Neuronopathic Gaucher disease: Rare in the West, common in the East.

Gaucher disease (GD) stands as one of the most prevalent lysosomal disorders, yet neuronopathic GD (nGD) is an uncommon subset characterized by a wide array of clinical manifestations that complicate diagnosis, particularly when neurological symptoms are understated. nGD may manifest as the acute neuronopathic type, or GD type 2 (GD2), either prenatally or within the first weeks to months of life, whereas GD type 3 (GD3) symptoms may emerge at any point during childhood or occasionally in adolescence. The clinical presentation encompasses severe systemic involvement to mild visceral disease, often coupled with a spectrum of progressive neurological signs and symptoms such as cognitive impairment, ataxia, seizures, myoclonus, varying degrees of brainstem dysfunction presenting with stridor, apneic episodes, and/or impaired swallowing. This manuscript aims to provide a comprehensive review of the incidence, distinctive presentations, and diverse clinical phenotypes of nGD across various countries and regions. It will explore the natural history of the neurodegenerative process in GD, shedding light on its various manifestations during infancy and childhood, and offer insights into the diagnostic journey, the challenges faced in the clinical management, and current and investigative therapeutic approaches for GD's neurological variants.

The Expression and Secretion Profile of TRAP5 Isoforms in Gaucher Disease.

BACKGROUND: Gaucher disease (GD) is caused by glucocerebrosidase (GCase) enzyme deficiency, leading to glycosylceramide (Gb-1) and glucosylsphingosine (Lyso-Gb-1) accumulation. The pathological hallmark for GD is an accumulation of large macrophages called Gaucher cells (GCs) in the liver, spleen, and bone marrow, which are associated with chronic organ enlargement, bone manifestations, and inflammation. Tartrate-resistant acid phosphatase type 5 (TRAP5 protein, ACP5 gene) has long been a nonspecific biomarker of macrophage/GCs activation; however, the discovery of two isoforms of TRAP5 has expanded its significance. The discovery of TRAP5's two isoforms revealed that it is more than just a biomarker of macrophage activity. While TRAP5a is highly expressed in macrophages, TRAP5b is secreted by osteoclasts. Recently, we have shown that the elevation of TRAP5b in plasma is associated with osteoporosis in GD. However, the role of TRAP isoforms in GD and how the accumulation of Gb-1 and Lyso-Gb-1 affects TRAP expression is unknown. METHODS: 39 patients with GD were categorized into cohorts based on bone mineral density (BMD). TRAP5a and TRAP5b plasma levels were quantified by ELISA. ACP5 mRNA was estimated using RT-PCR. RESULTS: An increase in TRAP5b was associated with reduced BMD and correlated with Lyso-Gb-1 and immune activator chemokine ligand 18 (CCL18). In contrast, the elevation of TRAP5a correlated with chitotriosidase activity in GD. Lyso-Gb-1 and plasma seemed to influence the expression of ACP5 in macrophages. CONCLUSIONS: As an early indicator of BMD alteration, measurement of circulating TRAP5b is a valuable tool for assessing osteopenia-osteoporosis in GD, while TRAP5a serves as a biomarker of macrophage activation in GD. Understanding the distinct expression pattern of TRAP5 isoforms offers valuable insight into both bone disease and the broader implications for immune system activation in GD.

Long-term safety and efficacy of cipaglucosidase alfa plus miglustat in individuals living with Pompe disease: an open-label phase I/II study (ATB200-02).

Cipaglucosidase alfa plus miglustat (cipa + mig) is a novel, two-component therapy for Pompe disease. We report data from the Phase I/II ATB200-02 study for up to 48 months of treatment. Four adult cohorts, including one non-ambulatory ERT-experienced (n = 6) and three ambulatory cohorts, (two enzyme replacement therapy [ERT]-experienced cohorts [2-6 years (n = 11) and ≥ 7 years (n = 6)]), one ERT-naïve cohort (n = 6), received 20 mg/kg intravenous-infused cipa plus 260 mg oral mig biweekly. Change from baseline (CFBL) for multiple efficacy endpoints at 12, 24, 36, and 48 months, pharmacodynamics, pharmacokinetics, safety, and immunogenicity data were assessed. Six-minute walking distance (% predicted) improved at 12, 24, 36, and 48 months: pooled ambulatory ERT-experienced cohorts, mean(± standard deviation [SD]) CFBL: 6.1(± 7.84), n = 16; 5.4(± 10.56), n = 13; 3.4(± 14.66), n = 12; 5.9(± 17.36), n = 9, respectively; ERT-naïve cohort: 10.7(± 3.93), n = 6; 11.0(± 5.06), n = 6; 9.0(± 7.98), n = 5; 11.7(± 7.69), n = 4, respectively. Percent predicted forced vital capacity was generally stable in ERT-experienced cohorts, mean(± SD) CFBL - 1.2(± 5.95), n = 16; 1.0(± 7.96), n = 13; - 0.3(± 6.68), n = 10; 1.0(± 6.42), n = 6, respectively, and improved in the ERT-naïve cohort: 3.2(± 8.42), n = 6; 4.7(± 5.09), n = 6; 6.2(± 3.35), n = 5; 8.3(± 4.50), n = 4, respectively. Over 48 months, CK and Hex4 biomarkers improved in ambulatory cohorts. Overall, cipa + mig was well tolerated with a safety profile like alglucosidase alfa. ATB200-02 results show the potential benefits of cipa + mig as a long-term treatment option for Pompe disease. Trial registration number: NCT02675465 January 26, 2016.

Head-to-head trial of pegunigalsidase alfa versus agalsidase beta in patients with Fabry disease and deteriorating renal function: results from the 2-year randomised phase III BALANCE study.

BACKGROUND: Pegunigalsidase alfa is a PEGylated α-galactosidase A enzyme replacement therapy. BALANCE (NCT02795676) assessed non-inferiority of pegunigalsidase alfa versus agalsidase beta in adults with Fabry disease with an annualised estimated glomerular filtration rate (eGFR) slope more negative than -2 mL/min/1.73 m2/year who had received agalsidase beta for ≥1 year. METHODS: Patients were randomly assigned 2:1 to receive 1 mg/kg pegunigalsidase alfa or agalsidase beta every 2 weeks for 2 years. The primary efficacy analysis assessed non-inferiority based on median annualised eGFR slope differences between treatment arms. RESULTS: Seventy-seven patients received either pegunigalsidase alfa (n=52) or agalsidase beta (n=25). At baseline, mean (range) age was 44 (18-60) years, 47 (61%) patients were male, median eGFR was 74.5 mL/min/1.73 m2 and median (range) eGFR slope was -7.3 (-30.5, 6.3) mL/min/1.73 m2/year. At 2 years, the difference between median eGFR slopes was -0.36 mL/min/1.73 m2/year, meeting the prespecified non-inferiority margin. Minimal changes were observed in lyso-Gb3 concentrations in both treatment arms at 2 years. Proportions of patients experiencing treatment-related adverse events and mild or moderate infusion-related reactions were similar in both groups, yet exposure-adjusted rates were 3.6-fold and 7.8-fold higher, respectively, with agalsidase beta than pegunigalsidase alfa. At the end of the study, neutralising antibodies were detected in 7 out of 47 (15%) pegunigalsidase alfa-treated patients and 6 out of 23 (26%) agalsidase beta-treated patients. There were no deaths. CONCLUSIONS: Based on rate of eGFR decline over 2 years, pegunigalsidase alfa was non-inferior to agalsidase beta. Pegunigalsidase alfa had lower rates of treatment-emergent adverse events and mild or moderate infusion-related reactions. TRIAL REGISTRATION NUMBER: NCT02795676.

Fabry disease biomarkers in patients switched from enzyme-replacement therapy to migalastat oral chaperone therapy.

Background: A biomarker profile was evaluated longitudinally in patients with Fabry disease switched from enzyme-replacement therapy (ERT) to migalastat. Methods: 16 Gb3 isoforms and eight lyso-Gb3 analogues were analyzed in plasma and urine by LC-MS/MS at baseline and at three different time points in naive participants and participants switching from either agalsidase α or ß to migalastat. Results: 29 adult participants were recruited internationally (seven centers). The Mainz Severity Score Index and mean biomarker levels remained stable (p ≥ 0.05) over a minimum of 12 months compared with baseline following the treatment switch. Conclusion: In this cohort of patients with Fabry disease with amenable mutations, in the short term, a switch from ERT to migalastat did not have a marked effect on the average biomarker profile.

Biofabrication of anin-vitrobone model for Gaucher disease.

Gaucher disease (GD), the most prevalent lysosomal disorder, is caused byGBA1gene mutations, leading to deficiency of glucocerebrosidase, and accumulation of glycosphingolipids in cells of the mononuclear phagocyte system. While skeletal diseases are the leading cause of morbidity and reduced quality of life in GD, the pathophysiology of bone involvement is not yet fully understood, partly due to lack of relevant human model systems. In this work, we present the first 3D human model of GD using aspiration-assisted freeform bioprinting, which enables a platform tool with a potential for decoding the cellular basis of the developmental bone abnormalities in GD. In this regard, human bone marrow-derived mesenchymal stem cells (obtained commercially) and peripheral blood mononuclear cells derived from a cohort of GD patients, at different severities, were co-cultured to form spheroids and differentiated into osteoblast and osteoclast lineages, respectively. Co-differentiated spheroids were then 3D bioprinted into rectangular tissue patches as a bone tissue model for GD. The results revealed positive alkaline phosphatase (ALP) and tartrate-resistant ALP activities, with multi-nucleated cells demonstrating the efficacy of the model, corroborating with gene expression studies. There were no significant changes in differentiation to osteogenic cells but pronounced morphological deformities in spheroid formation, more evident in the 'severe' cohort, were observed. Overall, the presented GD model has the potential to be adapted to personalized medicine not only for understanding the GD pathophysiology but also for personalized drug screening and development.

Circulated TGF-ß1 and VEGF-A as Biomarkers for Fabry Disease-Associated Cardiomyopathy.

Fabry disease (FD) is a lysosomal disorder caused by α-galactosidase A deficiency, resulting in the accumulation of globotriaosylceramide (Gb-3) and its metabolite globotriaosylsphingosine (Lyso-Gb-3). Cardiovascular complications and hypertrophic cardiomyopathy (HCM) are the most frequent manifestations of FD. While an echocardiogram and cardiac MRI are clinical tools to assess cardiac involvement, hypertrophic pattern variations and fibrosis make it crucial to identify biomarkers to predict early cardiac outcomes. This study aims to investigate potential biomarkers associated with HCM in FD: transforming growth factor-ß1 (TGF-ß1), TGF-ß active form (a-TGF-ß), vascular endothelial growth factor (VEGF-A), and fibroblast growth factor (FGF2) in 45 patients with FD, categorized into cohorts based on the HCM severity. TGF-ß1, a-TGF-ß, FGF2, and VEGF-A were elevated in FD. While the association of TGF-ß1 with HCM was not gender-related, VEGF was elevated in males with FD and HCM. Female patients with abnormal electrocardiograms but without overt HCM also have elevated TGF-ß1. Lyso-Gb3 is correlated with TGF-ß1, VEGF-A, and a-TGF-ß1. Elevation of TGF-ß1 provides evidence of the chronic inflammatory state as a cause of myocardial fibrosis in FD patients; thus, it is a potential marker of early cardiac fibrosis detected even prior to hypertrophy. TGF-ß1 and VEGF biomarkers may be prognostic indicators of adverse cardiovascular events in FD.

Long-term safety and efficacy of pegunigalsidase alfa: A multicenter 6-year study in adult patients with Fabry disease.

PURPOSE: Fabry disease (FD) is a rare lysosomal storage disorder caused by pathogenic variants in the GLA gene encoding α-galactosidase (α-Gal)-A. We evaluated long-term safety/efficacy of pegunigalsidase alfa, a novel PEGylated α-Gal-A enzyme replacement therapy (ERT) now approved for FD. METHODS: In a phase-1/2 dose-ranging study, 15 ERT-naive adults with FD completed 12 months of pegunigalsidase alfa and enrolled in this 60-month open-label extension of 1 mg/kg pegunigalsidase alfa infusions every 2 weeks. RESULTS: Fifteen patients enrolled (8 males; 7 females); 10 completed ≥48 months (60 months total treatment), and 2 completed 60 months (72 months total treatment). During treatment, most treatment-emergent adverse events were mild/moderate in severity and all infusion-related reactions were mild/moderate in severity. Four patients were transiently positive for anti-pegunigalsidase alfa IgG. Patients showed continuous reduction in plasma lyso-Gb3 concentrations with mean (standard error) reduction of 76.1 [25.1] ng/mL from baseline to month 24. At 60 months, the estimated glomerular filtration rate slope was comparable to that observed in patients treated with other ERTs. Cardiac function assessments revealed stability; no cardiac fibrosis was observed. CONCLUSION: In this first long-term assessment of pegunigalsidase alfa administration in patients with FD, we found favorable safety/efficacy. Our data suggest long-term continuous benefits of pegunigalsidase alfa treatment in adults with FD.

Reply to Mistry et al. The Two Substrate Reduction Therapies for Type 1 Gaucher Disease Are Not Equivalent. Comment on "Hughes et al. Switching between Enzyme Replacement Therapies and Substrate Reduction Therapies in Patients with Gaucher Disease: Data from the Gaucher Outcome Survey (GOS). J. Clin. Med. 2022, 11, 5158".

Thank you for allowing us the opportunity to respond to the commentary from Mistry and colleagues (Comment: The two substrate reduction therapies for type 1 Gaucher disease are not equivalent) [...].

The D409H variant in GBA1: Challenges in predicting the Gaucher phenotype in the newborn screening era.

Gaucher disease (GD) is an autosomal recessive disorder resulting from glucocerebrosidase deficiency due to pathologic variants in GBA1. While clinically heterogeneous, GD encompasses three types, non-neuronopathic (GD1), acute neuronopathic (GD2), and chronic neuronopathic (GD3). Newborn screening (NBS), which has made remarkable inroads in detecting certain diseases before detrimental health consequences and fatality ensues, is now being piloted for GD in several states and countries. Early on, clinical features of GD2 can overlap with GD3; hence, predicting outcome is challenging. As NBS for GD becomes more available, the increased detection of GD in neonates is inevitable. As a result, health care providers and families will be faced with uncertainty with respect to clinical management. Since more severe GBA1 variants are generally associated with neuronopathic GD, there has been an increased dependence on genotypic information. We present an infant detected by NBS with genotype D409H(p.Asp448His)/RecNciI (p.Leu483Pro; p.Ala495Pro;p.Val499=). To assist in genetic counseling, we performed a retrospective review of other patients in our cohort carrying D409H and reviewed the literature. The study illustrates the challenges faced in counseling for infants with neuronopathic GD, even with known GBA1 variants, and the tough management decisions that can ensue from detection in newborns.

Efficacy and Safety of Avalglucosidase Alfa in Patients With Late-Onset Pompe Disease After 97 Weeks: A Phase 3 Randomized Clinical Trial.

Importance: In the previously reported Comparative Enzyme Replacement Trial With neoGAA Versus rhGAA (COMET) trial, avalglucosidase alfa treatment for 49 weeks showed clinically meaningful improvements in upright forced vital capacity (FVC) percent predicted and 6-minute walk test (6MWT) compared with alglucosidase alfa. Objective: To report avalglucosidase alfa treatment outcomes during the COMET trial extension. Design, Setting, and Participants: This phase 3 double-blind randomized clinical trial with crossover in the extension period enrolled patients 3 years and older with previously untreated late-onset Pompe disease (LOPD) between November 2, 2016, and February 10, 2021, with primary analysis after 49 weeks. Patients were treated at 55 referral centers in 20 countries. Efficacy outcomes were assessed at 97 weeks and safety outcomes to last follow-up, with data cutoff at February 10, 2021. Data were analyzed from May to June 2021. Interventions: Random assignment (1:1) to receive 20 mg/kg of avalglucosidase alfa or alglucosidase alfa by intravenous infusion every other week for 49 weeks; thereafter, all patients received 20 mg/kg of avalglucosidase alfa every other week. Main Outcomes and Measures: The primary outcome was the least squares (LS) mean change from baseline in FVC percent predicted. Secondary outcomes included the LS mean change from baseline in 6MWT, muscle strength, motor function, quality of life, and disease biomarkers. Safety and tolerability were also assessed. Results: Of 100 participants from the double-blind treatment period, 95 entered the extension period. Of these, 51 (54%) were men, and the mean (range) age was 48.3 (10-79) years. At the start of this study, mean upright FVC percent predicted was similar between treatment arms, and 6MWT distance was greater in the avalglucosidase alfa arm. From baseline to week 97, LS mean (SE) FVC percent predicted increased by 2.65 (1.05) for those who continued avalglucosidase alfa and 0.36 (1.12) for those who switched to avalglucosidase alfa. The LS mean (SE) 6MWT distance increased by 18.60 (12.01) m and 4.56 (12.44) m, respectively. For participants who switched to avalglucosidase alfa, FVC percent predicted remained stable (LS mean [SE] change from week 49 to 97, 0.09 [0.88]) and 6MWT distance improved (LS mean [SE] change from week 49 to 97, 5.33 [10.81] m). Potentially treatment-related adverse events were reported in 29 patients (56.9%) who continued avalglucosidase alfa and in 25 patients (56.8%) who switched. Conclusions and Relevance: In this randomized clinical trial extension, maintenance of positive clinical outcomes was demonstrated for patients continuing avalglucosidase alfa treatment and, to a lesser extent, patients who switched from alglucosidase alfa. No new safety concerns were observed. Trial Registration: ClinicalTrials.gov Identifier: NCT02782741.

Venglustat, an orally administered glucosylceramide synthase inhibitor: Assessment over 3 years in adult males with classic Fabry disease in an open-label phase 2 study and its extension study.

Venglustat inhibits the enzymatic conversion of ceramide to glucosylceramide, reducing available substrate for the synthesis of more complex glycosphingolipids. It offers a potential new approach to the treatment of patients with Fabry disease (α-Gal A deficiency), in whom progressive accumulation of such glycosphingolipids, including globotriaosylceramide (GL-3), in the lysosomes of a wide range of cell types often leads to vital organ complications in adulthood. An international, open-label, single-arm, Phase 2a uncontrolled 26-week clinical study (NCT02228460) and a 130-week extension study (NCT02489344) were conducted to assess the safety, pharmacodynamics, pharmacokinetics, and exploratory efficacy of 15 mg once daily oral venglustat in treatment-naïve adult male patients with classic Fabry disease. Of 11 patients (18-37 years old) who initially enrolled, nine completed the 26-week study and seven completed the extension study. A total of 169 treatment-emergent adverse events (TEAEs) were reported by nine patients, the majority being mild (73%) and unrelated to the study drug (70%). Nine serious TEAEs (serious adverse events) and 11 severe TEAEs, including a self-harm event, were reported. No deaths or treatment-related life-threatening adverse events were reported. Skin GL-3 scores in superficial skin capillary endothelium (SSCE), estimated by light microscopy, were unchanged from baseline at Week 26 in five patients, decreased in three patients, and increased in one patient. There was no significant change in GL-3 scores or significant shift in grouped GL-3 scores. Five of six patients had reductions from baseline in GL-3 score at the end of the extension study. At Weeks 26 and 156 the mean (standard deviation) changes from baseline in the fraction of the volume of SSCE cytoplasm occupied by GL-3 inclusions, measured by electron microscopy unbiased stereology, were - 0.06 (0.03) (p = 0.0010) and - 0.12 (0.04) (p = 0.0008), respectively. Venglustat treatment reduced markers in the synthetic and degradative pathway of major glycosphingolipids; proximal markers reduced rapidly and more distal markers (plasma GL-3 and globotriaosylsphingosine) reduced progressively. There were no biochemical or histological indications of progression of Fabry disease over 3 years of follow-up. These findings confirm target engagement and the pharmacodynamic effects of venglustat in adult males with classic Fabry disease. However, further clinical evaluation in larger studies is needed to determine efficacy and safety.

Wnt signaling pathway inhibitors, sclerostin and DKK-1, correlate with pain and bone pathology in patients with Gaucher disease.

Patients with Gaucher disease (GD) have progressive bone involvement that clinically presents with debilitating bone pain, structural bone changes, bone marrow infiltration (BMI), Erlenmeyer (EM) flask deformity, and osteoporosis. Pain is referred by the majority of GD patients and continues to persist despite the type of therapy. The pain in GD is described as chronic deep penetrating pain; however, sometimes, patients experience severe acute pain. The source of bone pain is mainly debated as nociceptive pain secondary to bone pathology or neuropathic or inflammatory origins. Osteocytes constitute a significant source of secreted molecules that coordinate bone remodeling. Osteocyte markers, sclerostin (SOST) and Dickkopf-1 (DKK-1), inactivate the canonical Wnt signaling pathway and lead to the inhibition of bone formation. Thus, circulated sclerostin and DKK-1 are potential biomarkers of skeletal abnormalities. This study aimed to assess the circulating levels of sclerostin and DKK-1 in patients with GD and their correlation with clinical bone pathology parameters: pain, bone mineral density (BMD), and EM deformity. Thirty-nine patients with GD were classified into cohorts based on the presence and severity of bone manifestations. The serum levels of sclerostin and DKK-1 were quantified by enzyme-linked immunosorbent assays. The highest level of sclerostin was measured in GD patients with pain, BMI, and EM deformity. The multiparameter analysis demonstrated that 95% of GD patients with pain, BMI, and EM deformity had increased levels of sclerostin. The majority of patients with elevated sclerostin also have osteopenia or osteoporosis. Moreover, circulating sclerostin level increase with age, and GD patients have elevated sclerostin levels when compared with healthy control from the same age group. Pearson's linear correlation analysis showed a positive correlation between serum DKK-1 and sclerostin in healthy controls and GD patients with normal bone mineral density. However, the balance between sclerostin and DKK-1 waned in GD patients with osteopenia or osteoporosis. In conclusion, the osteocyte marker, sclerostin, when elevated, is associated with bone pain, BMI, and EM flask deformity in GD patients. The altered sclerostin/DKK-1 ratio correlates with the reduction of bone mineral density. These data confirm that the Wnt signaling pathway plays a role in GD-associated bone disease. Sclerostin and bone pain could be used as biomarkers to assess patients with a high risk of BMI and EM flask deformities.

Switching between Enzyme Replacement Therapies and Substrate Reduction Therapies in Patients with Gaucher Disease: Data from the Gaucher Outcome Survey (GOS).

Switching between enzyme replacement therapies (ERT) and substrate reduction therapies (SRT) in patients with type 1 Gaucher disease (GD1) is not uncommon; however, the reasons for switchng treatments have not been explored in detail. Data from the Gaucher Outcome Survey (GOS), an international registry for patients with confirmed GD, were used to evaluate the reasons for, and consequences of, switching between these treatment types. Of the 1843 patients enrolled in GOS on 25 February 2020, 245 had undergone a treatment switch: 222 from initial ERT to SRT (of whom 88 later switched back to ERT) and 23 from initial SRT to ERT. The most common reasons for ERT-SRT switching were duration of infusion (25.4%), drug shortage (22.0%), and adverse events (AEs; 11.9%), and for SRT-ERT switching, AEs (63.6%), lack of beneficial effect (16.4%), and participation in a clinical trial (9.1%). Bodyweight and hematologic parameters largely remained stable before and after switching between ERT and SRT, although with substantial variation between patients. These findings contribute to understanding why treatment switching occurs in patients with GD, and may help physicians recognize the real-world impact of treatment switching between ERT and SRT for patients with GD.

Lysosomal functions and dysfunctions: Molecular and cellular mechanisms underlying Gaucher disease and its association with Parkinson disease.

Lysosomes have a critical role in maintaining normal cellular homeostasis mediated by their involvement in secretion, plasma membrane repair, cell signaling and energy metabolism. Lysosomal storage disorders (LSDs) are a group of approximately 50 rare disorders caused by lysosomal dysfunction that occur due to mutations in a gene of a lysosomal protein. Gaucher disease (GD), an autosomal recessive disorder and one of the most common LSDs, is caused by the deficiency of the lysosomal enzyme acid-ß-glucocerebrosidase (GCase), due to biallelic mutations in the GBA1 gene. Reduced GCase activity leads to the accumulation of glucosylceramide (GlcCer), which is deacylated by lysosomal acid ceramidase to a toxic metabolite, glucosylshpingosine (GlcSph). Most GBA1 variants are recognized as misfolded in the ER, where the retention for refolding attempts initiates stress and activates the stress response known as the Unfolded Protein Response (UPR). The distinct clinical subtypes of GD are based on whether there is primary involvement of the central nervous system. Type 1 GD (GD1) is the nonneuropathic type, however, the recent recognition of the association of GD with the development of parkinsonism defies this classification. Patients with GD1 and carriers of GBA1 mutations are at risk for the development of parkinsonian manifestations. Parkinson disease (PD), the second most prevalent neurodegenerative disease, culminates in a movement disorder with the premature death of the patients. In PD and related disorders, collectively called synucleinopathies, the hallmark pathology is α-synuclein positive aggregates referred to as Lewy bodies or Lewy neurites and the death of dopaminergic neurons. While PD is mostly sporadic, in ∼5-10% of cases, the disease results from pathogenic variants in a growing number of genes. The most common genetic cause of PD is mutations in GBA1. Two mechanisms have been proposed for this link: (A) a "gain of function" mechanism, in which mutant GCase (protein) contributes to aggregate formation and to the development of PD, and the (B) "haploinsufficiency" ("loss of function") model, suggesting that one normal GBA1 allele is insufficient to carry adequate GCase activity and functional deficiency of GCase impedes α-synuclein metabolism. Lysosomal dysfunction, compromised autophagy and mitophagy further enhance the accumulation of α-synuclein, which results in the development of PD pathology. The present review will elaborate on the biology of GD, its association with PD and related disorders, and discuss the possible mechanisms underlying this association.

Long-term Safety and Efficacy of Avalglucosidase Alfa in Patients With Late-Onset Pompe Disease.

BACKGROUND AND OBJECTIVES: Pompe disease is a rare, progressive neuromuscular disorder caused by deficiency of lysosomal acid α-glucosidase (GAA) and subsequent glycogen accumulation. Avalglucosidase alfa, a recombinant human GAA enzyme replacement therapy designed for increased cellular uptake and glycogen clearance, has been studied for long-term efficacy and safety in patients with late-onset Pompe disease (LOPD). Here we report up to 6.5 years' experience with avalglucosidase alfa during the NEO1 and NEO-EXT studies. METHODS: NEO1 participants with LOPD, either treatment-naïve (Naïve Group) or receiving alglucosidase alfa for ≥9 months (Switch Group), received avalglucosidase alfa (5, 10, or 20 mg/kg every other week [qow]) for 6 months before entering NEO-EXT and continued their NEO1 dose until all proceeded with 20 mg/kg qow. Safety and efficacy, a pre-specified exploratory secondary outcome, were assessed; slopes of change for efficacy outcomes were calculated from a repeated mixed-measures model. RESULTS: Twenty-four participants enrolled in NEO1 (Naïve Group, n=10; Switch Group, n=14); 21 completed and 19 entered NEO-EXT; in February 2020, 17 participants remained in NEO-EXT, with data up to 6.5 years. Avalglucosidase alfa was generally well-tolerated during NEO-EXT, with a safety profile consistent with that in NEO1. No deaths or treatment-related life-threatening serious adverse events occurred. Eighteen participants developed anti-drug antibodies without apparent impact on clinical outcomes. No participants who were tested developed immunoglobulin E antibodies. Upright forced vital capacity (FVC) %predicted remained stable in most participants, with slope estimates (95% confidence intervals) of -0.473/year (-1.188, 0.242) and -0.648/year (-1.061, -0.236) in the Naïve and Switch Groups, respectively. Six-minute walk test (6MWT) %predicted was also stable for most participants, with slope estimates of -0.701/year (-1.571, 0.169) and -0.846/year (-1.567, -0.125) for the Naïve and Switch Groups, respectively. Improvements in 6MWT distance were observed in most participants aged <45 years at NEO1 enrollment, in both the Naïve and Switch Groups. DISCUSSION: Avalglucosidase alfa was generally well-tolerated for up to 6.5 years in adult participants with LOPD either naïve to alglucosidase alfa or who had previously received alglucosidase alfa for ≥9 months.Classification of Evidence: This study provides Class IV evidence of long-term tolerability and sustained efficacy of avalglucosidase alfa in patients with LOPD after up to 6.5 years.

The diagnosis and management of Gaucher disease in pediatric patients: Where do we go from here?

Gaucher disease (GD) is an autosomal recessive inherited lysosomal storage disease that often presents in early childhood and is associated with damage to multiple organ systems. Many challenges associated with GD diagnosis and management arise from the considerable heterogeneity of disease presentations and natural history. Phenotypic classification has traditionally been based on the absence (in type 1 GD) or presence (in types 2 and 3 GD) of neurological involvement of varying severity. However, patient management and prediction of prognosis may be best served by a dynamic, evolving definition of individual phenotype rather than by a rigid system of classification. Patients may experience considerable delays in diagnosis, which can potentially be reduced by effective screening programs; however, program implementation can involve ethical and practical challenges. Variation in the clinical course of GD and an uncertain prognosis also complicate decisions concerning treatment initiation, with differing stakeholder perspectives around efficacy and acceptable cost/benefit ratio. We review the challenges faced by physicians in the diagnosis and management of GD in pediatric patients. We also consider future directions and goals, including acceleration of accurate diagnosis, improvements in the understanding of disease heterogeneity (natural history, response to treatment, and prognosis), the need for new treatments to address unmet needs for all forms of GD, and refinement of the tools for monitoring disease progression and treatment efficacy, such as specific biomarkers.

Screening, patient identification, evaluation, and treatment in patients with Gaucher disease: Results from a Delphi consensus.

Several guidelines are available for identification and management of patients with Gaucher disease, but the most recent guideline was published in 2013. Since then, there have been significant advances in newborn screening, phenotypic characterization, identification of biomarkers and their integration into clinical practice, and the development and approval of new treatment options. Accordingly, the goal of this Delphi consensus exercise was to extend prior initiatives of this type by addressing issues related to newborn screening, diagnostic evaluations, and treatment (both disease directed and adjunctive). The iterative Delphi process involved creation of an initial slate of statements, review by a steering committee, and three rounds of consensus development by an independent panel. A preliminary set of statements was developed by the supporting agency based on literature searches covering the period from 1965 to 2020. The Delphi process reduced an initial set of 185 statements to 65 for which there was unanimous support from the panel. The statements supported may ultimately provide a framework for more detailed treatment guidelines. In addition, the statements for which unanimous support could not be achieved help to identify evidence gaps that are targets for future research.

Development and validation of Gaucher disease type 1 (GD1)-specific patient-reported outcome measures (PROMs) for clinical monitoring and for clinical trials.

BACKGROUND: Disease-specific patient-reported outcome measures (PROMs) are fundamental to understanding the impact on, and expectations of, patients with genetic disorders, and can facilitate constructive and educated conversations about treatments and outcomes. However, generic PROMs may fail to capture disease-specific concerns. Here we report the development and validation of a Gaucher disease (GD)-specific PROM for patients with type 1 Gaucher disease (GD1) a lysosomal storage disorder characterized by hepatosplenomegaly, thrombocytopenia, anemia, bruising, bone disease, and fatigue. RESULTS AND DISCUSSION: The questionnaire was initially developed with input from 85 patients or parents of patients with GD1 or GD3 in Israel. Owing to few participating patients with GD3, content validity was assessed for patients with GD1 only. Content validity of the revised questionnaire was assessed in 33 patients in the US, France, and Israel according to US Food and Drug Administration standards, with input from a panel of six GD experts and one patient advocate representative. Concept elicitation interviews explored patient experience of symptoms and treatments, and a cognitive debriefing exercise explored patients' understanding and relevance of instructions, items, response scales, and recall period. Two versions of the questionnaire were subsequently developed: a 24-item version for routine monitoring in clinical practice (rmGD1-PROM), and a 17-item version for use in clinical trials (ctGD1-PROM). Psychometric validation of the ctGD1-PROM was assessed in 46 adult patients with GD1 and re-administered two weeks later to examine test-retest reliability. Findings from the psychometric validation study revealed excellent internal consistency and strong evidence of convergent validity of the ctGD1-PROM based on correlations with the 36-item Short Form Health Survey. Most items were found to show moderate, good, or excellent test-retest reliability. CONCLUSIONS: Development of the ctGD1-PROM represents an important step forward for researchers measuring the impact of GD and its respective treatment.