Gene Transfer Therapy Research Articles

Long-Term Survival and Myocardial Function Following Systemic Delivery of Delandistrogene Moxeparvovec in DMDMDX Rats.

Delandistrogene moxeparvovec is a gene transfer therapy for Duchenne muscular dystrophy (DMD) that uses an adeno-associated viral vector to deliver a micro-dystrophin transgene to skeletal and cardiac muscle. This study evaluated the long-term survival and cardiac efficacy of delandistrogene moxeparvovec in a DMD-mutated (DMDMDX) rat model of DMD-related cardiomyopathy. DMDMDX male rats, aged 21-42 days, were injected with 1.33 × 1014 viral genomes/kilogram (vg/kg) delandistrogene moxeparvovec and followed for 12, 24, and 52 weeks. Ambulation was recorded via the Photobeam Activity System, whereas echocardiograms, cardiomyocyte contractility, calcium handling, and histological analysis of fibrosis were used to evaluate cardiac disease at 12-, 24-, and 52-weeks post-treatment. A separate cohort of rats was used to assess the impact of delandistrogene moxeparvovec on survival. Treatment with delandistrogene moxeparvovec extended median survival in DMDMDX rats to >25 months versus the 13-month median survival in saline-control-treated DMDMDX rats. Compared with saline control, delandistrogene moxeparvovec therapy elicited statistically significant improvements across cardiac parameters approaching wild-type values with additional benefits in mobility, histopathology, and fibrosis observed. Transgene expression was maintained up to >25 months and micro-dystrophin expression was broadly distributed across skeletal and cardiac muscle. Taken together, these findings demonstrate long-term cardiac efficacy and improved survival following delandistrogene moxeparvovec treatment in DMDMDX rats.

MicroRNA-18a-5p promotes vascular smooth muscle cell phenotypic switch by targeting Notch2 as therapeutic targets in vein grafts restenosis

Vascular smooth muscle cells (VSMCs) phenotype switching plays a crucial role in vein graft restenosis following coronary artery bypass grafting (CABG) surgery. To discover novel clinically relevant therapeutic targets for vein graft restenosis after CABG, we therefore investigated whether miRNA-18a-5p mediated phenotype switching plays a critical role in the development of vein graft restenosis. We studied miRNA-18a-5p expression in plasma samples of patients with or without vein graft restenosis at 1, 3 and 5 years after coronary artery bypass graft surgery, and in normal vs. atherosclerotic human femoral artery samples, to prove its role in VSMC phenotype switching. We found that the expression of miRNA-18a-5p significantly increased in vein grafts restenosis rat model after bypass surgery at 7, 14, 28 days and human blood specimens with vein grafts failure after grafting surgery. Through gain- and loss-of-function approaches, we determined that miRNA-18a-5p affects VSMC proliferation, migration, differentiation, and contractility. Notch2 was found to be a direct target of miRNA-18a-5p, which is critical for VSMC phenotype switching. Finally, miRNA-18a-5p knockdown used miRNA sponge via AAV6 locally delivery in vivo, miRNA-18a-5p sponge gene transfer therapy reduced the neointimal area, neointimal thickness, and intimal/media area ratio in vein grafts compared with the controls and improved vein graft hemodynamics. miRNA-18a-5p is a critical modulator of VSMC phenotypic switch during development of vein graft restenosis by downregulating Notch2, therefore targeting miRNA-18a-5p may be a helpful strategy for the treatment of vein grafts restenosis or failure after CABG surgery.

Real-world multidisciplinary outcomes of onasemnogene abeparvovec monotherapy in patients with spinal muscular atrophy type 1: experience of the French cohort in the first three years of treatment

BackgroundSpinal muscular atrophy type 1 (SMA1) is the most severe and early form of SMA, a genetic disease with motor neuron degeneration. Onasemnogene abeparvovec gene transfer therapy (GT) has changed the natural history of SMA1, but real-world data are scarce.MethodsA French national expert committee identified 95 newly diagnosed treatment-naive SMA1 patients between June 2019 and June 2022. We prospectively report on children treated with GT as the first and only therapy who had more than one-year of follow-up.ResultsForty-six SMA1 patients received GT. Twelve patients received other treatments. Patients with respiratory insufficiency were oriented toward palliative care after discussion with families. Twenty-nine of the treated patients with more than 12 months of follow-up were included in the follow-up analysis. Among them, 17 had 24 months of follow-up. The mean age at treatment was 7.5 (2.1–12.5) months. Twenty-two patients had two SMN2 copies, and seven had three copies. One infant died in the month following GT due to severe thrombotic microangiopathy, and another died due to respiratory distress. Among the 17 patients with 24 months of follow-up, 90% required spinal bracing (15/17), three patients required nocturnal noninvasive ventilation, and two needed gastrostomy. Concerning motor milestones at the 24-month follow-up, all patients held their head, 15/17 sat for 30 s unassisted, and 12/17 stood with aid. Motor scores (CHOPINTEND and HINE-2) and thoracic circumference significantly improved in all patients.ConclusionsOur study shows favorable motor outcomes and preserved respiratory and feeding functions in treatment-naive SMA1 infants treated by GT as the first and only therapy before respiratory and bulbar dysfunctions occurred. Nevertheless, almost all patients developed spinal deformities.

Muscular Dystrophies: An Update Review

A broad group of illnesses known as muscular dystrophies are defined by pathologic alterations found in muscle tissue following biopsy. A progressive weakening of the skeletal muscles characterises the clinical appearance of these disorders. The most common type of muscular dystrophy is Duchenne Muscular Dystrophy, an X-linked recessive disease. Distal muscular dystrophy is most common in people between the ages of 40 and 60 and primarily affects the lower limbs, such as the hands, feet, arms, and legs. The development of muscle weakness during infancy or early childhood, usually before the age of two, is a common symptom of congenital muscular dystrophy. The majority of MD types frequently result in respiratory issues that affect the diaphragm and other breathing muscles. Several MD subtypes are linked to cardiac arrhythmias or cardiomyopathy. This class of disorders is the main target of gene transfer and gene repair therapies.

GAPDH suppresses adenovirus-induced oxidative stress and enables a superfast production of recombinant adenovirus

Recombinant adenovirus (rAdV) is a commonly used vector system for gene transfer. Efficient initial packaging and subsequent production of rAdV remains time-consuming and labor-intensive, possibly attributable to rAdV infection-associated oxidative stress and reactive oxygen species (ROS) production. Here, we show that exogenous GAPDH expression mitigates adenovirus-induced ROS-associated apoptosis in HEK293 cells, and expedites adenovirus production. By stably overexpressing GAPDH in HEK293 (293G) and 293pTP (293GP) cells, respectively, we demonstrated that rAdV-induced ROS production and cell apoptosis were significantly suppressed in 293G and 293GP cells. Transfection of 293G cells with adenoviral plasmid pAd-G2Luc yielded much higher titers of Ad-G2Luc at day 7 than that in HEK293 cells. Similarly, Ad-G2Luc was amplified more efficiently in 293G than in HEK293 cells. We further showed that transfection of 293GP cells with pAd-G2Luc produced much higher titers of Ad-G2Luc at day 5 than that of 293pTP cells. 293GP cells amplified the Ad-G2Luc much more efficiently than 293pTP cells, indicating that exogenous GAPDH can further augment pTP-enhanced adenovirus production. These results demonstrate that exogenous GAPDH can effectively suppress adenovirus-induced ROS and thus accelerate adenovirus production. Therefore, the engineered 293GP cells represent a superfast rAdV production system for adenovirus-based gene transfer and gene therapy.

D.4 Safety and efficacy of delandistrogene moxeparvovec versus placebo in Duchenne muscular dystrophy (EMBARK): Pivotal Phase 3 primary results

Background: Duchenne muscular dystrophy (DMD) is caused by DMD gene mutations. Delandistrogene moxeparvovec is an investigational gene transfer therapy, developed to address the underlying cause of DMD. We report findings from Part 1 (52 weeks) of the two-part EMBARK trial (NCT05096221). Methods: Key inclusion criteria: Ambulatory patients aged ≥4-<8 years with a confirmed DMD mutation within exons 18–79 (inclusive); North Star Ambulatory Assessment (NSAA) score >16 and <29 at screening. Eligible patients were randomized 1:1 to intravenous delandistrogene moxeparvovec (1.33×1014 vg/kg) or placebo. The primary endpoint was change from baseline in NSAA total score to Week 52. Results: At Week 52 (n=125), the primary endpoint did not reach statistical significance, although there was a nominal difference in change from baseline in NSAA total score in the delandistrogene moxeparvovec (2.6, n=63) versus placebo groups (1.9, n=61). Key secondary endpoints (time to rise, micro-dystrophin expression, 10-meter walk/run) demonstrated treatment benefit in both age groups (4-5 and 6-7 years; p<0.05).There were no new safety signals, reinforcing the favorable and manageable safety profile observed to date. Conclusions: Based on the totality of functional assessments including the timed function tests, treatment with delandistrogene moxeparvovec indicates beneficial modification of disease trajectory.

Clinical immunogenicity outcomes from GENEr8-1, a phase 3 study of valoctocogene roxaparvovec, an AAV5-vectored gene therapy for hemophilia A

Gene transfer therapies utilizing adeno-associated virus (AAV) vectors involve a complex drug design with multiple components that may impact immunogenicity. Valoctocogene roxaparvovec is an AAV serotype 5 (AAV5)-vectored gene therapy for treatment of hemophilia A that encodes a B-domain–deleted human factor VIII (FVIII) protein controlled by a hepatocyte-selective promoter. Following previous results from the first-in-human phase 1/2 clinical trial, we assessed AAV5 capsid– and transgene-derived FVIII-specific immune responses with 2 years of follow-up data from GENEr8-1, a phase 3, single-arm, open-label study in 134 adult men with severe hemophilia A. No FVIII inhibitors were detected following administration of valoctocogene roxaparvovec. Immune responses were predominantly directed toward the AAV5 capsid, with all participants developing durable anti-AAV5 antibodies. Cellular immune responses specific for the AAV5 capsid were detected in most participants by interferon-ᵧ enzyme-linked immunosorbent spot assay 2 weeks following dose administration and declined or reverted to negative over the first 52 weeks. These responses were weakly correlated with alanine aminotransferase elevations and showed no association with changes in FVIII activity. FVIII-specific cellular immune responses were less frequent and more sporadic compared with those specific for AAV5 and showed no association with safety or efficacy parameters.

Practical Considerations for Delandistrogene Moxeparvovec Gene Therapy in Patients With Duchenne Muscular Dystrophy

BackgroundDelandistrogene moxeparvovec is a gene transfer therapy approved in the United States, United Arab Emirates, and Qatar for the treatment of ambulatory patients aged four through five years with a confirmed Duchenne muscular dystrophy (DMD)-causing mutation in the DMD gene. This therapy was developed to address the underlying cause of DMD through targeted skeletal, respiratory, and cardiac muscle expression of delandistrogene moxeparvovec micro-dystrophin, an engineered, functional dystrophin protein. MethodsDrawing on clinical trial experience from Study 101 (NCT03375164), Study 102 (NCT03769116), and ENDEAVOR (Study 103; NCT04626674), we outline practical considerations for delandistrogene moxeparvovec treatment. ResultsBefore infusion, the following are recommended: (1) screen for anti-adeno-associated virus rhesus isolate serotype 74 total binding antibody titers <1:400; (2) assess liver function, platelet count, and troponin-I; (3) ensure patients are up to date with vaccinations and avoid vaccine coadministration with infusion; (4) administer additional corticosteroids starting one day preinfusion (for patients already on corticosteroids); and (5) postpone dosing patients with any infection or acute liver disease until event resolution. Postinfusion, the following are recommended: (1) monitor liver function weekly (three months postinfusion) and, if indicated, continue until results are unremarkable; (2) monitor troponin-I levels weekly (first month postinfusion, continuing if indicated); (3) obtain platelet counts weekly (two weeks postinfusion), continuing if indicated; and (4) maintain the corticosteroid regimen for at least 60 days postinfusion, unless earlier tapering is indicated. ConclusionsAlthough the clinical safety profile of delandistrogene moxeparvovec has been consistent, monitorable, and manageable, these practical considerations may mitigate potential risks in a real-world clinical practice setting.

A Review of Genes Involved in Wound Healing.

Gene therapy holds immense potential in the field of wound healing. However, we still do not recognize this procedure well enough to give oversight effectively to improve healing processes. A wide range of information has been achieved from the database for gene expression profiling by clinical trials, So we performed this study to gain a better understanding of the mechanisms behind wound healing and how it could be utilized to develop new therapies and treatments. In this study, we have been focusing on wound-healing genes, conducting a thorough review to explore the various genes and pathways involved in this process. For this purpose, a total of 320 articles were collected. All experimental studies, systematic or narrative reviews, studies and clinical trials included in this paper were searched on PubMed, Medline, Embase, Science Direct, and Scopus databases in English using the following terms: Wound Healing, wound regeneration, Gene Transfer, and Gene Therapy were used to search the mentioned databases. Unfortunately, we didn't find a large sample cohort study on this topic. A total amount of 330 articles were collected based on the guidelines of the PRISMA method. Both inclusion and exclusion criteria were settled. During the last decade, different models of gene delivery have been introduced, which include viral transfection and Non-viral techniques. In this regard, TIMP-2 protein and VEGF mutants such as VEGF165, CARP, and HIF-1 are the genes that accelerate the rate of tissue repair. The process of wound healing is mainly related to the change of expression of genes that have a role in the parts of inflammation and repair. In our study, some of the most suitable genes involved in the wound-healing process are mentioned.

Loss of Mtm1 causes cholestatic liver disease in a model of X-linked myotubular myopathy.

X-linked myotubular myopathy (XLMTM) is a fatal congenital disorder caused by mutations in the MTM1 gene. Currently, there are no approved treatments, although AAV8-mediated gene transfer therapy has shown promise in animal models and preliminarily in patients. However, 4 patients with XLMTM treated with gene therapy have died from progressive liver failure, and hepatobiliary disease has now been recognized more broadly in association with XLMTM. In an attempt to understand whether loss of MTM1 itself is associated with liver pathology, we have characterized what we believe to be a novel liver phenotype in a zebrafish model of this disease. Specifically, we found that loss-of-function mutations in mtm1 led to severe liver abnormalities including impaired bile flux, structural abnormalities of the bile canaliculus, and improper endosome-mediated trafficking of canalicular transporters. Using a reporter-tagged Mtm1 zebrafish line, we established localization of Mtm1 in the liver in association with Rab11, a marker of recycling endosomes, and canalicular transport proteins and demonstrated that hepatocyte-specific reexpression of Mtm1 could rescue the cholestatic phenotype. Last, we completed a targeted chemical screen and found that Dynasore, a dynamin-2 inhibitor, was able to partially restore bile flow and transporter localization to the canalicular membrane. In summary, we demonstrate, for the first time to our knowledge, liver abnormalities that were directly caused by MTM1 mutation in a preclinical model, thus establishing the critical framework for better understanding and comprehensive treatment of the human disease.

Expression of SRP-9001 dystrophin and stabilization of motor function up to 2 years post-treatment with delandistrogene moxeparvovec gene therapy in individuals with Duchenne muscular dystrophy.

Introduction: Delandistrogene moxeparvovec (SRP-9001) is an investigational gene transfer therapy designed for targeted expression of SRP-9001 dystrophin protein, a shortened dystrophin retaining key functional domains of the wild-type protein. Methods: This Phase 2, double-blind, two-part (48weeks per part) crossover study (SRP-9001-102 [Study 102]; NCT03769116) evaluated delandistrogene moxeparvovec in patients, aged ≥4 to <8years with Duchenne muscular dystrophy. Primary endpoints (Part 1) were change from baseline (CFBL) in SRP-9001 dystrophin expression (Week 12), by Western blot, and in North Star Ambulatory Assessment (NSAA) score (Week 48). Safety assessments included treatment-related adverse events (TRAEs). Patients were randomized and stratified by age to placebo (n = 21) or delandistrogene moxeparvovec (n = 20) and crossed over for Part 2. Results: SRP-9001 dystrophin expression was achieved in all patients: mean CFBL to Week 12 was 23.82% and 39.64% normal in Parts 1 and 2, respectively. In Part 1, CFBL to Week 48 in NSAA score (least-squares mean, LSM [standard error]) was +1.7 (0.6) with treatment versus +0.9 (0.6) for placebo; p = 0.37. Disparity in baseline motor function between groups likely confounded these results. In 4- to 5-year-olds with matched baseline motor function, CFBL to Week 48 in NSAA scores was significantly different (+2.5 points; p = 0.0172), but not significantly different in 6-to-7-year-olds with imbalanced baseline motor function (-0.7 points; p = 0.5384). For patients treated with delandistrogene moxeparvovec in Part 2, CFBL to Week 48 in NSAA score was +1.3 (2.7), whereas for those treated in Part 1, NSAA scores were maintained. As all patients in Part 2 were exposed to treatment, results were compared with a propensity-score-weighted external control (EC) cohort. The LSM difference in NSAA score between the Part 2 treated group and EC cohort was statistically significant (+2.0 points; p = 0.0009). The most common TRAEs were vomiting, decreased appetite, and nausea. Most occurred within the first 90days and all resolved. Discussion: Results indicate robust expression of SRP-9001 dystrophin and overall stabilization in NSAA up to 2years post-treatment. Differences in NSAA between groups in Part 1 were not significant for the overall population, likely because cohorts were stratified only by age, and other critical prognostic factors were not well matched at baseline.

Gene transfer therapy in children with spinal muscular atrophy: A single-center experience with a cohort of 25 children.

New therapeutic strategies to increase survival motor neuron protein levels in spinal muscular atrophy (SMA) have focused on replacing the SMN1 gene. Onasemnogene abeparvovec was approved by the US Food and Drug Administration in 2019 for treatment of children with SMA less than 2 years of age. Postmarketing studies are limited, especially outside of Europe and the United States. Herein we describe a single-center experience with onasemnogene abeparvovec from the Middle East. Between November 17, 2020 and January 31, 2022, 25 children with SMA received onasemnogene abeparvovec at our center in the United Arab Emirates. Data were collected on patients' demographics, age at diagnosis, SMA type, genetic information, relevant medical history, laboratory investigations, and Children's Hospital of Philadelphia Infant Test of Neuromuscular Disorders (CHOP-INTEND) functional assessment scores at baseline and 1 and 3 months after gene therapy. Onasemnogene abeparvovec was well tolerated. Significant improvements in CHOP-INTEND scores were observed after the therapy. Elevation of liver enzymes and thrombocytopenia were the most common adverse events, but were transient and managed with high-dose corticosteroids. There were no life-threatening adverse events or deaths reported during the 3-month follow-up period. The study findings concurred with those of previously published studies. Side effects of gene transfer therapy are well tolerated, although serious complications can arise. In such cases, persistent transaminitis for example, steroid dose escalation is warranted with close observation of the patient's clinical status and lab values. Combination therapy should be explored as an alternative to gene transfer therapy only.

PK/PD Modeling to Inform Clinical Development of an Adeno-associated Virus Gene Transfer Therapy for Duchenne Muscular Dystrophy (S48.005)

<h3>Objective:</h3> To evaluate the pharmacokinetic (PK)/pharmacodynamic (PD) relationship between tissue vector genome exposure, biological efficacy and functional outcome in an animal model of Duchenne muscular dystrophy (DMD) (DMD^mdx mice) following treatment with delandistrogene moxeparvovec (SRP-9001). <h3>Background:</h3> Delandistrogene moxeparvovec is an investigational gene transfer therapy developed to address the root cause of DMD through targeted skeletal and cardiac muscle expression of SRP-9001 dystrophin protein, which contains key functional domains of dystrophin. <h3>Design/Methods:</h3> We evaluated vector biodistribution, expression, and clinical dose selection of delandistrogene moxeparvovec using a novel application of a PK and PD modeling approach applied to data collected from DMD^mdx mice. We analyzed PK/PD relationships between dose, tissue vector genome exposure, SRP-9001 dystrophin protein expression (percent dystrophin positive fibers [PDPF] and western blot), and functional improvement (relative specific force from tibialis anterior and diaphragm). <h3>Results:</h3> Linear kinetics with a dose-proportional increase in tissue drug exposure were demonstrated across the nearly 10-fold dose range (4.43×10¹³–4.01×10¹⁴ vg/kg), and in all tissues. The relationship between tissue vector exposure and PD endpoints (PDPF, motor function outcome) showed a saturable response across a wide range of vector exposures. The vector exposure at 1.33×10¹⁴ vg/kg (the clinical dose) approached the maximum treatment response. Relative specific force and PDPF were significantly correlated (<i>P</i>=4.43×10⁻⁶). However, the relationship appeared to be nonlinear, with increased PDPF expression approaching the maximal functional improvement. Relative specific force and western blot were not significantly correlated. <h3>Conclusions:</h3> For the first time, biodistribution, biomarker and functional efficacy data were used to quantify and demonstrate PK/PD relationships for an adeno-associated virus (AAV)-based gene transfer therapy in a DMD animal model. The results continue to support the expected therapeutic benefit and clinical dose of delandistrogene moxeparvovec, an AAV-based gene transfer therapy. <b>Disclosure:</b> Mrs. East has received personal compensation for serving as an employee of Sarepta Therapeutics. Rachael Potter has received stock or an ownership interest from Sarepta Therapeutics. Dr. Snedeker has received personal compensation for serving as an employee of Sarepta Therapeutics. Dr. Snedeker has stock in Sarepta Therapeutics. Dr. Haile has nothing to disclose. Christopher Wier has received personal compensation for serving as an employee of Sarepta Therapeutics. Christopher Wier has stock in Sarepta Therapeutics. Ms. Rodino-Klapac has received personal compensation for serving as an employee of Sarepta Therapeutics, Inc.. Ms. Rodino-Klapac has received stock or an ownership interest from Sarepta Therapeutics. Ms. Rodino-Klapac has received intellectual property interests from a discovery or technology relating to health care.

Evaluating Pharmacology and Efficacy of Delandistrogene Moxeparvovec in Young and Aged DMDmdx Rats (P3-8.008)

<h3>Objective:</h3> The purpose of this preclinical study is to evaluate the myocardial efficacy and safety of intended commercial process delandistrogene moxeparvovec (SRP-9001) material in Duchenne muscular dystrophy (DMD)^mdx rats. DMD^mdx rats are a valuable alternative animal model of DMD, as they demonstrate cardiac dysfunction that recapitulates cardiac dysfunction of patients with DMD. <h3>Background:</h3> Gene transfer therapy is a promising treatment for patients with DMD. Delandistrogene moxeparvovec is an investigational gene transfer therapy developed to address the root cause of DMD through targeted skeletal and cardiac muscle expression of SRP-9001 dystrophin protein, which contains key functional domains of dystrophin. <h3>Design/Methods:</h3> We performed systemic, intravenous delivery of intended commercial process delandistrogene moxeparvovec material in young (21–35 days old) and aged (3–5 months old) DMD^mdx rats. The older rats demonstrate a more severe phenotype in terms of fibrosis or cardiac disease progression. Rats received a dose of 1.33×10¹⁴ vg/kg or 7.00×10¹³ vg/kg. Ambulation activity was recorded via the Photobeam Activity System Open Field. Echocardiograms and histological analysis of fibrosis were used to evaluate cardiac disease. <h3>Results:</h3> Data from 12 weeks and 24 weeks post-systemic delivery demonstrated no evidence of cardiac toxicity. Importantly, there were no deaths attributed to treatment. Compared with the saline control, intended commercial process delandistrogene moxeparvovec material increased ambulation and vertical activity in young DMD^mdx rats and improved cardiac function. Protein expression was broadly distributed across skeletal muscle, the diaphragm and the heart. <h3>Conclusions:</h3> Taken together, these findings confirm expression in cardiac muscle of rats, as expected, and support the potential myocardial efficacy and safety of delandistrogene moxeparvovec. Further results of cardiac disease phenotypes at 12 and 24 weeks post-systemic delivery utilizing several indicators of cardiac function will also be presented. <b>Disclosure:</b> Rachael Potter has received stock or an ownership interest from Sarepta Therapeutics. Christopher Wier has received personal compensation for serving as an employee of Sarepta Therapeutics. Christopher Wier has stock in Sarepta Therapeutics. Dr. Cooper-Olson has received personal compensation for serving as an employee of Sarepta Therapeutics. Dr. Cooper-Olson has stock in Sarepta Therapeutics. Ms. Wheeler has nothing to disclose. Miss Anderbery has nothing to disclose. Ms. Kempton has received personal compensation for serving as an employee of Sarepta Therapeutics. Ms. Kempton has stock in Sarepta Therapeutics. Ms. Clements has received personal compensation for serving as an employee of Sarepta Therapeutics . Ms. Clements has stock in Sarepta Therapeutics. Mrs. Adegboye has nothing to disclose. Dr. Haile has nothing to disclose. Ms. Peterson has nothing to disclose. Ms. Rodino-Klapac has received personal compensation for serving as an employee of Sarepta Therapeutics, Inc.. Ms. Rodino-Klapac has received stock or an ownership interest from Sarepta Therapeutics. Ms. Rodino-Klapac has received intellectual property interests from a discovery or technology relating to health care.

One-year Data from ENDEAVOR, a Phase 1b Trial of Delandistrogene Moxeparvovec (SRP-9001) in Patients with Duchenne Muscular Dystrophy (DMD) (S48.003)

One-year Data from ENDEAVOR, a Phase 1b Trial of Delandistrogene Moxeparvovec (SRP-9001) in Patients with Duchenne Muscular Dystrophy (DMD) (S48.003)

Long-term Safety and Efficacy in Patients with DMD 4 Years Post-Treatment with Delandistrogene Moxeparvovec (SRP-9001) in a Phase 1/2a Study (P3-8.006)

Long-term Safety and Efficacy in Patients with DMD 4 Years Post-Treatment with Delandistrogene Moxeparvovec (SRP-9001) in a Phase 1/2a Study (P3-8.006)

EMBARK, a Phase 3 Trial Evaluating Safety and Efficacy of Delandistrogene Moxeparvovec (SRP- 9001) in Duchenne Muscular Dystrophy (DMD): Study Design and Baseline Characteristics (P5-8.012)

EMBARK, a Phase 3 Trial Evaluating Safety and Efficacy of Delandistrogene Moxeparvovec (SRP- 9001) in Duchenne Muscular Dystrophy (DMD): Study Design and Baseline Characteristics (P5-8.012)

Analysis of Vector Shedding Following Treatment with Delandistrogene Moxeparvovec (SRP-9001), an Investigational rAAVrh74-Based Gene Therapy for Duchenne Muscular Dystrophy (DMD) (P5-8.013)

<h3>Objective:</h3> To evaluate extent and magnitude of vector shedding following delandistrogene moxeparvovec (SRP-9001) administration. <h3>Background:</h3> Delandistrogene moxeparvovec is an investigational gene transfer therapy developed to address the root cause of DMD through targeted skeletal and cardiac muscle expression of SRP-9001 dystrophin protein, which contains key functional domains of dystrophin. The hypothetical risk of seroconversion in naive individuals through exposure to vector shed from treated patients is a point to consider for healthcare providers and the Duchenne community. <h3>Design/Methods:</h3> We evaluated extent of vector shedding and clearance following a single administration of delandistrogene moxeparvovec (1.33×10¹⁴ vg/kg body weight) in ENDEAVOR (NCT04626674; Study 103; N=20), a Phase 1 study in patients with DMD. Delandistrogene moxeparvovec vector exposure in saliva, urine, and feces was quantified by droplet digital polymerase chain reaction. In a nonclinical study, we tested naive mice to determine risk of AAVrh74 seroconversion following mucosal vector exposure, with doses based on exposure levels (vector genome copies) demonstrated in nonclinical and clinical studies. Mice were exposed to AAVrh74.CMV.eGFP via optic exposure and intramuscularly. Antibody levels were measured by AAVrh74 ELISA at baseline and 4 weeks post-delivery. <h3>Results:</h3> Following treatment in ENDEAVOR, the percentage decrease in amount of vector shed was &gt;99% in saliva (n=12), urine (n=18), and feces (n=11) by Week 4. In mice, topical optical delivery of the AAVrh74 vector at relevant concentrations did not produce seropositivity or detectable vector genomes throughout tissues at doses based on clinical vector shedding levels. <h3>Conclusions:</h3> Clinical findings show that peak vector shedding occurs in the first few days after delandistrogene moxeparvovec administration and exponentially declines to insignificant levels by Week 4. In mice, seroconversion was not observed by relevant exposure route at relevant concentrations. Results suggest that the risk of seroconversion following exposure to vector shed by individuals treated with AAVrh74-based gene therapy may be very low. <b>Disclosure:</b> Jyoti Malhotra has nothing to disclose. Dr. Smith has received personal compensation for serving as an employee of Sarepta Therapeutics, Inc. Dr. Smith has stock in Sarepta Therapeutics. Sarah Lewis has received stock or an ownership interest from Sarepta. Mrs. Zhang has nothing to disclose. Mr. Asher has received personal compensation for serving as an employee of Sarepta Therapeutics. Mr. Asher has stock in Sarepta Therapeutics. Shufang Wang has received personal compensation for serving as an employee of Sarepta Therapeutics INC. Shufang Wang has received stock or an ownership interest from Sarepta Therapeutics INC. Mrs. East has received personal compensation for serving as an employee of Sarepta Therapeutics. Rachael Potter has received stock or an ownership interest from Sarepta Therapeutics. Ms. Rodino-Klapac has received personal compensation for serving as an employee of Sarepta Therapeutics, Inc.. Ms. Rodino-Klapac has received stock or an ownership interest from Sarepta Therapeutics. Ms. Rodino-Klapac has received intellectual property interests from a discovery or technology relating to health care.

Integrated Analyses of Data from Clinical Trials of Delandistrogene Moxeparvovec (SRP-9001) in Duchenne Muscular Dystrophy (DMD) (S48.006)

Integrated Analyses of Data from Clinical Trials of Delandistrogene Moxeparvovec (SRP-9001) in Duchenne Muscular Dystrophy (DMD) (S48.006)

424 Clinical Translational Approach to Targeted Therapy in SLC6A1-related Neurodevelopmental Disorder

OBJECTIVES/GOALS: SLC6A1-Related Neurodevelopmental Disorder (SLC6A1-NDD) is a leading genetic cause of epilepsy and autism. Haploinsufficiency of SLC6A1 leads to reduced uptake of GABA from the synaptic cleft, and increased extracellular GABA in mice. It is a candidate for gene transfer therapy, but translational read outs are needed. EEG is a promising biomarker. METHODS/STUDY POPULATION: The SLC6A1-NDD program includes a specialty clinic and prospective cohort study run in parallel with pre-clinical gene therapy development. Characterization and pre-clinical testing of a homozygous knock-out, heterozygous knock-out, and two humanized knock-in models are on-going, including EEG analyses before and after treatment. Patients with a confirmed diagnosis of SLC6A1-NDD are seen annually in a specialty clinic and a subset participate in the cohort study which collects standardized questionnaires, EEGs, and MR Spectroscopy to measure glutamate and GABA. Gene Therapy Program investigators meet weekly to discuss progress on pre-clinical and clinical trial readiness on SLC6A1-NDD and to align efforts on translational read outs, including EEG, in both humans and the pre-clinical models. RESULTS/ANTICIPATED RESULTS: We have enrolled the full cohort of 20 participants in the prospective SLC6A1-NDD cohort study. Preliminary results have shown that all but 1 individual has a history of developmental delay, and 8 of the 24 individuals in our clinical cohort had at least one episode of developmental regression. Over 90% have epilepsy, and 17/20 in the cohort study have intermittent rhythmic delta activity on EEG. The full knock out mice have behavioral and learning deficits and abnormal electrical brain activity on telemetry, including bursts of spike trains, analogous to epileptiform activity seen in humans. Next steps include quantitative analysis of both mouse and human EEG to develop a translational brain-based biomarker. We plan to assess delta power and investigate genotype-phenotype correlations in mice and humans. DISCUSSION/SIGNIFICANCE: With targeted therapies in development for SLC6A1-NDD, translational biomarkers that demonstrate engagement with the brain are critical. With clinical heterogeneity in SLC6A1-NDD, biomarkers can objectively capture change. Collaborative translational projects may improve efficiency in rare disease research to facilitate early phase trials.