Comparative long-term outcomes of vitrectomy combined with anterior chamber intraocular lens to intra-scleral haptic fixation of posterior chamber intraocular lens.

PURPOSE: To evaluate the long-term clinical outcomes in patients with combined pars plana vitrectomy (PPV) with anterior chamber intraocular lens (ACIOL) to intrascleral haptic fixation (ISHF) using the Agarwal technique with fibrin glue to secure the scleral flap of a posterior chamber intraocular lens. METHODS: Retrospective, consecutive, single-center, comparative case series. 83 eyes were studied. Patients with < 8 months of follow-up were excluded. Detailed pre-, intra-, and post-operative complications were analyzed using mixed model univariate analysis and t-test. Pre- and post-operative best corrected visual acuity (BCVA) was analyzed. RESULTS: Twenty-five subjects met entry criteria. Mean age at time of surgery was 70.4 ± 17.7 years in the ACIOL group (n = 12) and 54.6 ± 21.1 years in the ISHF group (n = 13; p = 0.03). Mean follow-up was 38.2 months. Incidence of corneal decompensation was similar in the ACIOL and ISHF lens group (p = 0.93). There was no difference in the BCVA mean change or cystoid macular edema (CME) at the final visit between the groups (p = 0.47; p = 0.08), but there was a trend toward increased CME in the ACIOL group. CONCLUSIONS: PPV with concomitant placement of either ACIOL or ISHF lens result in improvement in BCVA. Both procedures are well tolerated and result in favorable outcomes with long-term follow-up though varying patient populations do not allow precise comparison between the two groups.

Surgical Management of Full-Thickness Macular Holes in Macular Telangiectasia Type 2: A Global Multicenter Study.

PURPOSE: To report on macular hole repair in macular telangiectasia type 2 (MacTel2). DESIGN: Global, multicenter, retrospective case series. PARTICIPANTS: Patients undergoing surgery for MacTel2-associated full-thickness macular hole (MTMH). METHODS: Standardized data collection sheet distributed to all surgeons. MAIN OUTCOME MEASURES: Anatomic closure and visual outcomes of MTMH. RESULTS: Sixty-three surgeries in 47 patients with MTMH were included from 30 surgeons. Mean age was 68.1 years, with 62% female, 72% White, 21% East or South Asian, 2% African American, and 2% Hispanic or Latino. Procedures included 34 internal limiting membrane (ILM) peeling alone, 22 ILM flaps, 5 autologous retinal transplantations (ARTs), 1 retinotomy, and 1 subretinal bleb. For ILM peeling, preoperative visual acuity (VA) was 0.667 ± 0.423 logarithm of the minimum angle of resolution (logMAR). Minimum hole diameter (MHD) was 305.5 ± 159.4 µm (range, 34-573 µm). Sixteen of 34 ILM peels (47%) resulted in MTMH closure. At postoperative month 6, VA was stable at 0.602 ± 0.516 logMAR (P = 0.65). VA improved by at least 2 lines in 43% and at least 4 lines in 24%. For ILM flaps, preoperative VA was 0.878 ± 0.552 logMAR. MHD was 440.8 ± 175.5 µm (range, 97-697 µm), which was significantly larger than for ILM peels (P < 0.01). Twenty of 22 ILM flaps (90%) resulted in MTMH closure, which was significantly higher than for ILM peels (P < 0.01). At postoperative month 6, VA improved to 0.555 ± 0.405 logMAR (P < 0.05). VA improved by at least 2 lines in 56% and at least 4 lines in 28%. For ARTs, preoperative VA was 1.460 ± 0.391 logMAR. MHD was 390.2 ± 203.7 µm (range, 132-687 µm). All 5 ARTs (100%) resulted in MTMH closure. At postoperative month 6, VA was stable at 1.000 ± 0.246 logMAR (P = 0.08). Visual acuity improved at least 2 lines in 25%. CONCLUSIONS: Surgical closure of macular holes improved VA in 57% of MTMHs. Internal limiting membrane flaps achieved better anatomic and functional outcomes than ILM peeling alone. Autologous retinal transplantation may be an option for refractory MTMHs. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

The Ocular Trauma Score Underestimates Visual Recovery for the Most Severe Open-Globe Injuries.

PURPOSE: To compare visual outcomes after open-globe injury (OGI) with those predicted by the Ocular Trauma Score (OTS), and to investigate the effect of treatment with pars plana vitrectomy (PPV). DESIGN: Retrospective cohort study. SUBJECTS: Patients presenting with OGI to an academic United States ophthalmology department from 2017 to 2020. METHODS: Best-corrected visual acuity (VA) measurements at the most recent follow-up were compared with final VA predicted by the OTS, based on preoperative injury characteristics. The most recently measured VA of patients treated with PPV during initial OGI repair (primary PPV group) was compared with patients treated with PPV after initial OGI repair (secondary PPV group) and patients never treated with PPV (No PPV group). MAIN OUTCOME MEASURES: Best-corrected VA in the injured eye at last follow-up; secondary outcome measures included the occurrence of vitreous hemorrhage at any time, occurrence of retinal detachment at any time, rates of additional surgery, and rates of enucleation. RESULTS: One-hundred and thirty-three subjects with OGI were identified and analyzed. The overall rate of PPV was 32%. Predictors of worse VA at last follow-up included older age (P = 0.047) and worse presenting VA (P < 0.001). Visual acuity outcomes for eyes in OTS categories 2 to 5 did not significantly differ from OTS predictions. However, eyes in OTS category 1 had a higher likelihood of last follow-up VA of light perception (LP) to hand motion (46% in the study cohort vs. 15% predicted by the OTS, P = 0.004) and a lower likelihood of no LP (33% vs. 74%, P < 0.001). The secondary PPV group had the worst VA at presentation among the 3 groups (P = 0.016), but VA at last follow-up did not significantly differ between the study groups (P = 0.338). CONCLUSIONS: The most severe OGIs (i.e., OTS category 1) had better visual outcomes than predicted by the published OTS expectations, and secondary PPV was associated with significant visual improvement despite poor prognostic predictions. Evaluation by a vitreoretinal surgeon should be considered for all patients with severe OGI, especially those in OTS category 1. FINANCIAL DISCLOSURE(S): Proprietary or commercial disclosure may be found after the references.

Biocompatibility of Human Induced Pluripotent Stem Cell-Derived Retinal Progenitor Cell Grafts in Immunocompromised Rats.

Loss of photoreceptor cells is a primary feature of inherited retinal degenerative disorders including age-related macular degeneration and retinitis pigmentosa. To restore vision in affected patients, photoreceptor cell replacement will be required. The ideal donor cells for this application are induced pluripotent stem cells (iPSCs) because they can be derived from and transplanted into the same patient obviating the need for long-term immunosuppression. A major limitation for retinal cell replacement therapy is donor cell loss associated with simple methods of cell delivery such as subretinal injections of bolus cell suspensions. Transplantation with supportive biomaterials can help maintain cellular integrity, increase cell survival, and encourage proper cellular alignment and improve integration with the host retina. Using a pig model of retinal degeneration, we recently demonstrated that polycaprolactone (PCL) scaffolds fabricated with two photon lithography have excellent local and systemic tolerability. In this study, we describe rapid photopolymerization-mediated production of PCL-based bioabsorbable scaffolds, a technique for loading iPSC-derived retinal progenitor cells onto the scaffold, methods of surgical transplantation in an immunocompromised rat model and tolerability of the subretinal grafts at 1, 3, and 6 months of follow-up (n = 150). We observed no local or systemic toxicity, nor did we observe any tumor formation despite extensive clinical evaluation, clinical chemistry, hematology, gross tissue examination and detailed histopathology. Demonstrating the local and systemic compatibility of biodegradable scaffolds carrying human iPSC-derived retinal progenitor cells is an important step toward clinical safety trials of this approach in humans.

Age-Related Macular Degeneration Masquerade: A Review of Pentosan Polysulfate Maculopathy and Implications for Clinical Practice.

ABSTRACT: Pentosan polysulfate (PPS) sodium (Elmiron) is the only Food and Drug Administration (FDA)-approved oral medication to treat interstitial cystitis, also known as bladder pain syndrome. A symptomatic pigmentary maculopathy associated with PPS was reported in 2018. Since then, recognition of this unique drug toxicity has increased rapidly. This potentially sight-threatening side effect prompted the FDA in June 2020 to update the label for PPS to warn about "retinal pigmentary changes." A challenging feature of pentosan maculopathy is its ability to mimic many other retinal conditions, including inherited retinal dystrophies such as pattern dystrophy, mitochondrially inherited diabetes and deafness, and Stargardt disease, and age-related macular degeneration. In this review, we discuss the history of PPS maculopathy and its implications for thousands of at-risk interstitial cystitis patients. We use published literature and an illustrative case from our institution to highlight the importance of diagnosing PPS maculopathy. We also compare PPS maculopathy to age-related macular degeneration, explain why differentiating between the 2 is clinically important, and highlight avenues for further research. Finally, we highlight the paucity of data on patients of color and why this lack of understanding may impact patient care.

Intravitreal antisense oligonucleotide sepofarsen in Leber congenital amaurosis type 10: a phase 1b/2 trial.

CEP290-associated Leber congenital amaurosis type 10 (LCA10) is a retinal disease resulting in childhood blindness. Sepofarsen is an RNA antisense oligonucleotide targeting the c.2991+1655A>G variant in the CEP290 gene to treat LCA10. In this open-label, phase 1b/2 ( NCT03140969 ), 12-month, multicenter, multiple-dose, dose-escalation trial, six adult patients and five pediatric patients received ≤4 doses of intravitreal sepofarsen into the worse-seeing eye. The primary objective was to evaluate sepofarsen safety and tolerability via the frequency and severity of ocular adverse events (AEs); secondary objectives were to evaluate pharmacokinetics and efficacy via changes in functional outcomes. Six patients received sepofarsen 160 µg/80 µg, and five patients received sepofarsen 320 µg/160 µg. Ten of 11 (90.9%) patients developed ocular AEs in the treated eye (5/6 with 160 µg/80 µg; 5/5 with 320 µg/160 µg) versus one of 11 (9.1%) in the untreated eye; most were mild in severity and dose dependent. Eight patients developed cataracts, of which six (75.0%) were categorized as serious (2/3 with 160 µg/80 µg; 4/5 with 320 µg/160 µg), as lens replacement was required. As the 160-µg/80-µg group showed a better benefit-risk profile, higher doses were discontinued or not initiated. Statistically significant improvements in visual acuity and retinal sensitivity were reported (post hoc analysis). The manageable safety profile and improvements reported in this trial support the continuation of sepofarsen development.

The effect of retinal scaffold modulus on performance during surgical handling.

Emerging treatment strategies for retinal degeneration involve replacing lost photoreceptors using supportive scaffolds to ensure cells survive the implantation process. While many design aspects of these scaffolds, including material chemistry and microstructural cues, have been studied in depth, a full set of design constraints has yet to be established. For example, while known to be important in other tissues and systems, the influence of mechanical properties on surgical handling has not been quantified. In this study, photocrosslinked poly(ethylene glycol) dimethacrylate (PEGDMA) was used as a model polymer to study the effects of scaffold modulus (stiffness) on surgical handling, independent of material chemistry. This was achieved by modulating the molecular weight and concentrations of the PEGDMA in various prepolymer solutions. Scaffold modulus of each formulation was measured using photo-rheology, which enabled the collection of real-time polymerization data. In addition to measuring scaffold mechanical properties, this approach gave insight on polymerization kinetics, which were used to determine the polymerization time required for each sample. Scaffold handling characteristics were qualitatively evaluated using both in vitro and ex vivo trials that mimicked the surgical procedure. In these trials, scaffolds with shear moduli above 35 kPa performed satisfactorily, while those below this limit performed poorly. In other words, scaffolds below this modulus were too fragile for reliable transplantation. To better compare these results with literature values, the compressive modulus was measured for select samples, with the lower shear modulus limit corresponding to roughly 115 kPa compressive modulus. While an upper mechanical property limit was not readily apparent from these results, there was increased variability in surgical handling performance in samples with shear moduli above 800 kPa. Overall, the knowledge presented here provides important groundwork for future studies designed to examine additional retinal scaffold considerations, including the effect of scaffold mechanical properties on retinal progenitor cell fate.

Retinal Tropism and Transduction of Adeno-Associated Virus Varies by Serotype and Route of Delivery (Intravitreal, Subretinal, or Suprachoroidal) in Rats.

Viral-mediated gene augmentation offers tremendous promise for the treatment of inherited retinal diseases. The development of effective gene therapy requires an understanding of the vector's tissue-specific behavior, which may vary depending on serotype, route of delivery, or target species. Using an ex vivo organotypic explant system, we previously demonstrated that retinal tropism and transduction of adeno-associated virus type 2 (AAV2) vary significantly depending on serotype in human eyes. However, the ex vivo system has limited ability to assess route of ocular delivery, and relatively little literature exists on tropic differences between serotypes and routes of delivery in vivo. In this study, we demonstrate that retinal tropism and transduction efficiency of five different AAV2 serotypes (AAV2/1, AAV2/2, AAV2/6, AAV2/8, and AAV2/9) expressing enhanced green fluorescent protein driven by a cytomegalovirus promoter vary greatly depending on serotype and route of delivery (intravitreal, subretinal, or suprachoroidal) in rats. With subretinal delivery, all serotypes successfully transduced the retinal pigmented epithelium and outer nuclear layer (ONL), with AAV2/1 displaying the highest transduction efficiency and AAV2/2 and AAV2/6 showing lower ONL transduction. There was minimal transduction of the inner retina through subretinal delivery for any serotype. Tropism by suprachoroidal delivery mirrored that of subretinal delivery for all AAV serotypes but resulted in a wider distribution and greater ONL transduction. With intravitreal delivery, retinal transduction was seen primarily in the inner retina (retinal nerve fiber, ganglion cell, and inner nuclear layers) for AAV2/1 and AAV2/6, with AAV2/6 showing the highest transduction. When compared with data from human explant models, there are substantial differences in tropism and transduction that are important to consider when using rats as preclinical models for the development of ocular gene therapies for humans.

Attaining functional levels of visual acuity after vitrectomy for retinal detachment secondary to proliferative diabetic retinopathy.

Most patients needing diabetic tractional retinal detachment (TRD) surgery are working-age adults that drive and participate in other vision-dependent activities of daily living. We sought to determine the proportion of patients that achieve functional visual acuity (VA) based on the World Health Organization (WHO) definition of 'low vision' (≤ 20/80) and US driving standards (≥ 20/40) after vitrectomy for diabetic TRD. In this 10-year retrospective review, consecutive patients who underwent primary vitrectomy for TRD from proliferative diabetic retinopathy were studied. 240 eyes in 203 patients met criteria for analysis (38 eyes were lost to follow up at 3 months; 68 at 12 months; 146 at 60 months). While most patients (nearly 80%) having TRD surgery had low vision pre-op, almost half attained VA that was > 20/80 five years post-op. Those most likely to achieve significant visual improvement (p < 0.0001) had concomitant vitreous hemorrhage pre-op. Only 6% of eyes met the US minimum driving standard before surgery based on VA compared to 28% after vitrectomy however this study did not examine visual fields which could warrant additional assessment depending on local requirements. In summary, significant gains in visual acuity are seen after vitrectomy for diabetic TRD that can result in functional improvement in activities of daily living.

Helper-Dependent Adenovirus Transduces the Human and Rat Retina but Elicits an Inflammatory Reaction When Delivered Subretinally in Rats.

The identification of >100 genes causing inherited retinal degeneration and the promising results of recent gene augmentation trials have led to an increase in the number of studies investigating the preclinical efficacy of viral-mediated gene transfer. Despite success using adeno-associated viruses, many disease-causing genes, such as ABCA4 or USH2A, are too large to fit into these vectors. One option for large gene delivery is the family of integration-deficient helper-dependent adenoviruses (HDAds), which efficiently transduce postmitotic neurons. However, HDAds have been shown in other organ systems to elicit an immune response, and the immunogenicity of HDAds in the retina has not been characterized. In this study, HDAd serotype 5 (HDAd5) was found to successfully transduce rod and cone photoreceptors in ex vivo human retinal organ cultures. The ocular inflammatory response to subretinal injection of the HDAd5 was evaluated using a rat model. Subretinal injection of HDAd5 carrying cytomegalovirus promoter-driven enhanced green fluorescent protein (HDAd5-CMVp-eGFP) elicited a robust inflammatory response by 3 days postinjection. This reaction included vitreous infiltration of ionized calcium-binding adapter molecule 1 (Iba1)-positive monocytes and increased expression of the proinflammatory protein, intercellular adhesion molecule 1 (ICAM-1). By 7 days postinjection, most Iba1-positive infiltrates migrated into the neural retina and ICAM-1 expression was significantly increased compared with buffer-injected control eyes. At 14 days postinjection, Iba1-positive cells persisted in the retinas of HDAd5-injected eyes, and there was thinning of the outer nuclear layer. Subretinal injection of an empty HDAd5 virus was used to confirm that the inflammatory response was in response to the HDAd5 vector and not due to eGFP-induced overexpression cytotoxicity. Subretinal injection of lower doses of HDAd5 dampened the inflammatory response, but also eGFP expression. Despite their larger carrying capacity, further work is needed to elucidate the inflammatory pathways involved and to identify an immunomodulation paradigm sufficient for safe and effective transfer of large genes to the retina using HDAd5.

Choriocapillaris Degeneration in Geographic Atrophy.

Early age-related macular degeneration (AMD) is characterized by degeneration of the choriocapillaris, the vascular supply of retinal photoreceptor cells. We assessed vascular loss during disease progression in the choriocapillaris and larger vessels in the deeper choroid. Human donor maculae from controls (n = 99), early AMD (n = 35), or clinically diagnosed with geographic atrophy (GA; n = 9, collected from outside the zone of retinal pigment epithelium degeneration) were evaluated using Ulex europaeus agglutinin-I labeling to discriminate between vessels with intact endothelial cells and ghost vessels. Morphometric analyses of choriocapillaris density (cross-sectional area of capillary lumens divided by length) and of vascular lumen/stroma ratio in the outer choroid were performed. Choriocapillaris loss was observed in early AMD (Bonferroni-corrected P = 0.024) with greater loss in GA (Bonferroni-corrected P < 10-9), even in areas of intact retinal pigment epithelium. In contrast, changes in lumen/stroma ratio in the outer choroid were not found to differ between controls and AMD or GA eyes (P > 0.05), suggesting choriocapillaris changes are more prevalent in AMD than those in the outer choroid. In addition, vascular endothelial growth factor-A levels were negatively correlated with choriocapillaris vascular density. These findings support the concept that choroidal vascular degeneration, predominantly in the microvasculature, contributes to dry AMD progression. Addressing capillary loss in AMD remains an important translational target.

Two-photon polymerized poly(caprolactone) retinal cell delivery scaffolds and their systemic and retinal biocompatibility.

Cell replacement therapies are often enhanced by utilizing polymer scaffolds to improve retention or direct cell orientation and migration. Obstacles to refinement of such polymer scaffolds often include challenges in controlling the microstructure of biocompatible molecules in three dimensions at cellular scales. Two-photon polymerization of acrylated poly(caprolactone) (PCL) could offer a means of achieving precise microstructural control of a material in a biocompatible platform. In this work, we studied the effect of various formulation and two-photon polymerization parameters on minimum laser power needed to achieve polymerization, resolution, and fidelity to a target 3D model designed to be used for retinal cell replacement. Overall, we found that increasing the concentration of crosslink-able groups decreased polymerization threshold and the size of resolvable features while increasing fidelity of the scaffold to the 3D model. In general, this improvement was achieved by increasing the number of acrylate groups per prepolymer molecule, increasing the acrylated PCL concentration, or decreasing its molecular weight. Resulting two-photon polymerized PCL scaffolds successfully supported human iPSC derived retinal progenitor cells in vitro. Sub-retinal implantation of cell free scaffolds in a porcine model of retinitis pigmentosa did not cause inflammation, infection or local or systemic toxicity after one month. In addition, comprehensive ISO 10993 testing of photopolymerized scaffolds revealed a favorable biocompatibility profile. These results represent an important step towards understanding how two-photon polymerization can be applied to a wide range of biologically compatible chemistries for various biomedical applications. STATEMENT OF SIGNIFICANCE: Inherited retinal degenerative blindness results from the death of light sensing photoreceptor cells. To restore high-acuity vision a photoreceptor cell replacement strategy will likely be necessary. Unfortunately, single cell injection typically results in poor cell survival and integration post-transplantation. Polymeric biomaterial cell delivery scaffolds can be used to promote donor cell viability, control cellular polarity and increase packing density. A challenge faced in this endeavor has been developing methods suitable for generating scaffolds that can be used to deliver stem cell derived photoreceptors in an ordered columnar orientation (i.e., similar to that of the native retina). In this study we combined the biomaterial poly(caprolactone) with two-photon lithography to generate a biocompatible, clinically relevant scaffold suitable for retina cell delivery.

Optimizing Donor Cellular Dissociation and Subretinal Injection Parameters for Stem Cell-Based Treatments.

Subretinal delivery of stem cell-derived retinal cells as a strategy to treat retinal degenerative blindness holds great promise. Currently, two clinical trials are underway in which human fetal retinal progenitor cells (RPCs) are being delivered to patients by intravitreal or subretinal injection to preserve or restore vision, respectively. With the advent of the induced pluripotent stem cell (iPSC), and in turn three-dimensional derivation of retinal tissue, it is now possible to generate autologous RPCs for cell replacement. The purpose of this study was to evaluate the effect of commonly used cell isolation and surgical manipulation strategies on donor cell viability. iPSC-RPCs were subjected to various conditions, including different dissociation and isolation methods, injection cannula sizes, and preinjection storage temperatures and times. The effects of commonly used surgical techniques on both host and donor cell viability were evaluated in Yucatan mini-pigs (n = 61 eyes). We found a significant increase in cell viability when papain was used for RPC isolation. In addition, a significant decrease in cell viability was detected when using the 41G cannula compared with 31G and at storage times of 4 hours compared with 30 minutes. Although 96.4% of all eyes demonstrated spontaneous retinal reattachment following injection, retinal pigment epithelium (RPE) abnormalities were seen more frequently in eyes receiving injections via a 31G cannula; interestingly, eyes that received cell suspensions were relatively protected against such RPE changes. These findings indicate that optimization of donor cell isolation and delivery parameters should be considered when developing a subretinal cell replacement strategy. Stem Cells Translational Medicine 2019;8:797&809.

APOPTOSIS AND ANGIOFIBROSIS IN DIABETIC TRACTIONAL MEMBRANES AFTER VASCULAR ENDOTHELIAL GROWTH FACTOR INHIBITION: Results of a Prospective Trial. Report No. 2.

PURPOSE: We sought to characterize the angiofibrotic and apoptotic effects of vascular endothelial growth factor (VEGF)-inhibition on fibrovascular epiretinal membranes in eyes with traction retinal detachment because of proliferative diabetic retinopathy. METHODS: Membranes were excised from 20 eyes of 19 patients (10 randomized to intravitreal bevacizumab, 10 controls) at vitrectomy. Membranes were stained with antibodies targeting connective tissue growth factor (CTGF) or VEGF and colabeled with antibodies directed against endothelial cells (CD31), myofibroblasts, or retinal pigment epithelium markers. Quantitative and colocalization analyses of antibody labeling were obtained through immunofluorescence confocal microscopy. Masson trichrome staining, cell counting of hematoxylin and eosin sections, and terminal dUTP nick-end labeling staining were performed. RESULTS: High levels of fibrosis were observed in both groups. Cell apoptosis was higher (P = 0.05) in bevacizumab-treated membranes compared with controls. The bevacizumab group had a nonsignificant reduction in colocalization in CD31-CTGF and cytokeratin-VEGF studies compared with controls. Vascular endothelial growth factor in extracted membranes was positively correlated with vitreous levels of VEGF; CTGF in extracted membranes was negatively correlated with vitreous levels of CTGF. CONCLUSION: Bevacizumab suppresses vitreous VEGF levels, but does not significantly alter VEGF or CTGF in diabetic membranes that may be explained by high baseline levels of fibrosis. Bevacizumab may cause apoptosis within fibrovascular membranes.

Effect of an intravitreal antisense oligonucleotide on vision in Leber congenital amaurosis due to a photoreceptor cilium defect.

Photoreceptor ciliopathies constitute the most common molecular mechanism of the childhood blindness Leber congenital amaurosis. Ten patients with Leber congenital amaurosis carrying the c.2991+1655A>G allele in the ciliopathy gene centrosomal protein 290 (CEP290) were treated (ClinicalTrials.gov no. NCT03140969 ) with intravitreal injections of an antisense oligonucleotide to restore correct splicing. There were no serious adverse events, and vision improved at 3 months. The visual acuity of one exceptional responder improved from light perception to 20/400.

Assessment of Adeno-Associated Virus Serotype Tropism in Human Retinal Explants.

Advances in the discovery of the causes of monogenic retinal disorders, combined with technologies for the delivery of DNA to the retina, offer enormous opportunities for the treatment of previously untreatable blinding diseases. However, for gene augmentation to be most effective, vectors that have the correct cell-type specificity are needed. While animal models are very useful, they often exhibit differences in retinal cell surface receptors compared to the human retina. This study evaluated the use of an ex vivo organotypic explant system to test the transduction efficiency and tropism of seven different adeno-associated virus type 2 (AAV2) serotypes in the human retina and retinal pigment epithelium-choroid-AAV2/1, AAV2/2, AAV2/4, AAV2/5, AAV2/6, AAV2/8, and AAV2/9-all driving expression of GFP under control of the cytomegalovirus promoter. After 7 days in culture, it was found that AAV2/4 and AAV2/5 were particularly efficient at transducing photoreceptor cells and that AAV2/5 was highly specific to the outer nuclear layer, whereas AAV2/8 displayed consistently low transduction of photoreceptors. To validate the authenticity of the organotypic culture system, the transduction of the same set of AAVs was also compared in a pig model, in which sub-retinal injections in vivo were compared to cultured and transduced organotypic cultures ex vivo. This study shows how different AAV serotypes behave in the human retina and provides insight for further investigation of each of these serotypes for gene augmentation-based treatment of inherited retinal degeneration.

Efficacy and safety of voretigene neparvovec (AAV2-hRPE65v2) in patients with RPE65-mediated inherited retinal dystrophy: a randomised, controlled, open-label, phase 3 trial.

BACKGROUND: Phase 1 studies have shown potential benefit of gene replacement in RPE65-mediated inherited retinal dystrophy. This phase 3 study assessed the efficacy and safety of voretigene neparvovec in participants whose inherited retinal dystrophy would otherwise progress to complete blindness. METHODS: In this open-label, randomised, controlled phase 3 trial done at two sites in the USA, individuals aged 3 years or older with, in each eye, best corrected visual acuity of 20/60 or worse, or visual field less than 20 degrees in any meridian, or both, with confirmed genetic diagnosis of biallelic RPE65 mutations, sufficient viable retina, and ability to perform standardised multi-luminance mobility testing (MLMT) within the luminance range evaluated, were eligible. Participants were randomly assigned (2:1) to intervention or control using a permuted block design, stratified by age (<10 years and ≥10 years) and baseline mobility testing passing level (pass at ≥125 lux vs <125 lux). Graders assessing primary outcome were masked to treatment group. Intervention was bilateral, subretinal injection of 1·5 × 1011 vector genomes of voretigene neparvovec in 0·3 mL total volume. The primary efficacy endpoint was 1-year change in MLMT performance, measuring functional vision at specified light levels. The intention-to-treat (ITT) and modified ITT populations were included in primary and safety analyses. This trial is registered with ClinicalTrials.gov, number NCT00999609, and enrolment is complete. FINDINGS: Between Nov 15, 2012, and Nov 21, 2013, 31 individuals were enrolled and randomly assigned to intervention (n=21) or control (n=10). One participant from each group withdrew after consent, before intervention, leaving an mITT population of 20 intervention and nine control participants. At 1 year, mean bilateral MLMT change score was 1·8 (SD 1·1) light levels in the intervention group versus 0·2 (1·0) in the control group (difference of 1·6, 95% CI 0·72-2·41, p=0·0013). 13 (65%) of 20 intervention participants, but no control participants, passed MLMT at the lowest luminance level tested (1 lux), demonstrating maximum possible improvement. No product-related serious adverse events or deleterious immune responses occurred. Two intervention participants, one with a pre-existing complex seizure disorder and another who experienced oral surgery complications, had serious adverse events unrelated to study participation. Most ocular events were mild in severity. INTERPRETATION: Voretigene neparvovec gene replacement improved functional vision in RPE65-mediated inherited retinal dystrophy previously medically untreatable. FUNDING: Spark Therapeutics.

Using CRISPR-Cas9 to Generate Gene-Corrected Autologous iPSCs for the Treatment of Inherited Retinal Degeneration.

Patient-derived induced pluripotent stem cells (iPSCs) hold great promise for autologous cell replacement. However, for many inherited diseases, treatment will likely require genetic repair pre-transplantation. Genome editing technologies are useful for this application. The purpose of this study was to develop CRISPR-Cas9-mediated genome editing strategies to target and correct the three most common types of disease-causing variants in patient-derived iPSCs: (1) exonic, (2) deep intronic, and (3) dominant gain of function. We developed a homology-directed repair strategy targeting a homozygous Alu insertion in exon 9 of male germ cell-associated kinase (MAK) and demonstrated restoration of the retinal transcript and protein in patient cells. We generated a CRISPR-Cas9-mediated non-homologous end joining (NHEJ) approach to excise a major contributor to Leber congenital amaurosis, the IVS26 cryptic-splice mutation in CEP290, and demonstrated correction of the transcript and protein in patient iPSCs. Lastly, we designed allele-specific CRISPR guides that selectively target the mutant Pro23His rhodopsin (RHO) allele, which, following delivery to both patient iPSCs in vitro and pig retina in vivo, created a frameshift and premature stop that would prevent transcription of the disease-causing variant. The strategies developed in this study will prove useful for correcting a wide range of genetic variants in genes that cause inherited retinal degeneration.