Pilot study using ambroxol as a pharmacological chaperone in type 1 Gaucher disease

GBA1-Associated Parkinson's Disease Is a Distinct Entity

GBA1-associated Parkinson's disease (GBA1-PD) is increasingly recognized as a distinct entity within the spectrum of parkinsonian disorders. This review explores the unique pathophysiological features, clinical progression, and genetic underpinnings that differentiate GBA1-PD from idiopathic Parkinson's disease (iPD). GBA1-PD typically presents with earlier onset and more rapid progression, with a poor response to standard PD medications. It is marked by pronounced cognitive impairment and a higher burden of non-motor symptoms compared to iPD. Additionally, patients with GBA1-PD often exhibit a broader distribution of Lewy bodies within the brain, accentuating neurodegenerative processes. The pathogenesis of GBA1-PD is closely associated with mutations in the GBA1 gene, which encodes the lysosomal enzyme beta-glucocerebrosidase (GCase). In this review, we discuss two mechanisms by which GBA1 mutations contribute to disease development: 'haploinsufficiency,' where a single functional gene copy fails to produce a sufficient amount of GCase, and 'gain of function,' where the mutated GCase acquires harmful properties that directly impact cellular mechanisms for alpha-synuclein degradation, leading to alpha-synuclein aggregation and neuronal cell damage. Continued research is advancing our understanding of how these mechanisms contribute to the development and progression of GBA1-PD, with the 'gain of function' mechanism appearing to be the most plausible. This review also explores the implications of GBA1 mutations for therapeutic strategies, highlighting the need for early diagnosis and targeted interventions. Currently, small molecular chaperones have shown the most promising clinical results compared to other agents. This synthesis of clinical, pathological, and molecular aspects underscores the assertion that GBA1-PD is a distinct clinical and pathobiological PD phenotype, necessitating specific management and research approaches to better understand and treat this debilitating condition.

Development of precision therapies for rare inborn errors of metabolism: Functional investigations in cell culture models

Due to the low number of patients, rare genetic diseases are a special challenge for the development of therapies, especially for diseases that result from numerous, patient-specific pathogenic variants. Precision medicine makes use of various kinds of molecular information about a specific variant, so that the possibilities for an effective therapy based on the molecular features of the variants can be elucidated. The attention to personalized precision therapies has increased among scientists and clinicians, since the "single drug for all patients" approach does not allow the classification of individuals in subgroups according to the differences in the disease genotype or phenotype. This review article summarizes some approaches of personalized precision medicine that can be used for a cost-effective and fast development of therapies, even for single patients. We have focused on specific examples on inborn errors of metabolism, with special attention on drug repurposing. Furthermore, we provide an overview of cell culture models that are suitable for precision medicine approaches.

Drug Repurposing and Lysosomal Storage Disorders: A Trick to Treat

Rare diseases, or orphan diseases, are defined as diseases affecting a small number of people compared to the general population. Among these, we find lysosomal storage disorders (LSDs), a cluster of rare metabolic diseases characterized by enzyme mutations causing abnormal glycolipid storage. Drug repositioning involves repurposing existing approved drugs for new therapeutic applications, offering advantages in cost, time savings, and a lower risk of failure. We present a comprehensive analysis of existing drugs, their repurposing potential, and their clinical implications in the context of LSDs, highlighting the necessity of mutation-specific approaches. Our review systematically explores the landscape of drug repositioning as a means to enhance LSDs therapies. The findings advocate for the strategic repositioning of drugs, accentuating its role in expediting the discovery of effective treatments. We conclude that drug repurposing represents a viable pathway for accelerating therapeutic discovery for LSDs, emphasizing the need for the careful evaluation of drug efficacy and toxicity in disease-specific contexts.

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.

The use of Ambroxol for the treatment of Gaucher disease: A systematic review

Gaucher disease (GD) is a heterogeneous condition requiring tailored treatment approaches. The aim of this systematic review was to synthesise and evaluate current evidence pertaining to the use of Ambroxol for the treatment of GD. Published and unpublished literature databases, conference proceedings and the reference lists of included studies were searched until 23 November 2023. A narrative synthesis was performed. Database search and risk of bias assessment were performed independently by two reviewers. Twenty-one studies (182 patients) were included. The evidence was low in quality. Variable responses to Ambroxol were observed. Response rates were 36% and 55% in two studies reporting on type 1 GD. One study found a 22% response rate in type 2 GD, whereas another study found 29% of patients with type 3 GD reported neurological improvements. No severe adverse events were reported in the literature, with mild and reversible side effects reported. Varying response rates are to be expected (29%-100%) when treating neurological manifestations. Varying degrees of symptomatic improvement for the treatment of GD were noted in the literature. Multidisciplinary team input and clinical judgement are advised to provide personalized treatment of this complex and multi-faceted condition.

Ambroxol as a disease-modifying treatment to reduce the risk of cognitive impairment in GBA-associated Parkinson's disease: a multicentre, randomised, double-blind, placebo-controlled, phase II trial. The AMBITIOUS study protocol

Background

Heterozygous mutations in the GBA gene, encoding the lysosomal enzyme β-glucocerebrosidase (GCase), are the most frequent genetic risk factor for Parkinson's disease (PD). GBA-related PD (GBA-PD) patients have higher risk of dementia and reduced survival than non-carriers. Preclinical studies and one open-label trial in humans demonstrated that the chaperone ambroxol (ABX) increases GCase levels and modulates α-synuclein levels in the blood and cerebrospinal fluid (CSF).

Methods and analysis

In this multicentre, double-blind, placebo-controlled, phase II clinical trial, we randomise patients with GBA-PD in a 1:1 ratio to either oral ABX 1.2 g/day or placebo. The duration of treatment is 52 weeks. Each participant is assessed at baseline and weeks 12, 26, 38, 52 and 78. Changes in the Montreal Cognitive Assessment score and the frequency of mild cognitive impairment and dementia between baseline and weeks 52 are the primary outcome measures. Secondary outcome measures include changes in validated scales/questionnaires assessing motor and non-motor symptoms. Neuroimaging features and CSF neurodegeneration markers are used as surrogate markers of disease progression. GCase activity, ABX and α-synuclein levels are also analysed in blood and CSF. A repeated-measures analysis of variance will be used for elaborating results. The primary analysis will be by intention to treat.

Ethics and dissemination

The study and protocols have been approved by the ethics committee of centres. The study is conducted according to good clinical practice and the Declaration of Helsinki. The trial findings will be published in peer-reviewed journals and presented at conferences.

Trial registration numbers

NCT05287503, EudraCT 2021-004565-13.

Inborn Errors of Metabolism with Ataxia: Current and Future Treatment Options

A number of hereditary ataxias are caused by inborn errors of metabolism (IEM), most of which are highly heterogeneous in their clinical presentation. Prompt diagnosis is important because disease-specific therapies may be available. In this review, we offer a comprehensive overview of metabolic ataxias summarized by disease, highlighting novel clinical trials and emerging therapies with a particular emphasis on first-in-human gene therapies. We present disease-specific treatments if they exist and review the current evidence for symptomatic treatments of these highly heterogeneous diseases (where cerebellar ataxia is part of their phenotype) that aim to improve the disease burden and enhance quality of life. In general, a multimodal and holistic approach to the treatment of cerebellar ataxia, irrespective of etiology, is necessary to offer the best medical care. Physical therapy and speech and occupational therapy are obligatory. Genetic counseling is essential for making informed decisions about family planning.

Therapeutic Role of Pharmacological Chaperones in Lysosomal Storage Disorders: A Review of the Evidence and Informed Approach to Reclassification

The treatment landscape for lysosomal storage disorders (LSDs) is rapidly evolving. An increase in the number of preclinical and clinical studies in the last decade has demonstrated that pharmacological chaperones are a feasible alternative to enzyme replacement therapy (ERT) for individuals with LSDs. A systematic search was performed to retrieve and critically assess the evidence from preclinical and clinical applications of pharmacological chaperones in the treatment of LSDs and to elucidate the mechanisms by which they could be effective in clinical practice. Publications were screened according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) reporting guidelines. Fifty-two articles evaluating 12 small molecules for the treatment of seven LSDs are included in this review. Overall, a substantial amount of preclinical and clinical data support the potential of pharmacological chaperones as treatments for Fabry disease, Gaucher disease, and Pompe disease. Most of the available clinical evidence evaluated migalastat for the treatment of Fabry disease. There was a lack of consistency in the terminology used to describe pharmacological chaperones in the literature. Therefore, the new small molecule chaperone (SMC) classification system is proposed to inform a standardized approach for new, emerging small molecule therapies in LSDs.

Potential Binding Sites of Pharmacological Chaperone NCGC00241607 on Mutant β-Glucocerebrosidase and Its Efficacy on Patient-Derived Cell Cultures in Gaucher and Parkinson's Disease

Mutations in the GBA1 gene, encoding the lysosomal enzyme glucocerebrosidase (GCase), cause Gaucher disease (GD) and are the most common genetic risk factor for Parkinson's disease (PD). Pharmacological chaperones (PCs) are being developed as an alternative treatment approach for GD and PD. To date, NCGC00241607 (NCGC607) is one of the most promising PCs. Using molecular docking and molecular dynamics simulation we identified and characterized six allosteric binding sites on the GCase surface suitable for PCs. Two sites were energetically more preferable for NCGC607 and located nearby to the active site of the enzyme. We evaluated the effects of NCGC607 treatment on GCase activity and protein levels, glycolipids concentration in cultured macrophages from GD (n = 9) and GBA-PD (n = 5) patients as well as in induced human pluripotent stem cells (iPSC)-derived dopaminergic (DA) neurons from GBA-PD patient. The results showed that NCGC607 treatment increased GCase activity (by 1.3-fold) and protein levels (by 1.5-fold), decreased glycolipids concentration (by 4.0-fold) in cultured macrophages derived from GD patients and also enhanced GCase activity (by 1.5-fold) in cultured macrophages derived from GBA-PD patients with N370S mutation (p < 0.05). In iPSC-derived DA neurons from GBA-PD patients with N370S mutation NCGC607 treatment increased GCase activity and protein levels by 1.1-fold and 1.7-fold (p < 0.05). Thus, our results showed that NCGC607 could bind to allosteric sites on the GCase surface and confirmed its efficacy on cultured macrophages from GD and GBA-PD patients as well as on iPSC-derived DA neurons from GBA-PD patients.

High-Dose Ambroxol Therapy in Type 1 Gaucher Disease Focusing on Patients with Poor Response to Enzyme Replacement Therapy or Substrate Reduction Therapy

Ambroxol hydrochloride (ABX), an oral mucolytic drug available over the counter for many years, acts as a pharmacological chaperone for mutant glucocerebrosidase, albeit at higher doses. Proof-of-concept reports have been published over the past decade on all three types of Gaucher disease (GD). Here, we assess the safety and efficacy of 12 months of 600 mg ambroxol per day in three groups of Type 1 GD patients with a suboptimal response to enzyme replacement therapy (ERT) or substrate reduction therapy (SRT), defined as platelet count < 100 × 10³/L, lumbar spine bone density T-score < -2.0, and/or LysoGb1 > 200 ng/mL, and for a group of naïve patients who had abnormal values in two of these three parameters. We enrolled 40 patients: 28 ERT- or SRT-treated, and 12 naïve. There were no severe adverse effects (AEs). There were 24 dropouts, mostly due to AEs (n = 12), all transient, and COVID-19 (n = 7). Among the 16 completers, 5 (31.2%) had a >20% increase in platelet count, 6 (37.5%) had a >0.2 increase in T-score, and 3 (18.7%) had a >20% decrease in Lyso-Gb1. This study expands the number of patients exposed to high-dose ABX, showing good safety and satisfactory efficacy, and provides an additional rationale for adding off-label ABX to the arsenal of therapies that could be offered to patients with GD1 and a suboptimal response or those unable to receive ERT or SRT.

Genetic variations in GBA1 and LRRK2 genes: Biochemical and clinical consequences in Parkinson disease

Variants in the GBA1 and LRRK2 genes are the most common genetic risk factors associated with Parkinson disease (PD). Both genes are associated with lysosomal and autophagic pathways, with the GBA1 gene encoding for the lysosomal enzyme, glucocerebrosidase (GCase) and the LRRK2 gene encoding for the leucine-rich repeat kinase 2 enzyme. GBA1-associated PD is characterized by earlier age at onset and more severe non-motor symptoms compared to sporadic PD. Mutations in the GBA1 gene can be stratified into severe, mild and risk variants depending on the clinical presentation of disease. Both a loss- and gain- of function hypothesis has been proposed for GBA1 variants and the functional consequences associated with each variant is often linked to mutation severity. On the other hand, LRRK2-associated PD is similar to sporadic PD, but with a more benign disease course. Mutations in the LRRK2 gene occur in several structural domains and affect phosphorylation of GTPases. Biochemical studies suggest a possible convergence of GBA1 and LRRK2 pathways, with double mutant carriers showing a milder phenotype compared to GBA1-associated PD. This review compares GBA1 and LRRK2-associated PD, and highlights possible genotype-phenotype associations for GBA1 and LRRK2 separately, based on biochemical consequences of single variants.

Therapeutic Strategies For Tay-Sachs Disease

Tay-Sachs disease (TSD) is an autosomal recessive disease that features progressive neurodegenerative presentations. It affects one in 100,000 live births. Currently, there is no approved therapy or cure. This review summarizes multiple drug development strategies for TSD, including enzyme replacement therapy, pharmaceutical chaperone therapy, substrate reduction therapy, gene therapy, and hematopoietic stem cell replacement therapy. In vitro and in vivo systems are described to assess the efficacy of the aforementioned therapeutic strategies. Furthermore, we discuss using MALDI mass spectrometry to perform a high throughput screen of compound libraries. This enables discovery of compounds that reduce GM2 and can lead to further development of a TSD therapy.

GCase Enhancers: A Potential Therapeutic Option for Gaucher Disease and Other Neurological Disorders

Pharmaceutical chaperones (PCs) are small compounds able to bind and stabilize misfolded proteins, allowing them to recover their native folding and thus their biological activity. In particular, lysosomal storage disorders (LSDs), a class of metabolic disorders due to genetic mutations that result in misfolded lysosomal enzymes, can strongly benefit from the use of PCs able to facilitate their translocation to the lysosomes. This results in a recovery of their catalytic activity. No PC for the GCase enzyme (lysosomal acid-β-glucosidase, or glucocerebrosidase) has reached the market yet, despite the importance of this enzyme not only for Gaucher disease, the most common LSD, but also for neurological disorders, such as Parkinson’s disease. This review aims to describe the efforts made by the scientific community in the last 7 years (since 2015) in order to identify new PCs for the GCase enzyme, which have been mainly identified among glycomimetic-based compounds.

GBA Variants and Parkinson Disease: Mechanisms and Treatments

The GBA gene encodes for the lysosomal enzyme glucocerebrosidase (GCase), which maintains glycosphingolipid homeostasis. Approximately 5–15% of PD patients have mutations in the GBA gene, making it numerically the most important genetic risk factor for Parkinson disease (PD). Clinically, GBA-associated PD is identical to sporadic PD, aside from the earlier age at onset (AAO), more frequent cognitive impairment and more rapid progression. Mutations in GBA can be associated with loss- and gain-of-function mechanisms. A key hallmark of PD is the presence of intraneuronal proteinaceous inclusions named Lewy bodies, which are made up primarily of alpha-synuclein. Mutations in the GBA gene may lead to loss of GCase activity and lysosomal dysfunction, which may impair alpha-synuclein metabolism. Models of GCase deficiency demonstrate dysfunction of the autophagic-lysosomal pathway and subsequent accumulation of alpha-synuclein. This dysfunction can also lead to aberrant lipid metabolism, including the accumulation of glycosphingolipids, glucosylceramide and glucosylsphingosine. Certain mutations cause GCase to be misfolded and retained in the endoplasmic reticulum (ER), activating stress responses including the unfolded protein response (UPR), which may contribute to neurodegeneration. In addition to these mechanisms, a GCase deficiency has also been associated with mitochondrial dysfunction and neuroinflammation, which have been implicated in the pathogenesis of PD. This review discusses the pathways associated with GBA-PD and highlights potential treatments which may act to target GCase and prevent neurodegeneration.

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.

Ambroxol chaperone therapy for Gaucher disease type I-associated liver cirrhosis and portal hypertension: a case report

BACKGROUND

Gaucher disease (GD) is a rare autosomal recessive inherited disease caused by the deficiency of glucocerebrosidase and characterized by a broad spectrum of clinical manifestations, including hepatosplenomegaly, bone infiltration, and cytopenia. Moreover, it is even involved in the central nervous system. GD is classified into three phenotypes on the ground of neurologic involvement: type 1 (GD1), the commonly adult-onset, non-neuropathic variant; type 2 (GD2), the acute neuropathic form; and type 3 (GD3), the severe chronic neuro-visceral form. Recently, several studies have shown a promising outcome of ambroxol chaperone therapy for the treatment of GD, but its therapeutic role in GD1-associated liver cirrhosis and portal hypertension was not verified.

CASE PRESENTATION

A 36-year-old male patient was admitted for esophageal varices lasting for one year with a 34-year history of liver and spleen enlargement. The patient was diagnosed with GD1 with cirrhosis and portal hypertension based on the identification of Gaucher cells and advanced fibrosis in the liver biopsy tissue and two known pathogenic mutations on the glucocerebrosidase (GBA) gene. The patient received 660 mg/d of ambroxol for up to two years. At his six-month follow-up, the patient exhibited a remarkable increase in GBA activity (+35.5%) and decrease in liver stiffness (-19.5%) and portal vein diameter (-41.2%) as examined by ultrasound elastography and computer tomography, respectively. At two-year follow-up, the liver stiffness was further reduced (-55.5%) in comparison with untreated patients.

CONCLUSION

This case report suggests that long-term treatment with high dose ambroxol may play a role in the reduction of hepatic fibrosis in GD1.

Cellular and biochemical response to chaperone versus substrate reduction therapies in neuropathic Gaucher disease

Gaucher disease (GD) is caused by deficiency of the lysosomal membrane enzyme glucocerebrosidase (GCase) and the subsequent accumulation of its substrate, glucosylceramide (GC). Mostly missense mutations of the glucocerebrosidase gene (GBA) cause GCase misfolding and inhibition of proper lysosomal trafficking. The accumulated GC leads to lysosomal dysfunction and impairs the autophagy pathway. GD types 2 and 3 (GD2-3), or the neuronopathic forms, affect not only the Central Nervous System (CNS) but also have severe systemic involvement and progressive bone disease. Enzyme replacement therapy (ERT) successfully treats the hematologic manifestations; however, due to the lack of equal distribution of the recombinant enzyme in different organs, it has no direct impact on the nervous system and has minimal effect on bone involvement. Small molecules have the potential for better tissue distribution. Ambroxol (AMB) is a pharmacologic chaperone that partially recovers the mutated GCase activity and crosses the blood-brain barrier. Eliglustat (EGT) works by inhibiting UDP-glucosylceramide synthase, an enzyme that catalyzes GC biosynthesis, reducing GC influx load into the lysosome. Substrate reduction therapy (SRT) using EGT is associated with improvement in GD bone marrow burden score and bone mineral density parallel with the improvement in hematological parameters. We assessed the effects of EGT and AMB on GCase activity and autophagy-lysosomal pathway (ALP) in primary cell lines derived from patients with GD2-3 and compared to cell lines from healthy controls. We found that EGT, same as AMB, enhanced GCase activity in control cells and that an individualized response, that varied with GBA mutations, was observed in cells from patients with GD2-3. EGT and AMB enhanced the formation of lysosomal/late endosomal compartments and improved autophagy, independent of GBA mutations. Both AMB and EGT increased mitochondrial mass and density in GD2-3 fibroblasts, suggesting enhancement of mitochondrial function by activating the mitochondrial membrane potential. These results demonstrate that EGT and AMB, with different molecular mechanisms of action, enhance GCase activity and improve autophagy-lysosome dynamics and mitochondrial functions.

Gaucher disease - therapeutic aspects in Romania

Gaucher disease is a rare autosomal recessive disease caused by the beta-glicosidase activity deficiency, which will lead to substrate accumulation mainly in the liver, spleen or bone marrow. The main symptoms are liver and spleen enlargement, anemia and low platelet count, bone crisis and fatigue. Several treatment options are available, as enzyme replacement therapy, substrate reduction therapy, or chaperones treatment whose effect is still studied. There are 77 adult patients treated at this time in Romania, 54 with intravenous enzyme replacement ant 23 with oral substrate reduction therapy. No severe adverse effects have been reported by now. All patients had improved disease related symptoms after the receiving of the treatment.

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.

Unraveling the mystery of Gaucher bone density pathophysiology

Gaucher disease (GD) is caused by pathogenic mutations in GBA1, the gene that encodes the lysosomal enzyme β-glucocerebrosidase. Despite the existence of a variety of specific treatments for GD, they cannot completely reverse bone complications. Many studies have evidenced the impairment in bone tissue of GD, and molecular mechanisms of bone density alterations in GD are being studied during the last years and different reports emphasized its efforts trying to unravel why and how bone tissue is affected. The cause of skeletal density affection in GD is a matter of debates between research groups. and there are two opposing hypotheses trying to explain reduced bone mineral density in GD: increased bone resorption versus impaired bone formation. In this review, we discuss the diverse mechanisms of bone alterations implicated in GD revealed until the present, along with a presentation of normal bone physiology and its regulation. With this information in mind, we discuss effectiveness of specific therapies, introduce possible adjunctive therapies and present a novel model for GD-associated bone density pathogenesis. Under the exposed evidence, we may conclude that both sides of the balance of remodeling process are altered. In GD the observed osteopenia/osteoporosis may be the result of contribution of both reduced bone formation and increased bone resorption.

Cross-talks among GBA mutations, glucocerebrosidase, and α-synuclein in GBA-associated Parkinson's disease and their targeted therapeutic approaches: a comprehensive review

Current therapies for Parkinson's disease (PD) are palliative, of which the levodopa/carbidopa therapy remains the primary choice but is unable to modulate the progression of neurodegeneration. Due to the complication of such a multifactorial disorder and significant limitations of the therapy, numerous genetic approaches have been proved effective in finding out genes and mechanisms implicated in this disease. Following the observation of a higher frequency of PD in Gaucher's disease (GD), a lysosomal storage condition, mutations of glycosylceramidase beta (GBA) encoding glucocerebrosidase (GCase) have been shown to be involved and have been explored in the context of PD. GBA mutations are the most common genetic risk factor of PD. Various studies have revealed the relationships between PD and GBA gene mutations, facilitating a better understanding of this disorder. Various hypotheses delineate that the pathological mutations of GBA minimize the enzymatic activity of GCase, which affects the proliferation and clearance of α-synuclein; this affects the lysosomal homeostasis, exacerbating the endoplasmic reticulum stress or encouraging the mitochondrial dysfunction. Identification of the pathological mechanisms underlying the GBA-associated parkinsonism (GBA + PD) advances our understanding of PD. This review based on current literature aims to elucidate various genetic and clinical characteristics correlated with GBA mutations and to identify the numerous pathological processes underlying GBA + PD. We also delineate the therapeutic strategies to interfere with the mutant GCase function for further improvement of the related α-synuclein-GCase crosstalks. Moreover, the various therapeutic approaches such as gene therapy, chaperone proteins, and histone deacetylase inhibitors for the treatment of GBA + PD are discussed.

Cross-talks among GBA mutations, glucocerebrosidase, and α-synuclein in GBA-associated Parkinson’s disease and their targeted therapeutic approaches: a comprehensive review

Current therapies for Parkinson’s disease (PD) are palliative, of which the levodopa/carbidopa therapy remains the primary choice but is unable to modulate the progression of neurodegeneration. Due to the complication of such a multifactorial disorder and significant limitations of the therapy, numerous genetic approaches have been proved effective in finding out genes and mechanisms implicated in this disease. Following the observation of a higher frequency of PD in Gaucher’s disease (GD), a lysosomal storage condition, mutations of glycosylceramidase beta (GBA) encoding glucocerebrosidase (GCase) have been shown to be involved and have been explored in the context of PD. GBA mutations are the most common genetic risk factor of PD. Various studies have revealed the relationships between PD and GBA gene mutations, facilitating a better understanding of this disorder. Various hypotheses delineate that the pathological mutations of GBA minimize the enzymatic activity of GCase, which affects the proliferation and clearance of α-synuclein; this affects the lysosomal homeostasis, exacerbating the endoplasmic reticulum stress or encouraging the mitochondrial dysfunction. Identification of the pathological mechanisms underlying the GBA-associated parkinsonism (GBA + PD) advances our understanding of PD. This review based on current literature aims to elucidate various genetic and clinical characteristics correlated with GBA mutations and to identify the numerous pathological processes underlying GBA + PD. We also delineate the therapeutic strategies to interfere with the mutant GCase function for further improvement of the related α-synuclein–GCase crosstalks. Moreover, the various therapeutic approaches such as gene therapy, chaperone proteins, and histone deacetylase inhibitors for the treatment of GBA + PD are discussed.

A patient with Gaucher disease and plasma cell dyscrasia: bidirectional impact

Patients with Gaucher disease (GD), a rare autosomal recessive glycosphingolipid storage disease, commonly present to hematologists with unexplained splenomegaly, thrombocytopenia, anemia, and bone symptoms. Patients with GD may develop other manifestations, such as autoimmune thrombocytopenia, monoclonal gammopathy, multiple myeloma, or, even more rarely, other hematological malignancies; sometimes they are first diagnosed during an assessment of those disorders. Although the diagnosis and management of patients with GD have significantly evolved over the last 30 years, some patients remain poor responders to GD-specific therapy, needing novel and investigational therapies. Ideally, patients with GD, like patients with other rare diseases, should be managed by a multidisciplinary team expert with the diverse clinical manifestations and potential GD-related or -unrelated comorbidities. The hematology community should be knowledgeable regarding the presentation and the variety of hematologic complications and comorbidities associated with Gaucher disease.

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.

Drug repositioning in neurodegeneration: An overview of the use of ambroxol in neurodegenerative diseases

Amyotrophic lateral sclerosis (ALS) is the most common motor neuron disease in adults. While it is primarily characterized by the death of upper and lower motor neurons, there is a significant metabolic component involved in the progression of the disease. Two-thirds of ALS patients have metabolic alterations that are associated with the severity of symptoms. In ALS, as in other neurodegenerative diseases, the metabolism of glycosphingolipids, a class of complex lipids, is strongly dysregulated. We therefore assume that this pathway constitutes an interesting avenue for therapeutic approaches. We have shown that the glucosylceramide degrading enzyme, glucocerebrosidase (GBA) 2 is abnormally increased in the spinal cord of the SOD1^G86R mouse model of ALS. Ambroxol, a chaperone molecule that inhibits GBA2, has been shown to have beneficial effects by slowing the development of the disease in SOD1^G86R mice. Currently used in clinical trials for Parkinson's and Gaucher disease, ambroxol could be considered as a promising therapeutic treatment for ALS.

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.

GBA1-associated parkinsonism: new insights and therapeutic opportunities

PURPOSE OF REVIEW

GBA1 mutations, which result in the lysosomal disorder Gaucher disease, are the most common known genetic risk factor for Parkinson disease and Dementia with Lewy Bodies (DLB). The pathogenesis of this association is not fully understood, but further elucidation of this link could lead to new therapeutic options.

RECENT FINDINGS

The characteristic clinical phenotype of GBA1-PD resembles sporadic Parkinson disease, but with an earlier onset and more severe course. Many different GBA1 mutations increase the risk of Parkinson disease, some primarily detected in specific populations. Glucocerebrosidase deficiency appears to be associated with increased α-synuclein aggregation and accumulation, mitochondrial dysfunction because of impaired autophagy, and increased endoplasmic reticulum stress.

SUMMARY

As our understanding of GBA1-associated Parkinson disease increases, new treatment opportunities emerge. MicroRNA profiles are providing examples of both up-regulated and down-regulated proteins related to GBA1 and may provide new therapeutic targets. Chaperone therapy, directed at either misfolded glucocerebrosidase or α-synuclein aggregation, is currently under development and there are several early clinical trials ongoing. Substrate reduction therapy, aimed at lowering the accumulation of metabolic by-products, especially glucosylsphingosine, is also being explored. Basic science insights from the rare disorder Gaucher disease are serving to catapult drug discovery for parkinsonism.

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.

Glucocerebrosidase as a therapeutic target for Parkinson's disease

Introduction: The association between Gaucher disease, caused by the inherited deficiency of glucocerebrosidase, and Parkinson's disease was first recognized in the clinic, noting that patients with Gaucher disease and their carrier relatives had an increased incidence of Parkinson's disease. Currently, mutations in glucocerebrosidase (GBA1) are the most common genetic risk factor for Parkinson's disease and dementia with Lewy bodies, with an inverse relationship between glucocerebrosidase and α-synuclein, a key factor in Parkinson pathogenesis. The hypothesis that therapeutic enhancement of brain glucocerebrosidase levels might reduce the aggregation, accumulation or spread of α-synuclein has spurred great interest in glucocerebrosidase as a novel therapeutic target.Area covered: This article explores the potential molecular mechanisms underlying the association between GBA1 mutations and Parkinson's disease and outlines therapeutic strategies to increase brain glucocerebrosidase, including gene therapy, targeted delivery of recombinant glucocerebrosidase to the brain, small-molecule chaperones to rescue mutant glucocerebrosidase, and small-molecule modulators to activate wild-type glucocerebrosidase.Expert opinion: Although an improved understanding of the mechanistic basis for GBA1-associated parkinsonism is essential, enhancing levels of brain glucocerebrosidase may have wide therapeutic implications. While gene therapy may ultimately be effective, less expensive and invasive small-molecule non-inhibitory chaperones or activators could significantly impact the disease course.

Dual-action ambroxol in treatment of chronic pain in Gaucher Disease

A significant number of patients with Gaucher disease (GD) suffer from chronic or acute pain that reduces their quality of life. A mutation in lysosomal enzyme β-glucosidase (GCase) leads to an accumulation of glucocerebroside in the macrophage-lineage cells, causing the development of clinical symptoms. Novel studies have revealed that ambroxol (trans-4-(2-amino-3,5-dibromobenzylamino)-cyclohexanol), the well-known mucolytic drug, acts as a chaperone for the mutant, misfolded enzyme. In addition, as has recently been shown, ambroxol is a Na_v 1.8 channel blocker in Aβ, Aδ and unmyelinated C fibres, and therefore reduces the transmission of sensory stimuli from the primary afferent neurons to the dorsal spinal cord. In this way, it can act analgetically. Thus, in addition to broncholytic properties, ambroxol combines two other important functions: it enhances enzyme replacement therapy (ERT) and pain management in patients with GD. We present a 38-year-old female patient with type 3 GD who had reported permanent bone pain in the lumbar-sacral part of the spine for over a year without any pathology evidenced in the undertaken, recommended diagnostic tests. The pain was partly controlled with standard analgesics, that is, paracetamol and tramadol. Ambroxol was introduced at a dose of 150mg/d without a noticeable effect. However, when the dose was increased up to 450mg/d, the intensity of pain diminished and subsided within the following months. Two of three attempts to reduce the dose of ambroxol resulted in a pain relapse within a week, which subsided after resetting the previous, higher dose. This observation of the effects of ambroxol in a GD patient is worth considering for other GD patients with chronic pain.

Glucocerebrosidase: Functions in and Beyond the Lysosome

Glucocerebrosidase (GCase) is a retaining β-glucosidase with acid pH optimum metabolizing the glycosphingolipid glucosylceramide (GlcCer) to ceramide and glucose. Inherited deficiency of GCase causes the lysosomal storage disorder named Gaucher disease (GD). In GCase-deficient GD patients the accumulation of GlcCer in lysosomes of tissue macrophages is prominent. Based on the above, the key function of GCase as lysosomal hydrolase is well recognized, however it has become apparent that GCase fulfills in the human body at least one other key function beyond lysosomes. Crucially, GCase generates ceramides from GlcCer molecules in the outer part of the skin, a process essential for optimal skin barrier property and survival. This review covers the functions of GCase in and beyond lysosomes and also pays attention to the increasing insight in hitherto unexpected catalytic versatility of the enzyme.

GBA1 mutations: Prospects for exosomal biomarkers in α-synuclein pathologies

The discovery that patients with Gaucher Disease (GD), a rare lysosomal storage disorder, were developing symptoms similar to Parkinson's disease (PD) led to investigation of the relationship between the two seemingly unrelated pathologies. GD, an autosomal recessive disorder, is the result of a biallelic mutation in the gene GBA1, which encodes for the enzyme glucocerebrosidase (GCase). Since the observation of its relation to PD, GBA1 mutations have become recognized as the most common genetic risk factor for development of synucleinopathies such as PD and dementia with Lewy bodies. Although the exact mechanism by which GBA1 mutations promote PD is unknown, current understanding suggests that impaired GCase inhibits lysosomal activity and decreases the overall ability of the cell to degrade proteins, specifically the neuronal protein α-synuclein. Decreased elimination of α-synuclein can lead to its abnormal accumulation and aggregation, an important component of PD development. Further understanding of how decreased GCase activity increases risk for α-synuclein pathology can assist with the development of clinical biomarkers for early detection of synucleinopathies, as well as promote novel treatments tailored for people with a GBA1 mutation. Historically, α-synuclein has not been a reliable biomarker for PD. However, recent research on α-synuclein content within exosomes, which are small vesicles released by cells that carry specific cellular cargo, has yielded encouraging results. Moreover, decreased GCase activity has been shown to influence exosomal contents. Exosomes have emerged as a promising new avenue for the identification of novel biomarkers and therapeutic targets aimed at improving neuronal GCase function and limiting the development of synucleinopathies.

Glycosphingolipids and lysosomal storage disorders as illustrated by gaucher disease

Glycosphingolipids are important building blocks of the outer leaflet of the cell membrane. They are continuously recycled, involving fragmentation inside lysosomes by glycosidases. Inherited defects in degradation cause lysosomal glycosphingolipid storage disorders. The relatively common glycosphingolipidosis Gaucher disease is highlighted here to discuss new insights in the molecular basis and pathophysiology of glycosphingolipidoses reached by fundamental research increasingly using chemical biology tools. We discuss improvements in the detection of glycosphingolipid metabolites by mass spectrometry and review new developments in laboratory diagnosis and disease monitoring as well as therapeutic interventions.

Molecular Mechanisms and Determinants of Innovative Correction Approaches in Coagulation Factor Deficiencies

Molecular strategies tailored to promote/correct the expression and/or processing of defective coagulation factors would represent innovative therapeutic approaches beyond standard substitutive therapy. Here, we focus on the molecular mechanisms and determinants underlying innovative approaches acting at DNA, mRNA and protein levels in inherited coagulation factor deficiencies, and in particular on: (i) gene editing approaches, which have permitted intervention at the DNA level through the specific recognition, cleavage, repair/correction or activation of target sequences, even in mutated gene contexts; (ii) the rescue of altered pre-mRNA processing through the engineering of key spliceosome components able to promote correct exon recognition and, in turn, the synthesis and secretion of functional factors, as well as the effects on the splicing of missense changes affecting exonic splicing elements; this section includes antisense oligonucleotide- or siRNA-mediated approaches to down-regulate target genes; (iii) the rescue of protein synthesis/function through the induction of ribosome readthrough targeting nonsense variants or the correction of folding defects caused by amino acid substitutions. Overall, these approaches have shown the ability to rescue the expression and/or function of potentially therapeutic levels of coagulation factors in different disease models, thus supporting further studies in the future aimed at evaluating the clinical translatability of these new strategies.

Gaucher disease type 3c: New patients with unique presentations and review of the literature

Gaucher disease (GD) is the most prevalent lysosomal disorder caused by GBA mutations and abnormal glucocerebrosidase function, leading to glucocerebrosideaccumulation mainly in the liver, spleen, bone marrow, lungs, and occasionally in the central nervous system. Gaucher disease type 3c (GD3c) is a rare subtype of the subacute/chronic neuronopathic GD3, caused by homozygosity for the GBA p.Asp448His (D409H) mutation. GD3c is characterized mainly by cardiovascular and neuro-ophthalmological findings. In this paper, we describe four new GD3c patients exhibiting rare cardiovascular, pulmonary and psychiatric findings, as well as atypical disease courses. Review of the GD3c-related literature revealed clinical descriptions of 36 patients, presenting predominantly with cardiovascular calcifications; 15%, including Patient 1b in this study, had non-calcified lesions - fibrosis and atherosclerosis. Only 7.5% of patients have been described without heart disease, including Patient 3; however, Patient 2 had a fulminant coronary disease. Neurological findings in GD3c consist mainly of oculomotor apraxia (80%), which is absent in Patient 3, while other neurological findings are common (65%) but diverse. Patient 1b developed a psychiatric behavioral disorder, which has not been previously described in GD3c. Patient 1b also had interstitial lung disease, which was only described in one GD3c patient as pulmonary fibrosis. In view of these unique features, we recommend a revised surveillance protocol; however, further studies are required to establish the management of these patients and the role of GBA in the described pathologies.

Exploring substituent diversity on pyrrolidine-aryltriazole iminosugars: Structural basis of β-glucocerebrosidase inhibition

The synthesis of a library of pyrrolidine-aryltriazole hybrids through CuAAC between two epimeric dihydroxylated azidomethylpyrrolidines and differently substituted phenylacetylenes is reported. The evaluation of the new compounds as inhibitors of lysosomal β-glucocerebrosidase showed the importance of the substitution pattern of the phenyl moiety in the inhibition. Crystallization and docking studies revealed key interactions of the pyrrolidine motif with aminoacid residues of the catalytic site while the aryltriazole moiety extended along a hydrophobic surface groove. Some of these compounds were able to increase the enzyme activity in Gaucher patient fibroblasts, acting as a new type of chemical chaperone for Gaucher disease.

Ambroxol as a novel disease-modifying treatment for Parkinson's disease dementia: protocol for a single-centre, randomized, double-blind, placebo-controlled trial

BACKGROUND

Currently there are no disease-modifying treatments for Parkinson's disease dementia (PDD), a condition linked to aggregation of the protein α-synuclein in subcortical and cortical brain areas. One of the leading genetic risk factors for Parkinson's disease is being a carrier in the gene for β-Glucocerebrosidase (GCase; gene name GBA1). Studies in cell culture and animal models have shown that raising the levels of GCase can decrease levels of α-synuclein. Ambroxol is a pharmacological chaperone for GCase and is able to raise the levels of GCase and could therefore be a disease-modifying treatment for PDD. The aims of this trial are to determine if Ambroxol is safe and well-tolerated by individuals with PDD and if Ambroxol affects cognitive, biochemical, and neuroimaging measures.

METHODS

This is a phase II, single-centre, double-blind, randomized placebo-controlled trial involving 75 individuals with mild to moderate PDD. Participants will be randomized into Ambroxol high-dose (1050 mg/day), low-dose (525 mg/day), or placebo treatment arms. Assessments will be undertaken at baseline, 6-months, and 12-months follow up times. Primary outcome measures will be the Alzheimer's disease Assessment Scale-cognitive subscale (ADAS-Cog) and the ADCS Clinician's Global Impression of Change (CGIC). Secondary measures will include the Parkinson's disease Cognitive Rating Scale, Clinical Dementia Rating, Trail Making Test, Stroop Test, Unified Parkinson's disease Rating Scale, Purdue Pegboard, Timed Up and Go, and gait kinematics. Markers of neurodegeneration will include MRI and CSF measures. Pharmacokinetics and pharmacodynamics of Ambroxol will be examined through plasma levels during dose titration phase and evaluation of GCase activity in lymphocytes.

DISCUSSION

If found effective and safe, Ambroxol will be one of the first disease-modifying treatments for PDD.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02914366, 26 Sep 2016/retrospectively registered.

Enzyme enhancement therapeutics for lysosomal storage diseases: Current status and perspective

Small-molecule- enzyme enhancement therapeutics (EETs) have emerged as attractive agents for the treatment of lysosomal storage diseases (LSDs), a broad group of genetic diseases caused by mutations in genes encoding lysosomal enzymes, or proteins required for lysosomal function. The underlying enzyme deficiencies characterizing LSDs cause a block in the stepwise degradation of complex macromolecules (e.g. glycosaminoglycans, glycolipids and others), such that undegraded or partially degraded substrates progressively accumulate in lysosomal and non-lysosomal compartments, a process leading to multisystem pathology via primary and secondary mechanisms. Missense mutations underlie many of the LSDs; the resultant mutant variant enzyme hydrolase is often impaired in its folding and maturation making it subject to rapid disposal by endoplasmic reticulum (ER)-associated degradation (ERAD). Enzyme deficiency in the lysosome is the result, even though the mutant enzyme may retain significant catalytic functioning. Small molecule modulators - pharmacological chaperones (PCs), or proteostasis regulators (PRs) are being identified through library screens and computational tools, as they may offer a less costly approach than enzyme replacement therapy (ERT) for LSDs, and potentially treat neuronal forms of the diseases. PCs, capable of directly stabilizing the mutant protein, and PRs, which act on other cellular elements to enhance protein maturation, both allow a proportion of the synthesized variant protein to reach the lysosome and function. Proof-of-principle for PCs and PRs as therapeutic agents has been demonstrated for several LSDs, yet definitive data of their efficacy in disease models and/or in downstream clinical studies in many cases has yet to be achieved. Basic research to understand the cellular consequences of protein misfolding such as perturbed organellar crosstalk, redox status, and calcium balance is needed. Likewise, an elucidation of the early in cellulo pathogenic events underlying LSDs is vital and may lead to the discovery of new small molecule modulators and/or to other therapeutic approaches for driving proteostasis toward protein rescue.

Dysregulation of the autophagic-lysosomal pathway in Gaucher and Parkinson's disease

The finding that mutations in the Gaucher's Disease (GD) gene GBA1 are a strong risk factor for Parkinson's Disease (PD) has allowed for unique insights into pathophysiology centered on disruption of the autophagic-lysosomal pathway. Protein aggregations in the form of Lewy bodies and the effects of canonical PD mutations that converge on the lysosomal degradation system suggest that neurodegeneration in PD is mediated by dysregulation of protein homeostasis. The well-characterized clinical and pathological relationship between PD and the lysosomal storage disorder GD emphasizes the importance of dysregulated protein metabolism in neurodegeneration, and one intriguing piece of this relationship is a shared phenotype of autophagic-lysosomal dysfunction in both diseases. Translational application of these findings may be accelerated by the use of midbrain dopamine neuronal models derived from induced pluripotent stem cells (iPSCs) that recapitulate several pathological features of GD and PD. In this review, we discuss evidence linking autophagic dysfunction to the pathophysiology of GD and GBA1-linked parkinsonism and focus more specifically on studies performed recently in iPSC-derived neurons.

Safety of ambroxol in the treatment of airway diseases in adult patients

INTRODUCTION

Ambroxol is a widely used secretolytic and mucoactive over-the-counter agent primarily used to treat respiratory diseases associated with viscid mucus. Following post-marketing reports of hypersensitivity reactions and severe cutaneous adverse reactions (SCARs) possibly linked to ambroxol, the European Union's Pharmacovigilance Risk Assessment Committee (PRAC) initiated in April 2014 a review of the safety of ambroxol in all its registered indications, which was finalized in 2016. Areas covered: Here, we evaluate the clinical safety of ambroxol and provide an expert opinion on the benefit-risk balance of ambroxol in the treatment of adult patients with bronchopulmonary diseases. The evidence for this review is derived from clinical trials of ambroxol that were provided to the PRAC by the marketing authorization holders of ambroxol-containing medicines. Expert opinion: Clinical experience accumulated from randomized clinical trials and observational studies suggests that ambroxol is a safe and well-tolerated treatment of bronchopulmonary diseases, with a well-balanced and favorable benefit-risk profile. All reported adverse events were mild and self-limiting, and the risk of SCARs with ambroxol is low. Further investigations could address the safety and efficacy of ambroxol in pediatric lung diseases and in additional therapeutic indications, such as biofilm-dependent airway disease and lysosomal storage disorders.

Drug Repurposing in Parkinson's Disease

The development of an intervention to slow or halt disease progression remains the greatest unmet therapeutic need in Parkinson's disease. Given the number of failures of various novel interventions in disease-modifying clinical trials in combination with the ever-increasing costs and lengthy processes for drug development, attention is being turned to utilizing existing compounds approved for other indications as novel treatments in Parkinson's disease. Advances in rational and systemic drug repurposing have identified a number of drugs with potential benefits for Parkinson's disease pathology and offer a potentially quicker route to drug discovery. Here, we review the safety and potential efficacy of the most promising candidates repurposed as potential disease-modifying treatments for Parkinson's disease in the advanced stages of clinical testing.

Neuraminidase 1 activates insulin receptor and reverses insulin resistance in obese mice

OBJECTIVES

Neuraminidase 1 (NEU1) cleaves terminal sialic acids of glycoconjugates during lysosomal catabolism. It also modulates the structure and activity of cellular surface receptors affecting diverse pathways. Previously we demonstrated that NEU1 activates the insulin receptor (IR) and that NEU1-deficient CathAS190A-Neo mice (hypomorph of the NEU1 activator protein, cathepsin A/CathA) on a high-fat diet (HFD) develop hyperglycaemia and insulin resistance faster than wild-type animals. The major objective of the current work was to reveal the molecular mechanism by which NEU1 desialylation activates the IR and to test if increase of NEU1 activity in insulin target tissues reverses insulin resistance and glucose intolerance.

METHODS

To test if desialylation causes a conformational change in the IR dimer we measured interaction between the receptor subunits by Bioluminescence Resonance Energy Transfer in the HEK293T cells either overexpressing NEU1 or treated with the NEU1 inhibitor. The influence of NEU1 overexpression on insulin resistance was studied in vitro in palmitate-treated HepG2 cells transduced with NEU1-expressing lentivirus and in vivo in C57Bl6 mice treated with HFD and either pharmacological inducer of NEU1, Ambroxol or NEU1-expressing adenovirus. NEU1-deficient CathAS190A-Neo mice were used as a control.

RESULTS

By desialylation of IR, NEU1 induced formation of its active dimer leading to insulin signaling. Overexpression of NEU1 in palmitate-treated HepG2 cells restored insulin signaling, suggesting that increased NEU1 levels may reverse insulin resistance. Five-day treatment of glycemic C57Bl6 mice receiving HFD with the activator of the lysosomal gene network, Ambroxol, increased NEU1 expression and activity in muscle tissue, normalized fasting glucose levels, and improved physiological and molecular responses to glucose and insulin. Ambroxol did not improve insulin sensitivity in obese insulin-resistant CathAS190A-Neo mice indicating that the Ambroxol effect is mediated through NEU1 induction. Sustained increase of liver NEU1 activity through adenovirus-based gene transfer failed to attenuate insulin resistance most probably due to negative feedback regulation of IR expression.

CONCLUSION

Together our results demonstrate that increase of NEU1 activity in insulin target tissues reverses insulin resistance and glucose intolerance suggesting that a pharmacological modulation of NEU1 activity may be potentially explored for restoring insulin sensitivity and resolving hyperglycemia associated with T2DM.

How we manage Gaucher Disease in the era of choices

Treatment of Gaucher Disease (GD) is now beset with the abundance of therapeutic options for an individual patient, making the choice of therapy complex for both expert and non-expert clinicians. The pathogenesis of all disease manifestations is a gene mutation-driven deficiency of glucocerebrosidase, but the clinical expression and response of each of the clinical manifestations to different therapies can be difficult to predict. Enzyme replacement therapy has been available since 1991 and is well-established, with known efficacy and minimal toxicity. Of interest, the three available enzymes are distinct molecules and were registered as new products, not biosimilars. Oral substrate reduction therapy has undergone a revitalisation with a newly approved agent in this class for which some efficacy and toxicity questions have been raised. Herein we present our approach to the management of GD in the era of choices, including a new algorithm for how to manage a newly diagnosed patient.

Glucocerebrosidase Mutations in Parkinson Disease

Following the discovery of a higher than expected incidence of Parkinson Disease (PD) in Gaucher disease, a lysosomal storage disorder, mutations in the glucocerebrocidase (GBA) gene, which encodes a lysosomal enzyme involved in sphingolipid degradation were explored in the context of idiopathic PD. GBA mutations are now known to be the single largest risk factor for development of idiopathic PD. Clinically, on imaging and pharmacologically, GBA PD is almost identical to idiopathic PD, other than certain features that can be identified in the specialist research setting but not in routine clinical practice. In patients with a known GBA mutation, it is possible to monitor for prodromal signs of PD. The clinical similarity with idiopathic PD and the chance to identify PD at a pre-clinical stage provides a unique opportunity to research therapeutic options for early PD, before major irreversible neurodegeneration occurs. However, to date, the molecular mechanisms which lead to this increased PD risk in GBA mutation carriers are not fully elucidated. Experimental models to define the molecular mechanisms and test therapeutic options include cell culture, transgenic mice and other in vivo models amenable to genetic manipulation, such as drosophilia. Some key pathological pathways of interest in the context of GBA mutations include alpha synuclein aggregation, lysosomal-autophagy axis changes and endoplasmic reticulum stress. Therapeutic agents that exploit these pathways are being developed and include the small molecule chaperone Ambroxol. This review aims to summarise the main features of GBA-PD and provide insights into the pathological relevance of GBA mutations on molecular pathways and the therapeutic implications for PD resulting from investigation of the role of GBA in PD.

Old wines in new bottles: Repurposing opportunities for Parkinson's disease

Parkinson's disease (PD) is a chronic progressive neurological disorder characterized by accumulation of Lewy bodies and profound loss of substantia nigra dopaminergic neurons. PD symptomatology is now recognized to include both cardinal motor as well as clinically significant non-motor symptoms. Despite intensive research, the current understanding of molecular mechanisms underlying neurodegeneration in PD is limited and has hampered the development of novel symptomatic and disease modifying therapies. The currently available treatment options are only partially or transiently effective and fail to restore the lost dopaminergic neurons or retard disease progression. Given the escalating drug development costs, lengthening timelines and declining R&D efficiency, industry and academia are increasingly focusing on ways to repurpose existing molecules as an accelerated route for drug discovery. The field of PD therapeutics is witnessing vigorous repurposing activity supported by big data analytics, computational models, and high-throughput drug screening systems. Here we review the mechanisms, efficacy, and safety of several emerging drugs currently aspiring to be repositioned for PD pharmacotherapy.

Tuning protein folding in lysosomal storage diseases: the chemistry behind pharmacological chaperones

Misfolding of proteins is the basis of several proteinopathies. Chemical and pharmacological chaperones are small molecules capable of inducing the correct conformation of proteins, thus being of interest for human therapeutics. The most recent developments in medicinal chemistry and in the drug development of pharmacological chaperones are discussed, with focus on lysosomal storage diseases.

Demographics and patient characteristics of 1209 patients with Gaucher disease: Descriptive analysis from the Gaucher Outcome Survey (GOS)

The Gaucher Outcome Survey (GOS) is an international Gaucher disease (GD) registry established in 2010 for patients with a confirmed GD diagnosis, regardless of GD type or treatment status, designed to evaluate the safety and long‐term effectiveness of velaglucerase alfa and other GD‐related treatments. As of February 25, 2017, 1209 patients had enrolled, the majority from Israel (44.3%) and the US (31.4%). Median age at GOS entry was 40.4 years, 44.1% were male, and 13.3% had undergone a total splenectomy. Most patients had type 1 GD (91.5%) and were of Ashkenazi Jewish ethnicity (55.8%). N370S/N370S was the most prevalent genotype, accounting for 44.2% of genotype‐confirmed individuals (n = 847); however, there was considerable variation between countries. A total of 887 (73.4%) patients had received ≥1 GD‐specific treatment at any time, most commonly imiglucerase (n = 587), velaglucerase alfa (n = 507), and alglucerase (n = 102). Hematological and visceral findings at the time of GOS entry were close to normal for most patients, probably a result of previous treatment; however, spleen volume of patients in Israel was almost double that of patients elsewhere (7.2 multiples of normal [MN] vs. 2.7, 2.9 and 4.9 MN in the US, UK and rest of world), which may be explained by a greater disease severity in this cohort. This analysis aimed to provide an overview of GOS and present baseline demographic and disease characteristics of participating patients to help improve the understanding of the natural history of GD and inform the overall management of patients with the disease.

Pharmacological Chaperones: Beyond Conformational Disorders

Pharmacological chaperones (PCs) are small molecules that bind to nascent protein targets to facilitate their biogenesis. The ability of PCs to assist in the folding and subsequent forward trafficking of disease-causative protein misfolding mutants has opened new avenues for the treatment of conformational diseases such as cystic fibrosis and lysosomal storage disorders. In this chapter, an overview of the use of PCs for the treatment of conformational disorders is provided. Beyond the therapeutic application of PCs for the treatment of these disorders, pharmacological chaperoning of wild-type integral membrane proteins is discussed. Central to this discussion is the notion that the endoplasmic reticulum is a reservoir of viable but inefficiently processed wild-type protein folding intermediates whose biogenesis can be facilitated by PCs to increase functional pools. To date, the potential therapeutic use of PCs to enhance the biogenesis of wild-type proteins has received little attention. Here the rationale for the development of PCs that target WT proteins is discussed. Also considered is the likelihood that some commonly used therapeutic agents may exert unrecognized pharmacological chaperoning activity on wild-type targets in patient populations.