Jun 13, 2022

Over Thirty Presentations Highlighted during the 2022 Retinal Cell & Gene Therapy Innovation Summit

Eye On the Cure Research News

In its seventh year, the Retinal Cell & Gene Therapy Innovation Summit featured 34 presentations from industry experts from around the world.

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The Seventh Annual Retinal Cell and Gene Therapy Innovation Summit was held on April 29, 2022, at the Grand Hyatt Denver. It was hosted by the Foundation Fighting Blindness and Casey Eye Institute, Oregon Health and Science University. The all-day program included 34 speakers representing 25 academic institutions and companies located in five different countries. 

Below are presentation summaries:

Jacque Duncan, MD – "Accelerating research in rare IRDs through an international consortium"

The FFB Consortium was established in 2016 with the goal of accelerating the development of treatments for inherited retinal disorders (IRDs). The Consortium consists of clinical centers with the expertise necessary to conduct collaborative research into rare IRDs. There are currently 40 sites and more than 150 investigators from around the world in the Consortium, and applications are open for new sites and investigators that meet the standardization required to participate in the studies. Rate of Progression in Usher syndrome type 2A (USH2A)-related Retinal Degeneration (RUSH2A, NCT03146078) is a 4-year natural history study that finished enrolling 127 patients in 2019 and is expected to be completed in early 2023. Two-year preliminary results were presented at the 2022 Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting. Rate of Progression in eyes shut homolog (EYS)-related Retinal Degeneration (Pro-EYS, NCT04127006) is a 4-year natural history study that finished enrolling 103 patients in 2021 and is expected to be completed in late 2025. Rate of Progression of protocadherin related 15 (PCDH15)-related Retinal Degeneration in Usher Syndrome 1F (RUSH1F, NCT04765345) is a 4-year natural history study cofunded by the Usher 1F Collaborative and the Marjorie C Adams Foundation. It has an enrollment goal of 40 patients, and enrollment is expected to be completed in June 2022, with a target end date of 2026. Universal Rare Gene Study (Uni-Rare) has 2 components. One part is a registry to characterize genotypes and cross-sectional phenotypes of more than 300 rare IRD genes with no previous studies. The other part is a natural history study that will collect prospective, longitudinal data on rare IRDs.

Kari Branham, MS, CGC – "Genetic testing for inherited retinal disease: Not always one and done"

A single-center, retrospective chart review was conducted on patients who had negative or inconclusive genetic testing and later had additional testing or analysis performed. The review included 181 patients with negative or inconclusive results  and 85 of them obtained positive results after additional testing or analysis. Thirty patients underwent segregation analysis and 12 received a positive test result. One hundred seventeen patients underwent additional genetic testing, with 36 out of 107 testing positive for new mutations of known genes or mutations in novel genes and 5 out of 10 testing positive for copy number variant analysis. Data from 34 patients were reinterpreted to include additional information that was not available at the time of the initial review. This study shows that there is value in revisiting old genetic testing results; testing an additional gene or using different laboratory and analysis techniques may be effective in identifying the cause of disease. And reanalysis of existing variants and segregation analysis may be a cost-effective approach before testing on a large panel and should be included in clinical trials.

Peter Zhao, MD – "A no-cost registry for inherited retinal dystrophies increases access to genetic testing"

A single-center, retrospective chart review was used to analyze the impact of the My Retina Tracker Genetic Testing Study (MRT-GTS), which provided free genetic testing and counseling services, on the probability of obtaining genetic testing for IRDs in the United States. Before MRT-GTS began, 51% of patients underwent genetic testing, and after MRT-GTS was implemented, 80% of patients underwent genetic testing. The time to genetic testing also improved among patients eligible for MRT-GTS, with almost double the number of patients having test results by 90 days after their clinical diagnosis. Two factors that increased the probability of having genetic testing done were eligibility for MRT-GTS and visual acuity increasing (logMar +1.0) in the better-seeing eye. Non-white race and English not being their preferred language significantly decreased a patient’s odds of undergoing genetic testing. Detection rates were significantly different in patients who self-identified as black with white patients more likely to have an overall positive detection rate and with rod-cone dystrophies and cone/cone-rod dystrophy. There was no difference in detection rate for macular dystrophy. For all patients, increasing age also negatively impacted detection rates. In general, the availability of a no-cost option for genetic testing increased the likelihood of patients undergoing testing, which suggests that cost is a barrier for many. However, individual characteristics such as race, primary language, and visual acuity affected the odds of obtaining testing, and patients of African ancestry may have lower rates of detection despite undergoing testing.

Thiran Jayasundera, MD, MS –"Psychometric analysis and test-retest variability of the Michigan Retinal Degeneration Questionnaire as an outcome measure of functional vision for clinical trials in inherited retinal diseases"

The Michigan Retinal Degeneration Questionnaire (MRDQ) and the Michigan Vision-related Anxiety Questionnaire (MVAQ) have been specifically developed to measure the patient-reported outcomes (PROs) and degree of anxiety for patients with IRDs. Both the MRDQ and MVAQ are reliable with low test-retest variability, and the MRDQ correlates well with other similar measurements of vision-related function and quality-of-life. MRDQ can be used to measure the severity of a patient’s disability in central vision, color vision, contrast sensitivity, photosensitivity, scotopic function, mesopic peripheral vision, and photopic vision. It can be used as an outcome measure for clinical trials, as a criterion for treatment, or as a target for low vision rehabilitation. The MVAQ can quantitate whether a patient’s rod or cone dysfunction is a cause of their anxiety, and the results can be used as an opportunity for mental health outreach to address specific anxiety-provoking situations.

Robert Lin, PhD, CFA – "Novel engineered AAV vectors for inherited retinal disease gene therapies created using the scAAVengr platform"

Avista Therapeutics is based on using the adeno-associated virus (AAV) engineering (scAAVenger) platform to create an AAV-based, cell-specific toolkit for IRD gene therapy via intravitreal injection. The scAAVenger platform was used to develop an AAV library whose cell-specific expression could be measured in an empirical, unbiased manner. Approximately 200 variants that were screened in a nonhuman primate (NHP) model perform as well as or better than AAV2.7m8 even at subclinical titers, which may help to reduce AAV-induced inflammation. Five variants show significant expression in retinal pigment epithelium (RPE) cells, as compared to standard AAV vectors. Secondary screening in NHPs is currently underway for 192 variants, and the first 3 high-expressing variants induced significant inflammation that necessitated triamcinolone injections and oral prednisone. A fourth NHP was given a lower dose and prophylactic oral prednisone, which has prevented the immune response. The development program will continue, with secondary screening of the current library and primary screening analysis with other libraries generated with different AAV backbones. Indications and gene therapy candidates are yet to be decided and will depend on the cell types that can be efficiently targeted by the selected variant(s).

Ying Kai Chan, PhD – "Targeting molecular determinants of gene therapy inflammation"

Previous research shows that toll-like receptor 9 (TLR9) recognizes the AAV genome and initiates the cytotoxic T cell response to the AAV capsid. Inhibitory DNA sequences can bind to TLR9 and inhibit dimerization and subsequent immune response activation. Therefore, an AAV vector can be engineered to include a TLR9-inhibitory oligo (io2) that can antagonize TLR9 when the vector is expressed. In a pig model of subretinal injection of an AAV8 vector with and without io2, the inclusion of io2 prevented the loss/shortening of cone outer segments, attenuated the innate immune response (microglial infiltration into photoreceptors), and reduced cytotoxic T cell recruitment to the retina. In a mouse model of intravitreal injection of an AAV2 vector with and without io2, the inclusion of io2 reduced the cytotoxic T cell response and increased transgene expression. This indicates that immune response may hamper transgene expression and reduce overall efficacy. An NHP model of intravitreal injection of an AAV2 vector showed that neither io2 nor systemic corticosteroids on their own could prevent the development of clinical uveitis, but each could delay it (io2 had an approximately 10-day delay, corticosteroids had an approximately 20-day delay). Combining the 2 had an additive effect and could further delay the development of uveitis to approximately 30 days. AAV-induced inflammation is likely due to a complex interplay of host, vector, and environment, and, therefore, will probably require a combination of approaches, including the use of engineered vectors, corticosteroids, and others.

William Beltran, DVM, PhD – "Proof of concept studies of gene therapy for NPHP5-LCA in a canine model: Efficacy of intervention at advanced stages of disease and long-term restoration of vision"

Previous work has shown that an early stage of nephrocystin protein 5 (NPHP5)-Leber congenital amaurosis (LCA) in a canine model can be rescued by gene therapy, which can restore photoreceptor (PR) structure and function. Advanced stages (mid-, late-, and very late-) are more clinically relevant, and gene therapy at these stages can induce long-term restoration of PR structure. There was also functional restoration of rods in all disease stages, as shown by electroretinogram (ERG), and restoration of cone function in mid- and late stages; restoration was detected as early as 6 to 8 weeks postinjection. This also corresponds to sustained rescue of visually guided behavior. Retinal function and vision restoration were stable for up to 2 to 5 years postinjection and there were no clinical signs of retinal inflammation or toxicity.

Simon Petersen-Jones, DVM, PhD, DVOphthal, DipECVO – "Assessment of a translatable AAV vector for gene augmentation therapy for CNGB1-retinitis pigmentosa"

An AAV5 vector containing the rhodopsin promoter and cyclic nucleotide-gated channel subunit beta 1 (CNGB1) was used in dose escalation studies to treat a dog model of early-stage CNGB1-retinitis pigmentosa (RP). Six months after injection, ERG and vision testing showed that rod function was restored and rod degeneration was slowed or halted with all dose groups. There is also preliminary evidence that cone function is restored in all dose groups. One year after injection, optical coherence tomography (OCT) showed that retinal structure and thickness were also preserved. Rod function and retinal structure remained for at least 3 years (the longest time period measured to date). Ongoing work is focusing on treating with AAV-CHNGB1 at a later stage, but preliminary evidence suggests that the same effectiveness can be seen in these animals too.

Ruslan Grishanin, PhD – "Nonclinical identification of dose range of ADVM-062, a novel intravitreal gene therapy for the treatment of blue cone monochromacy"

Adverum Biotechnologies is developing a novel intravitreal gene therapy, ADVM-062, that expresses L-opsin specifically in cone photoreceptors and can be used to treat blue cone monochromacy (BMC). The US Food and Drug Administration (FDA) has granted ADVM-062 an Orphan Drug Designation. Rodent models showed proof-of-concept that ADVM-062 can transduce cone cells and restore their function. An NHP model showed that there was dose-dependent transduction and that needle placement during the injection could affect transduction. The NPH also showed that even the highest dose of ADVM-062 was well tolerated, with only mild inflammation and no intraocular pressure (IOP) concerns occurring. Taken together, these data support moving ADVM-062 into a phase 1 clinical trial.

Ala Moshiri, MD, PhD – "Gene therapy rescues cone function in rhesus macaques with PDE6C cone disorder"

An NHP model of phosphodiesterase 6C (PDE6C)–related achromatopsia (ACHM) was treated with subretinal gene therapy with AAV-PDE6C. After 1 month of injection with a high dose of vector, retinal anatomy returned to normal, and some cone function was restored. Chromatic ERG showed that all 3 cone signals (green, red, and blue) were restored to a limited degree. Multifocal ERG showed functional restoration was sustained for at least 6 months. Future work will focus on comparing subretinal and intravitreal delivery and replacing lost cone cells with retinal organoids (ROs) derived from induced pluripotent stem cells (iPSCs)

Ashwath Jayagopal, PhD – "Opus Genetics, a patient-centric biotech committed to developing ultrarare IRD therapies"

Opus Genetics was founded by FFB and the Retinal Degeneration Fund to accelerate the development of gene therapies for IRDs. They plan to generate 1 Investigational New Drug (IND) application per year and to develop a manufacturing system for gene therapy that can easily be adjusted according to the number of patients that need treatment. The first IND application will be on lebercilin (LCA5) gene therapy; work on a mouse model showed that gene therapy can restore retina function and structure and functional vision. Retinol dehydrogenase 12 (RDH12) is the second target for gene therapy and preliminary research  has been shown it is possible to restore RDH12 expression and function via an AAV vector in a mouse model. Nicotinamide mononucleotide adenylyltransferase 1 (NMNAT1) is the third target for gene therapy and preliminary work in a mouse model has shown that retina structure and partial functional rescue are possible when expression is restored via an AAV vector. .

Linda Cuoto, PhD – "Preclinical evaluation of optimized dual AAV-MYO7A vectors for the treatment of Usher Syndrome 1B"

Atsena Therapeutics has developed a proprietary AAV capsid (AAV.SPR) that can be used to deliver gene therapy throughout the retina via subretinal injection. They have also developed 2 sets of AAV vectors that can recombine to express full-length myosin VIIA (MYO7A); 1 set are overlap vectors that use homologous recombination, and the other are hybrid vectors that recombine via alkaline phosphatase activity followed by splicing. One overlap and 1 hybrid vector were chosen to be injected into NHPs using the AAV.SPR capsid, which showed robust full-length MYO7A expression in photoreceptors and RPE throughout the retina. Both vectors produced physiologically relevant levels of MYO7A. Altogether, the data suggest that these are promising treatments for RP associated with USH1B.

Jack Auld – "Preclinical experience with the Advent R400e delivery device–dose tracking and precision drug delivery of subretinal gene therapies"

Altaviz has developed the Advent R400e, an injector that was specifically designed to deliver any gene therapy efficiently, consistently, and precisely via subretinal injection. Existing pressure-based systems produce inconsistent, variable blebs, so the Advent R400e provides consistent flow regardless of pressure drops, which enables easy bleb initiation and consistent bleb formation. It incorporates an activator that requires low force to use, a 400-μL syringe, and a 41g cannula with retractable tip protector. Additional features include a dose-monitoring system that can be projected out to an external device via Bluetooth to allow for external monitoring, a speaker for audible dosing guidance, and LEDs for visual cues about the injection state. Specific flow rates and doses can be programed into the device to accommodate individual needs.  

Andreas Lauer, MD – "Intraoperative injection pressure monitoring and trend analysis during gene therapy delivery in progressive inherited retinal degenerations"

Subretinal injections are the most common delivery method for gene therapy, but this requires the creation of a bleb that, if not done properly, can damage the retina. The speed of the injection correlates with the extent of retina damage, which may be because of the injection pressure used while creating the bleb. There was a large variation in the minimum and maximum amounts of injection pressure during both the initiation and propagation phases, but in general, the pressures used during bleb propagation were less variable and trended higher as patients got older. Over time, as more injections are performed, the pressure needed to propagate the bleb decreased, indicating that there is a learning curve associated with the procedure. These results suggest surgeons can refine their injection technique to minimize their use of excessive pressures and reduce operative injury.

Ninel (Nell) Gregori, MD – "Can suprachoroidal delivery replace subretinal or intravitreal delivery of gene therapy?"

Suprachoroidal injection is a newer, unexplored method of delivery for gene therapies and there are no registered clinical trials using it to treat IRDs. Suprachoroidal injection is under investigation in 3 trials to deliver gene therapy to treat neovascular age-related macular degeneration (nAMD) and diabetic retinopathy (DR). A rat model of suprachoroidal injection of AAV8 showed that transduction can occur on the side opposite to the injection site and expression was limited to the choroid, RPE, and the outer and inner segments of most photoreceptors. Similar results were seen in NHPs and porcine eyes, but 21 days after the injection, the NHPs developed AAV8-neutralizing antibodies (NABs). One study in rat eyes showed that transgene expression was comparable between suprachoroidal and subretinal expression. Five different AAV2 serotypes have been developed to use in suprachoroidal injections and are able to transduce RPE and the outer nuclear layer (ONL) with a wide distribution throughout the retina. Research also shows that it may be possible to use suprachoroidal injection to deliver nonviral particles.

Glenn Yiu, MD, PhD – "Suprachoroidal AAV delivery for retinal gene therapy–from nonhuman primates to clinical trials"

There are many benefits to delivering gene therapy via suprachoroidal injection, including broad, diffuse transduction, but it may also induce an immune response that reduces gene expression over time and causes mild punctate chorioretinitis and mild vitritis. Suprachoroidal injection results in high expression outside of the bleb area, which may explain why it triggers a greater antibody and T cell response than other delivery routes. RGX-314 is an AAV8-anti-vascular endothelial growth factor (VEGF) fab fragment injected suprachoroidally that is in clinical trials to treat nAMD and DR. In the nAMD trial, there was a reduction in the number of additional injections that patients needed and an increase in the number of patients who did not need any additional treatments. RGX-314 was less immunogenic, with only a few patients having intraocular inflammation that was mainly treated with topical corticosteroids. In the DR study, the DR severity significantly decreased.

Kathryn Pepple, MD, PhD – "Systemic corticosteroids and MyD88 deficiency decreased but did not prevent ocular inflammation following intravitreal gene therapy administration"

Gene therapy–associated uveitis (GTU), frequently occurs after intravitreal gene therapy, and it can threaten vision and reduce the therapeutic benefits of the gene therapy. Often, prophylactic corticosteroids are not sufficient to prevent GTU from occurring; instead, prophylactic immune modulation may be necessary to reduce the immune response. Mouse models show that the extent of inflammation after treatment varies between individuals, even if they are given tapering corticosteroid doses. Corticosteroid treatment selectively decreases the lymphoid and myeloid populations. AAV vectors may be engineered to target myeloid differentiation primary response 88 (MyD88), a key protein involved in the innate immune system, which may be a more effective approach to preventing inflammation than corticosteroids. However, the evidence suggests that a combination of strategies may be required to treat GTU.

Robert MacLaren, MD, PhD – "Assessment of safety and efficacy of subretinal timrepigene emparvovec in adult men with choroideremia in a randomized parallel-controlled phase 3 trial: The STAR Study"

The STAR Study is a phase 3 study of the safety and efficacy of 2 doses of subretinal timrepigene emparvovec, a gene therapy for the treatment of choroideremia. At 12 months, the study did not meet its primary endpoint of improved visual acuity (≥10-letter improvement) in those patients treated with the low dose, but it did meet the same endpoint in the high-dose treatment group, which was a secondary endpoint. A higher proportion of patients in the high-dose group also maintained a less than 5 letter drop from baseline visual acuity, as compared to both the low-dose and control groups. Adverse events were similar to other gene therapy treatments at the same dose and there were no unexpected safety results.

Dominik Fischer, MD, PhD – "AAV & ocular inflammation"

AAV vectors are the de facto gold standard for retinal gene therapy because it does not cause diseases in humans, transduces key retinal cell populations, does not integrate into the genome, and provides robust gene expression. It is currently used in 1 FDA-approved therapy, voretigene neparvovec-rzyl, which serves as a benchmark for IRD gene therapy. However, gene therapy is known to potentiate the development of uveitis (GTU) via an unknown mechanism. Data show that AAV gene therapy includes several contaminants that could cause an immune response, including free DNA, host cell proteins, endotoxins, and actual AAV with plasmid DNA that could cause an immune response. Assays performed in human plasmacytoid dendritic cells (pDCs) showed that the innate immune response is dependent on TLR-9 and can be attenuated by DNase treatment to remove free DNA. DNase treatment may also increase transduction efficacy. Other experiments showed that pattern recognition receptor (PRR) ligands do not elicit an immune response in retinal cells and iPSC-derived ROs do not release proinflammatory cytokines/chemokines in response to AAV vectors. Studies in NHPs show high doses of AAV8 induce a sustained inflammatory reaction. In humans, even those patients without clinical signs of inflammation may have a sustained, systemic inflammatory response to high-dose gene therapy. Preliminary data show that some patients may have a local inflammatory response, as measured by the release of proinflammatory cytokines into the aqueous humor. Ongoing research is working to identify biomarkers that predict the risk or severity of GTU and to study the real-world efficacy and safety of voretigene neparvovec-rzyl, of which preliminary data were shown at the 2022 ARVO Annual Meeting.

Paul Sieving, MD, PhD – "AV8-RS1 trial for X-linked retinoschisis: Preclinical and clinical inflammation studies"

A phase 1/2a National Institutes of Health (NIH)–sponsored trial of the intravitreal injection of AAV8-retinoschisin 1 (RS1) to treat X-linked retinoschisis (XLRS) (ClinicalTrials.gov: NCT02317887) has been conducted to test the efficacy and safety of different doses of the gene therapy. In this study, there was dose-dependent inflammation, with more inflammation occurring in those patients treated with the highest dose. However, this study also showed that having pre-existing AAV8 NABs and an NAB response does not correlate to clinical inflammation and steroid pretreatment was not sufficient to reduce the NAB response or clinical inflammation. Other work showed that humans with XLRS may have a proinflammatory immune phenotype at baseline that modestly correlates with the development of clinical inflammation. This baseline proinflammatory state should be taken into consideration for future clinical trials.

Mark Pennesi, MD, PhD – "Long-term follow-up of ocular inflammation after intravitreal delivery of rAAV2tYF-CB-hRS1 vector for gene augmentation therapy in X-linked retinoschisis"

A nonrandomized, open-label phase 1/2 Applied Genetics Technologies Corporation (AGTC)–sponsored trial of the intravitreal injection of AAV-RS1, to treat XLRS was conducted to test the safety and efficacy of different doses of gene therapy. This is a competing trial to the NIH-sponsored trial that Dr. Sieving described. At the 12-month follow up, only 3 out of 27 patients met the predefined responder criteria, indicating the treatment was not efficacious. Two patients met visual field improvement but only at a single time point and 1 patient had improved OCT imaging; however, the improved schisis disappeared at later follow ups. Despite the lack of efficacy, the trial showed that most patients did have ocular inflammation that could be treated with steroids. Almost all patients had increased NAbs that weakly correlated to dose but did not correlate to the development of inflammation. A minority of patients in the high-dose group developed recurrent or chronic GTU.

Byron Lam, MD – "Intravitreal gene therapy inflammation: Lessons learned from the Miami Leber hereditary optic neuropathy clinical trial"

A phase 1 G11778A Leber hereditary optic neuropathy (LHON) gene therapy clinical trial (NCT02161380) assessed the safety and tolerability of the intravitreal injection of AAV-NADH dehydrogenase 4 (ND4). Three patient groups were used in this study: chronic bilateral LHON, acute bilateral LHON, and acute unilateral LHON. No prophylactic steroids were given, and 8 out of 28 patients had incident uveitis (anterior chamber cells and flare, keratic precipitates), which was related to treatment dose. Half of the cases were mild and resolved without treatment, but 4 required additional treatment. Of the treated cases, 3 resolved and 1 is still ongoing at 24 months. No visual sequelae were found in patients with GTU. A laser flare meter reading of more than 20 may be more likely to be associated with uveitic complications and may be helpful to determine if chronic uveitis requires treatment.

José-Alain Sahel, MD – "Optogenetics for vision restoration, targeting ganglion cells"

GS030 optogenetic therapy for end-stage RP that combines the intravitreal injection of AAV-ChrimsonR (a version of microbial opsin) with the use of a photostimulating device that transforms light stimuli into a signal that can activate the remaining retinal ganglion cells (RGCs) and restore vision. The photostimulating device transforms external light stimuli into an appropriate and constant signal that helps activate the remaining RGCs in a manner that mimics natural visual processing. PIONEER is an ongoing phase 1/2, dose-escalation, first-in-man clinical trial studying the safety of GS030 as a treatment for RP. Preliminary results show that 1 patient has had partial recovery of visual function complete with the partial restoration of brain activity that corresponds to vision. Some patients (5 out of 9 patients) did develop inflammation but there was no detectable sequela.

Christine Kay, MD – "Safety findings from two phase I/II clinical trials of subretinal gene therapy drugs in adult and pediatric subjects with achromatopsia (ACHM)"

AGTC-401 and AGTC-402 are 2 gene therapies in development to potentially compensate for the most often mutated genes responsible for ACHM, cyclic nucleotide-gated channel subunit beta 3 (CNGB3) and cyclic nucleotide-gated channel subunit alpha 3 (CNGA3). The subretinal injection of AAV.PR1.7-CNGA3) and AAV.PR1.7-CNGB3 are currently under investigation in 2 ATGC-sponsored phase 1/2 dose-escalation clinical trials in both adults and pediatric patients with ACHM. Anecdotal evidence suggests that some patients respond positively to treatment, with some restoration of vision at 3 months after treatment. Efficacy results of both trials were presented at the 2022 ARVO Annual Meeting. Most adverse events in both trials were nonserious and all instances of inflammation were resolved with steroids. The safety profile was favorable in all adult patients through the highest dose and in pediatric patients through the second highest dose. These safety results highlight the need to have different gene therapy dosing regimens for adults and pediatric patients. More extensive safety results were presented at the 2022 ARVO Annual Meeting.

Aaron Nagiel, MD, PhD – "Perifoveal atrophy and subretinal deposits following treatment with voretigene neparvovec-rzyl"

Voretigene neparvovec-rzyl is the first retinal gene therapy approved for the treatment of retinoid isomerohydrolase (RPE65)–mediated retinal dystrophy and a retrospective case series is being conducted to assess real-world safety, in particular, the incidence of perifoveal chorioretinal atrophy and subretinal deposits. Real-world efficacy showed that while there was no significant improvement in visual acuity, there was 1 in full-field scotopic threshold (FST) that was sustained for 1 year. Sustained visual field expansion also occurred with treatment. Real-world safety showed that some patients developed perifoveal chorioretinal atrophy in the area of the bleb that was not described in the clinical trials. Despite having chorioretinal atrophy, patients otherwise had improved visual acuity and there may be some correlation between a significant, initial improvement in FST and its development, which may indicate that chorioretinal atrophy is related to vector-related toxicity. More information on such cases was presented at the 2022 ARVO Annual Meeting. Subretinal deposits have also been found to occur inferior to the bleb and eventually resolve on their own. Such deposits are likely to result from transient subretinal inflammation that then resolves, which allows the deposits to be cleared out by the immune system. Deposits provide definitive evidence of bleb migration, especially when it is not positioned properly in children who can have an increased inflammatory response to the vector.

Isabelle Audo, MD, PhD – "Prevalence of chorioretinal atrophic changes after subretinal voretigene neparvovec-rzyl injection in RPE65-related retinal dystrophy, the experience of a French cohort"

A French cohort of RPE65-related retinal dystrophy patients treated with voretigene neparvovec-rzyl provided more real-world evidence of the efficacy and safety of the treatment. There were no significant changes in visual acuity but there was definite improvement in FST, even in patients who developed chorioretinal atrophy. The majority of instances of chorioretinal atrophic lesions occurred at the site of retinotomy soon after the surgery; this may be a result of surgical trauma and inflammation. Chorioretinal atrophy within the bleb occurred only in adults and was foveal sparing, but all had additional progression of the atrophy outside of the bleb. Chorioretinal atrophy only outside the bleb affected mainly adults but was present in some pediatric patients. Chorioretinal atrophy involving the bleb took longer, over 1 year, to develop. There was no correlation with age or gender and the cohort was too small to determine if patient genotype was correlated with the appearance of chorioretinal atrophy. More research needs to be done to understand the role of disease natural progression and the inflammatory response in the development of atrophy. A larger cohort with longer follow up would also help to elucidate how and why atrophy occurs.

 Janet Davis, MD – "Does genetic predisposition to sympathetic ophthalmia matter in gene therapy research: A case report"

On behalf of Dr. Davis, Dr. Lam presented a case study of sympathetic ophthalmia that occurred after voretigene neparvovec-rzyl therapy. Two nontwin sisters underwent bilateral gene therapy surgeries on the same day under the same circumstances. Both sisters also had identical biallelic mutations of the RPE65 gene and underwent gene therapy in both eyes, with each eye being treated 1 week apart. Surgery was uncomplicated and initial follow ups (1 day and 1 month) were unremarkable. At 51 and 45 days after treatment, 1 patient presented with acute vitreous inflammation, elevated IOP, choroidal infiltrates, subretinal fluid, and bacillary detachment in both eyes. Laboratory tests revealed abnormal findings in the patient’s cerebrospinal fluid, which were consistent with Vogt-Koyanagi-Harada (VKH) sympathetic ophthalmia. The affected sister had biallelic human leukocyte antigen (HLA) haplotypes that are associated with an increased risk of sympathetic ophthalmia. However, the unaffected sister had the high-risk HLA haplotypes only on 1 allele, which may be the reason why she did not develop sympathetic ophthalmia. The patient was treated with steroids and, after referral to a rheumatologist, mycophenolate mofetil. After several months of treatment, the patient’s visual acuity slightly improved and the subretinal fluid decreased; however, there were persistent choroidal infiltrations. This case study illustrates that there should be a risk assessment prior to surgery to be prepared for the possibility of sympathetic ophthalmia or other conditions.

Artur Cideciyan, PhD – "AON treatment for CEP90-LCA: Efficacy, safety, and durability"

Centrosomal protein 290 (CEP290)-LCA10 is characterized by a triangular-shaped, hypofluorescent area seen in OCT that contains the PR nuclei and there is a slow decrease of foveal thickness and a constriction of the central area. RP patients present with a similar phenotype (a central cone tunnel) and were used to create an artificial intelligence framework that could model perimetry readings and predict treatment potential in CEP290-LCA patients. Using this information, it was determined that a subset of CEP290-LCA patients with central macular cone PR with defective vision may be ideal targets for treatment with sepofarsen, an antisense oligonucleotide. A phase 1/2 clinical trial of sepofarsen showed that it could improve visual acuity and FST readings but there were large differences in efficacy between individuals, despite all sharing the same intronic mutation. When the artificial intelligence framework was applied to those patients whose perimetry data were available, the treatment effect was similar to the predicted maximum treatment effect, indicating that the artificial intelligence framework could be applied to predict individual treatment potential in CEP290-LCA clinical trials.

Bart Leroy, MD, PhD – "Efficacy and safety of sepofarsen, an intravitreal RNA antisense oligonucleotide, for the treatment of CEP290-associated inherited retinal disease called Leber congenital amaurosis (LCA10): A randomized, double-masked, sham-controlled, phase III study (ILLUMINATE)"

A multicenter, pivotal phase 3 clinical trial (ILLUMINATE) was conducted to assess the safety and efficacy of different doses of sepofarsen for the treatment of CEP290-LCA10. Unfortunately, after 12 months of follow up, the study showed no additional benefit with sepofarsen treatment, as compared to sham treatment, in the efficacy endpoints of visual acuity, FST, and mobility course. However, sepofarsen-treated patients self-reported a significant improvement in vision. Given these results, the data were reanalyzed by comparing treated eyes to the contralateral, untreated eye instead of the sham-treated arm. One analysis showed that the interpatient variability between treatment arms was greater than the intrapatient variability of treated and untreated eyes, thereby indicating that the contralateral eye should be used as a control for intervisit variability. When data from the contralateral eye are subtracted from the results from the treated eye, the treatment difference between sepofarsen and sham becomes more apparent in visual acuity and FST. In terms of safety, sepofarsen treatment seemed to be well tolerated with ocular adverse events consistent with the phase 1/2 clinical trial. Based on this, the clinical trial will be continued into the second year and talks with regulatory agencies are ongoing to design future clinical trials.

Rajarshi Pal, PhD – "RPE generated from iPSC through a novel protocol demonstrated vision rescue in an RCS rat model"

Eyestem Research has developed a unique protocol to simulate in vivo retina development that differentiates iPSCs first into neural rosettes and then into RPE and photoreceptor progenitor (PRP) cells. The protocol has been confirmed by the presence of neural-, mature RPE-, and PRP-specific markers at each appropriate step of differentiation. The identity and purity of the differentiated cells were also confirmed by flow cytometry and transcriptome profiling. It was also confirmed that the cells were producing cytokines commonly secreted by the RPE and that they responded to KCl-induced depolarization, indicating their sensory neuron nature. The differentiated RPE cells were produced, frozen, and shipped to Casey Eye Institute, OHSU, where they were revived and subretinally transplanted into a rat model of retinal degeneration. The transplanted RPE cells survived, engrafted inside the host retina, and helped to maintain the ONL thickness and structural integrity of the host retina for at least 90 days. RPE transplantation also delayed the loss of visual acuity, as measured by ERG and optokinetic tracking threshold. Similarly, iPSC-derived, day 55 PRP cells were transplanted into a mouse model of RP where they survived, engrafted, provided neuroprotection, and improved ERG readings and light perception. Taken together, these results show that it is possible to produce affordable and effective iPSC-derived RPE and PRPs for the treatment of IRDs.

Kapil Bharti, PhD – "iPSC-derived RPE replacement therapy for macular degeneration"

The National Eye Institute has developed an autologous, patient-specific, iPSC-derived RPE patch on a biodegradable scaffold that can be transplanted into the transition zone of the RPE lesion. The scaffold supports the cells as they create a structure similar to the Bruch’s membrane and gradually degrades, which allows the cells to integrate as a natural RPE monolayer. The iPSC-RPE cells are functional and fully polarized with apical processes. It was confirmed that almost all of the iPSC-RPE cells expressed RPE-specific markers. When human iPSC-RPE cells were transplanted into a rat model and a pig model, the human cells survived and completely integrated into the host retina. In the pig model, the RPE patch protected the electrical responses over the area of the patch and prevented the retina from further damage. A phase 1/2a clinical trial has been initiated to assess safety, feasibility, and integration in patients with geographic atrophy associated with AMD. The first 2 patients have been enrolled and iPSCs and RPE patches are being created from them. The NEI is also working to create an artificial intelligence program and setup that can automatically choose and expand iPSC clones, which would help to reduce the cost of developing autologous iPSCs on a large scale.

Magdalene Seiler, PhD – "Noninvasive testing and sheet transplantation of retinal organoids to rat models of retinal degeneration"

One approach to retinal degeneration is to replace damaged PRs and RPE with a patch of new cells derived from human embryonic stem cells (hESCs) that can communicate with the still functioning inner retina. hESCs are differentiated into mature ROs, which can then be flattened and transplanted as a sheet into rat retinal degeneration models. Since it is time consuming to maintain the ROs during the development process, a bioreactor was developed to streamline and automate a large part of the process, which also induces less oxidative stress in the ROs. In rat models of retinal degeneration, RO sheet transplantation improves visual function and visual responses in the brain. Once transplanted, the RO sheets differentiate into PRs, integrate into the host retina, and form connections with the inner plexiform layer of the host. Cografts of RO sheets and RPE are also able to survive and integrate into the host retina. The cografts also improve visual function and visual responses in the brain to a greater degree than RO sheets alone, indicating that this is a promising future strategy. While the cografting process and bioreactor need to be further optimized, it is hoped that this work will eventually lead to the development of clinical therapy for patients with advanced retinal degeneration.

Amir Kashani, MD, PhD – "Long-term follow-up and clinicopathologic correlation in a phase I/IIa clinical trial of an allogeneic biosynthetic RPE implant for advanced dry AMD"

An implant composed of a layer of RPE cells on an ultrathin, parylene membrane that mimics the Bruch’s membrane has been developed to treat advanced dry AMD with geographic atrophy. The efficacy and safety of this implant are being assessed in a phase 1/2a clinical trial with a follow up of 2 to 5 years. Results from the primary endpoint, year 1, have been published and show that the procedure is safe and feasible with no evidence of implant migration, persistent pigmentation, and no clinical evidence of inflammation. Results from the 3-year follow up are consistent with, and somewhat better than, those from the 1-year follow up. The majority of treated eyes had stable or improved visual acuity (gain of more than 5 letters), which is exceedingly rare in patients with advanced geographic atrophy. Histopathological samples from a deceased patient indicate that the implanted RPE cells were polarized, expressed visual function proteins specific for RPE cells, and had phagosomes, all of which suggest that they were functioning similarly to normal RPE. Staining also showed that there did not appear to be an abnormal cellular immune response in the treated eye, as compared to the untreated eye, which correlates to the lack of clinical evidence of an immune response despite the patients not being on long-term immunosuppression. On the basis of these results, a phase 2b trial is being designed.

Rajesh Rao, MD – "Mechanistic insights into the function of PRDM13 in North Carolina Macular Dystrophy"

North Carolina Macular Dystrophy (NCMD) is an autosomal dominant congenital disease that has been linked to the overexpression of positive regulatory domain containing 13 (PRDM13), the function of which is still largely unknown. Mouse ESCs (mESCs) were used as an in vitro model to determine which functional domains of PRDM13 are necessary for the mESCs to differentiate into retinal cells. This model showed that the overexpression of full-length PRDM13 selectively inhibits retinal differentiation and favors differentiation into brain organoids. Deletion and point mutations showed that the positive regulatory (PR) domain does not regulate retinal differentiation, whereas the zinc finger domains (specifically, either the second or third) are necessary to inhibit retinal differentiation. Work on iPSCs derived from NCMD patients is ongoing to further elucidate the function of PRDM13 in the differentiation of retinal cells.