Efficacy and safety of enzyme replacement therapy with BMN 110 (elosulfase alfa) for Morquio A syndrome (mucopolysaccharidosis IVA): a phase 3 randomised placebo-controlled study

Identification of Surrogate Biomarkers for Mucopolysaccharidosis Type IVA

Mucopolysaccharidosis type IVA (MPS IVA, Morquio A syndrome) is a rare inherited disorder characterized by skeletal dysplasia due to deficient N-acetylgalactosamine-6-sulfate sulfatase activity, resulting in glycosaminoglycan (GAG) accumulation. Identifying accurate biomarkers reflecting clinical severity and therapeutic response remains challenging. This study evaluated potential surrogate biomarkers, including N-terminal pro-C-type natriuretic peptide (NT-proCNP), collagen types I and II, mono-sulfated keratan sulfate (KS), di-sulfated KS, and chondroitin-6-sulfate (C6S), in blood and urine samples from 60 patients ranging from 1 to 62 years of age. NT-proCNP levels were significantly elevated in patients of all ages and negatively correlated with growth impairment, especially after 8 years of age. Collagen type I levels significantly increased in adult patients, whereas collagen type II showed age-dependent elevations. Urinary KS, in mono- and di-sulfated forms, demonstrated moderate negative correlations with growth impairment. Moreover, NT-proCNP, mono- and di-sulfated KS in plasma, and urinary di-sulfated KS were not affected by enzyme replacement therapy in patients younger than 12 years, unlike urinary mono-sulfated KS. In conclusion, NT-proCNP has emerged as a promising independent biomarker reflecting the severity of skeletal dysplasia and possibly the near-future growth rate. These findings highlight the potential role of NT-proCNP in clinical assessment and monitoring therapeutic efficacy, addressing current unmet needs in MPS IVA management.

Role of Biomarkers in Diagnosing Disease, Assessing the Severity and Progression of Disease, and Evaluating the Efficacy of Therapies

This paper reviews biomarkers in lysosomal disease according to their categories and definitions. There are numerous biomarkers in lysosomal diseases. Some are disease or organ-specific, but most are not. Organ-specific biomarkers are especially useful, but most biomarkers help with diagnosis, assessing disease severity, prognosis, and pharmacodynamic response. There are as yet no truly validated biomarkers in lysosomal diseases by the Prentice, Fleming, and DeMets criteria. None so far can serve as surrogate endpoints in clinical trials, or as substitutes for clinically meaningful endpoints that evaluate how patients feel, function, or survive. The US Food and Drug Administration has thus far used surrogate biomarkers to license therapy only for 3 lysosomal diseases-Gaucher disease, Fabry disease, and lysosomal lipase deficiency. The paucity of surrogate biomarkers reflects success in using clinically important endpoints for the licensing of therapies for Pompe disease, mucopolysaccharidosis IVA, VI, and VII, Niemann-Pick type C, and CLN2. In conclusion, biomarkers in lysosomal diseases are best used for diagnosis, patient categorization, pharmacodynamic response, and sometimes for patient prognosis and risk. Thus far, they have been less useful as surrogate biomarkers in pivotal clinical trials.

Heliox in the management of respiratory failure in a Morquio A syndrome patient with trachea narrowing

Morquio A Syndrome is a mucopolysaccharide deposition disease where patients can develop respiratory failure due to airway narrowing by polysaccharide deposition, anatomical distortion and compression of the airway. Definitive management with surgery is high risk, only performed in the highly specialized centers, and by the time they develop respiratory failure they may not be a candidate for surgery due to difficulty intubation. Consequently, they often end up with long term BiPAP dependent and suffer from side effects of abdominal, facial pain and depression. Heliox is low density gas mixture which can facilitate oxygen delivery in narrowed airway. Here we report a case of Morquio A syndrome patient with 24-h BiPAP dependence and successfully treated with Heliox and weaned off BiPAP for 4 hours a day with improved quality of life.

Long-term outcomes of enzyme replacement therapy from a large cohort of Korean patients with mucopolysaccharidosis IVA (Morquio A syndrome)

Mucopolysaccharidosis (MPS) IVA (Morquio A syndrome) is an autosomal recessive lysosomal storage disorder caused by a mutation affecting the enzyme N-acetylgalactosamine-6-sulfatase (EC 3.1.6.4, GALNS). Enzyme replacement therapy (ERT) has been shown to improve physical performance, quality of life, and respiratory function in patients with MPS IVA; however, owing to the rarity of MPS IVA, data on Korean patient characteristics are limited. This retrospective study reports clinical, radiographic, biochemical, and molecular findings, and analyzes long-term clinical outcomes, from the largest cohort of Korean patients with MPS IVA in a single center. The analysis included 17 patients from 14 families (58.8 % females; median [range] age at diagnosis 5.2 [1.8-33.7] years). The majority of patients (64.7 %) were classified as having a severe phenotype, 23 % had an intermediate phenotype, and 11.8 % had an attenuated phenotype. Skeletal manifestations and radiologic abnormalities at initial diagnosis included gait abnormality (35.3 %), short stature (23.5 %), chest deformity (23.5 %), scoliosis (17.6 %), kyphosis (11.8 %), dysmorphic face (6 %), hip pain (6 %), and leg deformity (6 %). Twelve different GALNS mutations were identified. Patients received ERT for a median (range) 7.4 years (3.0-12.1). Twelve patients reached final adult height, and all patients with the severe/intermediate phenotype had short stature (<3rd percentile). Hemiepiphysiodesis was the most common surgical intervention among patients with the severe/intermediate phenotype. Drug-related adverse events (urticaria, rash, and anaphylaxis) were reported in four patients but were managed with antihistamines or desensitization. At follow-up, patients experienced improvements in functional independence measure score, ejection fraction, and the 6-min walk test compared with the pre-treatment baseline. This study provides real-world evidence for long-term stabilization of functional independence, endurance, and respiratory function among patients with MPS IVA treated with ERT, with no new safety concerns identified.

Hearing loss in patients with Morquio A syndrome: A scoping review

BACKGROUND

Hearing impairment is a prevalent clinical feature in Morquio syndrome (mucopolysaccharidosis IVA or MPS IVA) patients, often presenting in diverse forms: conductive, sensorineural, or a combination known as mixed hearing loss. The mixed form entails a blend of both conductive and sensorineural elements, typically exhibiting a progressive trajectory. This scoping review aimed to comprehensively analyze available evidence pertaining to the pathophysiology, classification, epidemiology, and clinical management of hearing loss in individuals with MPS IVA.

METHODS

Targeted literature was searched using MEDLINE, Literatura Latino-Americana e do Caribe em Ciências da Saúde, Web of Science, the Cochrane Library, Trip Medical Database, Embase, ScienceDirect, and Google Scholar, with a second search cycle to identify gray literature. A systematic search strategy using Medical Subject Headings keywords was implemented: "Hearing Disorders" OR "Hearing Loss" AND "Mucopolysaccharidosis IV" or "Hearing Disorders" OR "Hearing Loss" AND "Mucopolysaccharidosis IV." The identified bibliography was uploaded to COVIDENCE platform for information management. Articles were screened by 3 independent reviewers following the eligibility criteria.

RESULTS

Twenty-seven articles met the inclusion criteria, spanning information from 568 patients across 16 different countries. None of the studies had complete epidemiological information. Only 2 studies provided sufficient data to address the pathophysiology, while 3 addressed management and treatment. Hearing loss was reported in 210 of 568 patients. A total of 19.2% of patients reported recurrent ear infections. None of the studies reported vertigo, tinnitus, or dizziness in the patients. Pure-tone audiometry was the primary test used to diagnose and monitor auditory impairment in patients with Morquio syndrome.

CONCLUSIONS

Five hundred sixty-eight patients with MPS IVA were identified, of whom 210 (37%) developed hearing loss, the most common of which was moderate. Despite the lack of information on the diagnosis and management of hearing loss in Morquio syndrome, this study found that approximately one-third of participants exhibited some form of auditory impairment, with the majority of these cases being sensorineural in nature.

Evidence Following Conditional NICE Technology Appraisal Recommendations: A Critical Analysis of Methods, Quality and Risk of Bias

BACKGROUND

The National Institute for Health and Care Excellence (NICE) may approve health technologies on condition of more evidence generated only in research (OiR) or only with research (OwR). NICE specifies the information needed to comply with its request, although it may not necessarily guarantee good quality and timely evidence for re-appraisal, before reaching a final decision.

AIM

This study aimed to critically appraise the methods, quality and risk of bias of evidence generated in response to NICE OiR and OwR technology appraisal (TA) and highly specialised technologies (HSTs) recommendations.

METHODS

NICE TAs (between March 2000 and September 2020) and HST evaluations (to October 2023) of medicines were reviewed. Conditional recommendations were analysed to identify the evidence requested by NICE for re-appraisal. The new evidence was analysed for compliance with NICE's request and assessed using the Cochrane Collaboration's tools for risk of bias in randomised trials and the ROBINS-I tool for non-randomised evidence.

RESULTS

NICE made 54 conditional recommendations from TAs (13 OiR and 41 OwR) and five conditional recommendations for HSTs (all OwR). Of these, 16 TAs presented additional evidence for re-appraisal (9 OiR [69%] and 7 OwR [17%]) and three HSTs (3 OwR [60%]). Two of the nine re-appraised TAs with OiR recommendation and four of the seven OwR complied fully with NICE's request for further evidence, while all three from the HSTs complied. The majority of re-appraised TAs and HSTs included evidence that was deemed to be at serious, high, moderate or unclear risk of bias. Among the 26 randomised controlled trials from TAs assessed, eight were categorised as having low risk of bias in all domains and ten had at least one domain as a high risk of bias. Reporting was unclear for the remainder. Twenty-two non-randomised studies, primarily single-arm studies, were susceptible to biases mostly due to the selection of participants and to confounding. Two HSTs provided evidence from randomised controlled trials which were classified as unclear or high risk of bias. All non-randomised evidence from HSTs were categorised as moderate or serious risk of bias.

CONCLUSIONS

There is widespread non-compliance with agreed data requests and important variation in the quality of evidence submitted in response to NICE conditional approval recommendations. Quality standards ought to be stipulated in respect to evidence contributing to re-appraisals following NICE conditional approval recommendations.

Consensus-based expert recommendations on the management of MPS IVa and VI in Saudi Arabia

BACKGROUND

Mucopolysaccharidosis type IVa (Morquio A syndrome) and mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome) are rare inherited lysosomal storage diseases associated with significant functional impairment and a wide spectrum of debilitating clinical manifestations. These conditions are thought to have higher-than-average prevalence rates in Saudi Arabia due to high rates of consanguineous marriage in the country. There are several unmet needs associated with the management of these diseases in Saudi Arabia.

MAIN BODY

The aim of this manuscript is to contextualize unmet management needs and provide recommendations to optimize diagnosis, multidisciplinary care delivery, and local data generation in this disease area. An expert panel was assembled comprising seven consultant geneticists from across Saudi Arabia. The Delphi methodology was used to obtain a consensus on statements relating to several aspects of mucopolysaccharidosis types IVa and VI. A consensus was reached for all statements by means of an online, anonymized voting system. The consensus statements pertain to screening and diagnosis, management approaches, including recommendations pertaining to enzyme replacement therapy, and local data generation.

CONCLUSION

The consensus statements presented provide specific recommendations to improve diagnostic and treatment approaches, promote multidisciplinary care and data sharing, and optimize the overall management of these rare inherited diseases in Saudi Arabia.

Causes of death in mucopolysaccharidoses

Mucopolysaccharidoses are inherited metabolic diseases caused by mutations in genes encoding enzymes required for degradation of glycosaminoglycans. A lack or severe impairment of activity of these enzymes cause accumulation of GAGs which is the primary biochemical defect. Depending on the kind of the deficient enzyme, there are 12 types and subtypes of MPS distinguished. Despite the common primary metabolic deficit (inefficient GAG degradation), the course and symptoms of various MPS types can be different, though majority of the diseases from the group are characterized by severe symptoms and significantly shortened live span. Here, we analysed the frequency of specific, direct causes of death of patients with different MPS types, the subject which was not investigated comprehensively to date. We examined a total of 1317 cases of death among MPS patients, including 393 cases of MPS I, 418 cases of MPS II, 232 cases of MPS III, 45 cases of MPS IV, 208 cases of MPS VI, and 22 cases of MPS VII. Our analyses indicated that the most frequent causes of death differ significantly between MPS types, with cardiovascular and respiratory failures being predominant in MPS I, MPS II, and MPS VI, neurological deficits in MPS III, respiratory issues in MPS IV, and hydrops fetalis in MPS VII. Results of such studies suggest what specific clinical problems should be considered with the highest priority in specific MPS types, apart from attempts to correct the primary causes of the diseases, to improve the quality of life of patients and to prolong their lives.

Novel human recombinant N-acetylgalactosamine-6-sulfate sulfatase produced in a glyco-engineered Escherichia coli strain

Mucopolysaccharidosis IVA (MPS IVA) is a lysosomal storage disease caused by mutations in the gene encoding the lysosomal enzyme N-acetylgalactosamine-6-sulfate sulfatase (GALNS), resulting in the accumulation of keratan sulfate (KS) and chondroitin-6-sulfate (C6S). Previously, it was reported the production of an active human recombinant GALNS (rGALNS) in E. coli BL21(DE3). However, this recombinant enzyme was not taken up by HEK293 cells or MPS IVA skin fibroblasts. Here, we leveraged a glyco-engineered E. coli strain to produce a recombinant human GALNS bearing the eukaryotic trimannosyl core N-glycan, Man3GlcNAc2 (rGALNSoptGly). The N-glycosylated GALNS was produced at 100 mL and 1.65 L scales, purified and characterized with respect to pH stability, enzyme kinetic parameters, cell uptake, and KS clearance. The results showed that the addition of trimannosyl core N-glycans enhanced both protein stability and substrate affinity. rGALNSoptGly was capture through a mannose receptor-mediated process. This enzyme was delivered to the lysosome, where it reduced KS storage in human MPS IVA fibroblasts. This study demonstrates the potential of a glyco-engineered E. coli for producing a fully functional GALNS enzyme. It may offer an economic approach for the biosynthesis of a therapeutic glycoprotein that could prove useful for MPS IVA treatment. This strategy could be extended to other lysosomal enzymes that rely on the presence of mannose N-glycans for cell uptake.

Molecular therapy and nucleic acid adeno-associated virus-based gene therapy delivering combinations of two growth-associated genes to MPS IVA mice

Mucopolysaccharidosis type IVA (MPS IVA) is caused by a deficiency of the galactosamine (N-acetyl)-6-sulfatase (GALNS) enzyme responsible for the degradation of specific glycosaminoglycans (GAGs). The progressive accumulation of GAGs leads to various skeletal abnormalities (short stature, hypoplasia, tracheal obstruction) and several symptoms in other organs. To date, no treatment is effective for patients with bone abnormalities. To improve bone pathology, we propose a novel combination treatment with the adeno-associated virus (AAV) vectors expressing GALNS enzyme and a natriuretic peptide C (CNP; NPPC gene) as a growth-promoting agent for MPS IVA. In this study, an MPS IVA mouse model was treated with an AAV vector expressing GALNS combined with another AAV vector expressing NPPC gene, followed for 12 weeks. After the combination therapy, bone growth in mice was induced with increased enzyme activity in tissues (bone, liver, heart, lung) and plasma. Moreover, there were significant changes in bone morphology in CNP-treated mice with increased CNP activity in plasma. Delivering combinations of CNP and GALNS gene therapies enhanced bone growth in MPS IVA mice more than in GALNS gene therapy alone. Enzyme expression therapy alone fails to reach the bone growth region; our results indicate that combining it with CNP offers a potential alternative.

The top 100 most cited articles on mucopolysaccharidoses: a bibliometric analysis

Background: Bibliometrics can trace general research trends in a particular field. Mucopolysaccharidoses (MPS), as a group of rare genetic diseases, seriously affect the quality of life of patients and their families. Scholars have devoted themselves to studying MPS's pathogenesis and treatment modalities and have published many papers. Therefore, we conducted a bibliometric and visual study of the top 100 most highly cited articles to provide researchers with an indication of the current state of research and potential directions in the field. Methods: The Web of Science Core Collection was searched for articles on MPS from 1 January 1900, to 8 November 2023, and the top 100 most cited articles were screened. The title, year of publication, institution, country, and first author of the articles were extracted and statistically analyzed using Microsoft Excel 2007. Keyword co-occurrence and collaborative networks were analyzed using VOSviewer 1.6.16. Results: A total of 9,273 articles were retrieved, and the top 100 most cited articles were filtered out. The articles were cited 18,790 times, with an annual average of 188 citations (122-507). Forty-two journals published these articles, with Molecular Genetics and Metabolism and Proceedings of the National Academy of Sciences of the United States being the most published journal (N = 8), followed by Pediatrics (N = 7), Blood (N = 6). The United States (N = 68), the UK (N = 25), and Germany (N = 20) were the top contributing countries. The Royal Manchester Children's Hospital (N = 20) and the University of North Carolina (N = 18) were the most contributing institutions. Muenzer J was the most prolific author (N = 14). Conclusion: We conducted a bibliometric and visual analysis of the top 100 cited articles in MPS. This study identifies the most influential articles currently available in the field of MPS, which provides a good basis for a better understanding of the disease and informs future research directions.

C-Type Natriuretic Peptide Analogs: Current and Future Therapeutic Applications

BACKGROUND

Short stature is one of the most common reasons for referral to a pediatric endocrinologist that can be due to multitude of conditions, including an ever-growing list of genetic etiologies. Despite the numerous different causes, options for medical therapy remain quite limited, with the primary medication available being recombinant human growth hormone. A second option is recombinant insulin-like growth factor 1 (rIGF-1) in select patients with severe primary IGF-1 deficiency. Alternative strategies to increase height have been attempted such as delaying the onset of puberty with a gonadotropin-releasing hormone agonist or delaying epiphyseal fusion with an aromatase inhibitor. However, these options focus on increasing the duration of growth as opposed to directly stimulating growth at the growth plate.

SUMMARY

Novel approaches to growth promotion have recently been developed, including analogs of C-type natriuretic peptide (CNP). The purpose of this study is to review the function of CNP and its potential use in different conditions.

KEY MESSAGES

Alterations in the CNP/FGFR3 pathway can lead to multiple defined genetic causes of short stature. The CNP pathway has become the focus for treatment of children with short stature that suffer from such genetic conditions, with promising outcomes.

Iron oxide-coupled CRISPR-nCas9-based genome editing assessment in mucopolysaccharidosis IVA mice

Mucopolysaccharidosis (MPS) IVA is a lysosomal storage disorder caused by mutations in the GALNS gene that leads to the lysosomal accumulation of keratan sulfate (KS) and chondroitin 6-sulfate, causing skeletal dysplasia and cardiopulmonary complications. Current enzyme replacement therapy does not impact the bone manifestation of the disease, supporting that new therapeutic alternatives are required. We previously demonstrated the suitability of the CRISPR-nCas9 system to rescue the phenotype of human MPS IVA fibroblasts using iron oxide nanoparticles (IONPs) as non-viral vectors. Here, we have extended this strategy to an MPS IVA mouse model by inserting the human GALNS cDNA into the ROSA26 locus. The results showed increased GALNS activity, mono-KS reduction, partial recovery of the bone pathology, and non-IONPs-related toxicity or antibody-mediated immune response activation. This study provides, for the first time, in vivo evidence of the potential of a CRISPR-nCas9-based gene therapy strategy for treating MPS IVA using non-viral vectors as carriers.

A Critical Analysis of the FDA's Omics-Driven Pharmacodynamic Biomarkers to Establish Biosimilarity

Demonstrating biosimilarity entails comprehensive analytical assessment, clinical pharmacology profiling, and efficacy testing in patients for at least one medical indication, as required by the U.S. Biologics Price Competition and Innovation Act (BPCIA). The efficacy testing can be waived if the drug has known pharmacodynamic (PD) markers, leaving most therapeutic proteins out of this concession. To overcome this, the FDA suggests that biosimilar developers discover PD biomarkers using omics technologies such as proteomics, glycomics, transcriptomics, genomics, epigenomics, and metabolomics. This approach is redundant since the mode-action-action biomarkers of approved therapeutic proteins are already available, as compiled in this paper for the first time. Other potential biomarkers are receptor binding and pharmacokinetic profiling, which can be made more relevant to ensure biosimilarity without requiring biosimilar developers to conduct extensive research, for which they are rarely qualified.

Clinical and biochemical footprints of inherited metabolic diseases. XIII. Respiratory manifestations

At any age, respiratory manifestations are a major cause of increased morbidity and mortality of inherited metabolic diseases (IMDs). Type and severity are extremely variable, this depending on the type of the underlying disorder. Symptoms and signs originating from upper or lower airways and/or thoracic wall and/or respiratory muscles involvement can occur either at presentation or in the late clinical course. Acute respiratory symptoms can trigger metabolic decompensation which, in turn, makes airway symptoms worse, creating a vicious circle. We have identified 181 IMDs associated with various types of respiratory symptoms which were classified into seven groups according to the type of clinical manifestations affecting the respiratory system: (i) respiratory failure, (ii) restrictive lung disease, (iii) interstitial lung disease, (iv) lower airway disease, (v) upper airway obstruction, (vi) apnea, and (vii) other. We also provided a list of investigations to be performed based on the respiratory phenotypes and indicated the therapeutic strategies currently available for IMD-associated airway disease. This represents the thirteenth issue in a series of educational summaries providing a comprehensive and updated list of metabolic differential diagnoses according to system involvement.

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.

Hydrogel Delivery Device for the In Vitro and In Vivo Sustained Release of Active rhGALNS Enzyme

Morquio A disease is a genetic disorder resulting in N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency, and patients are currently treated with enzyme replacement therapy via weekly intravenous enzyme infusions. A means of sustained enzyme delivery could improve patient quality of life by reducing the administration time, frequency of hospital visits, and treatment cost. In this study, we investigated poly(ethylene-glycol) (PEG) hydrogels as a tunable, hydrolytically degradable drug delivery system for the encapsulation and sustained release of recombinant human GALNS (rhGALNS). We evaluated hydrogel formulations that optimized hydrogel gelation and degradation time while retaining rhGALNS activity and sustaining rhGALNS release. We observed the release of active rhGALNS for up to 28 days in vitro from the optimized formulation. rhGALNS activity was preserved in the hydrogel relative to buffer over the release window, and encapsulation was found to have no impact on the rhGALNS structure when measured by intrinsic fluorescence, circular dichroism, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In vivo, we monitored the retention of fluorescently labeled rhGALNS in C57BL/6 albino mice when administered via subcutaneous injection and observed rhGALNS present for up to 20 days when delivered in a hydrogel versus 7 days in the buffer control. These results indicate that PEG hydrogels are suitable for the encapsulation, preservation, and sustained release of recombinant enzymes and may present an alternative method of delivering enzyme replacement therapies that improve patient quality of life.

Inflammatory process and oxidative/nitrative stress: in vivo study in mucopolysaccharidosis type IV A patients under long-term enzyme replacement therapy

Mucopolysaccharidosis type IV A (MPS IVA) is an inborn error of the metabolism (IEM) caused by a deficiency of the enzyme N-acetylgalactosamine 6-sulfate sulfatase (GALNS). Since 2014, enzyme replacement therapy (ERT) is the recommended treatment for these patients. It is known that the inflammatory response is closely related to antioxidant defenses and oxidative stress, and literature shows involvement of oxidative stress in the pathogenesis of IEM. The aim of this study is to investigate the mechanisms of oxidative/nitrative stress and inflammation in patients with MPS IVA under long-term ERT. In the present work we investigate parameters of oxidative/nitrative stress in plasma and urine of MPS IVA patients under long-term ERT and controls, such as plasmatic nitrate/nitrite levels using the LDH Method, urinary di-tyrosine levels by fluorometric method, plasmatic content of sulfhydryl groups, urinary oxidized guanine species by ELISA kit and the plasmatic total antioxidant status. We next evaluated the plasmatic pro and anti-inflammatory cytokines concentration (IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, TNF-α) and the expression of factors and enzymes Nrf-2, NF-κβ and HO-1, main mediators between inflammation and oxidative stress. In concern to the oxidative/nitrative stress parameters, there was no significant difference between the groups MPS IVA patients under long-term ERT and controls, showing that there is no overproducing of RNS, no protein damage, no DNA/RNA oxidative damage and no modification in the non-enzymatic antioxidant capacity of a tissue to prevent the damage associated to free radical processes in these patients. It was also verified no significant difference between the MPS IVA patients under long-term ERT and controls groups regarding the production of proinflammatory cytokines. About anti-inflammatory cytokines, IL 10 was shown to be elevated in MPS IVA patients under long-term ERT in comparison to the control group. We next evaluated the genic expression of Nrf-2, NF-κβ and HO-1and there was no significant difference between the MPS IVA patients under long-term ERT and control groups. In conclusion, MPS IVA patients under long term ERT are not in an inflammatory state and there is no alteration in genic expression in the genes analyzed which are involved in oxidative stress and inflammatory pathways. It is,however, important to consider that absence of imbalance of antioxidant defenses in MPS IVA patients under long term ERT is so far preliminary it is supported by methodologies that are not highly sensitive nor very accurate. Further experiments in future using state-of-the-art methodologies will corroborate these findings. Nevertheless, our results demonstrated the protective effect of the treatment in relation to the parameters studied and the importance of starting treatment in the early stages of the disease.

Current and new therapies for mucopolysaccharidoses

The mucopolysaccharidoses (MPSs) are a subset of lysosomal storage diseases caused by deficiencies in the enzymes required to metabolize glycosaminoglycans (GAGs), a group of extracellular heteropolysaccharides that play diverse roles in human physiology. As a result, GAGs accumulate in multiple tissues, and affected patients typically develop progressive, multi-systemic symptoms in early childhood. Over the last 30 years, the treatments available for the MPSs have evolved tremendously. There are now multiple therapies that delay the progression of these debilitating disorders, although their effectiveness varies according to MPS sub-type. In this review, we discuss the basic principle underlying MPS treatment (enzymatic "cross correction"), and we review the three general modalities currently available: hematopoietic stem cell transplantation, enzymatic replacement, and gene therapy. For each treatment type, we discuss its effectiveness across the MPS subtypes, its inherent risks, and future directions. Long term, we suspect that treatment for the MPSs will continue to evolve, and through a combination of early diagnosis and effective management, these patients will continue to live longer lives with improved outcomes for quality of life.

Modifying enzyme replacement therapy - A perspective

Several diseases are caused by the lack of functional proteins, including lysosomal storage diseases or haemophilia A and B. Patients suffering from one of these diseases are treated via enzyme replacement therapies to restore the missing protein. Although this treatment strategy prevents some disease symptoms, enzyme replacement therapies are very expensive and require very frequent infusions, which can cause infusion adverse reactions and massively impair the quality of life of the patients. This review proposes a technology to sustainably produce proteins within the patient to potentially make frequent protein-infusions redundant. This technology is based on blood circulating immune cells as producers of the needed therapeutic protein. To ensure a stable protein concentration over time the cells are equipped with a system, which induces cell proliferation when low therapeutic protein levels are detected and a system inhibiting cell proliferation when high therapeutic protein levels are detected.

Brain transplantation of genetically corrected Sanfilippo type B neural stem cells induces partial cross-correction of the disease

Sanfilippo syndrome type B (mucopolysaccharidosis type IIIB) is a recessive genetic disorder that severely affects the brain due to a deficiency in the enzyme α-N-acetylglucosaminidase (NAGLU), leading to intra-lysosomal accumulation of partially degraded heparan sulfate. There are no effective treatments for this disorder. In this project, we carried out an ex vivo correction of neural stem cells derived from Naglu -/- mice (iNSCs) induced pluripotent stem cells (iPSC) using a modified enzyme in which human NAGLU is fused to an insulin-like growth factor II receptor binding peptide in order to improve enzyme uptake. After brain transplantation of corrected iNSCs into Naglu -/- mice and long-term evaluation of their impact, we successfully detected NAGLU-IGFII activity in all transplanted animals. We found decreased lysosomal accumulation and reduced astrocytosis and microglial activation throughout transplanted brains. We also identified a novel neuropathological phenotype in untreated Naglu -/- brains with decreased levels of the neuronal marker Map2 and accumulation of synaptophysin-positive aggregates. Upon transplantation, we restored levels of Map2 expression and significantly reduced formation of synaptophysin-positive aggregates. Our findings suggest that genetically engineered iNSCs can be used to effectively deliver the missing enzyme to the brain and treat Sanfilippo type B-associated neuropathology.

Natural History and Real-World Data in Rare Diseases: Applications, Limitations, and Future Perspectives

Rare diseases represent a highly heterogeneous group of disorders with high phenotypic and genotypic diversity within individual conditions. Due to the small numbers of people affected, there are unique challenges in understanding rare diseases and drug development for these conditions, including patient identification and recruitment, trial design, and costs. Natural history data and real-world data (RWD) play significant roles in defining and characterizing disease progression, final patient populations, novel biomarkers, genetic relationships, and treatment effects. This review provides an introduction to rare diseases, natural history data, RWD, and real-world evidence, the respective sources and applications of these data in several rare diseases. Considerations for data quality and limitations when using natural history and RWD are also elaborated. Opportunities are highlighted for cross-sector collaboration, standardized and high-quality data collection using new technologies, and more comprehensive evidence generation using quantitative approaches such as disease progression modeling, artificial intelligence, and machine learning. Advanced statistical approaches to integrate natural history data and RWD to further disease understanding and guide more efficient clinical study design and data analysis in drug development in rare diseases are also discussed.

Findings from the Morquio A Registry Study (MARS) after 6 years: Long-term outcomes of MPS IVA patients treated with elosulfase alfa

BACKGROUND

The Morquio A Registry Study (MARS) is an ongoing, multinational, observational study of patients with MPS IVA. Key objectives of MARS are to characterize the heterogeneity and natural history of disease and to evaluate long-term effectiveness and safety of elosulfase alfa enzyme replacement therapy (ERT). Enrollment began in September 2014; data on medical history, clinical outcomes, and safety assessments are collected as part of routine care.

RESULTS

As of February 2021, 381 subjects from 17 countries had enrolled in MARS: 58 ERT-naïve subjects and 323 ERT-treated subjects (≥1 infusion), with a mean ERT exposure of 5.5 years (SD 2.8) and median age at first ERT treatment of 9.8 years. ERT-treated subjects were younger at diagnosis (median 3.4 vs 6.5 years) relative to ERT-naïve subjects. Among ERT-treated subjects, urinary keratan sulfate (uKS) levels declined from pre-ERT baseline to last follow-up on treatment (mean % change [95% confidence interval]: -52.5% [-57.5%, -47.4%]; n = 115) and 6-min walk test distance remained stable (mean change: -6.1 [-27.6, 15.5] m; n = 131) over a mean follow-up of 5.5 years. Forced expiratory volume in 1 s (FEV₁) and forced vital capacity (FVC) increased in subjects who were < 18 years of age at ERT initiation (mean change: +0.3 [0.1, 0.4] L and + 0.4 [0.3, 0.5] L; mean follow-up: ∼6 years; n = 82) and were stable in subjects ≥18 years (mean change: 0.0 [-0.0, 0.1] L and 0.0 [-0.1, 0.1] L; mean follow-up: 4.6 years; n = 38). Overall, 148 (47.1%) ERT-treated subjects experienced ≥1 adverse event (AE) and 110 subjects (35%) reported ≥1 serious AE. Drug-related AEs were reported in 39 (12.4%) subjects; the most common were hypersensitivity (9 subjects [2.9%]), urticaria (8 subjects [2.5%]), and pyrexia (7 subjects [2.2%]).

CONCLUSIONS

MARS is the longest and largest observational study of MPS IVA patients to date, with a heterogenous population that is representative of the MPS IVA population overall. Data collected over the first 6 years of MARS provide real-world evidence for long-term stabilization of endurance and respiratory function among ERT-treated patients, with no new safety concerns identified.

Efficacy of Intravenous Elosulfase Alfa for Mucopolysaccharidosis Type IVA: A Systematic Review and Meta-Analysis

Mucopolysaccharidosis type IVA (MPS IVA or Morquio A), a lysosomal storage disease with an autosomal recessive inherited pattern, is induced by GALNS gene mutations causing deficiency in N-acetylgalactosamine-6-sulfatase activity (GALNS; EC 3.1.6.4). Currently, intravenous (IV) enzyme replacement therapy (ERT) with elosulfase alfa is employed for treating MPS IVA patients. A systematic literature review was conducted to evaluate the efficacy and safety of IV elosulfase alfa for MPS IVA by searching the National Center for Biotechnology Information, U.S. National Library of Medicine National Institutes of Health (PubMed), Excerpta Medica dataBASE, and Cochrane Library databases, limited to clinical trials. Four cohort studies and two randomized controlled trials, with a total of 550 participants (327 on ERT treatment versus 223 on placebo treatment), satisfied the inclusion criteria. Pooled analysis of proportions and confidence intervals were also utilized to systematically review clinical cohort studies and trials. Per the pooled proportions analysis, the difference in means of urinary keratan sulfate (uKS), 6-min walk test, 3-min stair climb test, self-care MPS-Health Assessment Questionnaire, caregiver assistance and mobility, forced vital capacity, the first second of forced expiration, and maximal voluntary ventilation between the ERT and placebo treatment groups were -0.260, -0.102, -0.182, -0.360, -0.408, -0.587, -0.293, -0.311, and -0.213, respectively. Based on the currently available data, our meta-analysis showed that there is uKS, physical performance, quality of life, and respiratory function improvements with ERT in MPS IVA patients. It is optimal to start ERT after diagnosis.

Chest wall volumes, diaphragmatic mobility, and functional capacity in patients with mucopolysaccharidoses

PURPOSE

We investigated respiratory muscle strength, diaphragm mobility, lung function, functional capacity, quality of life, body composition, breathing pattern, and chest wall (V_T,CW) and compartmental volumes of Mucopolysaccharidosis (MPS) patients and compared these variables with matched healthy individuals.

METHODS

A cross-sectional study with data analyzed separately according to age group. A total of 68 individuals (34 MPS and 34 matched-healthy subjects) were included. Six-minute walking test assessed functional capacity and ultrasound assessed diaphragm mobility during quiet spontaneous breathing (QB). Optoelectronic plethysmography assessed V_T,CW and breathing pattern during QB in two different positions: seated and supine (45° trunk inclination).

RESULTS

Body composition, lung function, respiratory muscle strength, and functional capacity were reduced in MPS (all p < 0.01). Diaphragm mobility was only reduced in adolescents (p = 0.01) and correlated with body composition and breathing pattern. Upper chest wall compartmental volumes were significantly lower in MPS, while abdominal volume only differed significantly in adolescents. Percentage contribution (%) of upper ribcage compartments to tidal volume was reduced in MPS children, whereas %AB was significantly increased compared with healthy subjects.

CONCLUSION

Lung function, respiratory muscle strength, functional capacity, diaphragm mobility, and quality of life are reduced in MPS compared with matched healthy subjects. V_T,CW was mainly reduced due to pulmonary and abdominal ribcage impairment. Implications for RehabilitationReduction in respiratory muscle strength, functional capacity, diaphragm excursion and low lung volumes were found in individuals with Mucopolysaccharidoses (MPS).Chest wall volumes and the upper chest wall compartmental volumes during quiet spontaneous breathing are reduced in MPS.Assessment and monitoring of the respiratory system for individuals with MPS should be performed periodically through standardized assessments to enable identification of changes and early intervention by rehabilitation protocols.This study may provide the necessary basis for carrying out respiratoty rehabilitation protocols that can improving chest wall mechanics with breathing exercise in this group.

Unmet Cardiac Clinical Needs in Adult Mucopolysaccharidoses

The Mucopolysaccharidoses (MPSs) are a group of heterogenous disorders with complex multisystemic presentations. Although Haematopoietic Cell Transplantation (HCT) and Enzyme Replacement Therapy (ERT) have extended the lifespan of individuals affected with MPS well into adulthood, reversal of pre-existing cardiac, skeletal and neurocognitive deficits does not occur, so there are no truly curative treatments available to these patients at present. The medical and surgical management of cardiovascular problems in adults with MPS is complicated by these pre-existing comorbidities, requiring the involvement of multidisciplinary and multispecialty perioperative teams. This review sets out to describe the unmet cardiac needs in adults with MPS disorders including the lack of effective treatments, monitoring guidelines, and the challenges regarding expertise and training, and psychosocial support.

Clinical characteristics and effects of enzyme replacement therapy with elosulfase alfa in Korean patients with mucopolysaccharidosis type IVA

Mucopolysaccharidosis type IVA (MPS IVA) is a rare autosomal recessive disorder caused by a deficiency in N-acetylgalactosamine-6-sulfatase, which results in skeletal and connective tissue abnormalities, as well as various non-skeletal manifestations. Although enzyme replacement therapy (ERT) is recommended as the first-line treatment, the outcomes of ERT on bone pathology remain controversial. We report clinical characteristics and outcomes of ERT in 9 patients with MPS IVA (6 males and 3 females) from 7 unrelated families. During ERT, results from pulmonary function tests, echocardiography, the 6-min walk test, and the Functional Independence Measure were monitored biannually. Anthropometric data were compared with previously reported growth charts of subjects with MPS IVA.

Among the 9 patients (5 severe, and 4 slowly progressive form), 7 patients (5 severe, 2 slowly progressive) commenced ERT at a median age of 3.8 years (range: 0.8–13.7 years) and were treated for a median duration of 1.9 years (range: 1.2–5.7 years). Mean height standard deviation scores using MPS IVA growth charts were + 0.4 (+0.0 in severe phenotypes) at initiation and + 0.7 (+0.2 in severe phenotypes) at the last follow-up. Four patients with severe phenotypes underwent surgery for cervical myelopathy and 1 patient with a slowly progressive phenotype underwent a bilateral pelvic osteotomy for hip pain during ERT. The parameters of pulmonary and heart function, endurance, and Functional Independence Measure scores were maintained or increased after ERT. Overall, ERT was well tolerated without deterioration of cardiorespiratory and functional outcomes during treatment, although skeletal outcomes, including growth, were limited.

Consensus statement on enzyme replacement therapy for mucopolysaccharidosis IVA in Central and South-Eastern European countries

BACKGROUND

Mucopolysaccharidosis IVA (MPS IVA), or Morquio A syndrome, is a rare inherited metabolic disorder caused by deficiency of the lysosomal enzyme N-acetylgalactosamine-6-sulfatase. A progressive systemic skeletal chondrodysplasia, leading to significant morbidity and reduced life expectancy is the main clinical feature of this multisystemic disease. Although enzyme replacement therapy with elosulfase alfa is established in Europe, the rarity of disease and other factors still set hurdles in having patients treated in some countries. Aim of this statement is to provide evidence-based guidance for the enzyme replacement treatment of Morquio A patients, harmonizing recommendations from published guidelines with the real-life clinical practice in the Central and South-Eastern European region.

PARTICIPANTS

The Consensus Group, convened by 8 Steering Committee (SC) members from 7 Central and South-Eastern European countries, consisted of a multidisciplinary group of 17 experts in the management of MPS in Central and South-Eastern Europe.

CONSENSUS PROCESS

The SC met in a first virtual meeting with an external scientific coordinator, to discuss on clinical issues to be analyzed in guidance statements. Statements were developed by the scientific coordinator, evaluated by the SC members in a first modified-Delphi voting and adapted accordingly, to be submitted to the widest audience in the Consensus Conference. Following discussion and further modifications, all participants contributed to a second round of modified-Delphi voting.

RESULTS

Nine of ten statements, concerning general guidelines for management of MPS IVA patients and specific recommendations for treatment, received final consensus.

CONCLUSIONS

European guidelines and evidence-based recommendations for Morquio A patients should be considered in the real life of Central and South-Eastern European countries and adapted to unique clinical practice approaches and criteria for patients' access to treatment and reimbursement in the region.

Advancing the Research and Development of Enzyme Replacement Therapies for Lysosomal Storage Diseases

With the increasing interest in developing gene therapies for rare diseases, it is easy to overlook that there are numerous rare lysosomal storage diseases (LSD) with treatments that have been approved by regulatory agencies in the United States and Europe. These primarily consist of enzyme replacement therapies (ERT), which are recombinant human proteins that are delivered for the life of the patient via different routes and may have distinct safety and distribution advantages over gene therapies. The research and development of ERT is a lengthy and expensive process, which is usually performed in academic laboratories before transfer to pharmaceutical companies and is hence a process ripe for disruption. There may still be considerable scientific and investment potential for ERT, however we need to develop a pipeline of proteins analogous to what has been created in some open science efforts as well as apply technologies to decrease manufacturing costs. In this Perspective, we illustrate the opportunity to fill the rare LSD treatment gap with ERTs while gene therapies are in development for these life-shortening diseases.

The landscape of Mucopolysaccharidosis in Southern and Eastern European countries: a survey from 19 specialistic centers

Background

Mucopolysaccharidoses (MPS) are a group of lysosomal storage disorders caused by defects in genes coding for different lysosomal enzymes which degrade glycosaminoglycans. Impaired lysosomal degradation causes cell dysfunction leading to progressive multiorgan involvement, disabling consequences and poor life expectancy. Enzyme replacement therapy (ERT) is now available for most MPS types, offering beneficial effects on disease progression and improving quality of life of patients. The landscape of MPS in Europe is not completely described and studies on availability of treatment show that ERT is not adequately implemented, particularly in Southern and Eastern Europe. In this study we performed a survey analysis in main specialist centers in Southern and Eastern European countries, to outline the picture of disease management in the region and understand ERT implementation. Since the considerable number of MPS IVA patients in the region, particularly adults, the study mainly focused on MPS IVA management and treatment.

Results

19 experts from 14 Southern and Eastern European countries in total responded to the survey. Results outlined a picture of MPS management in the region, with a high number of MPS patients managed in the centers and a high level of care. MPS II was the most prevalent followed by MPS IVA, with a particular high number of adult patients. The study particularly focused on management and treatment of MPS IVA patients. Adherence to current European Guidelines for follow-up of MPS IVA patients is generally adequate, although some important assessments are reported as difficult due to the lack of MPS skilled specialists. Availability of ERT in Southern and Eastern European countries is generally in line with other European regions, even though regulatory, organizational and reimbursement constrains are demanding.

Conclusions

The landscape of MPS in Southern and Eastern European countries is generally comparable to that of other European regions, regarding epidemiology, treatment accessibility and follow up difficulties. However, issues limiting ERT availability and reimbursement should be simplified, to start treatment as early as possible and make it available for more patients. Besides, educational programs dedicated to specialists should be implemented, particularly for pediatricians, clinical geneticists, surgeons, anesthesiologists and neurologists.

Clinical Utility of Elosulfase Alfa in the Treatment of Morquio A Syndrome

Mucopolysaccharidosis type IVA (MPS IVA or Morquio A) is an autosomal recessive disorder and is one of the lysosomal storage diseases. Patients with MPS IVA have a striking skeletal phenotype but normal intellect. The phenotypic continuum of MPS IVA ranges from severe and rapid progress to mild and slow progress. The diagnosis of MPS IVA is usually suspected based on abnormal bone findings and dysplasia on physical examination and radiographic investigation in the preschool years. In the past, only supportive care was available. Due to the early and severe skeletal abnormalities, the orthopedic specialist was usually the main care provider. However, patients need aggressive monitoring and management of their systemic disease. Therefore, they need an interdisciplinary team for their care, comprising medical geneticists, cardiologists, pulmonary specialists, gastroenterologists, otolaryngologists, audiologists, and ophthalmologists. After the US Food and Drug Administration approved elosulfase alfa in 2014, patients older than 5 years could benefit from this treatment. Clinical trials showed clinically meaningful improvements with once-a-week intravenous dosing (2.0 mg/kg per week), significantly improving the 6min walk test, the 3min stair climb test, and respiratory function when compared with placebo. Elosulfase alfa is well-tolerated, and there is a good response indicated by decreasing urine glycosaminoglycans.

Mucopolysaccharidosis type VI (Maroteaux-Lamy syndrome): defining and measuring functional impacts in pediatric patients

BACKGROUND

Research about pediatric patients' perspective on mucopolysaccharidosis type VI (MPS VI) and its impact on daily life is limited. We aimed to identify the disease concepts of interest that most impact function and day-to-day life of pediatric patients with MPS VI, and to consider clinical outcome assessments (COAs) that may potentially measure meaningful improvements in these concepts.

METHODS

Potential focus group participants were identified by the National MPS Society (USA) and invited to participate if they self-reported a clinician-provided diagnosis of MPS VI and were 4 to 18 years, receiving enzyme replacement therapy (ERT), and available to attend a 1-day focus group with their caregiver in Dallas, TX, USA. The focus group consisted of a series of polling and open-ended concept elicitation questions and a cognitive debriefing session. The discussion was audio recorded, transcribed verbatim, and analyzed to identify disease concepts of interest and functional impacts most relevant to participants.

RESULTS

Overall, caregivers (n = 9) and patients with MPS VI (n = 9) endorsed that although their children/they receive ERT, residual symptoms exist and impact health-related quality of life. The key disease concepts of interest identified were impaired mobility, upper extremity and fine motor deficits, pain, and fatigue. Pain was unanimously reported by all patients across many areas of the body and impacted daily activity. Key disease concepts were mapped to a selection of pediatric COAs including generic measures such as PROMIS®, PODCI, CHAQ, and PedsQL™. Caregivers endorsed the relevance of PODCI and PROMIS Upper Extremity, Mobility, and Pain items and all patients completed the NIH Toolbox Pegboard Dexterity Test. Additional COAs that aligned with the disease concepts included range of motion, the 2- and 6-min walk tests, timed stair climbs, Bruininks-Oseretsky Test of Motor Proficiency, 2nd edition, grip strength, pain visual analog scale, and the Faces Pain Scale-Revised.

CONCLUSION

An MPS VI focus group of pediatric patients and their caregivers identified impaired mobility, upper extremity and fine motor deficits, pain, and fatigue as key disease concepts of interest. These disease concepts were mapped to existing pediatric COAs, which were provided to the group for endorsement of their relevance.

Hyo-Mental Angle and Distance: An Important Adjunct in Airway Assessment of Adult Mucopolysaccharidosis

Background: Mucopolysaccharidosis (MPS) is a rare congenital lysosomal storage disorder with complex airways. High anterior larynx is assessed by thyromental distance (TMD) nasendoscopy. A simpler method to assess this hyoid bone is described. The distance between the central-hyoid and symphysis of the mandible (hyo-mental distance; HMD) and inclination of this line to the horizontal axis (hyo-mental angle; HMA) in neutrally positioned patients is investigated. Methods: HMA, HMD in MPS, and non-MPS were compared, and their correlation with height and weight were assessed. Results: 50 adult MPS patients (M = 32, F = 18, age range = 19–66 years; mean BMI = 26.8 kg/m²) of MPS I, II, III, IV, and VI were compared with 50 non-MPS (M = 25, F = 25; age range = 22–84 years; mean BMI = 26.5 kg/m²). Mean HMA in MPS was 25.72° (−10 to +50) versus 2.42° (−35 to +28) in non-MPS. Mean HMD was 46.5 (25.7–66) millimeters in MPS versus 41.8 (27–60.3) in non-MPS. HMA versus height and weight showed a moderate correlation (r = −0.4, p < 0.05) in MPS and no significant correlation (r < 0.4, p > 0.05) in non-MPS. HMD versus height and weight showed no correlation (r < 0.4, p > 0.05) in both groups. Conclusions: HMA seems more acute in MPS despite nearly the same HMD as non-MPS, signifying a high larynx, which may be missed by TMD.

Activity of daily living in mucopolysaccharidosis IVA patients: Evaluation of therapeutic efficacy

Background

Mucopolysaccharidosis IVA (MPS IVA, also called Morquio A syndrome) is caused by a deficiency of N‐acetylglucosamine‐6‐sulfate sulfatase (GALNS) and results in skeletal dysplasia symptoms such as short stature and abnormal gait. Treatments include enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT), but the effects are limited depending on the age of initiation and clinical phenotype. Thus, this study aims to assess the effects of treatments on MPS IVA patients compared to untreated MPS IVA patients and an age‐matched control group.

Methods

We used activity of daily living (ADL) survey with 4 sections: “movement,” “movement with cognition,” “cognition,” and “other MPS symptoms.” Lower scores indicate more assistance required. This study included 161 patients, 270 total surveys, and 70 patients with longitudinal data.

Results

We describe 134 severe patients and 25 attenuated patients. ERT and HSCT treatment improved only the “other MPS symptoms” section in severe patients. There were no differences between ERT and HSCT severe patient scores. A 19‐year‐old male patient, who had robust physical training, provided a significant increase in “movement” without treatment, suggesting the importance of exercise.

Conclusion

Overall, this ADL questionnaire has demonstrated validation and reliability in assessing the MPS IVA patients and therapeutic efficacy.

Elosulfase alfa in the treatment of mucopolysaccharidosis type IVA: insights from the first managed access agreement

Managed access agreements provide a crucial mechanism whereby real-world data can be collected systematically to reduce uncertainty around available clinical and economic data, whilst providing the opportunity to identify patient sub-populations who are most likely to benefit from a new treatment. This manuscript aims to share learnings from the first managed access agreement, which was initiated following positive conditional approval in 2015 from the National Institute for Health and Care Excellence (NICE) for elosulfase alfa, an enzyme replacement therapy for the treatment of mucopolysaccharidosis type IVA (MPS IVA). This managed access agreement enabled the collection of comprehensive real-world data for patients with MPS IVA, with results demonstrating that patients starting elosulfase alfa treatment showed gains similar to those seen in the pivotal trial for outcomes including endurance, respiratory and cardiac function, pain, quality of life measures and urinary keratan sulfate levels. In addition, former trial patients continued to see benefits in both clinical assessments and quality of life/activities of daily living nine years after beginning treatment. Key strengths of the process included recruitment of a high proportion of MPS IVA patients treated in England (72/89 known eligible patients) with a wide range of ages (2-58 years). Participation of a patient organisation (the MPS society) ensured that the patient voice was present throughout the process, whilst a contract research organisation (Rare Disease Research Partners) ensured that patients were represented when interpreting agreement criteria and during patient assessment meetings. Longer-term follow-up will be required for several MPS IVA outcomes (e.g. skeletal measures) to further reduce uncertainty, and continued follow-up of patients who had stopped treatment was found to be challenging. The burden associated with this managed access agreement was found to be high for patients, physicians, patient organisations, NHS England and the manufacturer, therefore costs and benefits of future agreements should be considered carefully before initiation. Through evaluation of the strengths and limitations of this process, it is hoped that learnings from this managed access agreement can be used to inform future agreements.

Treatment of skeletal and non-skeletal alterations of Mucopolysaccharidosis type IVA by AAV-mediated gene therapy

Mucopolysaccharidosis type IVA (MPSIVA) or Morquio A disease, a lysosomal storage disorder, is caused by N-acetylgalactosamine-6-sulfate sulfatase (GALNS) deficiency, resulting in keratan sulfate (KS) and chondroitin-6-sulfate accumulation. Patients develop severe skeletal dysplasia, early cartilage deterioration and life-threatening heart and tracheal complications. There is no cure and enzyme replacement therapy cannot correct skeletal abnormalities. Here, using CRISPR/Cas9 technology, we generate the first MPSIVA rat model recapitulating all skeletal and non-skeletal alterations experienced by patients. Treatment of MPSIVA rats with adeno-associated viral vector serotype 9 encoding Galns (AAV9-Galns) results in widespread transduction of bones, cartilage and peripheral tissues. This led to long-term (1 year) increase of GALNS activity and whole-body correction of KS levels, thus preventing body size reduction and severe alterations of bones, teeth, joints, trachea and heart. This study demonstrates the potential of AAV9-Galns gene therapy to correct the disabling MPSIVA pathology, providing strong rationale for future clinical translation to MPSIVA patients.

The youngest pair of siblings with Mucopolysaccharidosis type IVA to receive enzyme replacement therapy to date: A case report

Mucopolysaccharidosis type IVA (OMIM 253000) is an autosomal recessive disorder caused by defective activity of the N-acetylgalactosamine 6-sulfatase (GALNS) enzyme. In 2014, enzyme replacement therapy (ERT) using recombinant human GALNS became available for affected patients. There is a limited number of studies to date that have explored the effect of ERT in infancy and there is also a lack of data assessing the effect of ERT in systems other than the skeletal. Here, we report on the effect of ERT in the youngest pair of siblings treated to date: Patient A, currently 4 years old, who started treatment at the age of 5 months; and Patient B, currently 3 years old, who started treatment at 58 days of life. Moreover, we investigate the effect of early ERT on the cardiovascular system. Our results show that, even when ERT is started before 2 months of age, it cannot fully prevent disease progression. As for the effect of ERT on the cardiovascular system, our preliminary results suggest that early treatment might play a role in preserving a normal left ventricular mass index in affected patients at least up to 1 year, but further observation over time will be required. Overall, this report shows that early diagnosis remains crucial and that prompt initiation of ERT has limited effect in slowing progression of the skeletal phenotype, thus confirming the need for new therapeutic approaches that target the skeletal system in affected patients.

Molecular basis of mucopolysaccharidosis IVA (Morquio A syndrome): A review and classification of GALNS gene variants and reporting of 68 novel variants

Mucopolysaccharidosis IVA (MPS IVA, Morquio A syndrome) is a rare autosomal recessive lysosomal storage disorder caused by mutations in the N‐acetylgalactosamine‐6‐sulfatase (GALNS) gene. We collected, analyzed, and uniformly summarized all published GALNS gene variants, thus updating the previous mutation review (published in 2014). In addition, new variants were communicated by seven reference laboratories in Europe, the Middle East, Latin America, Asia, and the United States. All data were analyzed to determine common alleles, geographic distribution, level of homozygosity, and genotype‐phenotype correlation. Moreover, variants were classified according to their pathogenicity as suggested by ACMG. Including those previously published, we assembled 446 unique variants, among which 68 were novel, from 1190 subjects (including newborn screening positive subjects). Variants' distribution was missense (65.0%), followed by nonsense (8.1%), splicing (7.2%), small frameshift deletions(del)/insertions(ins) (7.0%), intronic (4.0%), and large del/ins and complex rearrangements (3.8%). Half (50.4%) of the subjects were homozygous, 37.1% were compound heterozygous, and 10.7% had only one variant detected. The novel variants underwent in silico analysis to evaluate their pathogenicity. All variants were submitted to ClinVar (https://www.ncbi.nlm.nih.gov/clinvar/) to make them publicly available. Mutation updates are essential for the correct molecular diagnoses, genetic counseling, prenatal and preimplantation diagnosis, and disease management.

Airway Abnormalities in Adult Mucopolysaccharidosis and Development of Salford Mucopolysaccharidosis Airway Score

(1) Background: Mucopolysaccharidoses (MPS) are a heterogeneous group of lysosomal storage disorders caused by the absence of enzymes required for degradation of glycosaminoglycans (GAGs). GAGs deposition in tissues leads to progressive airway narrowing and/or tortuosity. Increased longevity of patients has posed newer problems, especially the airway. This study aims to characterise various airway abnormalities in adult MPS from a regional centre and proposes a method to quantify the severity of the airway disease. (2) Methods: Retrospective analysis by case notes review, clinical examination, endoscopy, cross-sectional imaging, 3-dimensional reconstruction, and physiological investigations were used to assess the airway abnormalities. Quantitative assessment of the airway severity was performed a validated questionnaire of 15 parameters to derive Salford Mucopolysaccharidosis Airway Score (SMAS). (3) Results: Thirty-one adult MPS patients (21M/ 9F; median 26.7 years; range 19–42 years) were reviewed. There were 9 MPS I, 12 MPS II, 2 MPS III, 5 MPS IV, 2 MPS VI, and 1 MPS VII. Airway abnormalities in each MPS type are described. Patients scoring more than 35 on SMAS had some form of airway intervention. The area under curve of 0.9 was noted at a score of 25, so SMAS more than 25 may predict a difficult airway and potential to have complications. Pearson’s correlation between SMAS and height, weight, BMI were poor (p < 0.05). (4) Conclusions: Airway abnormalities in adult MPS are varied and complex. Assessment of the airway should be holistic and include multiple parameters. An objective multidimensional score such as SMAS may help to predict and manage difficult airways warranting further investigation and validation.

The Impact of Excluding Nonrandomized Studies From Systematic Reviews in Rare Diseases: "The Example of Meta-Analyses Evaluating the Efficacy and Safety of Enzyme Replacement Therapy in Patients With Mucopolysaccharidosis"

Nonrandomized studies are usually excluded from systematic reviews. This could lead to loss of a considerable amount of information on rare diseases. In this article, we explore the impact of excluding nonrandomized studies on the generalizability of meta-analyses results on mucopolysaccharidosis (MPS) disease. A comprehensive search of systematic reviews on MPS patients up to May 2020 was carried out (CRD42020191217). The primary endpoint was the rate of patients excluded from systematic reviews if only randomized studies were considered. Secondary outcomes included the differences in patient and study characteristics between randomized and nonrandomized studies, the methods used to combine data from studies with different designs, and the number of patients excluded from systematic reviews if case reports were not considered. More than 50% of the patients analyzed have been recruited in nonrandomized studies. Patient characteristics, duration of follow-up, and the clinical outcomes evaluated differ between the randomized and nonrandomized studies. There are feasible strategies to combine the data from different randomized and nonrandomized designs. The analyses suggest the relevance of including case reports in the systematic reviews, since the smaller the number of patients in the reference population, the larger the selection bias associated to excluding case reports. Our results recommend including nonrandomized studies in the systematic reviews of MPS to increase the representativeness of the results and to avoid a selection bias. The recommendations obtained from this study should be considered when conducting systematic reviews on rare diseases.

The future of newborn screening for lysosomal disorders

The goal of newborn screening is to enhance the outcome of individuals with serious, treatable disorders through early, pre-symptomatic detection. The lysosomal storage disorders (LSDs) comprise a group of more than 50 diseases with a combined frequency of approximately 1:7000. With the availability of existing and new enzyme replacement therapies, small molecule treatments and gene therapies, there is increasing interest in screening newborns for LSDs with the goal of reducing disease-related morbidity and mortality through early detection. Novel screening methods are being developed, including efforts to enhance accuracy of screening using an array of multi-tiered, genomic, statistical, and bioinformatic approaches. While NBS data for Gaucher disease, Fabry disease, Krabbe disease, MPS I, and Pompe disease has demonstrated the feasibility of widespread screening, it has also highlighted some of the complexities of screening for LSDs. These include the identification of infants with later-onset, untreatable, and uncertain phenotypes, raising interesting ethical concerns that should be addressed as part of the NBS implementation process. Taken together, these efforts will provide critical, detailed data to help guide objective, ethically sensitive decision-making about NBS for LSDs.

Enzyme Replacement Therapy for Genetic Disorders Associated with Enzyme Deficiency

Mutations in human genes might lead to loss of functional proteins, causing diseases. Among these genetic disorders, a large class is associated with the deficiency in metabolic enzymes, resulting in both an increase in the concentration of substrates and a loss in the metabolites produced by the catalyzed reactions. The identification of therapeutic actions based on small molecules represents a challenge to medicinal chemists because the target is missing. Alternative approaches are biology-based, ranging from gene and stem cell therapy, CRISPR/Cas9 technology, distinct types of RNAs, and enzyme replacement therapy (ERT). This review will focus on the latter approach that since the 1990s has been successfully applied to cure many rare diseases, most of them being lysosomal storage diseases or metabolic diseases. So far, a dozen enzymes have been approved by FDA/EMA for lysosome storage disorders and only a few for metabolic diseases. Enzymes for replacement therapy are mainly produced in mammalian cells and some in plant cells and yeasts and are further processed to obtain active, highly bioavailable, less degradable products. Issues still under investigation for the increase in ERT efficacy are the optimization of enzymes interaction with cell membrane and internalization, the reduction in immunogenicity, and the overcoming of blood-brain barrier limitations when neuronal cells need to be targeted. Overall, ERT has demonstrated its efficacy and safety in the treatment of many genetic rare diseases, both saving newborn lives and improving patients' life quality, and represents a very successful example of targeted biologics.

Disease burden, management patterns and multidisciplinary clinical approaches for patients with MPS IVA and VI in selected Latin American Countries

Background

There is a paucity of real-world epidemiological data on patients with mucopolysaccharidoses (MPS) in Latin America. This real-world study assessed the disease burden, management patterns and multidisciplinary clinical approaches for MPS-IVA and MPS-VI patients in Latin America (Colombia, Ecuador, Mexico, Peru).

Methods

Data were collected from physicians/specialists experienced in treating MPS patients between April–June 2020, via an online patient-diary survey.

Results

Overall, 29 physicians/specialists participated in this study. Data from 98 patients were analyzed (MPS-IVA, 71 patients and MPS-VI, 27 patients). Mean age for MPS-IVA patients was 17.5 years and for MPS-VI patients was 11.6 years, and the majority were females (52% and 78%, respectively). MPS-IVA and VI patients presented a high absenteeism from school (55% and 37%, respectively; <18 years age) and workplace (78% and 100%, respectively; >18 years age), indicating an impact of the disease on some aspects of the patients' quality of life. The onset of the first symptom occurred at the age of 3.1 years for MPS-IVA patients and at 1 year for MPS-VI, with delay in diagnosis (3.5–3.9 years from symptom onset) and enzyme replacement therapy (ERT) initiation (1.1–3.6 years from diagnosis). ERT interruptions were observed for MPS-IVA (48%) and MPS-VI patients (44%), with non-availability of medication recorded as the main reason for non-adherence (46% and 60% patients, respectively). ERT showed noticeable treatment benefits in MPS-IVA/VI patients, with stabilization/reduction in complications or the number of surgeries. A multidisciplinary clinical team approach was used for patient management.

Conclusion

The disease burden for MPS-IVA/VI was high in Latin America, with consistent management, treatment and socio-demographic trends throughout the region.

Morquio A syndrome and effect of enzyme replacement therapy in different age groups of Turkish patients: a case series

Background

This case series includes longitudinal clinical data of ten patients with Morquio A syndrome from south and southeastern parts of Turkey, which were retrospectively collected from medical records. All patients received enzyme replacement therapy (ERT). Clinical data collected included physical appearance, anthropometric data, neurological and psychological examinations, cardiovascular evaluation, pulmonary function tests, eye and ear-nose-throat examinations, endurance in the 6-min walk test and/or 3-min stair climb test, joint range of motion, and skeletal investigations (X-rays, bone mineral density).

Results

At the time of ERT initiation, two patients were infants (1.8 and 2.1 years), five were children (3.4–7.1 years), and three were adults (16.5–39.5 years). Patients had up to 4 years follow-up. Most patients had classical Morquio A, based on genotypic and phenotypic data. Endurance was considerably reduced in all patients, but remained relatively stable or increased over time in most cases after treatment initiation. Length/height fell below normal growth curves, except in the two infants who started ERT at ≤ 2.1 years of age. All patients had skeletal and/or joint abnormalities when ERT was started. Follow-up data did not suggest improvements in skeletal abnormalities, except in one of the younger infants. Nine patients had corneal clouding, which resolved after treatment initiation in the two infants, but not in the other patients. Hepatomegaly was reported in seven patients and resolved with treatment in five of them. Other frequent findings at treatment initiation were coarse facial features (N = 9), hearing loss (N = 6), and cardiac abnormalities (N = 6). Cardiac disease deteriorated over time in three patients, but did not progress in the others.

Conclusions

Overall, this case series with Morquio A patients confirms clinical trial data showing long-term stabilization of endurance after treatment initiation across ages and suggest that very early initiation of ERT optimizes growth outcomes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13023-021-01761-0.

Galactosialidosis: preclinical enzyme replacement therapy in a mouse model of the disease, a proof of concept

Galactosialidosis is a rare lysosomal storage disease caused by a congenital defect of protective protein/cathepsin A (PPCA) and secondary deficiency of neuraminidase-1 and β-galactosidase. PPCA is a lysosomal serine carboxypeptidase that functions as a chaperone for neuraminidase-1 and β-galactosidase within a lysosomal multi-protein complex. Combined deficiency of the three enzymes leads to accumulation of sialylated glycoproteins and oligosaccharides in tissues and body fluids and manifests in a systemic disease pathology with severity mostly correlating with the type of mutation(s) and age of onset of the symptoms. Here, we describe a proof-of-concept, preclinical study toward the development of enzyme replacement therapy for galactosialidosis, using a recombinant human PPCA. We show that the recombinant enzyme, taken up by patient-derived fibroblasts, restored cathepsin A, neuraminidase-1, and β-galactosidase activities. Long-term, bi-weekly injection of the recombinant enzyme in a cohort of mice with null mutation at the PPCA (CTSA) locus (PPCA -/- ), a faithful model of the disease, demonstrated a dose-dependent, systemic internalization of the enzyme by cells of various organs, including the brain. This resulted in restoration/normalization of the three enzyme activities, resolution of histopathology, and reduction of sialyloligosacchariduria. These positive results underscore the benefits of a PPCA-mediated enzyme replacement therapy for the treatment of galactosialidosis.

Enzyme replacement combinational therapy: effective treatments for mucopolysaccharidoses

INTRODUCTION

Mucopolysaccharidoses (MPS), as a group of inherited lysosomal storage disorders (LSDs), are clinically heterogeneous and characterized by multi-systemic manifestations, such as skeletal abnormalities and neurological dysfunctions. The currently used enzyme replacement therapy (ERT) might be associated with several limitations including the low biodistribution of the enzymes into the main targets, immunological responses against foreign enzymes, and the high cost of the treatment procedure. Therefore, a suitable combination approach can be considered for the successful treatment of each type of MPS.

AREAS COVERED

In this review, we provide comprehensive insights into the ERT-based combination therapies of MPS by reviewing the published literature on PubMed and Scopus. We also discuss the recent advancements in the treatment of MPS and bring up the hopes and hurdles in the futuristic treatment strategies.

EXPERT OPINION

Given the complex pathophysiology of MPS and its involvement in different tissues, the ERT of MPS in combination with stem cell therapy or gene therapy is deemed to provide a personalized precision treatment modality with the highest therapeutic responses and minimal side effects. By the same token, new combinational approaches need to be evaluated by using drugs that target alternative and secondary pathological pathways.

A 9-Month-Old with Skeletal Abnormalities and a Consanguineous Sibling with Mucopolysaccharidosis IVA: The Role of Urinary Glycosaminoglycan Testing in Disease Diagnosis and Treatment Monitoring

Mucopolysaccharidosis IVA (MPS IVA) is a rare autosomal recessive lysosomal storage disorder resulting from N-acetylgalactosamine-6-sulfatase (GALNS) deficiency that occurs in approximately 1 in 76 000 to 1 in 640 000 live births. Given that the diagnosis of MPS IVA relies heavily on the results of initial urine glycosaminoglycan (GAG) screening, cases that present with falsely normal urine GAG concentrations can delay the diagnosis and follow-up care for patients. This case study follows a patient diagnosed with MPS IVA at 9 months of age based on relation to a consanguineous 3-year-old sibling with MPS IVA and the use of direct enzyme activity analysis. Details regarding skeletal presentation and identification of genetic variants are presented along with data on follow-up urinary GAG monitoring during treatment with enzyme replacement therapy and treatment for a growth hormone disorder.

Enzyme replacement therapy interruption in mucopolysaccharidosis type IVA patients and its impact in different clinical outcomes

Mucopolysaccharidosis type IVA (MPS IVA) is an autosomal recessive lysosomal storage disorder caused by mutations in the GALNS gene, which leads to deficient activity of N-acetylglucosamine-6-sulfate sulfatase. MPS IVA patients usually present skeletal dysplasia, coarse features, short stature, airway obstruction, cervical spinal cord compression, dental abnormalities, and cardiac valvular alterations. Enzyme replacement therapy (ERT) with elosulfase alfa is the only disease-specific treatment available for MPS IVA patients and has been shown to improve important clinical and biochemical parameters; however, little is known about the effects of ERT interruption on these patients. In this article, we report the impact of different periods of treatment interruption on clinical outcomes of 18 MPS IVA patients. All MPS IVA patients included in this case series were treated and followed up in Latin American centers and had been receiving elosulfase alfa intravenously for at least 8 months before ERT was interrupted. Different clinical parameters and assessments were evaluated at variable timepoints following therapy interruption. Altogether, our report indicates that some beneficial ERT effects in MPS IVA patients may last after different periods of treatment interruption, as cardiac and respiratory function improvements. However, worsening of important disease parameters after ERT interruption, such as the increase in uGAGs, pain, joint and skeletal aspects, and surgery indications suggests that treatment discontinuation should be avoided in order to maintain the disease as stable as possible, aiming to optimize these patients' life expectancy and quality of life.

Impact of long-term elosulfase alfa treatment on clinical and patient-reported outcomes in patients with mucopolysaccharidosis type IVA: results from a Managed Access Agreement in England

Background

We present baseline characteristics and follow-up data of a Managed Access Agreement (MAA), including patients with mucopolysaccharidosis IVA (MPS IVA) receiving elosulfase alfa enzyme replacement therapy (ERT) in England on a conditional basis. Patients enrolled in the MAA programme are reviewed on an annual basis. Therapy can be continued if patients are compliant, able to tolerate infusions, and meet four out of five pre-defined clinical and patient-reported outcomes (PRO) criteria. Baseline and follow-up clinical and PRO data are presented for all participants who completed ≥ 1 year of assessments in the MAA.

Results

The analysis included data from 55 patients, including 26 patients previously enrolled in clinical trials and 29 who started ERT after enrolling in the MAA. In patients with both baseline and follow-up data, mean 6-min walk test distance increased from 217 m at baseline to 244 m after a mean follow-up of 4.9 years. Improvement or stabilisation was seen regardless of age at treatment initiation or duration of treatment. Mean forced vital capacity and forced expiratory volume in 1 s were 0.87 L and 0.78 L, respectively at baseline and 1.05 L and 0.88 L after a mean follow-up of 5.5 years. PRO data showed overall improvements over time in Mobility, Self-care, and Caregiver assistance scores of the MPS-Health Assessment Questionnaire, relatively stable quality of life, and some improvements in pain scores.

Conclusions

The MAA data confirm the effects of elosulfase alfa on clinical and PRO results observed in the clinical trials and provide real-world evidence for long-term stabilisation in these measures, suggesting a positive impact on the natural history of MPS IVA.