Efficient therapy for refractory Pompe disease by mannose 6-phosphate analogue grafting on acid α-glucosidase

Synthesis of a heptasaccharide N-glycan comprising two mannose-6-phosphate residues

A deprotected biantennary high mannose heptasaccharide N-glycan comprising two mannose-6-phosphate residues was synthesised as a putative ligand for the mannose 6-phosphate receptors, using a convergent [3 + 4] glycosylation strategy.

Therapeutic antibody engineering for efficient targeted degradation of membrane proteins in lysosomes

Targeted degradation of pathological proteins is a promising approach to enhance the effectiveness of therapeutic monoclonal antibodies (mAbs) in cancer therapy. In this study, we demonstrate that this objective can be efficiently achieved by the grafting of mannose 6-phosphate analogues called AMFAs2 onto the therapeutic antibodies trastuzumab and cetuximab, both directed against membrane antigens. The grafting of AMFAs confers to these antibodies the novel property of being internalized via the mannose 6-phosphate receptor (M6PR) pathway. AMFA conjugation to these mAbs significantly increases their cellular uptake and leads to enhanced degradation of the target antigens in cancer cells. This results in a drastic inhibition of cancer cell proliferation compared to unconjugated mAbs, as demonstrated in various cancer cell lines, and an increased therapeutic efficacy in mouse and zebrafish xenografted models. These findings highlight the potential of this technology to improve therapeutic outcomes in cancer treatment.

Engineered therapeutic antibodies with mannose 6-phosphate analogues as a tool to degrade extracellular proteins

Inducing the degradation of pathological soluble antigens could be the key to greatly enhancing the efficacy of therapeutic monoclonal antibodies (mAbs), extensively used in the treatment of autoimmune and inflammatory disorders or cancer. Lysosomal targeting has gained increasing interest in recent years due to its pharmaceutical applications far beyond the treatment of lysosomal diseases, as a way to address proteins to the lysosome for eventual degradation. Mannose 6-phosphonate derivatives (M6Pn), called AMFA, are unique glycovectors that can significantly enhance the cellular internalization of the proteins conjugated to AMFA via the cation-independent mannose 6-phosphate receptor (M6PR) pathway. AMFA engineering of mAbs results in the generation of a bifunctional antibody that is designed to bind both the antigen and the M6PR. The improvement of the therapeutic potential by AMFA engineering was investigated using two antibodies directed against soluble antigens: infliximab (IFX), directed against tumor necrosis factor α (TNF-α), and bevacizumab (BVZ), directed against the vascular endothelial growth factor (VEGF). AMFA conjugations to the antibodies were performed either on the oligosaccharidic chains of the antibodies or on the lysine residues. Both conjugations were controlled and reproducible and provided a novel affinity for the M6PR without altering the affinity for the antigen. The grafting of AMFA to mAb increased their cellular uptake through an M6PR-dependent mechanism. The antigens were also 2.6 to 5.7 times more internalized by mAb-AMFA and rapidly degraded in the cells. Additional cell culture studies also proved the significantly higher efficacy of IFX-AMFA and BVZ-AMFA compared to their unconjugated counterparts in inhibiting TNF-α and VEGF activities. Finally, studies in a zebrafish embryo model of angiogenesis and in xenografted chick embryos showed that BVZ-AMFA was more effective than BVZ in reducing angiogenesis. These results demonstrate that AMFA grafting induces the degradation of soluble antigens and a significant increase in the therapeutic efficacy. Engineering with mannose 6-phosphate analogues has the potential to develop a new class of antibodies for autoimmune and inflammatory diseases.

Cation-independent mannose 6-phosphate receptor: From roles and functions to targeted therapies

The cation-independent mannose 6-phosphate receptor (CI-M6PR) is a ubiquitous transmembrane receptor whose main intracellular role is to direct enzymes carrying mannose 6-phosphate moieties to lysosomal compartments. Recently, the small membrane-bound portion of this receptor has appeared to be implicated in numerous pathophysiological processes. This review presents an overview of the main ligand partners and the roles of CI-M6PR in lysosomal storage diseases, neurology, immunology and cancer fields. Moreover, this membrane receptor has already been noted for its strong potential in therapeutic applications thanks to its cellular internalization activity and its ability to address pathogenic factors to lysosomes for degradation. A number of therapeutic delivery approaches using CI-M6PR, in particular with enzymes, antibodies or nanoparticles, are currently being proposed.

Glycosylation shapes the efficacy and safety of diverse protein, gene and cell therapies

Over recent decades, therapeutic proteins have had widespread success in treating a myriad of diseases. Glycosylation, a near universal feature of this class of drugs, is a critical quality attribute that significantly influences the physical properties, safety profile and biological activity of therapeutic proteins. Optimizing protein glycosylation, therefore, offers an important avenue to developing more efficacious therapies. In this review, we discuss specific examples of how variations in glycan structure and glycoengineering impacts the stability, safety, and clinical efficacy of protein-based drugs that are already in the market as well as those that are still in preclinical development. We also highlight the impact of glycosylation on next generation biologics such as T cell-based cancer therapy and gene therapy.

Hypertrophic Cardiomyopathy versus Storage Diseases with Myocardial Involvement

One of the main causes of heart failure is cardiomyopathies. Among them, the most common is hypertrophic cardiomyopathy (HCM), characterized by thickening of the left ventricular muscle. This article focuses on HCM and other cardiomyopathies with myocardial hypertrophy, including Fabry disease, Pompe disease, and Danon disease. The genetics and pathogenesis of these diseases are described, as well as current and experimental treatment options, such as pharmacological intervention and the potential of gene therapies. Although genetic approaches are promising and have the potential to become the best treatments for these diseases, further research is needed to evaluate their efficacy and safety. This article describes current knowledge and advances in the treatment of the aforementioned cardiomyopathies.

Lysosomal Targeting of β-Cyclodextrin

β-Cyclodextrin (β-CD) and derivatives are approved therapeutics in >30 clinical settings. β-CDs have also shown promise as therapeutics for treatment of some lysosomal storage disorders, such as Niemann-Pick disease type C, and other disease states which involve metabolite accumulation in the lysosome. In these cases, β-CD activity relies on transport to the lysosome, wherein it can bind hydrophobic substrate and effect extraction. The post-translational attachment of N-glycans terminated in mannose-6-phosphate (M6P) residues is the predominant method by which lysosomal enzymes are targeted to the lysosome. In this work we covalently attach a synthetic biantennary bis-M6P-terminated N-glycan to β-CD and study the effect of the added glycans in a mammalian cell line. The formation of a host guest complex with a Cy5 fluorophore allows study of both cellular internalisation and transport to the lysosome by fluorescence microscopy. Results indicate that the rates of both internalisation and lysosomal transport are increased by the attachment of M6P-glycans to β-CD, indicating that M6P-glycan conjugation may improve the therapeutic effectiveness of β-CD for the treatment of disorders involving hydrophobic metabolite accumulation in the lysosome.

The new horizons for treatment of Late-Onset Pompe Disease (LOPD)

Late-onset Pompe disease (LOPD) is a genetic myopathy causing skeletal muscle weakness and severe respiratory impairment, due to the deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA) leading to lysosomal glycogen accumulation along with other complex pathophysiological processes. A major step for treatment of Pompe disease was reached in 2006 with the marketing of alglucosidase alfa, a first enzyme replacement therapy (ERT) that showed a significant motor and respiratory benefit. However, efficacy of alglucosidase alfa is limited in LOPD with a loss of efficacy over time, promoting research on new treatments. Next-generation ERT are new enzymes biochemically modified to increase the uptake of exogenous enzyme by target tissues, and the benefit of two recombinant enzymes (avalglucosidase alfa and cipaglucosidase alfa) has been recently studied in large phase III clinical trials, the latest combined with miglustat. Several innovative therapies, based on GAA gene transfer, antisense oligonucleotides or inhibition of glycogen synthesis with substrate reduction therapy, are currently under study, but are still at an early stage of development. Overall, active research for new treatments raises hope for LOPD patients but challenges remain for the clinician with the need for reliable efficacy assessment tools, long-term registry data, and evidence-based recommendations for the best use of these new molecules recently available or under development.

Synthesis and application of phosphorylated saccharides in researching carbohydrate-based drugs

Phosphorylated saccharides are valuable targets in glycochemistry and glycobiology, which play an important role in various physiological and pathological processes. The current research on phosphorylated saccharides primarily focuses on small molecule inhibitors, glycoconjugate vaccines and novel anti-tumour targeted drug carrier materials. It can maximise the pharmacological effects and reduce the toxicity risk caused by nonspecific off-target reactions of drug molecules. However, the number and types of natural phosphorylated saccharides are limited, and the complexity and heterogeneity of their structures after extraction and separation seriously restrict their applications in pharmaceutical development. The increasing demands for the research on these molecules have extensively promoted the development of carbohydrate synthesis. Numerous innovative synthetic methodologies have been reported regarding the continuous expansion of the potential building blocks, catalysts, and phosphorylation reagents. This review summarizes the latest methods for enzymatic and chemical synthesis of phosphorylated saccharides, emphasizing their breakthroughs in yield, reactivity, regioselectivity, and application scope. Additionally, the anti-bacterial, anti-tumour, immunoregulatory and other biological activities of some phosphorylated saccharides and their applications were also reviewed. Their structure-activity relationship and mechanism of action were discussed and the key phosphorylation characteristics, sites and extents responsible for observed biological activities were emphasised. This paper will provide a reference for the application of phosphorylated saccharide in the research of carbohydrate-based drugs in the future.

Chemoenzymatic glycan-selective remodeling of a therapeutic lysosomal enzyme with high-affinity M6P-glycan ligands. Enzyme substrate specificity is the name of the game

Functionalization of therapeutic lysosomal enzymes with mannose-6-phosphate (M6P) glycan ligands represents a major strategy for enhancing the cation-independent M6P receptor (CI-MPR)-mediated cellular uptake, thus improving the overall therapeutic efficacy of the enzymes. However, the minimal high-affinity M6P-containing N-glycan ligands remain to be identified and their efficient and site-selective conjugation to therapeutic lysosomal enzymes is a challenging task. We report here the chemical synthesis of truncated M6P-glycan oxazolines and their use for enzymatic glycan remodeling of recombinant human acid α-glucosidase (rhGAA), an enzyme used for treatment of Pompe disease which is a disorder caused by a deficiency of the glycogen-degrading lysosomal enzyme. Structure-activity relationship studies identified M6P tetrasaccharide oxazoline as the minimal substrate for enzymatic transglycosylation yielding high-affinity M6P glycan ligands for the CI-MPR. Taking advantage of the substrate specificity of endoglycosidases Endo-A and Endo-F3, we found that Endo-A and Endo-F3 could efficiently deglycosylate the respective high-mannose and complex type N-glycans in rhGAA and site-selectively transfer the synthetic M6P N-glycan to the deglycosylated rhGAA without product hydrolysis. This discovery enabled a highly efficient one-pot deglycosylation/transglycosylation strategy for site-selective M6P-glycan remodeling of rhGAA to obtain a more homogeneous product. The Endo-A and Endo-F3 remodeled rhGAAs maintained full enzyme activity and demonstrated 6- and 20-fold enhanced binding affinities for CI-MPR receptor, respectively. Using an in vitro cell model system for Pompe disease, we demonstrated that the M6P-glycan remodeled rhGAA greatly outperformed the commercial rhGAA (Lumizyme) and resulted in the reversal of cellular pathology. This study provides a general and efficient method for site-selective M6P-glycan remodeling of recombinant lysosomal enzymes to achieve enhanced M6P receptor binding and cellular uptake, which could lead to improved overall therapeutic efficacy of enzyme replacement therapy.

Development of Triantennary N-Acetylgalactosamine Conjugates as Degraders for Extracellular Proteins

Targeted protein degradation (TPD) technology has drawn significant attention from researchers in both academia and industry. It is rapidly evolved as a new therapeutic modality and also a useful chemical tool in selectively depleting various protein targets. As most efforts focus on cytosolic proteins using PROteolysis TArgeting Chimera (PROTAC), LYsosome TArgeting Chimera (LYTAC) recently emerged as a promising technology to deliver extracellular protein targets to lysosome for degradation through the cation-independent mannose-6-phosphate receptor (CI-M6PR). In this study, we exploited the potential of the asialoglycoprotein receptor (ASGPR), a lysosomal targeting receptor specifically expressed on liver cells, for the degradation of extracellular proteins including membrane proteins. The ligand of ASGPR, triantennary N-acetylgalactosamine (tri-GalNAc), was conjugated to biotin, antibodies, or fragments of antibodies to generate a new class of degraders. We demonstrated that the extracellular protein targets could be successfully internalized and delivered into lysosome for degradation in liver cell lines specifically by these degraders. This work will add a new dimension to TPD with cell type specificity.

Expansion of immature, nucleated red blood cells by transient low-dose methotrexate immune tolerance induction in mice

Biological treatments such as enzyme-replacement therapies (ERT) can generate anti-drug antibodies (ADA), which may reduce drug efficacy and impact patient safety and consequently led to research to mitigate ADA responses. Transient low-dose methotrexate (TLD-MTX) as a prophylactic ITI regimen, when administered concurrently with ERT, induces long-lived reduction of ADA to recombinant human alglucosidase alfa (rhGAA) in mice. In current clinical practice, a prophylactic ITI protocol that includes TLD-MTX, rituximab and intravenous immunoglobulin (optional), successfully induced lasting control of ADA to rhGAA in high-risk, cross-reactive immunological material (CRIM)-negative infantile-onset Pompe disease (IOPD) patients. More recently, evaluation of TLD-MTX demonstrated benefit in CRIM-positive IOPD patients. To more clearly understand the mechanism for the effectiveness of TLD-MTX, non-targeted transcriptional and proteomic screens were conducted and revealed up-regulation of erythropoiesis signatures. Confirmatory studies showed transiently larger spleens by weight, increased spleen cellularity and that following an initial reduction of mature red blood cells (RBCs) in the bone marrow and blood, a significant expansion of Ter-119+ CD71+ immature RBCs was observed in spleen and blood of mice. Histology sections revealed increased nucleated cells, including hematopoietic precursors, in the splenic red pulp of these mice. This study demonstrated that TLD-MTX induced a transient reduction of mature RBCs in the blood and immature RBCs in the bone marrow followed by significant enrichment of immature, nucleated RBCs in the spleen and blood during the time of immune tolerance induction, which suggested modulation of erythropoiesis may be associated with the induction of immune tolerance to rhGAA.

Moss-Derived Human Recombinant GAA Provides an Optimized Enzyme Uptake in Differentiated Human Muscle Cells of Pompe Disease

Pompe disease is an autosomal recessive lysosomal storage disorder (LSD) caused by deficiency of lysosomal acid alpha-glucosidase (GAA). The result of the GAA deficiency is a ubiquitous lysosomal and non-lysosomal accumulation of glycogen. The most affected tissues are heart, skeletal muscle, liver, and the nervous system. Replacement therapy with the currently approved enzyme relies on M6P-mediated endocytosis. However, therapeutic outcomes still leave room for improvement, especially with regard to skeletal muscles. We tested the uptake, activity, and effect on glucose metabolism of a non-phosphorylated recombinant human GAA produced in moss (moss-GAA). Three variants of moss-GAA differing in glycosylation pattern have been analyzed: two with terminal mannose residues in a paucimannosidic (Man3) or high-mannose (Man 5) configuration and one with terminal N-acetylglucosamine residues (GnGn). Compared to alglucosidase alfa the moss-GAA GnGn variant showed increased uptake in differentiated myotubes. Moreover, incubation of immortalized muscle cells of Gaa^-/- mice with moss-GAA GnGn led to similarly efficient clearance of accumulated glycogen as with alglucosidase alfa. These initial data suggest that M6P-residues might not always be necessary for the cellular uptake in enzyme replacement therapy (ERT) and indicate the potential of moss-GAA GnGn as novel alternative drug for targeting skeletal muscle in Pompe patients.

Mannose 6-phosphonate labelling: A key for processing the therapeutic enzyme in Pompe disease

In the search of a better enzyme therapy in Pompe disease, the conjugation of mannose 6‐phosphonates to the recombinant enzyme appeared as an enhancer of its efficacy. Here, we demonstrated that the increased efficacy of the conjugated enzyme is partly due to a higher intracellular maturation because of its insensitiveness to acid phosphatases during the routing to lysosomes.

Progress and challenges of gene therapy for Pompe disease

Pompe disease (PD) is a monogenic disorder caused by mutations in the acid alpha-glucosidase gene (Gaa). GAA is a lysosomal enzyme essential for the degradation of glycogen. Deficiency of GAA results in a severe, systemic disorder that, in its most severe form, can be fatal. About a decade ago, the prognosis of PD has changed dramatically with the marketing authorization of an enzyme replacement therapy (ERT) based on recombinant GAA. Despite the breakthrough nature of ERT, long-term follow-up of both infantile and late-onset Pompe disease patients (IOPD and LOPD, respectively), revealed several limitations of the approach. In recent years several investigational therapies for PD have entered preclinical and clinical development, with a few next generation ERTs entering late-stage clinical development. Gene therapy holds the potential to change dramatically the way we treat PD, based on the ability to express the Gaa gene long-term, ideally driving enhanced therapeutic efficacy compared to ERT. Several gene therapy approaches to PD have been tested in preclinical animal models, with a handful of early phase clinical trials started or about to start. The complexity of PD and of the endpoints used to measure efficacy of investigational treatments remains a challenge, however the hope is for a future with more therapeutic options for both IOPD and LOPD patients.

The glycosylation design space for recombinant lysosomal replacement enzymes produced in CHO cells

Lysosomal replacement enzymes are essential therapeutic options for rare congenital lysosomal enzyme deficiencies, but enzymes in clinical use are only partially effective due to short circulatory half-life and inefficient biodistribution. Replacement enzymes are primarily taken up by cell surface glycan receptors, and glycan structures influence uptake, biodistribution, and circulation time. It has not been possible to design and systematically study effects of different glycan features. Here we present a comprehensive gene engineering screen in Chinese hamster ovary cells that enables production of lysosomal enzymes with N-glycans custom designed to affect key glycan features guiding cellular uptake and circulation. We demonstrate distinct circulation time and organ distribution of selected glycoforms of α-galactosidase A in a Fabry disease mouse model, and find that an α2-3 sialylated glycoform designed to eliminate uptake by the mannose 6-phosphate and mannose receptors exhibits improved circulation time and targeting to hard-to-reach organs such as heart. The developed design matrix and engineered CHO cell lines enables systematic studies towards improving enzyme replacement therapeutics.

Lysosomal replacement enzymes are taken up by cell surface receptors that recognize glycans, the effects of different glycan features are unknown. Here the authors present a gene engineering screen in CHO cells that allows custom N-glycan-decorated enzymes with improved circulation time and organ distribution.

Pompe Disease: From Basic Science to Therapy

Pompe disease is a rare and deadly muscle disorder. As a clinical entity, the disease has been known for over 75 years. While an optimist might be excited about the advances made during this time, a pessimist would note that we have yet to find a cure. However, both sides would agree that many findings in basic science-such as the Nobel prize-winning discoveries of glycogen metabolism, the lysosome, and autophagy-have become the foundation of our understanding of Pompe disease. The disease is a glycogen storage disorder, a lysosomal disorder, and an autophagic myopathy. In this review, we will discuss how these past discoveries have guided Pompe research and impacted recent therapeutic developments.

[Research advances in the diagnosis and treatment of Pompe disease]

Pompe disease, also called type II glycogen storage disease, is a rare autosomal recessive inherited disease caused by the storage of glycogen in lysosome due to acid α-glucosidase (GAA) deficiency, with the most severe conditions in the skeletal muscle, the myocardium, and the smooth muscle. Patients may have the manifestations of dyspnea and dyskinesia, with or without hypertrophic cardiomyopathy. GAA gene mutation has ethnic and regional differences, and new mutation sites are found with the advances in research. Gene analysis is the gold standard for the diagnosis of Pompe disease. Conventional methods, such as skin and muscle biopsies and dried blood spot test, have certain limitations for the diagnosis of this disease. In recent years, prenatal diagnosis and newborn screening play an important role in early diagnosis of this disease. Enzyme replacement therapy (ERT) has a satisfactory effect in the treatment of this disease, but it may lead to immune intolerance. New targeted gene therapy and modified ERT will be put into practice in the future. This article reviews the research advances in the diagnosis and treatment of Pompe disease.

Autophagy in health and disease: A comprehensive review

Autophagy, a conserved catabolic process, plays an immensely significant role in a variety of diseases. However, whether it imparts a protective function in diseases remains debatable. During aging, autophagy gradually subsides, manifested by the reduced formation of autophagic vacuoles and improper fusion of these vacuoles with the lysosomes. Similarly, in neurodegenerative disorders, accumulation of tau and synuclein proteins has been attributed to the decline in the autophagic removal of proteins. Equivalently, lysosomal disorders show an impairment of the autophagic process leading to the accumulation of lipid molecules within lysosomes. On the other hand, activation of the autophagic pathway has also proved beneficial in evading various foreign pathogens, thereby contributing to the innate immunity. In the context of cancer, autophagy has shown to play a puzzling role where it serves as a tumor suppressor during initial stages but later protects the tumor cells from the immune system defense mechanisms. Similarly, muscular and heart disorders have been shown to be positively and negatively regulated by autophagy, respectively. In the present review, we, therefore, present a comprehensive review on the role of autophagy in various diseases and their corresponding outcomes.