Pharmacologic properties of high-dose ambroxol in four patients with Gaucher disease and myoclonic epilepsy

High-throughput screening for small-molecule stabilizers of misfolded glucocerebrosidase in Gaucher disease and Parkinson's disease

Glucocerebrosidase (GCase) is implicated in both a rare, monogenic disorder (Gaucher disease, GD) and a common, multifactorial condition (Parkinson's disease, PD); hence, it is an urgent therapeutic target. To identify correctors of severe protein misfolding and trafficking obstruction manifested by the pathogenic L444P-variant of GCase, we developed a suite of quantitative, high-throughput, cell-based assays. First, we labeled GCase with a small proluminescent HiBiT peptide reporter tag, enabling quantitation of protein stabilization in cells while faithfully maintaining target biology. TALEN-based gene editing allowed for stable integration of a single HiBiT-GBA1 transgene into an intragenic safe-harbor locus in GBA1-knockout H4 (neuroglioma) cells. This GD cell model was amenable to lead discovery via titration-based quantitative high-throughput screening and lead optimization via structure-activity relationships. A primary screen of 10,779 compounds from the NCATS bioactive collections identified 140 stabilizers of HiBiT-GCase-L444P, including both pharmacological chaperones (ambroxol and noninhibitory chaperone NCGC326) and proteostasis regulators (panobinostat, trans-ISRIB, and pladienolide B). Two complementary high-content imaging-based assays were deployed to triage hits: The fluorescence-quenched substrate LysoFix-GBA captured functional lysosomal GCase activity, while an immunofluorescence assay featuring antibody hGCase-1/23 directly visualized GCase lysosomal translocation. NCGC326 was active in both secondary assays and completely reversed pathological glucosylsphingosine accumulation. Finally, we tested the concept of combination therapy by demonstrating synergistic actions of NCGC326 with proteostasis regulators in enhancing GCase-L444P levels. Looking forward, these physiologically relevant assays can facilitate the identification, pharmacological validation, and medicinal chemistry optimization of small molecules targeting GCase, ultimately leading to a viable therapeutic for GD and PD.

Molecular mechanisms of the ambroxol action in Gaucher disease and GBA1 mutation-associated Parkinson disease

Glucocerebrosidase (GCase), encoded by the GBA1 gene, is one of the lysosomal enzymes responsible for hydrolyzing the glycosphingolipids. Deficiency in GCase activity (in patients with two defective alleles of GBA1) leads to glucosylceramide storage in lysosomes which in turn results in the development of the Gaucher diseases, a lysosomal storage disorder, while a heterozygous state may be correlated with the GBA1 mutation-associated Parkinson disease. One of the proposed forms of therapy for these two conditions is the use of pharmacological chaperones which work by facilitating the achievement of the correct conformation of abnormally folded enzymes. Several compounds with chaperone activities against GCase have already been tested, one of which turned out to be ambroxol. Studies conducted on the action of this compound have indeed indicated its effectiveness in increasing GCase levels and activity. However, some data have begun to question its activity as a chaperone against certain GCase variants. Then, a number of articles appeared pointing to other mechanisms of action of ambroxol, which may also contribute to the improvement of patients' condition. This paper summarizes the biological mechanisms of action of ambroxol in Gaucher disease and GBA1 mutation-associated Parkinson disease, focused on its activity as a chaperone, modulator of ERAD pathways, inducer of autophagy, and pain reliever in cellular and animal models as well as in patients. The effects of these activities on the reduction of disease markers and symptoms in patients are also discussed. Consideration of all the properties of ambroxol can help in the appropriate choice of therapy and the determination of the effective drug dose.

Clinical and preclinical insights into high-dose ambroxol therapy for Gaucher disease type 2 and 3: A comprehensive systematic review

RATIONALE

Gaucher disease (GD), an autosomal recessive lysosomal storage disease, results from GBA1 variants causing glucocerebrosidase (GCase) deficiency. While enzyme replacement therapy (ERT) helps with systemic symptoms, neurological complications in GD2 and GD3 persist due to the blood-brain-barrier (BBB) limiting ERT efficacy. Ambroxol, a BBB-permeable chaperone, enhances GCase activity. Our review explores high-dose ambroxol's therapeutic potential, both preclinical and clinical, in GD2 and GD3.

METHODS

PubMed was searched for studies published before March 2023, including clinical, animal, and in vitro studies focusing on the effect of high-dose ambroxol in GD2 and GD3. A narrative synthesis was performed.

RESULTS

Nine in vitro, three animal, and eight clinical studies were included, demonstrating varied responses to ambroxol across diverse outcome measures. In vitro and animal studies demonstrated reduced endoplasmatic reticulum stress due to the relocation of GCase from the ER to the lysosomes. In vitro cell lines exhibited varying degrees of increased GCase activity. Clinical trials observed reduced lyso-GL1 levels in plasma (41-89%) and cerebrospinal fluid (CSF) (26-97%), alongside increased GCase activity in GD3 patients. Ambroxol exhibited varying effects on neurological outcomes and development. No severe adverse events were reported.

CONCLUSION

High-dose ambroxol shows promise in managing neurological manifestations in GD3, albeit with uncertainties resulting from genetic heterogeneity and variable response. Further clinical trials, are essential for elucidating dosage-response relationships and refining treatment outcomes and strategies for neuronopathic GD.

Development of orphan drugs for rare diseases

Most rare diseases (orphan diseases) still lack approved treatment options despite major advances in research providing the necessary tools to understand their molecular basis and legislation providing regulatory and economic incentives to expedite the development of specific therapies. Addressing this translational gap is a multifaceted challenge, a key aspect of which is the selection of an optimal therapeutic modality to translate advances in rare disease knowledge to potential medicines known as orphan drugs. There are several strategies for developing orphan drugs for rare genetic disorders, including protein replacement therapies, small-molecule therapies (e.g., substrate reduction, chemical chaperone, cofactor, expression modification, and read-through therapies), monoclonal antibodies, antisense oligonucleotides, small interfering RNA or exon skipping therapies, gene replacement and direct genome-editing therapies, mRNA therapy, cell therapy, and drug repurposing. Each strategy has its own strengths and limitations in orphan drug development. Furthermore, numerous hurdles are present in clinical trials of rare genetic diseases because of difficulty with patient recruitment, unknown molecular physiology, the natural history of the disease, ethical concerns regarding pediatric patients, and regulatory challenges. To address these barriers, the rare genetic diseases community, including academic institutions, industry, patient advocacy groups, foundations, payers, and government regulatory and research organizations, must become engaged in discussions about these issues.

Study protocol of the GRoningen early-PD Ambroxol treatment (GREAT) trial: a randomized, double-blind, placebo-controlled, single center trial with ambroxol in Parkinson patients with a GBA mutation

BACKGROUND

To date, no disease modifying therapies are available for Parkinson's disease (PD). Since PD is the second most prevalent neurodegenerative disorder, there is a high demand for such therapies. Both environmental and genetic risk factors play an important role in the etiology and progression of PD. The most common genetic risk factor for PD is a mutation in the GBA1(GBA)-gene, encoding the lysosomal enzyme glucocerebrosidase (GCase). The mucolytic ambroxol is a repurposed drug, which has shown the property to upregulate GCase activity in-vitro and in-vivo. Ambroxol therefore has the potency to become a disease modifying therapy in PD, which was the reason to design this randomized controlled trial with ambroxol in PD patients.

METHODS

This trial is a single-center, double-blind, randomized, placebo-controlled study, including 80 PD patients with a GBA mutation, receiving either ambroxol 1800 mg/day or placebo for 48 weeks. The primary outcome measure is the Unified Parkinson's Disease Rating Scale motor subscore (part III) of the Movement Disorder Society (MDS-UPDRSIII) in the practically defined off-state at 60 weeks (after a 12-week washout period). Secondary outcomes include a 3,4-dihydroxy-6-18F-fluoro-I-phenylalanine ([18F]FDOPA) PET-scan of the brain, Magnetic Resonance Imaging (with resting state f-MRI and Diffusion Tensor Imaging), GCase activity, both intra- and extracellularly, sphingolipid profiles in plasma, Montreal Cognitive Assessment (MoCA), quality of life (QoL) measured by the Parkinson's Disease Questionnaire (PDQ-39) and the Non-Motor Symptom Scale (NMSS) questionnaire.

DISCUSSION

Ambroxol up to 1200 mg/day has shown effects on human cerebrospinal fluid endpoints, which supports at least passage of the blood-brain-barrier. The dose titration in this trial up to 1800 mg/day will reveal if this dose level is safe and also effective in modifying the course of the disease.

TRIAL REGISTRATION

NCT05830396. Registration date: March 20, 2023.

Rapid and long-lasting efficacy of high-dose ambroxol therapy for neuronopathic Gaucher disease: A case report and literature review

Gaucher disease (GD) is a lysosomal storage disorder caused by a deficiency in the GBA1-encoded enzyme, β-glucocerebrosidase. Enzyme replacement therapy is ineffective for neuronopathic Gaucher disease (nGD). High-dose ambroxol has been administered as an alternative treatment for a group of patients with nGD. However, little is known about the clinical indication and the long-term outcome of patients after ambroxol therapy. We herein report a case of a female patient who presented with a progressive disease of GD type 2 from 11 months of age and had the pathogenic variants of p.L483P (formerly defined as p.L444P) and p.R502H (p.R463H) in GBA1. A combined treatment of imiglucerase with ambroxol started improving the patient's motor activity in 1 week, while it kept the long-lasting effect of preventing the deteriorating phenotype for 30 months. A literature review identified 40 patients with nGD, who had received high-dose ambroxol therapy. More than 65% of these patients favorably responded to the molecular chaperone therapy, irrespective of p.L483P homozygous, heterozygous or the other genotypes. These results highlight the long-lasting effect of ambroxol-based chaperone therapy for patients with an expanding spectrum of mutations in GBA1.

Development of quantitative high-throughput screening assays to identify, validate, and optimize small-molecule stabilizers of misfolded β-glucocerebrosidase with therapeutic potential for Gaucher disease and Parkinson's disease

Glucocerebrosidase (GCase) is implicated in both a rare, monogenic disorder (Gaucher disease, GD) and a common, multifactorial condition (Parkinson's disease); hence, it is an urgent therapeutic target. To identify correctors of severe protein misfolding and trafficking obstruction manifested by the pathogenic L444P-variant of GCase, we developed a suite of quantitative, high-throughput, cell-based assays. First, we labeled GCase with a small pro-luminescent HiBiT peptide reporter tag, enabling quantitation of protein stabilization in cells while faithfully maintaining target biology. TALEN-based gene editing allowed for stable integration of a single HiBiT-GBA1 transgene into an intragenic safe-harbor locus in GBA1-knockout H4 (neuroglioma) cells. This GD cell model was amenable to lead discovery via titration-based quantitative high-throughput screening and lead optimization via structure-activity relationships. A primary screen of 10,779 compounds from the NCATS bioactive collections identified 140 stabilizers of HiBiT-GCase-L444P, including both pharmacological chaperones (ambroxol and non-inhibitory chaperone NCGC326) and proteostasis regulators (panobinostat, trans-ISRIB, and pladienolide B). Two complementary high-content imaging-based assays were deployed to triage hits: the fluorescence-quenched substrate LysoFix-GBA captured functional lysosomal GCase activity, while an immunofluorescence assay featuring antibody hGCase-1/23 provided direct visualization of GCase lysosomal translocation. NCGC326 was active in both secondary assays and completely reversed pathological glucosylsphingosine accumulation. Finally, we tested the concept of combination therapy, by demonstrating synergistic actions of NCGC326 with proteostasis regulators in enhancing GCase-L444P levels. Looking forward, these physiologically-relevant assays can facilitate the identification, pharmacological validation, and medicinal chemistry optimization of new chemical matter targeting GCase, ultimately leading to a viable therapeutic for two protein-misfolding diseases.

Exploring the efficacy and safety of Ambroxol in Gaucher disease: an overview of clinical studies

Gaucher disease (GD) is mainly caused by glucocerebrosidase (GCase) enzyme deficiency due to genetic variations in the GBA1 gene leading to the toxic accumulation of sphingolipids in various organs, which causes symptoms such as anemia, thrombocytopenia, hepatosplenomegaly, and neurological manifestations. GD is clinically classified into the non-neuronopathic type 1, and the acute and chronic neuronopathic forms, types 2 and 3, respectively. In addition to the current approved GD medications, the repurposing of Ambroxol (ABX) has emerged as a prospective enzyme enhancement therapy option showing its potential to enhance mutated GCase activity and reduce glucosylceramide accumulation in GD-affected tissues of different GBA1 genotypes. The variability in response to ABX varies across different variants, highlighting the diversity in patients' therapeutic outcomes. Its oral availability and safety profile make it an attractive option, particularly for patients with neurological manifestations. Clinical trials are essential to explore further ABX's potential as a therapeutic medication for GD to encourage pharmaceutical companies' investment in its development. This review highlights the potential of ABX as a pharmacological chaperone therapy for GD and stresses the importance of addressing response variability in clinical studies to improve the management of this rare and complex disorder.

Dependence of human cell survival and proliferation on the CASP3 prodomain

Mechanisms that regulate cell survival and proliferation are important for both the development and homeostasis of normal tissue, and as well as for the emergence and expansion of malignant cell populations. Caspase-3 (CASP3) has long been recognized for its proteolytic role in orchestrating cell death-initiated pathways and related processes; however, whether CASP3 has other functions in mammalian cells that do not depend on its known catalytic activity have remained unknown. To investigate this possibility, we examined the biological and molecular consequences of reducing CASP3 levels in normal and transformed human cells using lentiviral-mediated short hairpin-based knockdown experiments in combination with approaches designed to test the potential rescue capability of different components of the CASP3 protein. The results showed that a ≥50% reduction in CASP3 levels rapidly and consistently arrested cell cycle progression and survival in all cell types tested. Mass spectrometry-based proteomic analyses and more specific flow cytometric measurements strongly implicated CASP3 as playing an essential role in regulating intracellular protein aggregate clearance. Intriguingly, the rescue experiments utilizing different forms of the CASP3 protein showed its prosurvival function and effective removal of protein aggregates did not require its well-known catalytic capability, and pinpointed the N-terminal prodomain of CASP3 as the exclusive component needed in a diversity of human cell types. These findings identify a new mechanism that regulates human cell survival and proliferation and thus expands the complexity of how these processes can be controlled. The graphical abstract illustrates the critical role of CASP3 for sustained proliferation and survival of human cells through the clearance of protein aggregates.

Novel beta-glucocerebrosidase chaperone compounds identified from cell-based screening reduce pathologically accumulated glucosylsphingosine in iPS-derived neuronal cells

The beta-glucocerebrosidase (GBA1) gene encodes the lysosomal beta-glucocerebrosidase (GCase) that metabolizes the lipids glucosylceramide (GlcCer) and glucosylsphingosine (GlcSph). Biallelic loss-of-function mutations in GBA1 such as L444P cause Gaucher disease (GD), which is the most prevalent lysosomal storage disease and is histopathologically characterized by abnormal accumulation of the GCase substrates GlcCer and GlcSph. GD with neurological symptoms is associated with severe mutations in the GBA1 gene, most of which cause impairment in the process of GCase trafficking to lysosomes. Given that recombinant GCase protein cannot cross the blood-brain barrier due to its high molecular weight, it is invaluable to develop a brain-penetrant small-molecule pharmacological chaperone as a viable therapeutic strategy to boost GCase activity in the central nervous system. Despite considerable efforts to screen potent GCase activators/chaperones, cell-free assays using recombinant GCase protein have yielded compounds with only marginal efficacy and micromolar EC50 that would not have sufficient clinical efficacy or an acceptable safety margin. Therefore, we utilized a fluorescence-labeled GCase suicide inhibitor, MDW933, to directly monitor lysosomal GCase activity and performed a cell-based screening in fibroblasts from a GD patient with homozygotic L444P mutations. Here, we identified novel compounds that increase the fluorescence signal from labeled GCase with L444P mutations in a dose-dependent manner. Secondary assays using an artificial cell-permeable lysosomal GCase substrate also demonstrated that the identified compounds augment lysosomal GCase L444P in the fibroblast. Moreover, those compounds increased the total GCase L444P protein levels, suggesting the pharmacological chaperone-like mechanism of action. To further elucidate the effect of the compounds on the endogenous GCase substrate GlcSph, we generated iPSC-derived dopaminergic neurons with a GBA1 L444P mutation that exhibit GlcSph accumulation in vitro. Importantly, the identified compounds reduce GlcSph in iPSC-derived dopaminergic neurons with a GBA1 L444P mutation, indicating that the increase in lysosomal GCase resulting from application of the compounds leads to the clearance of pathologically-accumulated GlcSph. Together, our findings pave the way for developing potent and efficacious GCase chaperone compounds as a potential therapeutic approach for neurological GD.

Insights into the Value of Lyso-Gb1 as a Predictive Biomarker in Treatment-Naïve Patients with Gaucher Disease Type 1 in the LYSO-PROOF Study

Gaucher disease (GD) is a rare autosomal recessive disorder arising from bi-allelic variants in the GBA1 gene, encoding glucocerebrosidase. Deficiency of this enzyme leads to progressive accumulation of the sphingolipid glucosylsphingosine (lyso-Gb1). The international, multicenter, observational "Lyso-Gb1 as a Long-term Prognostic Biomarker in Gaucher Disease"-LYSO-PROOF study succeeded in enrolling a cohort of 160 treatment-naïve GD patients from diverse geographic regions and evaluated the potential of lyso-Gb1 as a specific biomarker for GD. Using genotypes based on established classifications for clinical presentation, patients were stratified into type 1 GD (n = 114) and further subdivided into mild (n = 66) and severe type 1 GD (n = 48). Due to having previously unreported genotypes, 46 patients could not be classified. Though lyso-Gb1 values at enrollment were widely distributed, they displayed a moderate and statistically highly significant correlation with disease severity measured by the GD-DS3 scoring system in all GD patients (r = 0.602, p < 0.0001). These findings support the utility of lyso-Gb1 as a sensitive biomarker for GD and indicate that it could help to predict the clinical course of patients with undescribed genotypes to improve personalized care in the future.

The ANeED study - ambroxol in new and early dementia with Lewy bodies (DLB): protocol for a phase IIa multicentre, randomised, double-blinded and placebo-controlled trial

Background

Currently, there are no disease-modifying pharmacological treatment options for dementia with Lewy bodies (DLB). The hallmark of DLB is pathological alpha-synuclein (aS) deposition. There are growing amounts of data suggesting that reduced aS clearance is caused by failure in endolysosomal and authophagic pathways, as well as and glucocerebrosidase (GCase) dysfunction and mutations in the GCase gene (GBA). The population's studies demonstrated that the incidence of GBA mutations is higher among Parkinson's disease (PD) patients, and carriers of such mutations have a higher risk of developing PD. The incidence of GBA mutations is even higher in DLB and a genome-wide association study (GWAS) confirmed the correlation between GBA mutations and DLB. In vivo experiments have shown that ambroxol (ABX) may increase GCase activity and GCase levels and therefore enhance aS autophagy-lysosome degradation pathways. Moreover, there is an emerging hypothesis that ABX may have an effect as a DLB modifying drug. The aims of the study "Ambroxol in new and early Dementia with Lewy Bodies (ANeED) are to investigate the tolerability, safety and effects of ABX in patients with DLB.

Methods

This is a multicentre, phase IIa, double-blinded, randomised and placebo-controlled clinical trial, using a parallel arm design for 18 months' follow-up. The allocation ratio is 1:1 (treatment:placebo).

Discussion

The ANeED study is an ongoing clinical drug trial with ABX. The unique, but not fully understood mechanism of ABX on the enhancement of lysosomal aS clearance may be promising as a possible modifying treatment in DLB.

Trial Registration

The clinical trial is registered in the international trials register - clinicaltrials.com (NCT0458825) and nationally at the Current Research Information System in Norway (CRISTIN 2235504).

Targeting the GBA1 pathway to slow Parkinson disease: Insights into clinical aspects, pathogenic mechanisms and new therapeutic avenues

The GBA1 gene encodes the lysosomal enzyme glucocerebrosidase (GCase), which is involved in sphingolipid metabolism. Biallelic variants in GBA1 cause Gaucher disease (GD), a lysosomal storage disorder characterised by loss of GCase activity and aberrant intracellular accumulation of GCase substrates. Carriers of GBA1 variants have an increased risk of developing Parkinson disease (PD), with odds ratio ranging from 2.2 to 30 according to variant severity. GBA1 variants which do not cause GD in homozygosis can also increase PD risk. Patients with PD carrying GBA1 variants show a more rapidly progressive phenotype compared to non-carriers, emphasising the need for disease modifying treatments targeting the GBA1 pathway. Several mechanisms secondary to GCase dysfunction are potentially responsible for the pathological changes leading to PD. Misfolded GCase proteins induce endoplasmic reticulum stress and subsequent unfolded protein response and impair the autophagy-lysosomal pathway. This results in α-synuclein accumulation and spread, and promotes neurodegenerative changes. Preclinical evidence also shows that products of GCase activity can promote accumulation of α-synuclein, however there is no convincing evidence of substrate accumulation in GBA1-PD brains. Altered lipid homeostasis secondary to loss of GCase activity could also contribute to PD pathology. Treatments that target the GBA1 pathway could reverse these pathological processes and halt/slow the progression of PD. These range from augmentation of GCase activity via GBA1 gene therapy, restoration of normal intracellular GCase trafficking via molecular chaperones, and substrate reduction therapy. This review discusses the pathways associated with GBA1-PD and related novel GBA1-targeted interventions for PD treatment.

Venglustat combined with imiglucerase for neurological disease in adults with Gaucher disease type 3: the LEAP trial

Gaucher disease type 3 is a chronic neuronopathic disorder with wide-ranging effects, including hepatosplenomegaly, anaemia, thrombocytopenia, skeletal disease and diverse neurological manifestations. Biallelic mutations in GBA1 reduce lysosomal acid β-glucosidase activity, and its substrates, glucosylceramide and glucosylsphingosine, accumulate. Enzyme replacement therapy and substrate reduction therapy ameliorate systemic features of Gaucher disease, but no therapies are approved for neurological manifestations. Venglustat is an investigational, brain-penetrant, glucosylceramide synthase inhibitor with potential to improve the disease by rebalancing influx of glucosylceramide with impaired lysosomal recycling. The Phase 2, open-label LEAP trial (NCT02843035) evaluated orally administered venglustat 15 mg once-daily in combination with maintenance dose of imiglucerase enzyme replacement therapy during 1 year of treatment in 11 adults with Gaucher disease type 3. Primary endpoints were venglustat safety and tolerability and change in concentration of glucosylceramide and glucosylsphingosine in CSF from baseline to Weeks 26 and 52. Secondary endpoints included change in plasma concentrations of glucosylceramide and glucosylsphingosine, venglustat pharmacokinetics in plasma and CSF, neurologic function, infiltrative lung disease and systemic disease parameters. Exploratory endpoints included changes in brain volume assessed with volumetric MRI using tensor-based morphometry, and resting functional MRI analysis of regional brain activity and connectivity between resting state networks. Mean (SD) plasma venglustat AUC0-24 on Day 1 was 851 (282) ng•h/ml; Cmax of 58.1 (26.4) ng/ml was achieved at a median tmax 2.00 h. After once-daily venglustat, plasma concentrations (4 h post-dose) were higher compared with Day 1, indicating ∼2-fold accumulation. One participant (Patient 9) had low-to-undetectable venglustat exposure at Weeks 26 and 52. Based on mean plasma and CSF venglustat concentrations (excluding Patient 9), steady state appeared to be reached on or before Week 4. Mean (SD) venglustat concentration at Week 52 was 114 (65.8) ng/ml in plasma and 6.14 (3.44) ng/ml in CSF. After 1 year of treatment, median (inter-quartile range) glucosylceramide decreased 78% (72, 84) in plasma and 81% (77, 83) in CSF; median (inter-quartile range) glucosylsphingosine decreased 56% (41, 60) in plasma and 70% (46, 76) in CSF. Ataxia improved slightly in nine patients: mean (SD, range) total modified Scale for Assessment and Rating of Ataxia score decreased from 2.68 [1.54 (0.0 to 5.5)] at baseline to 1.55 [1.88 (0.0 to 5.0)] at Week 52 [mean change: -1.14 (95% CI: -2.06 to -0.21)]. Whole brain volume increased slightly in patients with venglustat exposure and biomarker reduction in CSF (306.7 ± 4253.3 mm3) and declined markedly in Patient 9 (-13894.8 mm3). Functional MRI indicated stronger connectivity at Weeks 26 and 52 relative to baseline between a broadly distributed set of brain regions in patients with venglustat exposure and biomarker reduction but not Patient 9, although neurocognition, assessed by Vineland II, deteriorated in all domains over time, which illustrates disease progression despite the intervention. There were no deaths, serious adverse events or discontinuations. In adults with Gaucher disease type 3 receiving imiglucerase, addition of once-daily venglustat showed acceptable safety and tolerability and preliminary evidence of clinical stability with intriguing but intrinsically inconsistent signals in selected biomarkers, which need to be validated and confirmed in future research.

Mechanistic Insight into the Mode of Action of Acid β-Glucosidase Enhancer Ambroxol

Ambroxol (ABX) is a mucolytic agent used for the treatment of respiratory diseases. Bioactivity has been demonstrated as an enhancement effect on lysosomal acid β-glucosidase (β-Glu) activity in Gaucher disease (GD). The positive effects observed have been attributed to a mechanism of action similar to pharmacological chaperones (PCs), but an exact mechanistic description is still pending. The current study uses cell culture and in vitro assays to study the effects of ABX on β-Glu activity, processing, and stability upon ligand binding. Structural analogues bromohexine, 4-hydroxybromohexine, and norbromohexine were screened for chaperone efficacy, and in silico docking was performed. The sugar mimetic isofagomine (IFG) strongly inhibits β-Glu, while ABX exerts its inhibitory effect in the micromolar range. In GD patient fibroblasts, IFG and ABX increase mutant β-Glu activity to identical levels. However, the characteristics of the banding patterns of Endoglycosidase-H (Endo-H)-digested enzyme and a substantially lower half-life of ABX-treated β-Glu suggest different intracellular processing. In line with this observation, IFG efficiently stabilizes recombinant β-Glu against thermal denaturation in vitro, whereas ABX exerts no significant effect. Additional β-Glu enzyme activity testing using Bromohexine (BHX) and two related structures unexpectedly revealed that ABX alone can refunctionalize β-Glu in cellula. Taken together, our data indicate that ABX has little in vitro ability to act as PC, so the mode of action requires further clarification.

Protein structural features predict responsiveness to pharmacological chaperone treatment for three lysosomal storage disorders

Three-dimensional structures of proteins can provide important clues into the efficacy of personalized treatment. We perform a structural analysis of variants within three inherited lysosomal storage disorders, comparing variants responsive to pharmacological chaperone treatment to those unresponsive to such treatment. We find that predicted ΔΔG of mutation is higher on average for variants unresponsive to treatment, in the case of datasets for both Fabry disease and Pompe disease, in line with previous findings. Using both a single decision tree and an advanced machine learning approach based on the larger Fabry dataset, we correctly predict responsiveness of three Gaucher disease variants, and we provide predictions for untested variants. Many variants are predicted to be responsive to treatment, suggesting that drug-based treatments may be effective for a number of variants in Gaucher disease. In our analysis, we observe dependence on a topological feature reporting on contact arrangements which is likely connected to the order of folding of protein residues, and we provide a potential justification for this observation based on steady-state cellular kinetics.

Pharmacological chaperones are small molecule drugs that bind to proteins to help stabilize the folded state. One set of diseases for which this treatment has been effective is the lysosomal storage disorders, which are caused by defective lysosomal enzymes. However, not all genotypes are equally responsive to treatment. For instance, missense mutants that are particularly destabilized relative to WT are less likely to respond. The availability of datasets containing responsiveness data for large numbers of mutants, along with crystal structures of the protein involved in each disease, make machine learning methods incorporating sequence-based and structural data feasible. We hypothesize that data from two diseases, Fabry and Pompe disease, may be useful for predicting responsiveness of variants in the related Gaucher disease. Results suggest that many rare variants in Gaucher disease could be amenable to existing drugs. Results also suggest that drug responsiveness depends on protein topology in such a way that mutations in early-to-fold residues are more likely to be non-responsive to pharmacological chaperone treatment, which is consistent with a simple kinetic model of stability rescue. This study provides an example of how machine learning can be used to inform further studies towards personalized treatment in medicine.

Current and emerging pharmacotherapy for Gaucher disease in pediatric populations

INTRODUCTION

The past decades have witnessed a remarkable improvement in the health of patients with Gaucher disease, the inherited deficiency of the lysosomal enzyme glucocerebrosidase, resulting from the availability of enzyme replacement and substrate reduction therapies. Especially in pediatric populations, early diagnosis and initiation of treatment is essential to achieving optimal outcomes.

AREAS COVERED

The authors review the literature pertaining to the effectiveness of currently available therapies and describe new pharmacotherapies under development, especially for young patients.

EXPERT OPINION

For pediatric patients with non-neuronopathic Gaucher disease, there may be new therapeutic options on the horizon in the form of gene therapy or small molecule glucocerebrosidase chaperones. These have the potential to result in a cure for systemic disease manifestations and/or to reduce the cost and convenience of treatment. For children with neuronopathic Gaucher disease, the challenge of targeting therapy to the central nervous system is being explored through new modalities including brain-targeted gene therapy, in-utero therapy, brain-penetrant small molecule chaperones, and other methods that convey enzyme across the blood-brain barrier. Indeed, these are exciting times for both pediatric patients with Gaucher disease and those with other lysosomal storage disorders.

Upgrading the evidence for the use of ambroxol in Gaucher disease and GBA related Parkinson: Investigator initiated registry based on real life data

Ambroxol hydrochloride is an oral mucolytic drug available over-the-counter for many years as cough medicine. In 2009 it was identified as a pharmacological chaperone for mutant glucocerebrosidase, albeit in a several-fold higher dose. Unfortunately, there have been no pharma-driven clinical trials to establish its use. Thus, real-world observational data are needed on the safety and efficacy of ambroxol for patients with Gaucher disease (GD) and GBA-Parkinson disease (GBA-PD). Clinicians treating patients with ambroxol for GD and GBA-PD were approached to collaborate in an investigator-initiated registry. Anonymized data were collected, including demographics, GD type, GD-specific therapy (when applicable), adverse events (AEs), and, when available, efficacy data. We report the data of the first 41 patients (25 females) at a median (range) age 17 (1.5-74) from 13 centers; 11 with GD type 1(four diagnosed with PD), 27 with neuronopathic GD (nGD), and three GBA mutation carriers with PD. The median (range) treatment period and maximum dose of ambroxol were 19 (1-76) months and 435 (75-1485) mg/day, respectively. One patient with type 2 GD died of her disease. No other severe AEs were reported. Twelve patients experienced AE, including minor bowel discomfort, cough, allergic reaction, mild proteinuria, dizziness and disease progression. Clinical benefits were reported in 25 patients, including stable or improved neurological status, increased physical activity, and reduced fatigue. Until the approval of specific therapies for nGD and disease-modification for GBA-PD, these preliminary data may be encouraging to physicians and patients who consider an off-label use of ambroxol.

Early initiation of ambroxol treatment diminishes neurological manifestations of type 3 Gaucher disease: A long-term outcome of two siblings

Gaucher disease type 3 (GD3) is a severely debilitating disorder characterized by multisystemic manifestations and neurodegeneration. Enzyme replacement therapy alleviates visceral signs and symptoms but has no effect on neurological features. Ambroxol has been suggested as an enzyme enhancement agent. Some studies have confirmed its effectiveness in preventing the progression of neurological manifestations of neuronopathic Gaucher disease. In this study, we report two GD3 siblings in whom ambroxol combined with enzyme replacement therapy was initiated at different stages of the disease. We demonstrate the enzyme enhancement effect of ambroxol on L444P/H225Q;D409H glucocerebrosidase activity through results of fibroblast studies and long-term clinical outcomes of the two patients. The sibling diagnosed at the age of four-and-a-half years with significant neurological involvement manifested relatively rapid improvement on ambroxol treatment, followed by stabilization of further course. The younger sibling, in whom the treatment was started at seven weeks, displayed attention deficit and low average cognitive functioning at the age of seven years, but did not manifest other neurological symptoms. The difference in neurological outcomes indicates that ambroxol delayed or even halted the evolution of neurological manifestations in the younger sibling. This observation suggests that early initiation of ambroxol treatment may arrest neurological involvement in some GD3 patients.

Diagnosing neuronopathic Gaucher disease: New considerations and challenges in assigning Gaucher phenotypes

Gaucher disease (GD), resulting from biallelic mutations in the gene GBA1, is a monogenic recessively inherited Mendelian disorder with a wide range of phenotypic presentations. The more severe forms of the disease, acute neuronopathic GD (GD2) and chronic neuronopathic GD (GD3), also have a continuum of disease severity with an overlap in manifestations and limited genotype-phenotype correlation. In very young patients, assigning a definitive diagnosis can sometimes be challenging. Several recent studies highlight specific features of neuronopathic GD that may provide diagnostic clues. Distinguishing between the different GD types has important therapeutic implications. Currently there are limited treatment options specifically for neuronopathic GD due to the difficulty in delivering therapies across the blood-brain barrier. In this work, we present both classic and newly appreciated aspects of the Gaucher phenotype that can aid in discriminating between acute and chronic neuronopathic GD, and highlight the continuing therapeutic challenges.

In vitro and in vivo effects of Ambroxol chaperone therapy in two Italian patients affected by neuronopathic Gaucher disease and epilepsy

Gaucher disease (GD) is an autosomal recessive lysosomal storage disorder caused by mutations in the acid β-glucosidase encoding gene (GBA1), resulting in the deficient activity of acid β-glucosidase (GCase). To date, there is no approved treatment for the neurological manifestations of the disease. The role of Ambroxol as a chaperone for mutant GCase has been extensively demonstrated in vitro. Furthermore, different authors have reported beneficial effects of high doses of Ambroxol on neurological manifestations in patients affected by GD.

In this report, we describe the in vitro and in vivo effects of Ambroxol in two patients (P1 and P2) affected by the neurological form of GD and epilepsy, carrying mutations already reported as responsive to the chaperone. Indeed, P1 presented the N188S mutation in compound heterozygous with a null allele (IVS2 + 1G > A) and P2 was homozygous for the L444P mutation. As expected, a beneficial effect of Ambroxol was observed in cultured fibroblasts as well as in vivo, both on epilepsy and on biomarkers of GD, in P1. However, Ambroxol was completely undefective in P2, suggesting that other factors besides the GBA1 mutation itself would be involved in the response therapy which would be difficult to predict based on the patient genotype. The present report expands the experience of Ambroxol treatment in neurological GD patients and highlights the need to in vitro test the individual response to Ambroxol even in patients carrying mutations already classified as responsive to the chaperone.

Sphingolipids metabolism alteration in the central nervous system: Amyotrophic lateral sclerosis (ALS) and other neurodegenerative diseases

Sphingolipids are complex lipids. They play a structural role in neurons, but are also involved in regulating cellular communication, and neuronal differentiation and maturation. There is increasing evidence to suggest that dysregulated metabolism of sphingolipids is linked to neurodegenerative processes in amyotrophic lateral sclerosis (ALS), Parkinson's disease and Gaucher's disease. In this review, we provide an overview of the role of sphingolipids in the development and maintenance of the nervous system. We describe the implications of altered metabolism of sphingolipids in the pathophysiology of certain neurodegenerative diseases, with a primary focus on ALS. Finally, we provide an update of potential treatments that could be used to target the metabolism of sphingolipids in neurodegenerative diseases.

Ambroxol and Ciprofloxacin Show Activity Against SARS-CoV2 in Vero E6 Cells at Clinically-Relevant Concentrations

We studied the activity of a range of weakly basic and moderately lipophilic drugs against SARS CoV2 in Vero E6 cells, using Vero E6 survival, qPCR of viral genome and plaque forming assays. No clear relationship between their weakly basic and hydrophobic nature upon their activity was observed. However, the approved drugs ambroxol and ciprofloxacin showed potent activity at concentrations that are clinically relevant and within their known safety profiles, and so may provide potentially useful agents for preclinical and clinical studies in COVID-19.

The natural history of type 2 Gaucher disease in the 21st century: A retrospective study

OBJECTIVE

To gather natural history data to better understand the changing course of type 2 Gaucher disease (GD2) in order to guide future interventional protocols.

METHODS

A structured interview was conducted with parents of living or deceased patients with GD2. Retrospective information obtained included disease presentation, progression, medical and surgical history, medications, family history, management, complications, and cause of death, as well as the impact of disease on families.

RESULTS

Data from 23 patients were analyzed (20 deceased and 3 living), showing a mean age at death of 19.2 months, ranging from 3 to 55 months. Fourteen patients were treated with enzyme replacement therapy, 2 were treated with substrate reduction therapy, and 3 underwent bone marrow transplantation. Five patients received ambroxol and one was on N-acetylcysteine, both considered experimental treatments. Fifteen patients had gastrostomy tubes placed; 10 underwent tracheostomies. Neurologic disease manifestations included choking episodes, myoclonic jerks, autonomic dysfunction, apnea, seizures, and diminished blinking, all of which worsened as disease progressed.

CONCLUSIONS

Current available therapies appear to prolong life but do not alter neurologic manifestations. Despite aggressive therapeutic interventions, GD2 remains a progressive disorder with a devastating prognosis that may benefit from new treatment approaches.

Precision Medicine for Lysosomal Disorders

Precision medicine (PM) is an emerging approach for disease treatment and prevention that accounts for the individual variability in the genes, environment, and lifestyle of each person. Lysosomal diseases (LDs) are a group of genetic metabolic disorders that include approximately 70 monogenic conditions caused by a defect in lysosomal function. LDs may result from primary lysosomal enzyme deficiencies or impairments in membrane-associated proteins, lysosomal enzyme activators, or modifiers that affect lysosomal function. LDs are heterogeneous disorders, and the phenotype of the affected individual depends on the type of substrate and where it accumulates, which may be impacted by the type of genetic change and residual enzymatic activity. LDs are individually rare, with a combined incidence of approximately 1:4000 individuals. Specific therapies are already available for several LDs, and many more are in development. Early identification may enable disease course prediction and a specific intervention, which is very important for clinical outcome. Driven by advances in omics technology, PM aims to provide the most appropriate management for each patient based on the disease susceptibility or treatment response predictions for specific subgroups. In this review, we focused on the emerging diagnostic technologies that may help to optimize the management of each LD patient and the therapeutic options available, as well as in clinical developments that enable customized approaches to be selected for each subject, according to the principles of PM.

Treatment Efficiency in Gaucher Patients Can Reliably Be Monitored by Quantification of Lyso-Gb1 Concentrations in Dried Blood Spots

Gaucher disease (GD) is a lysosomal storage disorder that responds well to enzyme replacement therapy (ERT). Certain laboratory parameters, including blood concentration of glucosylsphingosine (Lyso-Gb1), the lyso-derivate of the common glycolipid glucocerebroside, correlate with clinical improvement and are therefore considered candidate-monitoring biomarkers. Whether they can indicate a reduction or loss of treatment efficiency, however, has not been systematically addressed for obvious reasons. We established and validated measurement of Lyso-Gb1 from dried blood spots (DBSs) by mass spectrometry. We then characterized the assay’s longitudinal performance in 19 stably ERT-treated GD patients by dense monitoring over a 3-year period. The observed level of fluctuation was accounted for in the subsequent development of a unifying data normalization concept. The resulting approach was eventually applied to data from Lyso-Gb1 measurements after an involuntary treatment break for all 19 patients. It enabled separation of the “under treatment” versus “not under treatment” conditions with high sensitivity and specificity. We conclude that Lyso-Gb1 determination from DBSs indicates treatment issues already at an early stage before clinical consequences arise. In addition to its previously shown diagnostic utility, Lyso-Gb1 thereby qualifies as a monitoring biomarker in GD patients.

Small Molecule Chaperones for the Treatment of Gaucher Disease and GBA1-Associated Parkinson Disease

Parkinson disease, the second most common movement disorder, is a complex neurodegenerative disorder hallmarked by the accumulation of alpha-synuclein, a neural-specific small protein associated with neuronal synapses. Mutations in the glucocerebrosidase gene (GBA1), implicated in the rare, autosomal recessive lysosomal disorder Gaucher disease, are the most common known genetic risk factor for Parkinson disease. Insights into the inverse relationship between glucocerebrosidase and alpha-synuclein have led to new therapeutic approaches for the treatment of Gaucher disease and GBA1-associated Parkinson disease. Unlike the current drugs used to treat Gaucher disease, which are highly expensive and do not cross the blood-brain-barrier, new small molecules therapies, including competitive and non-competitive chaperones that enhance glucocerebrosidase levels are being developed to overcome these limitations. Some of these include iminosugars, ambroxol, other competitive glucocerebrosidase inhibitors, and non-inhibitory chaperones or activators that do not compete for the active site. These drugs, which have been shown in different disease models to increase glucocerebrosidase activity, could have potential as a therapy for Gaucher disease and GBA1- associated Parkinson disease. Some have been demonstrated to reduce α-synuclein levels in pre-clinical studies using cell-based or animal models of GBA1-associated Parkinson disease, and may also have utility for idiopathic Parkinson disease.

Altered Sphingolipids Metabolism Damaged Mitochondrial Functions: Lessons Learned From Gaucher and Fabry Diseases

Sphingolipids represent a class of bioactive lipids that modulate the biophysical properties of biological membranes and play a critical role in cell signal transduction. Multiple studies have demonstrated that sphingolipids control crucial cellular functions such as the cell cycle, senescence, autophagy, apoptosis, cell migration, and inflammation. Sphingolipid metabolism is highly compartmentalized within the subcellular locations. However, the majority of steps of sphingolipids metabolism occur in lysosomes. Altered sphingolipid metabolism with an accumulation of undigested substrates in lysosomes due to lysosomal enzyme deficiency is linked to lysosomal storage disorders (LSD). Trapping of sphingolipids and their metabolites in the lysosomes inhibits lipid recycling, which has a direct effect on the lipid composition of cellular membranes, including the inner mitochondrial membrane. Additionally, lysosomes are not only the house of digestive enzymes, but are also responsible for trafficking organelles, sensing nutrients, and repairing mitochondria. However, lysosomal abnormalities lead to alteration of autophagy and disturb the energy balance and mitochondrial function. In this review, an overview of mitochondrial function in cells with altered sphingolipid metabolism will be discussed focusing on the two most common sphingolipid disorders, Gaucher and Fabry diseases. The review highlights the status of mitochondrial energy metabolism and the regulation of mitochondria-autophagy-lysosome crosstalk.