Efficacy of recombinant human alpha-L-iduronidase (laronidase) on restricted range of motion of upper extremities in mucopolysaccharidosis type I patients

MPSI Manifestations and Treatment Outcome: Skeletal Focus

Mucopolysaccharidosis type I (MPSI) (OMIM #252800) is an autosomal recessive disorder caused by pathogenic variants in the IDUA gene encoding for the lysosomal alpha-L-iduronidase enzyme. The deficiency of this enzyme causes systemic accumulation of glycosaminoglycans (GAGs). Although disease manifestations are typically not apparent at birth, they can present early in life, are progressive, and include a wide spectrum of phenotypic findings. Among these, the storage of GAGs within the lysosomes disrupts cell function and metabolism in the cartilage, thus impairing normal bone development and ossification. Skeletal manifestations of MPSI are often refractory to treatment and severely affect patients’ quality of life. This review discusses the pathological and molecular processes leading to impaired endochondral ossification in MPSI patients and the limitations of current therapeutic approaches. Understanding the underlying mechanisms responsible for the skeletal phenotype in MPSI patients is crucial, as it could lead to the development of new therapeutic strategies targeting the skeletal abnormalities of MPSI in the early stages of the disease.

Non-cardiac Manifestations in Adult Patients With Mucopolysaccharidosis

Mucopolysaccharidoses (MPS) are a heterogeneous group of disorders that results in the absence or deficiency of lysosomal enzymes, leading to an inappropriate storage of glycosaminoglycans (GAGs) in various tissues of the body such as bones, cartilage, heart valves, arteries, upper airways, cornea, teeth, liver and nervous system. Clinical manifestations can become progressively exacerbated with age and affect their quality of life. Developments in advanced supportive treatment options such as enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT) may have improved patients' life span. Adult MPS patients require specialist clinical surveillance long-term. In many cases, in addition to the MPS-related health problems, they may develop age-related complications. Considering the complexity of their clinical manifestations and lack of guidelines on the management of adult MPS disorders, multispecialty and multidisciplinary teams' care is essential to diagnose and treat health problems that are likely to be encountered. This review presents non-cardiac clinical manifestations, their pathophysiology, management and long-term outcomes in adult MPS patients.

Issues of COVID-19-related distance learning for children with neuronopathic mucopolysaccharidoses

The COVID-19 pandemic has impacted the education of children around the world, forcing a large proportion of teaching to be carried out remotely. The implications of this disruption have yet to be fully elucidated, but initial assessments suggest that COVID-19-related school closures and reliance on virtual learning may have a long-term negative impact on educational attainment and future earnings as well as life expectancy of children in the United States. Among children with neurodegenerative disorders, such as neuronopathic mucopolysaccharidoses (MPS disorders), the effects of the pandemic are likely to be even greater. We aim to shine a spotlight on the impact of COVID-19 on the education, treatment and general wellbeing of children and families affected by MPS disorders by highlighting the important role that educators and therapists play in supporting the neurocognitive function and quality of life of children with neuronopathic MPS disorders. This article will serve as a resource that caregivers, educators, clinicians and therapists can use when considering how best to advocate for children with neuronopathic MPS disorders in circumstances where in-school teaching or in-clinic treatment is compromised or not possible. Given that the current pandemic is likely to have a prolonged course and impact and that similar epidemics and pandemics are a near certainty in the future, it is essential that steps are taken to support the learning and care of children with neuronopathic MPS disorders. We must prioritize strategies to safely resume this fragile community's access to in-person education and supportive care, and to address gaps that have emerged during prolonged pauses in access, whenever possible.

Mucopolysaccharidosis Type I: Current Treatments, Limitations, and Prospects for Improvement

Mucopolysaccharidosis type I (MPS I) is a lysosomal disease, caused by a deficiency of the enzyme alpha-L-iduronidase (IDUA). IDUA catalyzes the degradation of the glycosaminoglycans dermatan and heparan sulfate (DS and HS, respectively). Lack of the enzyme leads to pathologic accumulation of undegraded HS and DS with subsequent disease manifestations in multiple organs. The disease can be divided into severe (Hurler syndrome) and attenuated (Hurler-Scheie, Scheie) forms. Currently approved treatments consist of enzyme replacement therapy (ERT) and/or hematopoietic stem cell transplantation (HSCT). Patients with attenuated disease are often treated with ERT alone, while the recommended therapy for patients with Hurler syndrome consists of HSCT. While these treatments significantly improve disease manifestations and prolong life, a considerable burden of disease remains. Notably, treatment can partially prevent, but not significantly improve, clinical manifestations, necessitating early diagnosis of disease and commencement of treatment. This review discusses these standard therapies and their impact on common disease manifestations in patients with MPS I. Where relevant, results of animal models of MPS I will be included. Finally, we highlight alternative and emerging treatments for the most common disease manifestations.

Intravenous Enzyme Replacement Therapy in Mucopolysaccharidoses: Clinical Effectiveness and Limitations

The aim of this review is to summarize the evidence on efficacy, effectiveness and safety of intravenous enzyme replacement therapy (ERT) available for mucopolysaccharidoses (MPSs) I, II, IVA, VI and VII, gained in phase III clinical trials and in observational post-approval studies. Post-marketing data are sometimes conflicting or controversial, possibly depending on disease severity, differently involved organs, age at starting treatment, and development of anti-drug antibodies (ADAs). There is general agreement that ERT is effective in reducing urinary glycosaminoglycans and liver and spleen volume, while heart and joints outcomes are variable in different studies. Effectiveness on cardiac valves, trachea and bronchi, hearing and eyes is definitely poor, probably due to limited penetration in the specific tissues. ERT does not cross the blood-brain barrier, with the consequence that the central nervous system is not cured by intravenously injected ERT. All patients develop ADAs but their role in ERT tolerance and effectiveness has not been well defined yet. Lack of reliable biomarkers contributes to the uncertainties about effectiveness. The data obtained from affected siblings strongly indicates the need of neonatal screening for treatable MPSs. Currently, other treatments are under evaluation and will surely help improve the prognosis of MPS patients.

Limited data to evaluate real-world effectiveness of enzyme replacement therapy for mucopolysaccharidosis type I

Orphan medicinal products (OMPs) are often authorized based on pivotal phase II and III trials that do not always meet high quality criteria. Laronidase is an example of an OMP used for treatment of mucopolysaccharidosis I (MPS I). One randomized controlled trial demonstrated efficacy on several somatic symptoms. However, effectiveness in the real-world setting remains to be determined. We performed a systematic review to evaluate the effectiveness of enzyme replacement therapy (ERT) on clinically relevant outcomes in MPS I. A search in OVID MEDLINE and OVID EMBASE was performed. Postmarketing studies including MPS I patients treated with ERT and reporting data on any of 19 predefined clinical outcome measures obtained before the start of ERT and at follow-up were eligible. Three scenarios were used to define effectiveness of ERT. The first scenario (A) assumes that improvement is essential, while the second scenario (B) also includes stabilization of signs and symptoms. The third scenario (C) defines failure of therapy. Twenty case series were included. The criteria indicating effectiveness (A), were met for four of 19 outcome measures while the criteria, indicating unclear effectiveness (B) were met for five of 19. For one of 19 nonverifiable data were reported and for nine of 19 no overall conclusions could be drawn (ambiguous results). Real-world effectiveness of laronidase is extremely difficult to assess, 15 years after marketing authorization. This is partially due to insufficient natural history data. We recommend the conduct of rigorous and independent postmarketing studies including core outcome sets for OMPs, enforced by marketing and/or reimbursing authorities aiming to demonstrate real-world effectiveness within a reasonable time frame.

Healthcare Resource Utilization and the Cost of Care for Mucopolysaccharidosis I Patients in Iran

BACKGROUND

Mucopolysaccharidosis I (MPS-I) is one of the most common types of MPS and lysosomal storage diseases, which impose considerable amount of economic burden on society.

OBJECTIVES

The aim of this study was to examine the cost drivers in the treatment of MPS-I patients in Iran.

METHODS

This is a cost-analysis study. The prevalence approach was used to evaluate costs from the healthcare payer's perspective. The number of patients found to have α-L-iduronidase deficiency was identified using the national registry database of the Ministry of Health (MOH). The direct medical costs of the patients were evaluated. Prescriptions; medical interventions; inpatient, outpatient, and diagnostic services, and also their costs were extracted from the patient's profiles in Iran Food and Drug Administration (IFDA). The prices of the medical services were taken out from Iranian medical tariff book 2014-15. Data extraction was performed from January 2017 to March 2018.

RESULTS

Sixty-six patients were registered as MPS-I in MOH databases. The average annual healthcare cost for every patient was $87 971.99, 96.9% of which was allocated to medication therapy. Therapeutic and diagnostic services costs (2.4% and 0.7% correspondingly) were ranked second and third, respectively, but with huge differences in medication cost.

CONCLUSIONS

The average annual cost of treatment for MPS-I patients is as high as 16.2 times the GDP per capita in Iran. The highest share of the cost belongs to medication. Selecting appropriate strategies for reducing the birth of a child with MPS could support allocative efficiency of the limited resources effectively.

Enzyme replacement therapy: efficacy and limitations

Enzyme replacement therapy (ERT) is available for mucopolysaccharidosis (MPS) I, MPS II, MPS VI, and MPS IVA. The efficacy of ERT has been evaluated in clinical trials and in many post-marketing studies with a long-term follow-up for MPS I, MPS II, and MPS VI. While ERT is effective in reducing urinary glycosaminoglycans (GAGs) and liver and spleen volume, cartilaginous organs such as the trachea and bronchi, bones and eyes are poorly impacted by ERT probably due to limited penetration in the specific tissue. ERT in the present formulations also does not cross the blood–brain barrier, with the consequence that the central nervous system is not cured by ERT. This is particularly important for severe forms of MPS I and MPS II characterized by cognitive decline. For severe MPS I patients (Hurler), early haematopoietic stem cell transplantation is the gold standard, while still controversial is the role of stem cell transplantation in MPS II. The use of ERT in patients with severe cognitive decline is the subject of debate; the current position of the scientific community is that ERT must be started in all patients who do not have a more effective treatment. Neonatal screening is widely suggested for treatable MPS, and many pilot studies are ongoing. The rationale is that early, possibly pre-symptomatic treatment can improve prognosis. All patients develop anti-ERT antibodies but only a few have drug-related adverse reactions. It has not yet been definitely clarified if high-titre antibodies may, at least in some cases, reduce the efficacy of ERT.

Pain in Mucopolysaccharidoses: Analysis of the Problem and Possible Treatments

Mucopolysaccharidosis (MPS) are a group of lysosomal storage disorders that are caused by the deficiency of enzymes involving in the catabolism of glycosaminoglycan (GAGs). GAGs incompletely degraded accumulate in many sites, damaging tissues and cells, leading to a variety of clinical manifestations. Many of these manifestations are painful, but few data are available in the literature concerning the prevalence, etiology, and pathogenesis of pain in children with MPS. This review, through the analysis of the data available the in literature, underscores the relevant prevalence of pain in MPSs’ children, provides the instruments to discern the etiopathogenesis of the disease and of pain, illustrates the available molecules for the management of pain and the possible advantages of non-pharmacological pain therapy in MPSs’ patients.

Bone health in patients with inborn errors of metabolism

Inborn errors of metabolism encompass a wide spectrum of disorders, frequently affecting bone. The most important metabolic disorders that primarily influence calcium or phosphate balance, resulting in skeletal pathology, are hypophosphatemic rickets and hypophosphatasia. Conditions involving bone marrow or affecting skeletal growth and development are mainly the lysosomal storage disorders, in particular the mucopolysaccharidoses. In these disorders skeletal abnormalities are often the presenting symptom and early recognition and intervention improves outcome in many of these diseases. Many disorders of intermediary metabolism may impact bone health as well, resulting in higher frequencies of osteopenia and osteoporosis. In these conditions factors contributing to the reduced bone mineralization can be the disorder itself, the strict dietary treatment, reduced physical activity or sunlight exposure and/or early ovarian failure. Awareness of these primary or secondary bone problems amongst physicians treating patients with inborn errors of metabolism is of importance for optimization bone health and recognition of skeletal complications.

Efficacy and safety of intravenous laronidase for mucopolysaccharidosis type I: A systematic review and meta-analysis

Mucopolysaccharidosis type I (MPS I) is an autosomal recessive disease caused by deficient activity of alpha-L-iduronidase. Intravenous (IV) enzyme replacement therapy (ERT) with laronidase is currently used for treating patients with MPS I.

Outcomes of Long-Term Treatment with Laronidase in Patients with Mucopolysaccharidosis Type I

OBJECTIVE

To evaluate long-term outcomes of laronidase enzyme replacement therapy in patients with attenuated mucopolysaccharidosis type I.

STUDY DESIGN

Retrospective analyses of case notes, laboratory results, and data from clinical trials were used to evaluate urinary glycosaminoglycans, forced vital capacity (FVC), 6-minute walk test (6MWT), height-for-age Z score, cardiac valve function, corneal clouding, and visual acuity in 35 patients with attenuated mucopolysaccharidosis type I (Hurler-Scheie and Scheie syndromes) for up to 10 years following the initiation of laronidase therapy.

RESULTS

Statistically significant (P < .001) reductions in mean urinary glycosaminoglycan levels relative to baseline were observed 6 months after treatment initiation and were sustained throughout follow-up. Disease remained stable after treatment initiation with no statistically significant changes in mean FVC, 6MWT, or height-for-age Z score. At last assessments, mitral and aortic valve function remained stable in 65% (22/34) of patients; corneal clouding remained stable in 78% (18/23); visual acuity remained stable in 33% (8/24) and improved in 42% (10/24) of patients. Younger patients (<10 years at treatment initiation) maintained disease measures closer to norms for age for FVC, 6MWT, and height and showed fewer deteriorations in mitral and aortic valve disease and corneal clouding compared with patients aged ≥10 years at treatment initiation.

CONCLUSION

Laronidase treatment resulted in disease stabilization in the majority of patients with a mean follow-up of 6.1 years. Data suggest that early treatment may result in better outcomes.

Health-related quality of life in mucopolysaccharidosis: looking beyond biomedical issues

The mucopolysaccharidoses (MPS) comprise a heterogeneous family of rare, genetic lysosomal storage disorders that result in severe morbidity and reduced life expectancy. Emerging treatments for several of these disorders have triggered the search for clinically relevant biomarkers and clinical markers associated with treatment efficacy in populations and individuals. However, biomedical measures do not tell the whole story when characterizing a complex chronic disorder such as MPS. Health-related quality of life (HRQoL) tools that utilize patient reported outcomes to address patient parameters such as symptoms (pain, fatigue, psychological health), functioning (activity and limitations), or quality of life, have been used to supplement traditional biomedical endpoints. Many of these HRQoL tools have demonstrated that quality of life is negatively impacted in patients with MPS. There is both the opportunity and need to formally standardize and validate HRQoL tools for the different MPS disorders.

Therapies for the bone in mucopolysaccharidoses

Patients with mucopolysaccharidoses (MPS) have accumulation of glycosaminoglycans in multiple tissues which may cause coarse facial features, mental retardation, recurrent ear and nose infections, inguinal and umbilical hernias, hepatosplenomegaly, and skeletal deformities. Clinical features related to bone lesions may include marked short stature, cervical stenosis, pectus carinatum, small lungs, joint rigidity (but laxity for MPS IV), kyphoscoliosis, lumbar gibbus, and genu valgum. Patients with MPS are often wheelchair-bound and physical handicaps increase with age as a result of progressive skeletal dysplasia, abnormal joint mobility, and osteoarthritis, leading to 1) stenosis of the upper cervical region, 2) restrictive small lung, 3) hip dysplasia, 4) restriction of joint movement, and 5) surgical complications. Patients often need multiple orthopedic procedures including cervical decompression and fusion, carpal tunnel release, hip reconstruction and replacement, and femoral or tibial osteotomy through their lifetime. Current measures to intervene in bone disease progression are not perfect and palliative, and improved therapies are urgently required. Enzyme replacement therapy (ERT), hematopoietic stem cell transplantation (HSCT), and gene therapy are available or in development for some types of MPS. Delivery of sufficient enzyme to bone, especially avascular cartilage, to prevent or ameliorate the devastating skeletal dysplasias remains an unmet challenge. The use of an anti-inflammatory drug is also under clinical study. Therapies should start at a very early stage prior to irreversible bone lesion, and damage since the severity of skeletal dysplasia is associated with level of activity during daily life. This review illustrates a current overview of therapies and their impact for bone lesions in MPS including ERT, HSCT, gene therapy, and anti-inflammatory drugs.

Diagnosing lysosomal storage disorders: mucopolysaccharidosis type I

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disorder due to deficiency of alpha iduronidase (IDUA). Progressive storage of dermatan and heparan sulfate throughout the body lead to a multiorgan presentation including short stature, dysostosis multiplex, corneal clouding, hearing loss, coarse facies, hepatosplenomegaly, and intellectual disability. Diagnosis of MPS I is based on IDUA enzyme analysis in leukocytes or dried blood spots (DBS) followed by molecular confirmation of the IDUA gene mutations in individuals with low enzyme activity. The advent of mass spectrometry methods for enzyme analysis in DBS has enabled high-throughput screening for MPS I in symptomatic individuals and newborn infants. The following unit provides the detailed analytical protocol for measurement of IDUA activity in DBS using tandem mass spectrometry.

A simple and rapid method based on liquid chromatography-tandem mass spectrometry for the measurement of α-L-iduronidase activity in dried blood spots: an application to mucopolysaccharidosis I (Hurler) screening

Background

We developed an analytical method to measure α-L-iduronidase (IDUA) activity in dried blood spots. This was achieved by using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) with electrospray ionization in the positive ion mode.

Methods

Chromatographic separation was completed using mobile phase involving water-formic acid and acetonitrile-formic acid over 2.8 min of run time on a column with a Kinetex XB-C18 (Phenomenex, USA). The detection of column effluent was performed using a Xevo TQ-S triple quadrupole mass spectrometer (Waters, USA) in the multiple-reaction monitoring mode. This method was verified with blank and control samples at four activity levels: base, low, medium, and high. Control materials were provided from Centers for Disease Control and Prevention (CDC).

Results

Intra- and inter-day precisions were between 2.6% and 16.5% and between 7.9% and 17.0%, respectively. A correlative regression study on the IDUA activity in CDC-control samples performed to assess the validity of the developed method showed a highly significant linear association (r²=0.9976) between the calculated and CDC-reported values and an obvious difference in activity among the four levels. This reliable analytical method was applied to mucopolysaccharidosis I (Hurler) screening of patients under treatment (n=4) and in normal controls (n=129). IDUA activity ranged from 8.98 to 77.12 µmol/hr/L) in normal controls, and patients undergoing medical treatment showed low IDUA activity.

Conclusions

This method had advantages of simplicity, rapid sample preparation, and liquid chromatographic separation, which efficiently inhibited ionization suppression induced by matrix effects in mass spectrometric detection.

p.L18P: a novel IDUA mutation that causes a distinct attenuated phenotype in mucopolysaccharidosis type I patients

Mucopolysaccharidosis type I is a rare autosomal recessive disorder caused by deficiency of α-l-iduronidase (IDUA) which leads to a wide spectrum of clinical severity. Here, we describe the case of four male patients who present the previously undescribed p.L18P mutation. Patient 1 (p.L18P/p.L18P) presents, despite multiple joint contractures, an attenuated phenotype. Patient 2 (p.L18P/p.W402X) was diagnosed at 4 years of age with bone dysplasia, coarse facies, limited mobility, claw hands and underwent bilateral carpal tunnel surgery at 6 years of age. Patients 3 and 4 (both p.L18P/p.L18P) are brothers. Patient 3 was diagnosed at 4 years of age, when presented claw hands, lower limb and shoulder pain, restricted articular movement and bilateral carpal tunnel syndrome. Patient 4 was diagnosed at 17 months of age when presented lower limb pain at night, respiratory allergy and repeated upper airways infections. Bioinformatics analysis indicates that p.L18P mutation reduces the signal peptide to 25 amino acids and alters its secondary structure. In conclusion, we report a new IDUA variant that alters the structure of the signal peptide, which likely impairs transport to lysosomes. Moreover, it leads to a distinct attenuated phenotype with mainly bone and cartilage symptoms, without visceromegalies, heart disease, or cognitive impairment.

Early initiation of enzyme replacement therapy for the mucopolysaccharidoses

The mucopolysaccharidoses (MPS), a group of rare genetic disorders caused by defects in glycosaminoglycan (GAG) catabolism, are progressive, multi-systemic diseases with a high burden of morbidity. Enzyme replacement therapy (ERT) is available for MPS I, II, and VI, and may improve walking ability, endurance, and pulmonary function as evidenced by data from pivotal trials and extension studies. Despite these demonstrable benefits, cardiac valve disease, joint disease, and skeletal disease, all of which cause significant morbidity, do not generally improve with ERT if pathological changes are already established. Airway disease improves, but usually does not normalize. These limitations can be well understood by considering the varied functions of GAG in the body. Disruption of GAG catabolism has far-reaching effects due to the triggering of secondary pathogenic cascades. It appears that many of the consequences of these secondary pathogenic events, while they may improve on treatment, cannot be fully corrected even with long-term exposure to enzyme, thereby supporting the treatment of patients with MPS before the onset of clinical disease. This review examines the data from clinical trials and other studies in human patients to explore the limits of ERT as currently used, then discusses the pathophysiology, fetal tissue studies, animal studies, and sibling reports to explore the question of how early to treat an MPS patient with a firm diagnosis. The review is followed by an expert opinion on the rationale for and the benefits of early treatment.

Osteoimmunology in mucopolysaccharidoses type I, II, VI and VII. Immunological regulation of the osteoarticular system in the course of metabolic inflammation

BACKGROUND

Mucopolysaccharidoses (MPSs) are rare genetic diseases caused by a deficient activity of one of the lysosomal enzymes involved in the glycosaminoglycan (GAG) breakdown pathway. These metabolic blocks lead to the accumulation of GAGs in various organs and tissues, resulting in a multisystemic clinical picture. The pathological GAG accumulation begins a cascade of interrelated responses: metabolic, inflammatory and immunological with systemic effects. Metabolic inflammation, secondary to GAG storage, is a significant cause of osteoarticular symptoms in MPS disorders.

OBJECTIVE AND METHOD

The aim of this review is to present recent progress in the understanding of the role of inflammatory and immune processes in the pathophysiology of osteoarticular symptoms in MPS disorders and potential therapeutic interventions based on published reports in MPS patients and studies in animal models.

RESULTS AND CONCLUSIONS

The immune and skeletal systems have a number of shared regulatory molecules and many relationships between bone disorders and aberrant immune responses in MPS can be explained by osteoimmunology. The treatment options currently available are not sufficiently effective in the prevention, inhibition and treatment of osteoarticular symptoms in MPS disease. A lot can be learnt from interactions between skeletal and immune systems in autoimmune diseases such as rheumatoid arthritis (RA) and similarities between RA and MPS point to the possibility of using the experience with RA in the treatment of MPS in the future. The use of different anti-inflammatory drugs requires further study, but it seems to be an important direction for new therapeutic options for MPS patients.

Characterization of joint disease in mucopolysaccharidosis type I mice

Mucopolysaccharidoses (MPS) are lysosomal storage disorders characterized by mutations in enzymes that degrade glycosaminoglycans (GAGs). Joint disease is present in most forms of MPS, including MPS I. This work aimed to describe the joint disease progression in the murine model of MPS I. Normal (wild-type) and MPS I mice were sacrificed at different time points (from 2 to 12 months). The knee joints were collected, and haematoxylin-eosin staining was used to evaluate the articular architecture. Safranin-O and Sirius Red staining was used to analyse the proteoglycan and collagen content. Additionally, we analysed the expression of the matrix-degrading metalloproteinases (MMPs), MMP-2 and MMP-9, using immunohistochemistry. We observed progressive joint alterations from 6 months, including the presence of synovial inflammatory infiltrate, the destruction and thickening of the cartilage extracellular matrix, as well as proteoglycan and collagen depletion. Furthermore, we observed an increase in the expression of MMP-2 and MMP-9, which could conceivably explain the degenerative changes. Our results suggest that the joint disease in MPS I mice may be caused by a degenerative process due to increase in proteases expression, leading to loss of collagen and proteoglycans. These results may guide the development of ancillary therapies for joint disease in MPS I.

Therapies of mucopolysaccharidosis IVA (Morquio A syndrome)

INTRODUCTION

Morquio A syndrome (mucopolysaccharidosis type IVA, MPS IVA) is one of the lysosomal storage diseases and is caused by the deficiency of N-acetylgalactosamine-6-sulfate sulfatase (GALNS). Deficiency of this enzyme leads to accumulation of glycosaminoglycans (GAGs), keratan sulfate (KS) and chondroitin-6-sulfate (C6S). The majority of KS is produced by chondrocytes, and therefore, the undegraded substrates accumulate mainly in cells and extracelluar matrix (ECM) of cartilage. This has a direct impact on cartilage and bone development, leading to systemic skeletal dysplasia. In patients with Morquio A, cartilage cells are vacuolated, and this results in abnormal chondrogenesis and/or endochondral ossification.

AREAS COVERED

This article describes the advanced therapies of Morquio A, focused on enzyme replacement therapy (ERT) and gene therapy to deliver the drug to avascular bone lesions. ERT and gene therapies for other types of MPS are also discussed, which provide therapeutic efficacy to bone lesions.

EXPERT OPINION

ERT, gene therapy and hematopietic stem therapy are clinically and/or experimentally conducted. However, there is no effective curative therapy for bone lesion to date. One of the limitations for Morquio A therapy is that targeting avascular cartilage tissues remains an unmet challenge. ERT or gene therapy with bone-targeting system will improve the bone pathology and skeletal manifestations more efficiently.

Enzyme replacement therapy started at birth improves outcome in difficult-to-treat organs in mucopolysaccharidosis I mice

Since we previously observed that in patients with mucopolysaccharidosis (MPS) the storage of undegraded glycosaminoglycans (GAG) occurs from birth, in the present study we aimed to compare normal, untreated MPS I mice (knockout for alpha-l-iduronidase-IDUA), and MPS I mice treated with enzyme replacement therapy (ERT, Laronidase, 1.2mg/kg every 2 weeks) started from birth (ERT-neo) or from 2 months of age (ERT-ad). All mice were sacrificed at 6 months. Both treatments were equally effective in normalizing GAG levels in the viscera but had no detectable effect on the joint. Heart function was also improved with both treatments. On the other hand, mice treated from birth presented better outcomes in the difficult-to-treat aortas and heart valves. Surprisingly, both groups had improvements in behavior tests, and normalization of GAG levels in the brain and IDUA injection resulted in detectable levels of enzyme in the brain tissue 1h after administration. ERT-ad mice developed significantly more anti-IDUA-IgG antibodies, and mice that didn't develop antibodies had better performances in behavior tests, indicating that development of antibodies may reduce enzyme bioavailability. Our results suggest that ERT started from birth leads to better outcomes in the aorta and heart valves, as well as a reduction in antibody levels. Some poor vascularized organs, such as the joints, had partial or no benefit and ancillary therapies might be needed for patients. The results presented here support the idea that ERT started from birth leads to better treatment outcomes and should be considered whenever possible, a observation that gains relevance as newborn screening programs are being considered for MPS and other treatable lysosomal storage disorders.

Enzyme replacement therapy in an attenuated case of mucopolysaccharidosis type I (Scheie syndrome): a 6.5-year detailed follow-up

We present the 6.5-year follow-up of a boy with Scheie syndrome whose therapy was initiated at age 2.5 years. Detailed anthropometric features, echocardiography, ophthalmologic and audiologic examinations, psychologic tests, joint range of motion, skeletal radiographs, ultrasound studies of liver and spleen volumes, urinary glycosaminoglycans, and antibodies were documented. After 6.5 years of enzyme replacement therapy, the patient experienced a decline in overall status, and the disease progressed significantly despite treatment. The patient's height at age 9 was equal to that at age 6. The patient developed heart insufficiency and a deterioration of airway flow. The patient's intelligence quotient remained unchanged, i.e., at the average level of 86 on the Terman-Merill Scale. Magnetic resonance imaging revealed cervical spinal canal stenosis and marked spinal cord compression with myelopathy. A worsening of carpal tunnel syndrome was also evident. Ophthalmologic evaluation revealed increased central corneal thickness and intraocular pressure. In audiologic assessment, the patient's results were similar to those after 3 years of treatment. The only benefit involved temporarily improved passive and active shoulder flexion. Overall, the benefit of enzyme replacement therapy with laronidase on Scheie syndrome appeared minimal.

Skeletal response to lentiviral mediated gene therapy in a mouse model of MPS VII

Mucopolysaccharidosis VII (MPS VII) is an autosomal recessive, lysosomal storage disorder caused by β-glucuronidase (GUSB) deficiency, resulting in the accumulation of glycosaminoglycans (GAGs), in a variety of cell types. Severe, progressive skeletal pathology, termed dysostosis multiplex, is a prominent clinical feature of MPS VII. We have evaluated a gene therapy protocol for its efficacy in preventing the development and progression of bone pathology in MPS VII mice treated with a lentiviral vector at birth or at 7 weeks. Two weeks after injections, high levels of vector expression were observed in liver, spleen and bone marrow and to a lesser extent in kidney, lung and heart. Widespread clearance of GAG storage was observed in somatic tissues of both groups and some clearance of neuronal storage was observed in mice treated from birth. Micro-CT analysis demonstrated a significant decrease in vertebral and femoral bone mineral volume, trabecular number, bone surface density and cortical bone thickness in both treatment groups. Lumbar and femoral bone lengths were significantly decreased in untreated MPS VII mice, while growth plate heights were increased and these parameters did not change upon treatment. Small improvements in performance in the open field and rotarod behaviour tests were noted. Overall, systemic lentiviral-mediated gene therapy results in a measurable improvement in parameters of bone mass and architecture as well as biochemical and enzymatic correction. Conversely, growth plate chondrocytes were not responsive to treatment, as evidenced by the lack of improvement in vertebral and femoral bone length and growth plate height.

Restricted joint range of motion in patients with MPS II: correlation with height, age and functional status

AIM

The aims of the study were to assess shoulder range of motion (ROM) in patients with mucopolysaccharidosis type II (MPS II) and to correlate joint mobility with patients' height, age and functional status.

METHODS

Passive ROM and Z-score of height were followed in 29 patients with MPS II (mean age 11.5 years, range 2-29 years) between the years 2005 and 2010. Passive ROM was measured by a goniometer, and height, by a stadiometer. Functional status was assessed by an age-appropriate health assessment questionnaire (HAQ).

RESULTS

(i) A strong correlation was observed between patients' age and Z-score of patients' height (R = 0.78, p < 0.001). (ii) A medium correlation was observed between Z-score of patients' height and passive shoulder flexion and abduction (R = 0.697, p < 0.001 and R = 0.63, p < 0.001, respectively). The progression of restriction was slower in attenuated patients. (iii) Restrictions in shoulder flexion and abduction were already observed before the second year of life. (iv) ROM limitations intensified and became more severe with age. (v) Activities of daily living depended on cognitive impairment of patients with MPS II.

CONCLUSION

Range of motion limitations in patients with MPS II correlate with patients' height, increase with patients' age and are more pronounced in a severe form of MPS II.

Musculoskeletal manifestations of mucopolysaccharidosis type VI and effects of enzyme replacement therapy

The aim of this study was to describe the musculoskeletal manifestations of mucopolysaccharidosis VI and to assess the effectiveness of enzyme replacement therapy (ERT) with recombinant human arylsulfatase B on the bone and joint involvement in a patient with a severe phenotype of the disease. Before the initiation of ERT, the patient presented with significant range of motion (ROM) limitations at multiple joints. Flexion contractures were noticeable in all joints. After 48 weeks of ERT, improvement in active and passive shoulder flexion, as well as passive elbow and wrist flexion, was noticed. ROM improvements were reflected in patient’s enhanced self-care.

Laronidase for the treatment of mucopolysaccharidosis type I

A decade has passed since the initial report that parenteral use of recombinant human α-L-iduronidase results in amelioration of symptoms in patients with mucopolysaccharidosis type I (MPS I). As a result, MPS I became the first mucopolysaccharide storage disorder to benefit from enzyme replacement therapy (ERT); subsequent ERTs have been approved for MPS II and VI. The ability of lysosomal storage disorders to respond to ERT is unique among genetic disorders and relates to the capability of cells to take up recombinant lysosomal enzymes through cell surface receptors and deliver them to the lysosome, a processed coined as 'cross-correction'. Although the concept of ERT is straightforward, the evaluation of its efficacy in disorders like MPS I is challenging. This article reviews the use of laronidase in the management of MPS I, with a particular emphasis on the unique issues inherent in the evaluation of therapeutics for such a rare, complex and progressive disorder.

Glycosaminoglycan storage disorders: a review

Impaired degradation of glycosaminoglycans (GAGs) with consequent intralysosomal accumulation of undegraded products causes a group of lysosomal storage disorders known as mucopolysaccharidoses (MPSs). Characteristically, MPSs are recognized by increased excretion in urine of partially degraded GAGs which ultimately result in progressive cell, tissue, and organ dysfunction. There are eleven different enzymes involved in the stepwise degradation of GAGs. Deficiencies in each of those enzymes result in seven different MPSs, all sharing a series of clinical features, though in variable degrees. Usually MPS are characterized by a chronic and progressive course, with different degrees of severity. Typical symptoms include organomegaly, dysostosis multiplex, and coarse facies. Central nervous system, hearing, vision, and cardiovascular function may also be affected. Here, we provide an overview of the molecular basis, enzymatic defects, clinical manifestations, and diagnosis of each MPS, focusing also on the available animal models and describing potential perspectives of therapy for each one.

Cell microencapsulation: a potential tool for the treatment of neuronopathic lysosomal storage diseases

Lysosomal storage disorders (LSD) are monogenic diseases caused by the deficiency of different lysosomal enzymes that degrade complex substrates such as glycosaminoglycans, sphingolipids, and others. As a consequence there is multisystemic storage of these substrates. Most treatments for these disorders are based in the fact that most of these enzymes are soluble and can be internalized by adjacent cells via mannose-6-phosphate receptor. In that sense, these disorders are good candidates to be treated by somatic gene therapy based on cell microencapsulation. Here, we review the existing data about this approach focused on the LSD treatments, the advantages and limitations faced by these studies.

Enzyme replacement therapy and/or hematopoietic stem cell transplantation at diagnosis in patients with mucopolysaccharidosis type I: results of a European consensus procedure

Background

Mucopolysaccharidosis type I (MPS I) is a lysosomal storage disorder that results in the accumulation of glycosaminoglycans causing progressive multi-organ dysfunction. Its clinical spectrum is very broad and varies from the severe Hurler phenotype (MPS I-H) which is characterized by early and progressive central nervous system (CNS) involvement to the attenuated Scheie phenotype (MPS I-S) with no CNS involvement. Indication, optimal timing, safety and efficacy of the two available treatment options for MPS I, enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT), are subject to continuing debate. A European consensus procedure was organized to reach consensus about the use of these two treatment strategies.

Methods

A panel of specialists, including 8 specialists for metabolic disorders and 7 bone marrow transplant physicians, all with acknowledged expertise in MPS I, participated in a modified Delphi process to develop consensus-based statements on MPS I treatment. Fifteen MPS I case histories were used to initiate the discussion and to anchor decisions around either treatment mode. Before and at the meeting all experts gave their opinion on the cases (YES/NO transplantation) and reasons for their decisions were collected. A set of draft statements on MPS I treatment options composed by a planning committee were discussed and revised during the meeting until full consensus.

Results

Full consensus was reached on several important issues, including the following: 1) The preferred treatment for patients with MPS I-H diagnosed before age 2.5 yrs is HSCT; 2) In individual patients with an intermediate phenotype HSCT may be considered if there is a suitable donor. However, there are no data on efficacy of HSCT in patients with this phenotype; 3) All MPS I patients including those who have not been transplanted or whose graft has failed may benefit significantly from ERT; 4) ERT should be started at diagnosis and may be of value in patients awaiting HSCT.

Conclusions

This multidisciplinary consensus procedure yielded consensus on the main issues related to therapeutic choices and research for MPS I. This is an important step towards an international, collaborative approach, the only way to obtain useful evidence in rare diseases.

Improvement in the range of joint motion in seven patients with mucopolysaccharidosis type II during experimental gene expression-targeted isoflavone therapy (GET IT)

Mucopolysaccharidosis type II (MPS II, Hunter disease) is an X chromosome-linked inherited metabolic disease caused by mutations resulting in deficiency of activity of iduronate-2-sulfatase (IDS) and accumulation of undegraded glycosaminoglycans (GAGs), heparan sulfate, and dermatan sulfate. Previous experiments with cell cultures and studies on animal model of MPS II suggested that gene expression-targeted isoflavone therapy (GET IT), based on genistein-mediated reduction of efficiency of GAG synthesis, might be a suitable therapy for this disease. In this report, we demonstrate efficacy of GET IT in connective tissue elasticity, particularly in improving the range of joint motion in seven patients with MPS II after 26 weeks of treatment with an isoflavone extract at the dose corresponding to 5 mg/kg/day of genistein.