Nuclear modifier YARS2 allele correction restored retinal ganglion cells-specific deficiencies in Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy (LHON) is a maternally transmitted eye disease due to the degeneration of retinal ganglion cells (RGCs). Mitochondrial 11778G > A mutation is the most common LHON-associated mitochondrial DNA (mtDNA) mutation. Our recent studies demonstrated some LHON families manifested by synergic interaction between m.11778G > A mutation and YARS2 allele (c.572G > T, p.Gly191Val) encoding mitochondrial tyrosyl-tRNA synthetase. However, the RGC-specific effects of LHON-associated mtDNA mutations remain elusive and there is no highly effective therapy for LHON. Here, we generated patients-derived induced pluripotent stem cells (iPSCs) from fibroblasts derived from a Chinese LHON family (both m.11778G > A and c.572G > T mutations, only m.11778G > A mutation, and control subject). The c.572G > T mutation in iPSC lines from a syndromic individual was corrected by CRISPR/Cas9. Those iPSCs were differentiated into neural progenitor cells and subsequently induced RGC-like cells using a stepwise differentiation procedure. Those RGC-like cells derived from symptomatic individual harboring both m.11778G > A and c.572G > T mutations exhibited greater defects in neuronal differentiation, morphology including reduced area of soma, numbers of neurites and shortened length of axons, electrophysiological properties than those in cells bearing only m.11778G > A mutation. Furthermore, these RGC-like cells revealed more drastic reductions in oxygen consumption rates, levels of mitochondrial ATP and increasing productions of reactive oxygen species than those in other cell models. These mitochondrial dysfunctions promoted the apoptotic process for RGC degenerations. Correction of YARS2 c.572G > T mutation rescued deficiencies of patient-derived RGC-like cells. These findings provide new insights into pathophysiology of LHON arising from RGC-specific mitochondrial dysfunctions and step toward therapeutic intervention for this disease.

Randomized trial of bilateral gene therapy injection for m.11778G>A MT-ND4 Leber optic neuropathy.

Leber hereditary optic neuropathy (LHON) is an important example of mitochondrial blindness with the m.11778G>A mutation in the MT-ND4 gene being the most common disease-causing mtDNA variant worldwide. The REFLECT phase 3 pivotal study is a randomized, double-masked, placebo-controlled trial investigating the efficacy and safety of bilateral intravitreal injection of lenadogene nolparvovec in patients with a confirmed m.11778G>A mutation, using a recombinant adeno-associated virus vector 2, serotype 2 (rAAV2/2-ND4). The first-affected eye received gene therapy; the fellow (affected/not-yet-affected) eye was randomly injected with gene therapy or placebo. The primary end point was the difference in change from baseline of best-corrected visual acuity (BCVA) in second-affected/not-yet-affected eyes treated with lenadogene nolparvovec versus placebo at 1.5 years post-treatment, expressed in logarithm of the minimal angle of resolution (LogMAR). Forty-eight patients were treated bilaterally and 50 unilaterally. At 1.5 years, the change from baseline in BCVA was not statistically different between second-affected/not-yet-affected eyes receiving lenadogene nolparvovec and placebo (primary end point). A statistically significant improvement in BCVA was reported from baseline to 1.5 years in lenadogene nolparvovec-treated eyes: -0.23 LogMAR for the first-affected eyes of bilaterally treated patients (P < 0.01); and -0.15 LogMAR for second-affected/not-yet-affected eyes of bilaterally treated patients and the first-affected eyes of unilaterally treated patients (P < 0.05). The mean improvement in BCVA from nadir to 1.5 years was -0.38 (0.052) LogMAR and -0.33 (0.052) LogMAR in first-affected and second-affected/not-yet-affected eyes treated with lenadogene nolparvovec, respectively (bilateral treatment group). A mean improvement of -0.33 (0.051) LogMAR and -0.26 (0.051) LogMAR was observed in first-affected lenadogene nolparvovec-treated eyes and second-affected/not-yet-affected placebo-treated eyes, respectively (unilateral treatment group). The proportion of patients with one or both eyes on-chart at 1.5 years was 85.4% and 72.0% for bilaterally and unilaterally treated patients, respectively. The gene therapy was well tolerated, with no systemic issues. Intraocular inflammation, which was mostly mild and well controlled with topical corticosteroids, occurred in 70.7% of lenadogene nolparvovec-treated eyes versus 10.2% of placebo-treated eyes. Among eyes treated with lenadogene nolparvovec, there was no difference in the incidence of intraocular inflammation between bilaterally and unilaterally treated patients. Overall, the REFLECT trial demonstrated an improvement of BCVA in LHON eyes carrying the m.11778G>A mtDNA mutation treated with lenadogene nolparvovec or placebo to a degree not reported in natural history studies and supports an improved benefit/risk profile for bilateral injections of lenadogene nolparvovec relative to unilateral injections.

Leber hereditary optic neuropathy gene therapy.

PURPOSE OF REVIEW: To discuss relevant clinical outcomes, challenges, and future opportunities of gene therapy in Leber hereditary optic neuropathy (LHON). RECENT FINDINGS: Results of G11778A LHON Phase 3 randomized clinical trials with unilateral intravitreal rAAV2/2-ND4 allotopic gene therapy show good safety and unexpected bilateral partial improvements of BCVA (best-corrected visual acuity) with mean logMAR BCVA improvements of up to near ∼0.3 logMAR (3 lines) in the treated eyes and ∼0.25 logMAR (2.5 lines) in the sham-treated or placebo-treated fellow eyes. Final mean BCVA levels after gene therapy were in the range of ∼1.3 logMAR (20/400) bilaterally. SUMMARY: Bilateral partial improvement with unilateral LHON gene therapy was unanticipated and may be due to treatment efficacy, natural history, learning effect, and other mediators. The overall efficacy is limited given the final BCVA levels. The sequential progressive visual loss and varied occurrence of spontaneous partial improvement in LHON confound trial results. Future clinical trials with randomization of patients to a group not receiving gene therapy in either eye would help to assess treatment effect. Promising future LHON gene therapy strategies include mitochondrially-targeted-sequence adeno-associated virus ('MTS-AAV') for direct delivery of the wild-type mitochondrial DNA into the mitochondria and CRISPR-free, RNA-free mitochondrial base editing systems. Signs of anatomical optic nerve damage and objective retinal ganglion cell dysfunction are evident in the asymptomatic eyes of LHON patients experiencing unilateral visual loss, indicating the therapeutic window is narrowing before onset of visual symptoms. Future treatment strategies utilizing mitochondrial base editing in LHON carriers without optic neuropathy holds the promise of a more advantageous approach to achieve optimal visual outcome by reducing disease penetrance and mitigating retinal ganglion cell loss when optic neuropathy develops.

Recessive MECR pathogenic variants cause an LHON-like optic neuropathy.

BACKGROUND: Leber's hereditary optic neuropathy (LHON) is a mitochondrial disorder characterised by complex I defect leading to sudden degeneration of retinal ganglion cells. Although typically associated with pathogenic variants in mitochondrial DNA, LHON was recently described in patients carrying biallelic variants in nuclear genes DNAJC30, NDUFS2 and MCAT. MCAT is part of mitochondrial fatty acid synthesis (mtFAS), as also MECR, the mitochondrial trans-2-enoyl-CoA reductase. MECR mutations lead to a recessive childhood-onset syndromic disorder with dystonia, optic atrophy and basal ganglia abnormalities. METHODS: We studied through whole exome sequencing two sisters affected by sudden and painless visual loss at young age, with partial recovery and persistent central scotoma. We modelled the candidate variant in yeast and studied mitochondrial dysfunction in yeast and fibroblasts. We tested protein lipoylation and cell response to oxidative stress in yeast. RESULTS: Both sisters carried a homozygous pathogenic variant in MECR (p.Arg258Trp). In yeast, the MECR-R258W mutant showed an impaired oxidative growth, 30% reduction in oxygen consumption rate and 80% decrease in protein levels, pointing to structure destabilisation. Fibroblasts confirmed the reduced amount of MECR protein, but failed to reproduce the OXPHOS defect. Respiratory complexes assembly was normal. Finally, the yeast mutant lacked lipoylation of key metabolic enzymes and was more sensitive to H2O2 treatment. Lipoic Acid supplementation partially rescued the growth defect. CONCLUSION: We report the first family with homozygous MECR variant causing an LHON-like optic neuropathy, which pairs the recent MCAT findings, reinforcing the impairment of mtFAS as novel pathogenic mechanism in LHON.

Mitochondrially Targeted Gene Therapy Rescues Visual Loss in a Mouse Model of Leber's Hereditary Optic Neuropathy.

Leber's hereditary optic neuropathy (LHON) is a common mitochondrial genetic disease, causing irreversible blindness in young individuals. Current treatments are inadequate, and there is no definitive cure. This study evaluates the effectiveness of delivering wildtype human NADH ubiquinone oxidoreductase subunit 4 (hND4) gene using mito-targeted AAV(MTSAAV) to rescue LHOH mice. We observed a declining pattern in electroretinograms amplitudes as mice aged across all groups (p < 0.001), with significant differences among groups (p = 0.023; Control vs. LHON, p = 0.008; Control vs. Rescue, p = 0.228). Inner retinal thickness and intraocular pressure did not change significantly with age or groups. Compared to LHON mice, those rescued with wildtype hND4 exhibited improved retinal visual acuity (0.29 ± 0.1 cy/deg vs. 0.15 ± 0.1 cy/deg) and increased functional hyperemia response (effect of flicker, p < 0.001, effect of Group, p = 0.004; Interaction Flicker × Group, p < 0.001). Postmortem analysis shows a marked reduction in retinal ganglion cell density in the LHON group compared to the other groups (Effect of Group, p < 0.001, Control vs. LHON, p < 0.001, Control vs. Rescue, p = 0.106). These results suggest that MTSAAV-delivered wildtype hND4 gene rescues, at least in part, visual impairment in an LHON mouse model and has the therapeutic potential to treat this disease.

Gene therapy restores mitochondrial function and protects retinal ganglion cells in optic neuropathy induced by a mito-targeted mutant ND1 gene.

Therapies for genetic disorders caused by mutated mitochondrial DNA are an unmet need, in large part due barriers in delivering DNA to the organelle and the absence of relevant animal models. We injected into mouse eyes a mitochondrially targeted Adeno-Associated-Virus (MTS-AAV) to deliver the mutant human NADH ubiquinone oxidoreductase subunit I (hND1/m.3460 G > A) responsible for Leber's hereditary optic neuropathy, the most common primary mitochondrial genetic disease. We show that the expression of the mutant hND1 delivered to retinal ganglion cells (RGC) layer colocalizes with the mitochondrial marker PORIN and the assembly of the expressed hND1 protein into host respiration complex I. The hND1-injected eyes exhibit hallmarks of the human disease with progressive loss of RGC function and number, as well as optic nerve degeneration. We also show that gene therapy in the hND1 eyes by means of an injection of a second MTS-AAV vector carrying wild-type human ND1 restores mitochondrial respiratory complex I activity, the rate of ATP synthesis and protects RGCs and their axons from dysfunction and degeneration. These results prove that MTS-AAV is a highly efficient gene delivery approach with the ability to create mito-animal models and has the therapeutic potential to treat mitochondrial genetic diseases.

Absence of lenadogene nolparvovec DNA in a brain tumor biopsy from a patient in the REVERSE clinical study, a case report.

BACKGROUND: Leber Hereditary Optic Neuropathy (LHON) is a rare, maternally-inherited mitochondrial disease that primarily affects retinal ganglion cells (RGCs) and their axons in the optic nerve, leading to irreversible, bilateral severe vision loss. Lenadogene nolparvovec gene therapy was developed as a treatment for patients with vision loss from LHON caused by the most prevalent m.11778G > A mitochondrial DNA point mutation in the MT-ND4 gene. Lenadogene nolparvovec is a replication-defective recombinant adeno-associated virus vector 2 serotype 2 (AAV2/2), encoding the human wild-type MT-ND4 protein. Lenadogene nolparvovec was administered by intravitreal injection (IVT) in LHON patients harboring the m.11778G > A ND4 mutation in a clinical development program including one phase 1/2 study (REVEAL), three phase 3 pivotal studies (REVERSE, RESCUE, REFLECT), and one long-term follow-up study (RESTORE, the follow-up of REVERSE and RESCUE patients). CASE PRESENTATION: A 67-year-old woman with MT-ND4 LHON, included in the REVERSE clinical study, received a unilateral IVT of lenadogene nolparvovec in the right eye and a sham injection in the left eye in May 2016, 11.4 months and 8.8 months after vision loss in her right and left eyes, respectively. The patient had a normal brain magnetic resonance imaging with contrast at the time of diagnosis of LHON. Two years after treatment administration, BCVA had improved in both eyes. The product was well tolerated with mild and resolutive anterior chamber inflammation in the treated eye. In May 2019, the patient was diagnosed with a right temporal lobe glioblastoma, IDH-wildtype, World Health Organization grade 4, based on histological analysis of a tumor excision. The brain tumor was assessed for the presence of vector DNA by using a sensitive validated qPCR assay targeting the ND4 sequence of the vector. CONCLUSION: ND4 DNA was not detected (below 15.625 copies/µg of genomic DNA) in DNA extracted from the brain tumor, while a housekeeping gene DNA was detected at high levels. Taken together, this data shows the absence of detection of lenadogene nolparvovec in a brain tumor (glioblastoma) of a treated patient in the REVERSE clinical trial 3 years after gene therapy administration, supporting the long-term favorable safety of lenadogene nolparvovec.

Developments in the Treatment of Leber Hereditary Optic Neuropathy.

PURPOSEOF REVIEW: To outline the current landscape of treatments for Leber hereditary optic neuropathy (LHON) along the therapeutic delivery pipeline, exploring the mechanisms of action and evidence for these therapeutic approaches. RECENT FINDINGS: Treatments for LHON can be broadly classified as either mutation-specific or mutation-independent. Mutation-specific therapies aim to correct the underlying mutation through the use of a gene-editing platform or replace the faulty mitochondrial DNA-encoded protein by delivering the wild-type gene using a suitable vector. Recent gene therapy clinical trials assessing the efficacy of allotopically expressed MT-ND4 for the treatment of LHON due to the m.11778G > A mutation in MT-ND4 have shown positive results when treated within 12 months of symptom onset. Mutation-independent therapies can have various downstream targets that aim to improve mitochondrial respiration, reduce mitochondrial stress, inhibit or delay retinal ganglion cell apoptosis, and/or promote retinal ganglion cell survival. Idebenone, a synthetic hydrosoluble analogue of co-enzyme Q10 (ubiquinone), is the only approved treatment for LHON. Mutation-independent approaches to gene therapy under pre-clinical investigation for other neurodegenerative disorders may have the potential to benefit patients with LHON. Although approved treatments are presently limited, innovations in gene therapy and editing are driving the expansion of the therapeutic delivery pipeline for LHON.

Leber hereditary optic neuropathy: new and emerging therapies.

PURPOSE OF REVIEW: To review recent therapeutic advances in Leber hereditary optic neuropathy (LHON). RECENT FINDINGS: Idebenone, a synthetic analog of ubiquinone (Coenzyme Q10) is an antioxidant and component of the mitochondrial electron transport chain. Since the initial approval of the drug in 2015 in Europe, recent trials have evaluated its role as prolonged treatment in LHON. Gene therapy has recently emerged as a promising alternative for the treatment of LHON. Among several investigations, RESCUE and REVERSE are two phase 3 clinical trials of gene therapy in patients with LHON in early stages. Results in these trials have shown a bilateral visual acuity improvement with unilateral intravitreal injections at 96 weeks and sustained visual improvement after 3 years of treatment. The most recent REFLECT phase 3 clinical trial in LHON has shown significant improvement of vision after bilateral intravitreal injections compared with the group that received unilateral injections. SUMMARY: Historically, LHON has been considered an untreatable disease, but recent developments show that new pharmacological and gene therapy approaches may lead to visual recovery. Further studies are needed to support these data.

Induced Pluripotent Stem Cells for Inherited Optic Neuropathies-Disease Modeling and Therapeutic Development.

BACKGROUND: Inherited optic neuropathies (IONs) cause progressive irreversible visual loss in children and young adults. There are limited disease-modifying treatments, and most patients progress to become severely visually impaired, fulfilling the legal criteria for blind registration. The seminal discovery of the technique for reprogramming somatic nondividing cells into induced pluripotent stem cells (iPSCs) has opened several exciting opportunities in the field of ION research and treatment. EVIDENCE ACQUISITION: A systematic review of the literature was conducted with PubMed using the following search terms: autosomal dominant optic atrophy, ADOA, dominant optic atrophy, DOA, Leber hereditary optic neuropathy, LHON, optic atrophy, induced pluripotent stem cell, iPSC, iPSC derived, iPS, stem cell, retinal ganglion cell, and RGC. Clinical trials were identified on the ClinicalTrials.gov website. RESULTS: This review article is focused on disease modeling and the therapeutic strategies being explored with iPSC technologies for the 2 most common IONs, namely, dominant optic atrophy and Leber hereditary optic neuropathy. The rationale and translational advances for cell-based and gene-based therapies are explored, as well as opportunities for neuroprotection and drug screening. CONCLUSIONS: iPSCs offer an elegant, patient-focused solution to the investigation of the genetic defects and disease mechanisms underpinning IONs. Furthermore, this group of disorders is uniquely amenable to both the disease modeling capability and the therapeutic potential that iPSCs offer. This fast-moving area will remain at the forefront of both basic and translational ION research in the coming years, with the potential to accelerate the development of effective therapies for patients affected with these blinding diseases.

Solutions to a Radical Problem: Overview of Current and Future Treatment Strategies in Leber's Hereditary Opic Neuropathy.

Leber's Hereditary Optic Neuropathy (LHON) is the most common primary mitochondrial DNA disorder. It is characterized by bilateral severe central subacute vision loss due to specific loss of Retinal Ganglion Cells and their axons. Historically, treatment options have been quite limited, but ongoing clinical trials show promise, with significant advances being made in the testing of free radical scavengers and gene therapy. In this review, we summarize management strategies and rational of treatment based on current insights from molecular research. This includes preventative recommendations for unaffected genetic carriers, current medical and supportive treatments for those affected, and emerging evidence for future potential therapeutics.

Relative Leukocyte Telomere Length and Telomerase Complex Regulatory Markers Association with Leber's Hereditary Optic Neuropathy.

Background and Objectives: To evaluate the association of relative leukocyte telomere length (RLTL) and telomerase complex regulatory markers with Leber's hereditary optic neuropathy (LHON). Material and Methods: A case-control study was performed in patients with LHON (≥18 years) and healthy subjects. The diagnosis of LHON was based on a genetic blood test (next-generation sequencing with Illumina MiSeq, computer analysis: BWA2.1 Illumina BaseSpace, Alamut, and mtDNA Variant analyzer 1000 were performed) and diagnostic criteria approved by the LHON disease protocol. Statistical analysis was performed using the standard statistical software package, IBM SPSS Statistics 27. Statistically significant results were considered when p < 0.05. Results: Significantly longer RLTL was observed in LHON patients than in healthy controls (p < 0.001). RLTL was significantly longer in women and men with LOHN than in healthy women and men in the control group (p < 0.001 and p = 0.003, respectively). In the elderly group (>32 years), RLTL was statistically significantly longer in LHON patients compared with healthy subjects (p < 0.001). The GG genotype of the TERC rs12696304 polymorphism was found to be statistically significantly higher in the LHON group (p = 0.041), and the C allele in the TERC rs12696304 polymorphism was found to be statistically significantly less common in the LHON group (p < 0.001). The RLTL of LHON patients was found to be statistically significantly longer in the TERC rs12696304 polymorphism in all tested genotypes (CC, p = 0.005; CG, p = 0.008; GG, p = 0.025), TEP1 rs1760904 polymorphism in the GA genotype (p < 0.001), and TEP1 gene rs1713418 in the AA and AG genotypes (p = 0.011 and p < 0.001, respectively). Conclusions: The RLTL in LHON patients was found to be longer than in healthy subjects regardless of treatment with idebenone. The TERC rs12696304 polymorphism, of all studied polymorphisms, was the most significantly associated with changes in LHON and telomere length.

Efficacy and Safety of Intravitreal Gene Therapy for Leber Hereditary Optic Neuropathy Treated within 6 Months of Disease Onset.

PURPOSE: To evaluate the efficacy of a single intravitreal injection of rAAV2/2-ND4 in subjects with visual loss from Leber hereditary optic neuropathy (LHON). DESIGN: RESCUE is a multicenter, randomized, double-masked, sham-controlled, phase 3 clinical trial. PARTICIPANTS: Subjects with the m.11778G>A mitochondrial DNA mutation and vision loss ≤6 months from onset in 1 or both eyes were included. METHODS: Each subject's right eye was randomly assigned (1:1) to treatment with rAAV2/2-ND4 (single injection of 9 × 1010 viral genomes in 90 µl) or to sham injection. The left eye received the treatment not allocated to the right eye. MAIN OUTCOME MEASURES: The primary end point was the difference of the change from baseline in best-corrected visual acuity (BCVA) between rAAV2/2-ND4-treated and sham-treated eyes at week 48. Other outcome measures included contrast sensitivity, Humphrey visual field perimetry, retinal anatomic measures, and quality of life. Follow-up extended to week 96. RESULTS: Efficacy analysis included 38 subjects. Mean age was 36.8 years, and 82% were male. Mean duration of vision loss at time of treatment was 3.6 months and 3.9 months in the rAAV2/2-ND4-treated eyes and sham-treated eyes, respectively. Mean baseline logarithm of the minimum angle of resolution (logMAR) BCVA (standard deviation) was 1.31 (0.52) in rAAV2/2-ND4-treated eyes and 1.26 (0.62) in sham-treated eyes, with a range from -0.20 to 2.51. At week 48, the difference of the change in BCVA from baseline between rAAV2/2-ND4-treated and sham-treated eyes was -0.01 logMAR (P = 0.89); the primary end point of a -0.3 logMAR (15-letter) difference was not met. The mean BCVA for both groups deteriorated over the initial weeks, reaching the worst levels at week 24, followed by a plateau phase until week 48, and then an improvement of +10 and +9 Early Treatment Diabetic Retinopathy Study letters equivalent from the plateau level in the rAAV2/2-ND4-treated and sham-treated eyes, respectively. CONCLUSIONS: At 96 weeks after unilateral injection of rAAV2/2-ND4, LHON subjects carrying the m.11778G>A mutation treated within 6 months after vision loss achieved comparable visual outcomes in the injected and uninjected eyes.

Gene editing prospects for treating inherited retinal diseases.

Retinal diseases (RD) include inherited retinal dystrophy (IRD), for example, retinitis pigmentosa and Leber's congenital amaurosis, or multifactorial forms, for example, age-related macular degeneration (AMD). IRDs are clinically and genetically heterogeneous in nature. To date, more than 200 genes are known to cause IRDs, which perturb the development, function and survival of rod and cone photoreceptors or retinal pigment epithelial cells. Conversely, AMD, the most common cause of blindness in the developed world, is an acquired disease of the macula characterised by progressive visual impairment. To date, available therapeutic approaches for RD include nutritional supplements, neurotrophic factors, antiangiogenic drugs for wet AMD and gene augmentation/interference strategy for IRDs. However, these therapies do not aim at correcting the genetic defect and result in inefficient and expensive treatments. The genome editing technology based on clustered regularly interspaced short palindromic repeat (CRISPR)-associated protein (Cas) and an RNA that guides the Cas protein to a predetermined region of the genome, represents an attractive strategy to tackle IRDs without available cure. Indeed, CRISPR/Cas system can permanently and precisely replace or remove genetic mutations causative of a disease, representing a molecular tool to cure a genetic disorder. In this review, we will introduce the mechanism of CRISPR/Cas system, presenting an updated panel of Cas variants and delivery systems, then we will focus on applications of CRISPR/Cas genome editing in the retina, and, as emerging treatment options, in patient-derived induced pluripotent stem cells followed by transplantation of retinal progenitor cells into the eye.

Leber hereditary optic neuropathy-new insights and old challenges.

Leber hereditary optic neuropathy (LHON) is the most common primary mitochondrial DNA (mtDNA) disorder with the majority of patients harboring one of three primary mtDNA point mutations, namely, m.3460G>A (MTND1), m.11778G>A (MTND4), and m.14484T>C (MTND6). LHON is characterized by bilateral subacute loss of vision due to the preferential loss of retinal ganglion cells (RGCs) within the inner retina, resulting in optic nerve degeneration. This review describes the clinical features associated with mtDNA LHON mutations and recent insights gained into the disease mechanisms contributing to RGC loss in this mitochondrial disorder. Although treatment options remain limited, LHON research has now entered an active translational phase with ongoing clinical trials, including gene therapy to correct the underlying pathogenic mtDNA mutation.

Long-Term Follow-Up After Unilateral Intravitreal Gene Therapy for Leber Hereditary Optic Neuropathy: The RESTORE Study.

BACKGROUND: RESCUE and REVERSE were 2 Phase 3 clinical trials that assessed the efficacy and safety of intravitreal gene therapy with lenadogene nolparvovec (rAAV2/2-ND4) for the treatment of Leber hereditary optic neuropathy (LHON). RESTORE is the long-term follow-up study of subjects treated in the RESCUE and REVERSE trials. METHODS: In RESCUE and REVERSE, 76 subjects with LHON because of the m.11778 G>A mutation in the mitochondrial gene ND4 received a single unilateral intravitreal injection of lenadogene nolparvovec. After 96 weeks, 61 subjects were enrolled in the long-term follow-up study RESTORE. The best-corrected visual acuity (BCVA) was assessed over a period of up to 52 months after onset of vision loss. A locally estimated scatterplot smoothing regression model was used to analyze changes in BCVA over time. Vision-related quality of life was reported using the visual function questionnaire-25 (VFQ-25). RESULTS: The population of MT-ND4 subjects enrolled in RESTORE was representative of the combined cohorts of RESCUE and REVERSE for mean age (35.1 years) and gender distribution (79% males). There was a progressive and sustained improvement of BCVA up to 52 months after the onset of vision loss. The final mean BCVA was 1.26 logarithm of the minimal angle of resolution 48 months after the onset of vision loss. The mean VFQ-25 composite score increased by 7 points compared with baseline. CONCLUSION: The treatment effect of lenadogene nolparvovec on BCVA and vision-related quality of life observed 96 weeks (2 years) after treatment in RESCUE and REVERSE was sustained at 3 years in RESTORE, with a maximum follow-up of 52 months (4.3 years) after the onset of vision loss.

Cross-Sectional Analysis of Baseline Visual Parameters in Subjects Recruited Into the RESCUE and REVERSE ND4-LHON Gene Therapy Studies.

OBJECTIVE: This report presents a cross-sectional analysis of the baseline characteristics of subjects with Leber hereditary optic neuropathy enrolled in the gene therapy trials RESCUE and REVERSE, to illustrate the evolution of visual parameters over the first year after vision loss. METHODS: RESCUE and REVERSE were 2 phase III clinical trials designed to assess the efficacy of rAAV2/2-ND4 gene therapy in ND4-LHON subjects. At enrollment, subjects had vision loss for ≤6 months in RESCUE, and between 6 and 12 months in REVERSE. Functional visual parameters (best-corrected visual acuity [BCVA], contrast sensitivity [CS], and Humphrey Visual Field [HVF]) and structural parameters assessed by spectral-domain optical coherence tomography were analyzed in both cohorts before treatment. The cross-sectional analysis of functional and anatomic parameters included the baseline values collected in all eyes at 2 different visits (Screening and Inclusion). RESULTS: Seventy-six subjects were included in total, 39 in RESCUE and 37 in REVERSE. Mean BCVA was significantly worse in RESCUE subjects compared with REVERSE subjects (1.29 and 1.61 LogMAR respectively, P = 0.0029). Similarly, mean CS and HVF were significantly more impaired in REVERSE vs RESCUE subjects (P < 0.005). The cross-sectional analysis showed that the monthly decrease in BCVA, ganglion cell layer macular volume, and retinal nerve fiber layer thickness was much more pronounced in the first 6 months after onset (+0.24 LogMAR, -0.06 mm3, and -6.00 µm respectively) than between 6 and 12 months after onset (+0.02 LogMAR, -0.01 mm3, and -0.43 µm respectively). CONCLUSION: LHON progresses rapidly in the first months following onset during the subacute phase, followed by relative stabilization during the dynamic phase.

[Clinical characteristics and research progress on the treatment of mitochondrial optic neuropathy].

Mitochondrial optic neuropathy (MON) describes a group of optic neuropathies that exhibit mitochondrial dysfunction in retinal ganglion cells. Pathogenesis of MON includes genetic factors, such as Leber hereditary optic neuropathy and dominant optic atrophy, or acquired factors, such as drug intoxication and nutritional deficiencies, or the combination of both genetic factors and acquired factors. Regardless of different causes, MON shares similar features including bilateral central visual acuity loss, equally normal or slightly sluggish reaction of pupils to light and so on. Many novel therapies, such as pharmacological strategies, genetic therapy and stem cell therapy, are being widely studied in order to limit or reverse the damage of retinal ganglion cells. This article review the pathogenesis, clinical manifestations, ancillary testing, differential diagnosis and treatment progress of MON. (Chin J Ophthalmol, 2021, 57: 386-390).

Pathophysiology of Conversion to Symptomatic Leber Hereditary Optic Neuropathy and Therapeutic Implications: a Review.

PURPOSE: Leber's hereditary optic neuropathy (LHON) is a genetic disease of the mitochondrial genome that mainly affects the retinal ganglion cells (RGC) of the inner retina resulting in central vision loss. New understandings in mitochondrial genetics are helping to elucidate the nuances of conversion and allow for new therapeutic options. RECENT FINDINGS: Appreciation of the mitochondrial fission-fusion balance has allowed for increased understanding of the cascade of events that leads to clinical conversion in LOHN. Mathematical and computational models have helped to interpret the role of ROS in conversion, both as oxidative agents and as signaling molecules for cell death. The conversion from the LHON carrier to the affected patient has been clinically characterized, but the pathophysiology is just beginning to be understood. External stressors alter the mitochondrial dynamics of RGCs, leading to ROS buildup, energy shortages, decreased biogenesis and increased mitophagy, and ultimately axon degeneration and ganglion cell death. New therapeutic alternatives targeting these newly understood pathophysiological changes in the mitochondria and directly addressing the genetic mutations involved in LHON are being developed.

Multilocus Mitochondrial Mutations Do Not Directly Affect the Efficacy of Gene Therapy for Leber Hereditary Optic Neuropathy.

PURPOSE: Clinical trials of gene therapy for Leber hereditary optic neuropathy (LHON) were conducted in 9 volunteers with the mitochondrial mutation, G11778A in ND4. The purpose of this study was to investigate whether multilocus mitochondrial mutations directly influence the efficacy of gene therapy for LHON. METHODS: Nine volunteers with LHON participated in a clinical trial with intravitreal injection of an adenoviral vector expressing wild-type ND4. Patients were subsequently divided into 2 groups: according to the differences in therapy efficacy and based on improvements in visual acuity. Full mitochondrial DNA sequences of the 2 groups of patients were generated and compared using PubMed, PolyPhen, and PROVEAN. Furthermore, the association between the detected mutations and clinical effects of gene therapy was analyzed. RESULTS: Best-corrected visual acuity (BCVA) significantly improved (≥0.3 log of minimum angle of resolution [logMAR]) in 7 patients 6 months after gene therapy, whereas there was no significant change in BCVA (<0.3 logMAR) of the remaining 2 patients. All 9 patients carried the G1178A mutation in addition to other nonsynonymous mutations. Among these mutations, some were predicted to be neutral and deleterious. Meanwhile, different mitochondrial mutations in the group in which treatment was ineffective, compared with those in responders, were at nucleotide positions 6569 (CO1; Patient 3), 9641 (CO3; Patient 3), and 4491 (ND2; Patient 5). CONCLUSIONS: Detection of the 3 primary mitochondrial mutations causing LHON is sufficient for screening before gene therapy; sequencing of the entire mitochondrial genome is unnecessary before treatment. Patients with LHON can respond to targeted gene therapy irrespective of additional multilocus mitochondrial mutations.