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Background: The current standard of care for infantile-onset Pompe disease (IOPD), a severe form of acid α-glucosidase enzyme activity deficiency is: (1) detection by newborn screening, (2) early initiation of intravenous enzyme replacement therapy (ERT) using recombinant human acid alpha-glucosidase (rhGAA), with higher doses of rhGAA increasingly used to improve clinical outcomes, and (3) immune tolerization induction (ITI) using to prevent anti-rhGAA antibody formation, with methotrexate (MTX), rituximab, and IVIG used for patients who are cross-reactive immunologic material negative (CRIM-) and monotherapy with MTX used in patients who are cross-reactive immunologic material positive (CRIM+). Objectives/methods: A pilot study evaluates a dose-intensive therapy (DIT) using high-dose ERT (40 mg/kg/week) and more frequent exposure to ERT (i.e., 3 times weekly administration) to mitigate anti-rhGAA antibody formation, as an alternative to the standard therapeutic approach for IOPD. Results: In the first patient, DIT resulted in rapid normalization of the following: (1) bi-ventricular hypertrophy, (2) urine HEX-4, (3) CK, (4) liver transaminases. At 7 years of age, the patient continues the DIT regimen. To date, all pediatric developmental milestones have been met on time, anti-rhGAA antibodies have been negative and the patient is able to attend school and maintain normal activities of daily living. Conclusions: Over a 7-year period, DIT for CRIM-positive IOPD was well tolerated in the first patient treated. Excellent clinical outcomes were achieved, and anti-rhGAA antibodies levels were consistently undetectable. Assessments of more patients, that includes patients with CRIM-, as well as CRIM+ IOPD, will determine if this approach consistently achieves improved clinical outcomes and immune tolerization.

Background: Lysosomal diseases are a group of over 70 rare genetic conditions in which a protein deficiency (most often an enzyme deficiency) leads to multi-system disease. Current therapies for lysosomal diseases are limited in their ability to treat certain tissues that are major contributors to morbidity and mortality, such as the central nervous system (CNS) and cardiac valves. For this study, the lysosomal disease mucopolysaccharidosis type I (MPS I) was selected as the disease model. In MPS I, mutations in the IDUA gene cause a deficiency of the α-L-iduronidase (IDUA) enzyme activity, leading to disease pathology in tissues throughout the body, including the CNS and cardiac valves. Current therapies have been unable to prevent neurodevelopmental deficits and cardiac valvular disease in patients with MPS I. This study aimed to evaluate the delivery of IDUA enzyme, via a novel gene therapy construct, to target tissues. Methods: MPS I mice were hydrodynamically injected through the tail vein with plasmids containing either a codon-optimized cDNA encoding the wild-type IDUA protein or one of four modified IDUAs under the control of the liver-specific human α1-antitrypsin (hAAT) promoter. Two modified IDUAs contained a ligand for the CB1 receptor, which is a highly expressed receptor in the CNS. Iduronidase activity levels were measured in the tissues and plasma using an enzyme activity assay. Results: The modified IDUAs did not appear to have improved activity levels in the brain compared with the unmodified IDUA. However, one modified IDUA exhibited higher activity levels than the unmodified IDUA in the heart (p = 0.0211). This modified iduronidase (LT-IDUA) contained a sequence for a six amino acid peptide termed LT. LT-IDUA was further characterized using a noncompartmental pharmacokinetic approach that directly analyzed enzyme activity levels after gene delivery. LT-IDUA had a 2-fold higher area under the curve (AUC) than the unmodified IDUA (p = 0.0034) when AUC was estimated using enzyme activity levels in the plasma. Conclusion: The addition of a six amino acid peptide improved iduronidase's activity levels in the heart and plasma. The short length of this LT peptide facilitates its use as fusion enzymes encoded as gene therapy or administered as enzyme replacement therapy. More broadly, the LT peptide may aid in developing therapies for numerous lysosomal diseases.

Elevated serum chitotriosidase (CHITO) is an indication of macrophage activation, and its capacity have been explored as a marker of inflammation in a number of disease states. For over a decade, CHITO plasma levels have been used by clinicians as a biomarker of inflammation in the lysosomal disease, Gaucher disease, including monitoring response to therapies in patients with Gaucher disease type I. Although it is becoming increasingly recognized that inflammation is a prominent component of many lysosomal diseases, the relation of CHITO levels to disease burden has not been well-characterized in the large majority of lysosomal diseases. Moreover, the role of CHITO in lysosomal diseases that affect the central nervous system (CNS) has not been systematically studied. In this study, one hundred and thirty-four specimens of CSF and serum were collected from 34 patients with lysosomal diseases affecting the CNS. This study included patients with GM1-gangliosidosis, GM2-gangliosidosis, mucopolysaccharidoses (MPS), multiple sulfatase deficiency and Gaucher disease. CHITO levels in the CSF were significantly higher in patients with more rapidly progressing severe neurological impairment: GM1-gangliosidosis vs MPS (p

GM1-gangliosidosis is a lysosomal disease resulting from a deficiency in the hydrolase β-galactosidase (β-gal) and subsequent accumulation of gangliosides, primarily in neuronal tissue, leading to progressive neurological deterioration and eventually early death. Lysosomal diseases with neurological involvement have limited non-invasive therapies due to the inability of lysosomal enzymes to cross the blood-brain barrier (BBB). A novel fusion enzyme, labeled mTfR-GLB1, was designed to act as a ferry across the BBB by fusing β-gal to the mouse monoclonal antibody against the mouse transferrin receptor and tested in a murine model of GM1-gangliosidosis (β-gal−/−). Twelve hours following a single intravenous dose of mTfR-GLB1 (5.0 mg/kg) into adult β-gal−/− mice showed clearance of enzyme activity in the plasma and an increase in β-gal enzyme activity in the liver and spleen. Long-term efficacy of mTfR-GLB1 was assessed by treating β-gal−/− mice intravenously twice a week with a low (2.5 mg/kg) or high (5.0 mg/kg) dose of mTfR-GLB1 for 17 weeks. Long-term studies showed high dose mice gained weight normally compared to vehicle-treated β-gal−/− mice, which are significantly heavier than heterozygous controls. Behavioral assessment at six months of age using the pole test showed β-gal−/− mice treated with mTfR-GLB1 had improved motor function. Biochemical analysis showed an increase in β-gal enzyme activity in the high dose group from negligible levels to 20% and 11% of heterozygous levels in the liver and spleen, respectively. Together, these data show that mTfR-GLB1 is a catalytically active β-gal fusion enzyme in vivo that is readily taken up into tissues.Despite these indications of bioactivity, behavior tests other than the pole test, including the Barnes maze, inverted screen, and accelerating rotarod, showed limited or no improvement of treated mice compared to β-gal−/− mice receiving vehicle only. Further, administration of mTfR-GLB1 was insufficient to create measurable increases in β-gal enzyme activity in the brain or reduce ganglioside content (biochemically and morphologically).

Gaucher disease is an autosomal recessive metabolic disorder caused by mutations in GBA1, which encodes for the lysosomal hydrolase enzyme, β-glucocerebrosidase. The resulting misfolded protein can trigger endoplasmic reticulum stress and an unfolded protein response within the affected cells. The enzyme deficiency leads to accumulation of its substrates, glucosylceramide and glucosylsphingosine, within macrophage lysosomes and with prominent disease manifestations in macrophage rich tissues. Resultant lysosomal pathology and impaired autophagy leads to redox imbalance, mitochondrial dysfunction and intracellular oxidative stress. Here we have systematically examined a role for oxidative stress in individuals affected by Gaucher disease. We compared multiple oxidative stress biomarkers in plasma and red blood cell samples from patients who are currently untreated, with those who are stable on standard-of-care therapy, and with healthy controls. We found significant differences in key oxidative stress biomarkers in untreated patients compared to healthy control. In treated patients, results generally fell between the controls and the untreated patients. Interestingly, even asymptomatic and minimally symptomatic untreated patients had evidence of significant systemic oxidative stress. We conclude that underlying oxidative stress may contribute to Gaucher disease pathophysiology including long-term adverse outcomes such as Parkinsonism and malignancies. Therapies targeting oxidative stress may prove useful as adjuvant treatments for Gaucher disease and other lysosomal storage disorders.

Background: The gangliosidoses are rare inherited diseases that result in pathologic accumulation of gangliosides in the central nervous system and other tissues, leading to severe and progressive neurological impairment and early death in the childhood forms. No treatments are currently approved for the gangliosidoses, and development of treatments is impaired by limited understanding of the natural history of these diseases. Objective: The objective of this study is to improve understanding of the juvenile gangliosidoses phenotypes and the late-infantile phenotypic subtype. Methods: Through a prospective natural history study of subjects with juvenile GM1- and GM2-gangliosidosis, a timeline of clinical changes was developed for the classic juvenile phenotypes and the late-infantile phenotypes and results of serial neurodevelopmental testing was analyzed. Results: Several candidate ‘outcome measures’ were identified: changes in ambulation and verbalization skills, the communication domain from neurodevelopmental testing and the caregiver-reported socialization domain. Conclusions: The most common symptoms leading caregivers to seek a genetic diagnosis were changes in ambulation and verbalization.

Gangliosidoses, including GM1-gangliosidosis and GM2-gangliosidosis (Tay-Sachs disease and Sandhoff disease), are lysosomal disorders resulting from enzyme deficiencies and accumulation of gangliosides. Phenotypes of gangliosidoses range from infantile, late-infantile, juvenile, and to the adult form. The genotype-phenotype correlation is essential for prognosis and clinical care planning for patients with a gangliosidosis condition. Previously, we have developed a method to establish the genotype-phenotype correlation of another lysosomal disease, mucopolysaccharidosis type I, with in silico tools. This same method was applied to analyze the genotype and phenotype of 38 patients diagnosed with a gangliosidosis disease in the United States. Out of 40 mutations identified, 3 were novel, including p.Tyr192His and p.Phe556Ser of the GLB1 gene and p.Gly461Val of the HEXA gene. Furthermore, the mutant protein structure of all missense mutations was constructed by homology modeling. A systemic structural analysis of these models revealed the specific mechanisms of how each mutation may lead to the disease. In summary, the method developed in this study holds promise as a tool that can be broadly applicable to other lysosomal diseases and monogenic diseases. Keywords: Genotype-phenotype correlation, In silico, Gangliosidosis, Disease subtype, Lysosomal disorder

Background: There are currently ten intravenous enzyme replacement therapy (ERT) products available for the treatment of eight different lysosomal diseases (LD) in the USA. Additional ERT products are in clinical trials. The most common ERT adverse events are infusion reactions (IR). While IR are often defined as hypersensitivity or anaphylactoid reactions occurring concurrently with (i.e., during) infusion administration (CIR), there exists the potential for delayed infusion reactions (DIR), which present after completion of infusion administration., Hypothesis: Concurrent infusion reactions (CIR) are not the only infusion reactions associated with enzyme therapy., Methods: This study evaluated the occurrence of infusion reactions in 46 patients with LD who had received ERT for a minimum of 2 years. Infusion reactions were evaluated according to symptoms, time of onset, and duration of reactions. The frequency of infusion reactions with each ERT product was compared to that reported in the FDA-approved product package insert., Results and Conclusions: In this study, DIR were observed and occurred as often as CIR in the study population, despite not being characterized or reported in most ERT product package inserts. Effective methods for managing DIR and CIR differed, thus emphasizing the importance of monitoring for both types of infusion reactions in order to optimize outcomes for patients using ERT.