Rare lysosomal disease registries: lessons learned over three decades of real-world evidence

Quantitative Systems Pharmacology-Based Digital Twins Approach Supplements Clinical Trial Data for Enzyme Replacement Therapies in Pompe Disease

Pompe disease is a rare, progressive neuromuscular disease caused by deficient lysosomal glycogen degradation, and includes both late-onset (LOPD) and severe infantile-onset (IOPD) phenotypes. Due to very small patient numbers in IOPD and the high phenotypic heterogeneity observed in this population, a quantitative systems pharmacology (QSP)-based "digital twin" approach was developed to perform an in silico comparison of the efficacy of avalglucosidase alfa vs. the standard of care, in a virtual population of IOPD patients. A QSP model was developed that represents key elements of Pompe disease pathophysiology, including tissue glycogen accumulation and the elevation of the biomarker urine Hex4 in both LOPD and IOPD patients. In this approach, the QSP model was used to generate digital twins of each IOPD patient enrolled in the avalglucosidase alfa clinical program, considering their respective disease burden, demographics, and treatment history. This virtual cohort supplemented clinical observations by simulating and comparing tissue glycogen and urine Hex4 following avalglucosidase alfa treatment vs. the standard of care. The digital twin analysis supports the interpretation that the enhanced reduction in urine Hex4 observed following avalglucosidase alfa treatment is attributable to greater tissue glycogen clearance. Overall, this study provides mechanism-based insight into avalglucosidase alfa efficacy across the phenotypic spectrum of Pompe disease and demonstrates the value of applying a QSP-based digital twin analysis to support rare disease drug development.

Assessment of genes involved in lysosomal diseases using the ClinGen clinical validity framework

Lysosomal diseases (LDs) are a heterogeneous group of rare genetic disorders that result in impaired lysosomal function, leading to progressive multiorgan system dysfunction. Accurate diagnosis is paramount to initiating targeted therapies early in the disease process in addition to providing prognostic information and appropriate support for families. In recent years, genomic sequencing technologies have become the first-line approach in the diagnosis of LDs. Understanding the clinical validity of the role of a gene in a disease is critical for the development of genomic technologies, such as which genes to include on next generation sequencing panels, and the interpretation of results from exome and genome sequencing. To this aim, the ClinGen Lysosomal Diseases Gene Curation Expert Panel utilized a semi-quantitative framework incorporating genetic and experimental evidence to assess the clinical validity of the 56 LD-associated genes on the Lysosomal Disease Network's list. Here, we describe the results, and the key themes and challenges encountered.

Long-term effectiveness of eliglustat treatment: A real-world analysis from the International Collaborative Gaucher Group Gaucher Registry

Gaucher disease type 1 (GD1) is known for phenotypic heterogeneity and varied natural history. Registrational clinical trials enrolled narrowly defined phenotypes, but greater diversity is encountered in clinical practice. We report real-world outcomes with long-term eliglustat treatment in adults with GD1 in the International Collaborative Gaucher Group Gaucher Registry. Among 5985 GD1 patients in the Registry as of January 6, 2023, 872 started eliglustat at ≥18 years old; of these, 469 met inclusion criteria. We compared clinical parameters at eliglustat initiation (i.e., baseline) and follow-up in treatment-naïve patients and used linear mixed models to estimate annual change from baseline in parameters among patients who switched to eliglustat after ≥1 year on enzyme replacement therapy. Over 4 years of follow-up in non-splenectomized treatment-naïve patients, hemoglobin and platelet count increased, liver and spleen volume decreased, and total lumbar spine bone mineral density (BMD) Z-score decreased slightly. Among non-splenectomized switch patients, on average, hemoglobin decreased -0.030 (95% CI: -0.053, -0.008) g/dL (N = 272) and platelet count increased 2.229 (95% CI: 0.751, 3.706) × 103/mm3 (N = 262) annually up to 10 years; liver volume decreased (-0.009 [95% CI: -0.015, -0.003] MN) (N = 102) and spleen volume remained stable (-0.070 [95% CI: -0.150, 0.010] MN) (N = 106) annually up to 7 years; and total lumbar spine BMD Z-score increased 0.041 (95% CI: 0.015, 0.066) (N = 183) annually up to 8 years. Among splenectomized switch patients, clinical parameters were stable over time. These long-term, real-world outcomes are consistent with the eliglustat clinical trials and emerging real-world experience across the GD phenotypic spectrum.

A rare partnership: patient community and industry collaboration to shape the impact of real-world evidence on the rare disease ecosystem

People with rare lysosomal storage diseases face challenges in their care that arise from disease complexity and heterogeneity, compounded by many healthcare professionals being unfamiliar with these diseases. These challenges can result in long diagnostic journeys and inadequate care. Over 30 years ago, the Rare Disease Registries for Gaucher, Fabry, Mucopolysaccharidosis type I and Pompe diseases were established to address knowledge gaps in disease natural history, clinical manifestations of disease and treatment outcomes. Evidence generated from the real-world data collected in these registries supports multiple stakeholders, including patients, healthcare providers, drug developers, researchers and regulators. To maximise the impact of real-world evidence from these registries, engagement and collaboration with the patient communities is essential. To this end, the Rare Disease Registries Patient Council was established in 2019 as a partnership between the Rare Disease Registries and global and local patient advocacy groups to share perspectives on how registry data are used and disseminated. The Patient Council has resulted in a number of patient initiatives including patient representation at Rare Disease Registries advisory boards; development of plain language summaries of registry publications to increase availability of real-world evidence to patient communities; and implementation of digital innovations such as electronic patient-reported outcomes, and patient-facing registry reports and electronic consent (in development), all to enhance patient engagement. The Patient Council is building on the foundations of industry-patient advocacy group collaboration to fully integrate patient communities in decision-making and co-create solutions for the rare disease community.

Hypomyelinated vps16 Mutant Zebrafish Exhibit Systemic and Neurodevelopmental Pathologies

Homotypic Fusion and Protein Sorting (HOPS) and Class C-core Vacuole/Endosome Tethering (CORVET) complexes regulate the correct fusion of endolysosomal bodies. Mutations in core proteins (VPS11, VPS16, VPS18, and VPS33) have been linked with multiple neurological disorders, including mucopolysaccharidosis (MPS), genetic leukoencephalopathy (gLE), and dystonia. Mutations in human Vacuolar Protein Sorting 16 (VPS16) have been associated with MPS and dystonia. In this study, we generated and characterized a zebrafish vps16(-/-) mutant line using immunohistochemical and behavioral approaches. The loss of Vps16 function caused multiple systemic defects, hypomyelination, and increased neuronal cell death. Behavioral analysis showed a progressive loss of visuomotor response and reduced motor response and habituation to acoustic/tap stimuli in mutants. Finally, using a novel multiple-round acoustic/tap stimuli test, mutants showed intermediate memory deficits. Together, these data demonstrate that zebrafish vps16(-/-) mutants show systemic defects, neurological and motor system pathologies, and cognitive impairment. This is the first study to report behavior abnormalities and memory deficiencies in a zebrafish vps16(-/-) mutant line. Finally, we conclude that the deficits observed in vps16(-/-) zebrafish mutants do not mimic pathologies associated with dystonia, but more align to abnormalities associated with MPS and gLE.

Anderson-Fabry disease management: role of the cardiologist

Anderson-Fabry disease (AFD) is a lysosomal storage disorder characterized by glycolipid accumulation in cardiac cells, associated with a peculiar form of hypertrophic cardiomyopathy (HCM). Up to 1% of patients with a diagnosis of HCM indeed have AFD. With the availability of targeted therapies for sarcomeric HCM and its genocopies, a timely differential diagnosis is essential. Specifically, the therapeutic landscape for AFD is rapidly evolving and offers increasingly effective, disease-modifying treatment options. However, diagnosing AFD may be difficult, particularly in the non-classic phenotype with prominent or isolated cardiac involvement and no systemic red flags. For many AFD patients, the clinical journey from initial clinical manifestations to diagnosis and appropriate treatment remains challenging, due to late recognition or utter neglect. Consequently, late initiation of treatment results in an exacerbation of cardiac involvement, representing the main cause of morbidity and mortality, irrespective of gender. Optimal management of AFD patients requires a dedicated multidisciplinary team, in which the cardiologist plays a decisive role, ranging from the differential diagnosis to the prevention of complications and the evaluation of timing for disease-specific therapies. The present review aims to redefine the role of cardiologists across the main decision nodes in contemporary AFD clinical care and drug discovery.

The international cooperative Gaucher group (ICCG) Gaucher registry

Gaucher disease GD), is a rare lysosomal storage disorder caused by deficient acid β-glucosylceramidase activity and accumulation of glucosylceramide in tissue macrophages. With the 1991 advent of alglucerase enzyme replenishment therapy (ERT), the manufacturer (Genzyme Corporation) created the ICGG Gaucher Registry to collect longitudinal observational "real word" information about GD world-wide in heterogeneous patient populations, to annotate phenotypes and genotypes that define the natural history of GD in untreated patients, and to document and analyze treatment outcomes for alglucerase and any other future treatments. For 32 years, the ICGG Gaucher Registry has functioned as an educational tool for patients, clinicians, and other stakeholders to increase scientific knowledge of GD, to provide practical management guidance, and to positively impact patient care. This paper illustrates how an industry sponsored registry guided by a company independent scientific advisory board has successfully addressed its mission and evolved in step with technologic and scientific advances.

Global reach of over 20 years of experience in the patient-centered Fabry Registry: Advancement of Fabry disease expertise and dissemination of real-world evidence to the Fabry community

Fabry disease (FD, α-galactosidase A deficiency) is a rare, progressive, complex lysosomal storage disorder affecting multiple organ systems with a diverse spectrum of clinical phenotypes, particularly among female patients. Knowledge of its clinical course was still limited in 2001 when FD-specific therapies first became available and the Fabry Registry (NCT00196742; sponsor: Sanofi) was initiated as a global observational study. The Fabry Registry has now been operational for over 20 years, overseen by expert Boards of Advisors, and has collected real-world demographic and longitudinal clinical data from more than 8000 individuals with FD. Leveraging the accumulating evidence base, multidisciplinary collaborations have resulted in the creation of 32 peer-reviewed scientific publications, which have contributed to the greatly expanded knowledge on the onset and progression of FD, its clinical management, the role of sex and genetics, the outcomes of enzyme replacement therapy with agalsidase beta, and prognostic factors. We review how the Fabry Registry has evolved from its inception to become the largest global source of real-world FD patient data, and how the generated scientific evidence has helped to better inform the medical community, individuals living with FD, patient organizations, and other stakeholders. The patient-centered Fabry Registry fosters collaborative research partnerships with the overarching goal of optimizing the clinical management of patients with FD and is well positioned to add to its past achievements.

Metabolic Cardiomyopathies and Cardiac Defects in Inherited Disorders of Carbohydrate Metabolism: A Systematic Review

Heart failure (HF) is a progressive chronic disease that remains a primary cause of death worldwide, affecting over 64 million patients. HF can be caused by cardiomyopathies and congenital cardiac defects with monogenic etiology. The number of genes and monogenic disorders linked to development of cardiac defects is constantly growing and includes inherited metabolic disorders (IMDs). Several IMDs affecting various metabolic pathways have been reported presenting cardiomyopathies and cardiac defects. Considering the pivotal role of sugar metabolism in cardiac tissue, including energy production, nucleic acid synthesis and glycosylation, it is not surprising that an increasing number of IMDs linked to carbohydrate metabolism are described with cardiac manifestations. In this systematic review, we offer a comprehensive overview of IMDs linked to carbohydrate metabolism presenting that present with cardiomyopathies, arrhythmogenic disorders and/or structural cardiac defects. We identified 58 IMDs presenting with cardiac complications: 3 defects of sugar/sugar-linked transporters (GLUT3, GLUT10, THTR1); 2 disorders of the pentose phosphate pathway (G6PDH, TALDO); 9 diseases of glycogen metabolism (GAA, GBE1, GDE, GYG1, GYS1, LAMP2, RBCK1, PRKAG2, G6PT1); 29 congenital disorders of glycosylation (ALG3, ALG6, ALG9, ALG12, ATP6V1A, ATP6V1E1, B3GALTL, B3GAT3, COG1, COG7, DOLK, DPM3, FKRP, FKTN, GMPPB, MPDU1, NPL, PGM1, PIGA, PIGL, PIGN, PIGO, PIGT, PIGV, PMM2, POMT1, POMT2, SRD5A3, XYLT2); 15 carbohydrate-linked lysosomal storage diseases (CTSA, GBA1, GLA, GLB1, HEXB, IDUA, IDS, SGSH, NAGLU, HGSNAT, GNS, GALNS, ARSB, GUSB, ARSK). With this systematic review we aim to raise awareness about the cardiac presentations in carbohydrate-linked IMDs and draw attention to carbohydrate-linked pathogenic mechanisms that may underlie cardiac complications.