Enzyme Replacement or Substrate Reduction? A Review of Gaucher Disease Treatment Options

Opportunities for nanomaterials in enzyme therapy

In recent years, enzyme therapy strategies have rapidly evolved to catalyze essential biochemical reactions with therapeutic potential. These approaches hold particular promise in addressing rare genetic disorders, cancer treatment, neurodegenerative conditions, wound healing, inflammation management, and infectious disease control, among others. There are several primary reasons for the utilization of enzymes as therapeutics: their substrate specificity, their biological compatibility, and their ability to generate a high number of product molecules per enzyme unit. These features have encouraged their application in enzyme replacement therapy where the enzyme serves as the therapeutic agent to rectify abnormal metabolic and physiological processes, enzyme prodrug therapy where the enzyme initiates a clinical effect by activating prodrugs, and enzyme dynamic or starving therapy where the enzyme acts upon host substrate molecules. Currently, there are >20 commercialized products based on therapeutic enzymes, but approval rates are considerably lower than other biologicals. This has stimulated nanobiotechnology in the last years to develop nanoparticle-based solutions that integrate therapeutic enzymes. This approach aims to enhance stability, prevent rapid clearance, reduce immunogenicity, and even enable spatio-temporal activation of the therapeutic catalyst. This comprehensive review delves into emerging trends in the application of therapeutic enzymes, with a particular emphasis on the synergistic opportunities presented by incorporating enzymes into nanomaterials. Such integration holds the promise of enhancing existing therapies or even paving the way for innovative nanotherapeutic approaches.

Advancements in Viral Gene Therapy for Gaucher Disease

Gaucher disease, an autosomal recessively inherited lysosomal storage disorder, results from biallelic mutations in the GBA1 gene resulting in deficient activity of the enzyme glucocerebrosidase. In Gaucher disease, the reduced levels and activity of glucocerebrosidase lead to a disparity in the rates of formation and breakdown of glucocerebroside and glucosylsphingosine, resulting in the accumulation of these lipid substrates in the lysosome. This gives rise to the development of Gaucher cells, engorged macrophages with a characteristic wrinkled tissue paper appearance. There are both non-neuronopathic (type 1) and neuronopathic (types 2 and 3) forms of Gaucher disease, associated with varying degrees of severity. The visceral and hematologic manifestations of Gaucher disease respond well to both enzyme replacement therapy and substrate reduction therapy. However, these therapies do not improve the neuronopathic manifestations, as they cannot cross the blood-brain barrier. There is now an established precedent for treating lysosomal storage disorders with gene therapy strategies, as many have the potential to cross into the brain. The range of the gene therapies being employed is broad, but this review aimed to discuss the progress, advances, and challenges in developing viral gene therapy as a treatment for Gaucher disease.

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.

Long-Term Outcomes of Disease Modifying Therapies in Gaucher Disease

OBJECTIVES

To study clinical response to treatment with enzyme replacement therapy (ERT) and substrate reduction therapy (SRT) in a cohort of Gaucher disease.

METHODS

Retrospective data of 8 patients of Gaucher disease was compiled. The treatment included all three currently available enzyme replacement therapies as well as substrate reduction therapy with Eliglustat. The relevant blood investigations were done in follow-up visits. The assessment of the effects of long-term treatment over varying periods up to 13 y was done with various issues related to the course of therapy documented.

RESULTS

Improvement in hematological parameters was seen in all patients. Reduction of spleen size occurred in 7 of 8 patients (87.5%). One patient had 2 successful pregnancies while on therapy. A distinct patient with type 3 Gaucher disease developed complication in the form of Gaucheroma within the spleen.

CONCLUSIONS

Awareness about the disease and the efficacy of the therapies amongst pediatricians will help in early diagnosis and better outcomes. The available therapies have changed the outcome of the patients and improved the quality of life in patients with Gaucher disease. The data of Indian patients is important at this juncture when under Rare Disease Policy, government funding has become available for ERT for Gaucher disease patients in India.

Cardiovascular Involvement in Fabry's Disease: New Advances in Diagnostic Strategies, Outcome Prediction and Management

Cardiovascular involvement is common in Fabry's disease and is the leading cause of morbidity and mortality. The research is focused on identifying diagnostic clues suggestive of cardiovascular involvement in the preclinical stage of the disease through clinical and imaging markers. Different pathophysiologically driven therapies are currently or will soon be available for the treatment of Fabry's disease, with the most significant benefit observed in the early stages of the disease. Thus, early diagnosis and risk stratification for adverse outcomes are crucial to determine when to start an aetiological treatment. This review describes the cardiovascular involvement in Fabry's disease, focusing on the advances in diagnostic strategies, outcome prediction and disease management.

Identification of pyrimidinyl piperazines as non-iminosugar glucocerebrosidase (GCase) pharmacological chaperones

Glucocerebrosidase (GCase) is a lysosomal enzyme encoded by the GBA1 gene, loss of function variants of which cause an autosomal recessive lysosomal storage disorder, Gaucher disease (GD). Heterozygous variants of GBA1 are also known as the strongest common genetic risk factor for Parkinson's disease (PD). Restoration of GCase enzymatic function using a pharmacological chaperone strategy is considered a promising therapeutic approach for PD and GD. We identified compound 4 as a GCase pharmacological chaperone with sub-micromolar activity from a high-throughput screening (HTS) campaign. Compound 4 was further optimised to ER-001230194 (compound 25). ER-001230194 shows improved ADME and physicochemical properties and therefore represents a novel pharmacological chaperone with which to investigate GCase pharmacology further.

Treatment of glutaric aciduria type I (GA-I) via intracerebroventricular delivery of GCDH

Glutaric aciduria type I (GA-I) is an autosomal recessive genetic disorder caused by a deficiency in glutaryl-CoA dehydrogenase (GCDH). Patients who do not receive proper treatment may die from acute encephalopathic crisis. Current treatments for GA-I include a low-lysine diet combined with oral supplementation of L-carnitine. A mouse model of Gcdh c.422_428del/c.422_428del (Gcdh -/-) was generated in our laboratory using CRISPR/Cas9. Gcdh -/- mice had significantly higher levels of glutaric acid (GA) in the plasma, liver, and brain than those in wild-type C57BL/6 mice. When given a high-protein diet (HPD) for two days, approximately 60% of Gcdh -/- mice did not survive the metabolic stress. To evaluate whether GCDH gene replacement therapy could be used to provide sustained treatment for patients with GA-1, we prepared a recombinant adeno-associated virus (rAAV) carrying a human GCDH expression cassette and injected it into Gcdh -/- neonates for a proof-of-concept (PoC) study. Our study demonstrated that delivering rAAV to the central nervous system (CNS), but not the peripheral system, significantly increased the survival rate under HPD exposure. Our study also demonstrated that rAAVPHP.eB mediated a higher efficiency than that of rAAV9 in increasing the survival rate. Surviving mice showed dose-dependent GCDH protein expression in the CNS and downregulation of GA levels. Our study demonstrated that AAV-based gene replacement therapy was effective for GA-I treatment and provided a feasible solution for this unmet medical need.

Gaucher Disease for Hematologists

Gaucher disease (GD) is a rare hereditary lysosomal storage disease that arises due to deficiency of glucocerebrosidase. Early diagnosis is very important for starting proper treatment and preventing complications. Splenomegaly, anemia, and thrombocytopenia are the most common findings in GD and so most patients are initially referred to hematologists. The Turkish Society of Hematology established its Rare Hematological Diseases Subcommittee in 2015. One of the main topics of this subcommittee was to increase and improve awareness and education of rare diseases among hematologists in Turkey. This review presents GD with an overview of its clinical features, pathophysiology, and treatment options for hematologists.

The clinical spectrum of SARS-CoV-2 infection in Gaucher disease: Effect of both a pandemic and a rare disease that disrupts the immune system

INTRODUCTION

The impact of SARS-CoV-2 in rare disease populations has been underreported. Gaucher disease (GD) is a prototype rare disease that shares with SARS-CoV-2 a disruption of the lysosomal pathway.

MATERIALS-METHODS

Retrospective analysis of 11 patients with Type 1 GD who developed COVID-19 between March 2020 and March 2021.

RESULTS

Seven male and 4 female patients with Type 1 GD developed COVID-19. One was a pediatric patient (8 years old) while the remainder were adults, median age of 44 years old (range 21 to 64 years old). Two patients required hospitalization though none required intensive care or intubation. All 11 patients recovered from COVID-19 and there were no reported deaths.

CONCLUSIONS

Our case series suggests that GD patients acquired COVID-19 at a similar frequency as the general population, though experienced a milder overall course despite harboring underlying immune system dysfunction and other known co-morbidities that confer high risk of adverse outcomes from SARS-CoV-2 infection.

Neurocognitive profile of adults with the Norrbottnian type of Gaucher disease

INTRODUCTION

Gaucher disease (GD) is a monogenic, lysosomal storage disorder, classified according to the presence of acute (type 2), chronic (type 3), or no (type 1) neurological manifestations. The Norrbottnian subtype of neuronopathic GD type 3 (GD3) is relatively frequent in the northern part of Sweden. It exhibits a wide range of neurological symptoms but is characterized by extended life expectancy compared to GD3 in other countries. The aim of our study was to describe the cognitive profile of adult patients with Norrbottnian GD3.

MATERIALS AND METHODS

Ten patients with GD3 (five males and five females) underwent neurocognitive testing with the Repeatable Battery for Assessment of Neuropsychological Status (RBANS). RBANS consists of different short tests that assess Immediate Memory, Visuospatial and Constructional function, Language, Attention, and Delayed Memory. General neurological symptoms of the patients were assessed with the modified severity scoring tool.

RESULTS

Patients (median age 41.5 range 24-57) performed lower than average in all cognitive domains. The overall index score was low (median 58.5, Interquartile range [IQR] 25.5), with the most profound deficit in attention (median 57, IQR 32.5) and immediate memory (median 76.5, IQR 13). Higher scores were found in language (median 83, IQR 21.5), delayed memory (median 81, IQR 41), and visuospatial/constructional function (median 86, IQR 32.35).

CONCLUSION

Norrbottnian GD3 patients showed a unique neurocognitive profile with low overall performance, mostly derived from low scores in attention and memory domains whereas language and visuospatial/constructional ability were relatively spared.

Long-term safety and effectiveness of velaglucerase alfa in Gaucher disease: 6-year interim analysis of a post-marketing surveillance in Japan

BACKGROUND

Gaucher disease (GD) is caused by reduced lysosomal enzyme β-glucocerebrosidase activity. Heterogeneous genotypes and phenotypes have been observed within GD types and across ethnicities. Enzyme replacement therapy is generally recommended for patients with type 1 GD, the least severe form of GD. In Japan, velaglucerase alfa has a broad indication covering type 1, 2 or 3 GD.  METHODS: All patients with type 1, 2, or 3 GD administered velaglucerase alfa 60 U/kg every 2 weeks via intravenous infusion after its launch date in Japan in 2014, were enrolled in a non-interventional, observational post-marketing surveillance (PMS). Individual patient data were reported via case report forms (CRFs). Key safety endpoints investigated included the incidence of infusion-related reactions (IRRs), the safety of velaglucerase alfa in patients with types 2 and 3 GD, from patients under one year of age to elderly patients (≥ 65 years of age). Long-term efficacy was also assessed.  RESULTS: In total, 53 patients with GD were registered. CRFs were available for 41 (77.4%) patients at the 6-year interim analysis. Fourteen adverse drug reactions (ADRs) were reported in seven patients. All reported ADRs occurred in patients with type 2 GD. ADRs were reported by 63.6% (7/11) of patients with type 2 GD. Ten ADRs were reported in five patients aged < 4 years. No elderly patients experienced any ADR during the surveillance period. Five ADRs occurring in three (10.0%) patients were classified as IRRs, with one case of vomiting (moderate severity) resulting in treatment discontinuation. Ten serious adverse events were reported in five (16.7%) patients. Three fatal events were considered to be unrelated to treatment with velaglucerase alfa. Platelet counts increased after the administration of velaglucerase alfa and were generally maintained within the normal range over the administration period. Among eleven patients tested for neutralizing anti-velaglucerase alfa antibodies, two (18.2%) were assessed as positive results.  CONCLUSION: PMS data from patients with types 1-3 GD in Japan indicate that long-term treatment with velaglucerase alfa was well-tolerated and associated with increased platelet counts, which is consistent with observations made in studies outside of Japan.

TRIAL REGISTRATION

NCT03625882 registered July 2014.

C5a Activates a Pro-Inflammatory Gene Expression Profile in Human Gaucher iPSC-Derived Macrophages

Gaucher disease (GD) is an autosomal recessive disorder caused by bi-allelic GBA1 mutations that reduce the activity of the lysosomal enzyme β-glucocerebrosidase (GCase). GCase catalyzes the conversion of glucosylceramide (GluCer), a ubiquitous glycosphingolipid, to glucose and ceramide. GCase deficiency causes the accumulation of GluCer and its metabolite glucosylsphingosine (GluSph) in a number of tissues and organs. In the immune system, GCase deficiency deregulates signal transduction events, resulting in an inflammatory environment. It is known that the complement system promotes inflammation, and complement inhibitors are currently being considered as a novel therapy for GD; however, the mechanism by which complement drives systemic macrophage-mediated inflammation remains incompletely understood. To help understand the mechanisms involved, we used human GD-induced pluripotent stem cell (iPSC)-derived macrophages. We found that GD macrophages exhibit exacerbated production of inflammatory cytokines via an innate immune response mediated by receptor 1 for complement component C5a (C5aR1). Quantitative RT-PCR and ELISA assays showed that in the presence of recombinant C5a (rC5a), GD macrophages secreted 8-10-fold higher levels of TNF-α compared to rC5a-stimulated control macrophages. PMX53, a C5aR1 blocker, reversed the enhanced GD macrophage TNF-α production, indicating that the observed effect was predominantly C5aR1-mediated. To further analyze the extent of changes induced by rC5a stimulation, we performed gene array analysis of the rC5a-treated macrophage transcriptomes. We found that rC5a-stimulated GD macrophages exhibit increased expression of genes involved in TNF-α inflammatory responses compared to rC5a-stimulated controls. Our results suggest that rC5a-induced inflammation in GD macrophages activates a unique immune response, supporting the potential use of inhibitors of the C5a-C5aR1 receptor axis to mitigate the chronic inflammatory abnormalities associated with GD.

Sphingolipid lysosomal storage diseases: from bench to bedside

Johann Ludwig Wilhelm Thudicum described sphingolipids (SLs) in the late nineteenth century, but it was only in the past fifty years that SL research surged in importance and applicability. Currently, sphingolipids and their metabolism are hotly debated topics in various biochemical fields. Similar to other macromolecular reactions, SL metabolism has important implications in health and disease in most cells. A plethora of SL-related genetic ailments has been described. Defects in SL catabolism can cause the accumulation of SLs, leading to many types of lysosomal storage diseases (LSDs) collectively called sphingolipidoses. These diseases mainly impact the neuronal and immune systems, but other systems can be affected as well. This review aims to present a comprehensive, up-to-date picture of the rapidly growing field of sphingolipid LSDs, their etiology, pathology, and potential therapeutic strategies. We first describe LSDs biochemically and briefly discuss their catabolism, followed by general aspects of the major diseases such as Gaucher, Krabbe, Fabry, and Farber among others. We conclude with an overview of the available and potential future therapies for many of the diseases. We strive to present the most important and recent findings from basic research and clinical applications, and to provide a valuable source for understanding these disorders.

Therapeutic Potential of αS Evolvability for Neuropathic Gaucher Disease

Gaucher disease (GD), the most common lysosomal storage disorder (LSD), is caused by autosomal recessive mutations of the glucocerebrosidase gene, GBA1. In the majority of cases, GD has a non-neuropathic chronic form with adult onset (GD1), while other cases are more acute and severer neuropathic forms with early onset (GD2/3). Currently, no radical therapies are established for GD2/3. Notably, GD1, but not GD2/3, is associated with increased risk of Parkinson's disease (PD), the elucidation of which might provide a clue for novel therapeutic strategies. In this context, the objective of the present study is to discuss that the evolvability of α-synuclein (αS) might be differentially involved in GD subtypes. Hypothetically, aging-associated PD features with accumulation of αS, and the autophagy-lysosomal dysfunction might be an antagonistic pleiotropy phenomenon derived from αS evolvability in the development in GD1, without which neuropathies like GD2/3 might be manifested due to the autophagy-lysosomal dysfunction. Supposing that the increased severity of GD2/3 might be attributed to the decreased activity of αS evolvability, suppressing the expression of β-synuclein (βS), a potential buffer against αS evolvability, might be therapeutically efficient. Of interest, a similar view might be applicable to Niemann-Pick type C (NPC), another LSD, given that the adult type of NPC, which is comorbid with Alzheimer's disease, exhibits milder medical symptoms compared with those of infantile NPC. Thus, it is predicted that the evolvability of amyloid β and tau, might be beneficial for the adult type of NPC. Collectively, a better understanding of amyloidogenic evolvability in the pathogenesis of LSD may inform rational therapy development.

Identification of a Reliable Biomarker Profile for the Diagnosis of Gaucher Disease Type 1 Patients Using a Mass Spectrometry-Based Metabolomic Approach

Gaucher disease (GD) is a rare autosomal recessive multisystemic lysosomal storage disorder presenting a marked phenotypic and genotypic variability. GD is caused by a deficiency in the glucocerebrosidase enzyme. The diagnosis of GD remains challenging because of the large clinical spectrum associated with the disease. Moreover, GD biomarkers are often not sensitive enough and can be subject to polymorphic variations. The main objective of this study was to perform a metabolomic study using an ultra-performance liquid chromatography system coupled to a time-of-flight mass spectrometer to identify novel GD biomarkers. Following the analysis of plasma samples from patients with GD, and age- and gender-matched control samples, supervised statistical analyses were used to find the best molecules to differentiate the two groups. Targeted biomarkers were structurally elucidated using accurate mass measurements and tandem mass spectrometry. This metabolomic study was successful in highlighting seven biomarkers associated with GD. Fragmentation tests revealed that these latter biomarkers were lyso-Gb₁ (glucosylsphingosine) and four related analogs (with the following modifications on the sphingosine moiety: -C₂H₄, -H₂, -H₂+O, and +H₂O), sphingosylphosphorylcholine, and N-palmitoyl-O-phosphocholineserine. Based on the plasma biomarker distribution, we suggest the evaluation of this GD biomarker profile, which might facilitate early diagnosis, monitoring, and follow-up of patients.

Allogeneic hematopoietic stem cell transplantation for treating severe lung involvement in Gaucher disease

Objective

To provide strategies for monitoring and treating severe lung involvement in Gaucher disease.

Study design

We reviewed the chart of a 5-year-old boy who developed rapidly progressive, severe infiltrative lung involvement of Gaucher disease (GD) and improved after allogeneic hematopoietic stem cell transplant (HSCT), along with other case studies reported before December 2019. He was diagnosed with GD (homozygous mutation at c.1448 T > C, p.L483P), and started receiving enzyme replacement therapy (ERT) at 17 months old. He developed respiratory distress symptoms after 45 months of ERT; chest imaging reported diffuse interstitial infiltration of the bilateral lungs and consolidations at the right lungs. Allogeneic HSCT using cells from a matched unrelated donor was performed four months upon progressive respiratory symptoms.

Results

His respiratory symptoms subsided in one month; chest imaging improvement, pulmonary function test improvement, and normalized activity of β-glucocerebrosidase were reported in three months.

Conclusion

This is the first report of a patient who received early and regular ERT but developed severe infiltrative lung involvement and recovered after allogeneic HSCT. Based on study results, we suggest regular chest imaging, even for asymptomatic patients. For patients with severe lung involvement, rapid deterioration, and unresponsive to higher ERT dosages, allogeneic HSCT should be considered.

Multiplexed Comparative Analysis of Intact Glycopeptides Using Electron-Transfer Dissociation and Synchronous Precursor Selection Based Triple-Stage Mass Spectrometry

A recently developed synchronous precursor selection (SPS) mass spectrometry to the third (MS3) protocol enables more accurate multiplexed quantification of proteins/peptides using tandem mass tags (TMT) through comparison of reporter ion intensities at the MS3 level. However, challenges still exist for TMT-based simultaneous quantification and identification of intact glycopeptides due to inefficient peptide backbone fragmentation when using collision-induced dissociation (CID). To overcome this limitation, here we report an improved SPS/ETD workflow for TMT-based intact glycopeptide quantification and identification. The SPS/ETD approach was implemented on an Orbitrap Tribrid mass spectrometer and begins with selection of a parent ion in the MS scan, followed by tandem mass spectrometry (MS2) fragmentation by CID in the ion trap. Following MS2 fragmentation, SPS enables simultaneous isolation of the top 10 MS2 fragment ions for further higher energy collisional dissociation (HCD) fragmentation with the resulting MS3 fragments detected in an Orbitrap analyzer. Here, in addition to the standard SPS workflow, an electron-transfer dissociation (ETD) MS2 was performed and analyzed in the ion trap. The resultant ETD and CID spectra were used for the identification of the intact glycopeptides, while the quantitative comparison of site-specific glycans was achieved utilizing TMT reporter ions from HCD MS3 spectra. For intact glycopeptides, through systematic optimization and evaluation using a glycoprotein interference model, the SPS/ETD approach was demonstrated to offer improved accuracy, precision, and sensitivity compared to traditional data-dependent MS2 quantification, while maintaining the glycopeptide identification capability. Finally, this workflow was applied for the site-specific quantitative comparison of the glycoforms for two therapeutic enzymes (Cerezyme and VPRIV) and their different lots. The results demonstrate that this workflow is suitable for TMT-based intact glycopeptide characterization of glycoproteins.

Effect of Substrate Reduction Therapy in Comparison to Enzyme Replacement Therapy on Immune Aspects and Bone Involvement in Gaucher Disease

Gaucher disease (GD) is caused by mutations in the GBA gene, leading to deficient activity of the lysosomal enzyme glucocerebrosidase. Among all the symptoms across various organ systems, bone disease is a major concern as it causes high morbidity and reduces quality of life. Enzyme replacement therapy (ERT) is the most accepted treatment; however, there are still unmet needs. As an alternative, substrate reduction therapy (SRT) was developed using glucosylceramide synthase inhibitors. In the current study, the effects of ERT vs. SRT were compared, particularly the immunological and bone remodeling aspects. GD subjects were divided into three cohorts based on their treatment at initial visit: ERT, SRT, and untreated (UT). Immunophenotyping showed no significant immune cell alterations between the cohorts. Expression of RANK/RANKL/Osteoprotegerin pathway components on immune cells and the secreted markers of bone turnover were analyzed. In the ERT cohort, no significant changes were observed in RANK, RANKL or serum biomarkers. RANKL on T lymphocytes, Osteopontin and MIP-1β decreased with SRT treatment indicating probable reduction in osteoclast activity. Other secreted factors, Osteocalcin and RANKL/Osteoprotegerin did not change with the treatment status. Insights from the study highlight personalized differences between subjects and possible use of RANK pathway components as markers for bone disease progression.

Generating comparative evidence on new drugs and devices before approval

Fewer than half of new drugs have data on their comparative benefits and harms against existing treatment options at the time of regulatory approval in Europe and the USA. Even when active-comparator trials exist, they might not produce meaningful data to inform decisions in clinical practice and health policy. The uncertainty associated with the paucity of well designed active-comparator trials has been compounded by legal and regulatory changes in Europe and the USA that have created a complex mix of expedited programmes aimed at facilitating faster access to new drugs. Comparative evidence generation is even sparser for medical devices. Some have argued that the current process for regulatory approval needs to generate more evidence that is useful for patients, clinicians, and payers in health-care systems. We propose a set of five key principles relevant to the European Medicines Agency, European medical device regulatory agencies, US Food and Drug Administration, as well as payers, that we believe will provide the necessary incentives for pharmaceutical and device companies to generate comparative data on drugs and devices and assure timely availability of evidence that is useful for decision making. First, labelling should routinely inform patients and clinicians whether comparative data exist on new products. Second, regulators should be more selective in their use of programmes that facilitate drug and device approvals on the basis of incomplete benefit and harm data. Third, regulators should encourage the conduct of randomised trials with active comparators. Fourth, regulators should use prospectively designed network meta-analyses based on existing and future randomised trials. Last, payers should use their policy levers and negotiating power to incentivise the generation of comparative evidence on new and existing drugs and devices, for example, by explicitly considering proven added benefit in pricing and payment decisions.

Liver involvement in patients with Gaucher disease types I and III

Background & aims

Gaucher disease (GD) is a multisystemic disease. Liver involvement in GD is not well characterised and ranges from hepatomegaly to cirrhosis and hepatocellular carcinoma. We aim to describe, and assess the effect of treatment, on the hepatic phenotype of a cohort of patients with GD types I and II.

Methods

Retrospective study based on the review of the medical files of the Gaucher Reference Centre of the Hospital de Clínicas de Porto Alegre, Brazil. Data from all GD types I and III patients seen at the centre since 2003 were analysed. Variables were compared as pre- (“baseline”) and post-treatment (“follow-up”).

Results

Forty-two patients (types I: 39, III: 3; female: 22; median age: 35 y; enzyme replacement therapy: 37; substrate reduction therapy: 2; non-treated: 3; median time on treatment-MTT: 124 months) were included. Liver enzyme abnormalities, hepatomegaly, and steatosis at baseline were seen in 19/28 (68%), 28/42 (67%), and 3/38 patients (8%), respectively; at follow-up, 21/38 (55%), 15/38 (39%) and 15/38 (39%). MRI iron quantification showed overload in 7/8 patients (treated: 7; MTT: 55 months), being severe in 2/7 (treated: 2/2; MTT: 44.5 months). Eight patients had liver biopsy (treated: 6; MTT: 58 months), with fibrosis in 3 (treated: 1; time on treatment: 108 months) and steatohepatitis in 2 (treated: 2; time on treatment: 69 and 185 months). One patient developed hepatocellular carcinoma.

Conclusions

GD is a heterogeneous disease that causes different patterns of liver damage even during treatment. Although treatment improves the hepatocellular damage, it is associated with an increased rate of steatosis. This study highlights the importance of a follow-up of liver integrity in these patients.

CRISPR/Cas9-mediated glycolate oxidase disruption is an efficacious and safe treatment for primary hyperoxaluria type I

CRISPR/Cas9 technology offers novel approaches for the development of new therapies for many unmet clinical needs, including a significant number of inherited monogenic diseases. However, in vivo correction of disease-causing genes is still inefficient, especially for those diseases without selective advantage for corrected cells. We reasoned that substrate reduction therapies (SRT) targeting non-essential enzymes could provide an attractive alternative. Here we evaluate the therapeutic efficacy of an in vivo CRISPR/Cas9-mediated SRT to treat primary hyperoxaluria type I (PH1), a rare inborn dysfunction in glyoxylate metabolism that results in excessive hepatic oxalate production causing end-stage renal disease. A single systemic administration of an AAV8-CRISPR/Cas9 vector targeting glycolate oxidase, prevents oxalate overproduction and kidney damage, with no signs of toxicity in Agxt1^−/− mice. Our results reveal that CRISPR/Cas9-mediated SRT represents a promising therapeutic option for PH1 that can be potentially applied to other metabolic diseases caused by the accumulation of toxic metabolites.

Substrate reduction therapies (SRT) are a promising therapeutic approach for monogenic inherited metabolic diseases. Here the authors evaluate the therapeutic potential of an in vivo CRISPR/Cas9-mediated SRT to treat primary hyperoxaluria type I and demonstrate its safety and efficacy.

Small-Molecule Screening for Genetic Diseases

The genetic determinants of many diseases, including monogenic diseases and cancers, have been identified; nevertheless, targeted therapy remains elusive for most. High-throughput screening (HTS) of small molecules, including high-content analysis (HCA), has been an important technology for the discovery of molecular tools and new therapeutics. HTS can be based on modulation of a known disease target (called reverse chemical genetics) or modulation of a disease-associated mechanism or phenotype (forward chemical genetics). Prominent target-based successes include modulators of transthyretin, used to treat transthyretin amyloidoses, and the BCR-ABL kinase inhibitor Gleevec, used to treat chronic myelogenous leukemia. Phenotypic screening successes include modulators of cystic fibrosis transmembrane conductance regulator, splicing correctors for spinal muscular atrophy, and histone deacetylase inhibitors for cancer. Synthetic lethal screening, in which chemotherapeutics are screened for efficacy against specific genetic backgrounds, is a promising approach that merges phenotype and target. In this article, we introduce HTS technology and highlight its contributions to the discovery of drugs and probes for monogenic diseases and cancer.

A Mechanistic Overview of Triptolide and Celastrol, Natural Products from Tripterygium wilfordii Hook F

Triptolide and celastrol are predominantly active natural products isolated from the medicinal plant Tripterygium wilfordii Hook F. These compounds exhibit similar pharmacological activities, including anti-cancer, anti-inflammation, anti-obesity, and anti-diabetic activities. Triptolide and celastrol also provide neuroprotection and prevent cardiovascular and metabolic diseases. However, toxicity restricts the further development of triptolide and celastrol. In this review, we comprehensively review therapeutic targets and mechanisms of action, and translational study of triptolide and celastrol. We systemically discuss the structure-activity-relationship of triptolide, celastrol, and their derivatives. Furthermore, we propose the use of structural derivatives, targeted therapy, and combination treatment as possible solutions to reduce toxicity and increase therapeutic window of these potent natural products from T. wilfordii Hook F.

The Complicated Relationship between Gaucher Disease and Parkinsonism: Insights from a Rare Disease

The discovery of a link between mutations in GBA1, encoding the lysosomal enzyme glucocerebrosidase, and the synucleinopathies directly resulted from the clinical recognition of patients with Gaucher disease with parkinsonism. Mutations in GBA1 are now the most common known genetic risk factor for several Lewy body disorders, and an inverse relationship exists between levels of glucocerebrosidase and oligomeric α-synuclein. While the underlying mechanisms are still debated, this complicated association is shedding light on the role of lysosomes in neurodegenerative disorders, demonstrating how insights from a rare disorder can direct research into the pathogenesis and therapy of seemingly unrelated common diseases.

Attitudes of Individuals with Gaucher Disease toward Substrate Reduction Therapies

Type 1 Gaucher disease (GD) is the most common lysosomal storage disorder. Previously, treatment for GD was limited to intravenous enzyme replacement therapies (ERTs). More recently, oral substrate reduction therapies (SRTs) were approved for treatment of GD. Although both therapies alleviate disease symptoms, attitudes toward SRTs and patient perceptions of health while using SRT have not been well established. Electronic surveys were administered to adults with GD and asked about treatment history, attitudes toward SRTs, and perception of health while using SRTs as compared to ERTs, if applicable to the participant. ERT users that were offered treatment with SRTs cited potential side effects, wanting more research on SRTs, and satisfaction with their current treatment regimen as reasons for declining SRTs. SRT users expressed convenience and less invasiveness as reasons for choosing SRTs. Additionally, those using SRTs most often perceived their health to be similar to when they previously used ERT. Participant responses illustrate that attitudes toward SRTs can be variable and that one particular treatment may not be ideal for all patients with GD depending on individual perceptions of factors such as convenience, invasiveness, or side effects. Thus, individuals with GD should be counseled adequately by healthcare providers about both ERTs and SRTs for treatment of GD now that SRTs are clinically available.

Treatment of profound thrombocytopenia in a patient with Gaucher disease type 1: Is there a role for substrate reduction therapy

The availability of three enzyme replacement therapy (ERT) drugs and two substrate reduction therapy (SRT) drugs to treat Gaucher disease provides an opportunity to tailor therapies to a patient's specific clinical concerns. However, there is a gap in the literature regarding individual drug effectiveness in treating particular symptoms and the potential benefits of combination treatment.

This report details treatment of a patient with Gaucher disease type 1 whose main clinical concern was profound thrombocytopenia (around 20 × 10⁹/L, normal range: 150–450 × 10⁹/L) with several episodes of bleeding with minimal trauma and bruises. The patient was treated with ERT at doses up to 60 units/kg weekly, with no improvement in platelet levels for 6 years. Subsequently, the patient transitioned to SRT and platelet levels increased almost two fold within the first month, and have remained stable at safe levels (30–60 × 10⁹/L) for almost 2.5 years at the time of publication.

This report demonstrates a possible therapeutic benefit of SRT in individual patients who do not meet therapeutic goals in terms of thrombocytopenia after a considerable period on first-line ERT treatment. Oral administration of SRT also improved this patient's quality of life allowing discontinuation of weekly ERT infusions, which better accommodated her demanding career and busy lifestyle.

Lysosomal Storage Disorders and Malignancy

Lysosomal storage disorders (LSDs) are infrequent to rare conditions caused by mutations that lead to a disruption in the usual sequential degradation of macromolecules or their transit within the cell. Gaucher disease (GD), a lipidosis, is among the most common LSD, with an estimated incidence of 1 in 40,000 among the Caucasian, non-Jewish population. Studies have indicated an increased frequency of polyclonal and monoclonal gammopathy among patients with GD. It has been shown that two major sphingolipids that accumulate in GD, namely, β-glucosylceramide 22:0 (βGL1-22) and glucosylsphingosine (LGL1), can be recognized by a distinct subset of CD1d-restricted human and murine type II natural killer T (NKT) cells. Investigations undertaken in an affected mouse model revealed βGL1-22- and LGL1-specific NKT cells were present and constitutively promoted the expression of a T-follicular helper (TFH) phenotype; injection of these lipids led to downstream induction of germinal center B cells, hypergammaglobulinemia, and the production of antilipid antibodies. Subsequent studies have found clonal immunoglobulin in 33% of sporadic human monoclonal gammopathies is also specific for the lysolipids LGL1 and lysophosphatidylcholine (LPC). Furthermore, substrate reduction ameliorated GD-associated gammopathy in mice. It had been hypothesized that chronic antigenic stimulation by the abnormal lipid storage and associated immune dysregulation may be the underlying mechanism for the increased incidence of monoclonal and polyclonal gammopathies, as well as an increased incidence of multiple myeloma in patients with GD. Current observations support this proposition and illustrate the value of investigations into rare diseases, which as 'experiments of nature' may provide insights into conditions found in the general population that continue to remain incompletely understood.

Enzyme replacement therapy reverses B lymphocyte and dendritic cell dysregulations in patients with Gaucher Disease

Gaucher disease (GD) is caused by mutations in the GBA gene encoding lysosomal enzyme, β-glucocerebrosidase (GCase). GCase deficiency results in accumulation of its substrates in cells of macrophage lineage, affecting multiple organ systems. Enzyme replacement therapy (ERT) with recombinant human GCase is the standard of care to treat GD. In GD, it is well established that there are immune alterations, clinically presenting as lymphadenopathy, gammopathies, and predisposition to hematological cancers. We examined the effect of ERT on immune dysregulations in treatment-naïve GD patients longitudinally after the initiation of ERT. Immunophenotyping was performed in peripheral blood samples obtained before and after ERT. T and B lymphocyte subsets, NK, NKT and dendritic cells were evaluated. In all treatment naïve patients at baseline, transitional B cells, characterized by CD21^low expression were markedly elevated. After establishment of stable-dose therapy, CD21^low cells were significantly reduced and subsequent increase in CD21^Hi B lymphocytes indicated improved B cell maturation. Class-switching and memory B cell defects which were noted prior to treatment were found to be normalized. An increase in dendritic cells also resulted after the treatment. Our data shows that GD affects across various immune cell types and ERT or its effects directly improve affected immunological parameters.