takes two forms, neovascular (wet) and atrophic (dry). Stargardt disease (STGD) is the commonest form of inherited macular dystrophy. OBJECTIVE: To carry out a systematic review of treatments for dry AMD and STGD, and to identify emerging treatments where future NIHR research might be commissioned. DESIGN: Systematic review. METHODS: We searched MEDLINE, EMBASE, Web of Science and The Cochrane Library from 2005 to 13 July 2017 for reviews, journal articles and meeting abstracts. We looked for studies of interventions that aim to preserve or restore vision in people with dry AMD or STGD. The most important outcomes are those that matter to patients: visual acuity (VA), contrast sensitivity, reading speed, ability to drive, adverse effects of treatment, quality of life, progression of disease and patient preference. However, visual loss is a late event and intermediate predictors of future decline were accepted if there was good evidence that they are strong predictors of subsequent visual outcomes. These include changes detectable by investigation, but not necessarily noticed by people with AMD or STGD. ClinicalTrials.gov, the World Health Organization search portal and the UK Clinical Trials gateway were searched for ongoing and recently completed clinical trials. RESULTS: The titles and abstracts of 7948 articles were screened for inclusion. The full text of 398 articles were obtained for further screening and checking of references and 112 articles were included in the final report. Overall, there were disappointingly few good-quality studies (including of sufficient size and duration) reporting useful outcomes, particularly in STGD. However we did identify a number of promising research topics, including drug treatments, stem cells, new forms of laser treatment, and implantable intraocular lens telescopes. In many cases, research is already under way, funded by industry or governments. LIMITATIONS: In AMD, the main limitation came from the poor quality of much of the evidence. Many studies used VA as their main outcome despite not having sufficient duration to observe changes. The evidence on treatments for STGD is sparse. Most studies tested interventions with no comparison group, were far too short term, and the quality of some studies was poor. FUTURE WORK: We think that the topics on which the Health Technology Assessment (HTA) and Efficacy Mechanism and Evaluation (EME) programmes might consider commissioning primary research are in STGD, a HTA trial of fenretinide (ReVision Therapeutics, San Diego, CA, USA), a visual cycle inhibitor, and EME research into the value of lutein and zeaxanthin supplements, using short-term measures of retinal function. In AMD, we suggest trials of fenretinide and of a potent statin. There is epidemiological evidence from the USA that the drug, levodopa, used for treating Parkinson's disease, may reduce the incidence of AMD. We suggest that similar research should be carried out using the large general practice databases in the UK. Ideally, future research should be at earlier stages in both diseases, before vision is impaired, using sensitive measures of macular function. This may require early detection of AMD by screening. STUDY REGISTRATION: This study is registered as PROSPERO CRD42016038708. FUNDING: The National Institute for Health Research HTA programme.

Bisretinoid Photodegradation Is Likely Not a Good Thing.

Retinaldehyde adducts (bisretinoids) accumulate in retinal pigment epithelial (RPE) cells as lipofuscin. Bisretinoids are implicated in some inherited and age-related forms of macular degeneration that lead to the death of RPE cells and diminished vision. By comparing albino and black-eyed mice and by rearing mice in darkness and in cyclic light, evidence indicates that bisretinoid fluorophores undergo photodegradation in the eye (Ueda et al. Proc Natl Acad Sci 113:6904-6909, 2016). Given that the photodegradation products modify and impair cellular and extracellular molecules, these processes likely impart cumulative damage to retina.

Long-term follow-up of autosomal dominant Stargardt macular dystrophy (STGD3) subjects enrolled in a fish oil supplement interventional trial.

BACKGROUND: Earlier studies have raised the notion that docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) supplementation could be a useful intervention in autosomal dominant Stargardt macular dystrophy (STGD3). We sought to assess whether fish oil supplementation has a beneficial effect on the clinical course of STGD3 secondary to a mutation in the ELOVL4 gene. MATERIALS AND METHODS: Eleven patients with STGD3 were enrolled in an 8-year open-label, clinical interventional study of over-the-counter fish oil supplements at a recommended daily dose of 650 mg EPA and 350 mg DHA (NCT00420602). Subjects had annual eye examinations with complete imaging, visual function testing, and blood lipid analyses. Compliance with therapy was measured by periodic patient self-report and with serum and red blood cell biomarkers of lipid consumption. Paired sample t-tests were used to measure differences in mean values of visual acuity, lipid biomarkers, and contrast sensitivity obtained at baseline and the last follow-up. RESULTS: All subjects showed progression of their maculopathy, and we could not discern a beneficial effect of the intervention. Compliance with the recommended fish oil supplement intervention was poor as assessed by patient self-report and biomarkers of lipid consumption. CONCLUSIONS: Our inability to detect a benefit of fish oil could be the result of small subject numbers, poor compliance, or intervention too late in the course of the disease. We still advise STGD3 patients to consume fish or fish oil regularly, and we recommend that pre-symptomatic children with ELOVL4 mutations should be especially targeted for these interventions.

Dual AAV Vectors for Stargardt Disease.

Stargardt disease (STGD1), due to mutations in the large ABCA4 gene, is the most common inherited macular degeneration in humans. Attempts at developing gene therapy approaches for treatment of STGD1 are currently ongoing. Among all the vectors available for gene therapy of inherited retinal diseases, those based on adeno-associated viruses (AAV) are the most promising given the efficacy shown in various animal models and their excellent safety profile in humans, as confirmed in many ongoing clinical trials. However, one of the main obstacles for the use of AAV is their limited effective packaging capacity of about 5 kb. Taking advantage of the AAV genome's ability to concatemerize , others and we have recently developed dual AAV vectors to overcome this limit. We tested dual AAV vectors for ABCA4 delivery, and found that they transduce efficiently both mouse and pig photoreceptors , and rescue the Abca4-/- mouse retinal phenotype, indicating their potential for gene therapy of STGD1. This chapter details how we designed dual AAV vectors for the delivery of the ABCA4 gene and describes the techniques that can be explored to evaluate dual AAV transduction efficiency in vitro and in the retina, and their efficacy in the mouse model of STGD1.

Suprachoroidal Adipose Tissue-Derived Mesenchymal Stem Cell Implantation in Patients with Dry-Type Age-Related Macular Degeneration and Stargardt's Macular Dystrophy: 6-Month Follow-Up Results of a Phase 2 Study.

This prospective clinical case series aimed to investigate the safety and efficacy of suprachoroidal adipose tissue-derived mesenchymal stem cell (ADMSC) implantation in patients with dry-type age-related macular degeneration (AMD) and Stargardt's macular dystrophy (SMD). This study included four patients with advanced-stage dry-type AMD and four patients with SMD who underwent suprachoroidal implantation of ADMSCs. The best-corrected visual acuity (BCVA) in the study was 20/200. The worse eye of the patient was operated on. Patients were evaluated on the first day, first week, and first, third, and sixth months postoperatively. BCVA, anterior segment and fundus examination, color photography, fundus autofluorescence, optical coherence tomography, and visual field examination were carried out at each visit. Fundus fluorescein angiography and multifocal electroretinography (mf-ERG) recordings were performed at the end of the first, third, and sixth months and anytime if necessary during the follow-up. All eight patients completed the sixth month follow-up. None of them had any systemic or ocular complications. All of the eight patients experienced visual acuity improvement, visual field improvement, and improvement in mf-ERG recordings. Stem cell treatment with suprachoroidal implantation of ADMSCs seems to be safe and effective in the treatment of dry-type AMD and SMD.

Gene therapy for inherited retinal and optic nerve degenerations.

INTRODUCTION: The eye is a target for investigational gene therapy due to the monogenic nature of many inherited retinal and optic nerve degenerations (IRD), its accessibility, tight blood-ocular barrier, the ability to non-invasively monitor for functional and anatomic outcomes, as well as its relative immune privileged state.Vectors currently used in IRD clinical trials include adeno-associated virus (AAV), small single-stranded DNA viruses, and lentivirus, RNA viruses of the retrovirus family. Both can transduce non-dividing cells, but AAV are non-integrating, while lentivirus integrate into the host cell genome, and have a larger transgene capacity. AREAS COVERED: This review covers Leber's congenital amaurosis, choroideremia, retinitis pigmentosa, Usher syndrome, Stargardt disease, Leber's hereditary optic neuropathy, Achromatopsia, and X-linked retinoschisis. EXPERT OPINION: Despite great potential, gene therapy for IRD raises many questions, including the potential for less invasive intravitreal versus subretinal delivery, efficacy, safety, and longevity of response, as well as acceptance of novel study endpoints by regulatory bodies, patients, clinicians, and payers. Also, ultimate adoption of gene therapy for IRD will require widespread genetic screening to identify and diagnose patients based on genotype instead of phenotype.

Juvenile Macular Degenerations.

In this article, we review the following 3 common juvenile macular degenerations: Stargardt disease, X-linked retinoschisis, and Best vitelliform macular dystrophy. These are inherited disorders that typically present during childhood, when vision is still developing. They are sufficiently common that they should be included in the differential diagnosis of visual loss in pediatric patients. Diagnosis is secured by a combination of clinical findings, optical coherence tomography imaging, and genetic testing. Early diagnosis promotes optimal management. Although there is currently no definitive cure for these conditions, therapeutic modalities under investigation include pharmacologic treatment, gene therapy, and stem cell transplantation.

Visual Acuity Change over 12 Months in the Prospective Progression of Atrophy Secondary to Stargardt Disease (ProgStar) Study: ProgStar Report Number 6.

PURPOSE: To estimate the yearly rate of change of best-corrected visual acuity (BCVA) and the risk of loss 1 line or more over 1 year and to identify risk factors for BCVA loss in patients with Stargardt disease (STGD1). DESIGN: Multicenter, prospective cohort study. PARTICIPANTS: Two hundred fifty-nine patients (489 eyes) with molecularly confirmed STGD1 enrolled at 9 centers in the United States and Europe. METHODS: Participants were followed up every 6 months, and data at the baseline and 6- and 12-month visits were analyzed. Best-corrected visual acuity was measured using the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol. Standardized reporting forms were used to collect participants' characteristics and clinical observations. Linear mixed effects models were used to estimate the rate of BCVA loss. Linear models with generalized estimating equations were used to identify risk factors for BCVA loss of 1 line or more over 1 year. MAIN OUTCOME MEASURES: Change in BCVA over 1 year. RESULTS: Cross-sectional analysis at baseline showed that earlier symptom onset and longer duration since onset was associated with worse BCVA. Longitudinal analysis showed no overall significant change of BCVA within 12 months, but the rate of BCVA change was significantly different by baseline BCVA (P < 0.001). The BCVA of eyes with baseline BCVA of 20/25 or better declined at a rate of 2.8 ETDRS letters per year (P = 0.10), eyes with baseline BCVA between 20/25 and 20/70 declined at a rate of 2.3 ETDRS letters per year (P = 0.002), eyes with baseline BCVA between 20/70 and 20/200 declined at a rate of 0.8 ETDRS letters per year (P = 0.08), and eyes with baseline BCVA worse than 20/200 showed a significant improvement of 2.3 ETDRS letters per year (P < 0.001). Overall, 12.9% of eyes lost 1 line or more, and the risk of such BCVA loss was different by baseline BCVA level (P = 0.016). Smoking and vitamin A use was not associated significantly with baseline BCVA, nor with rate of BCVA loss over 1 year. CONCLUSIONS: Change in BCVA in STGD1 patients over a 12-month period was small, but varied depending on baseline BCVA. Given the slow change during 1 year, BCVA is unlikely to be a sensitive outcome measure for STGD1 treatment trials with 1 year's duration.

Incidence of Atrophic Lesions in Stargardt Disease in the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) Study: Report No. 5.

Importance: Outcome measures that are sensitive to disease progression are needed as clinical end points for future treatment trials in Stargardt disease. Objective: To examine the incidence of atrophic lesions of the retinal pigment epithelium in patients with Stargardt disease as determined by fundus autofluorescence imaging. Design, Setting, and Participants: In this retrospective multicenter cohort study, 217 patients 6 years and older at baseline at tertiary referral centers in Europe, the United States, and the United Kingdom who were harboring disease-causing variants in the adenosine triphosphate (ATP)-binding cassette subfamily A member 4 (ABCA4) gene and who met the following criteria were enrolled: (1) at least 1 well-demarcated area of atrophy with a minimum diameter of 300 µm, with the total area of all atrophic lesions being less than or equal to 12 mm2 in at least 1 eye at the most recent visit, and (2) fundus autofluorescence images for at least 2 visits with a minimum of 6 months between at least 2 visits. Data were collected between August 22, 2013, and December 12, 2014. Data analysis was performed from March 15, 2015, through January 31, 2017. Exposures: Images were evaluated by staff at a central reading center. Areas of definitely decreased autofluorescence (DDAF) and questionably decreased autofluorescence (QDAF) were outlined and quantified. Lesion-free survival rates were estimated using Kaplan-Meier survival curves. Main Outcomes and Measures: Incidence of atrophic lesions as determined by fundus autofluorescence. Results: The 217 patients (mean [SD] age, 21.8 [13.3] years; 127 female [57.5%]; 148 white [68.2%]) contributed 390 eyes for which the mean (SD) follow-up time was 3.9 (1.6) years (range, 0.7-12.1 years). Among eyes without DDAF at first visit, the median time to develop a DDAF lesion was 4.9 years (95% CI, 4.3-5.6 years). Among eyes without QDAF, the median time to develop a QDAF lesion was 6.3 years (95% CI, 5.6-9.7 years). Eyes with a lesion of DDAF at the first visit were less likely to develop a QDAF lesion compared with eyes without a lesion of DDAF (hazard ratio, 0.19; 95% CI, 0.05-0.70; P = .01). Conclusions and Relevance: An estimated 50% of the eyes without DDAF at first visit will develop the lesion in less than 5 years, suggesting that incidence of DDAF could serve as an outcome measure for treatment trials.

Complement modulation in the retinal pigment epithelium rescues photoreceptor degeneration in a mouse model of Stargardt disease.

Recessive Stargardt macular degeneration (STGD1) is caused by mutations in the gene for the ABCA4 transporter in photoreceptor outer segments. STGD1 patients and Abca4-/- (STGD1) mice exhibit buildup of bisretinoid-containing lipofuscin pigments in the retinal pigment epithelium (RPE), increased oxidative stress, augmented complement activation and slow degeneration of photoreceptors. A reduction in complement negative regulatory proteins (CRPs), possibly owing to bisretinoid accumulation, may be responsible for the increased complement activation seen on the RPE of STGD1 mice. CRPs prevent attack on host cells by the complement system, and complement receptor 1-like protein y (CRRY) is an important CRP in mice. Here we attempted to rescue the phenotype in STGD1 mice by increasing expression of CRRY in the RPE using a gene therapy approach. We injected recombinant adeno-associated virus containing the CRRY coding sequence (AAV-CRRY) into the subretinal space of 4-wk-old Abca4-/- mice. This resulted in sustained, several-fold increased expression of CRRY in the RPE, which significantly reduced the complement factors C3/C3b in the RPE. Unexpectedly, AAV-CRRY-treated STGD1 mice also showed reduced accumulation of bisretinoids compared with sham-injected STGD1 control mice. Furthermore, we observed slower photoreceptor degeneration and increased visual chromophore in 1-y-old AAV-CRRY-treated STGD1 mice. Rescue of the STGD1 phenotype by AAV-CRRY gene therapy suggests that complement attack on the RPE is an important etiologic factor in STGD1. Modulation of the complement system by locally increasing CRP expression using targeted gene therapy represents a potential treatment strategy for STGD1 and other retinopathies associated with complement dysregulation.