Clinical manifestations and treatment of mucopolysaccharidosis type I patients in Latin America as compared with the rest of the world

BACKGROUND

Mucopolysaccharidosis I (MPS I) comprises a spectrum of clinical manifestations and is divided into three phenotypes reflecting clinical severity: Hurler, Hurler-Scheie, and Scheie syndromes. There may be important variations in clinical manifestations of this genetic disease in patients residing in different regions of the world.

METHODS

Using data from the MPS I Registry (as of September 2009), we evaluated patients from Latin America (n = 118) compared with patients from the rest of the world [ROW (n = 727)].

RESULTS

Phenotype distribution differed among patients in Latin America compared to ROW (Hurler 31 vs. 62%, Hurler-Scheie 36 vs. 21%, Scheie 10 vs. 11%, and unknown 22 vs. 6%). The frequency of certain symptoms, such as cardiac valve abnormalities, sleep impairment, and joint contractures, also differed between Latin America and ROW for some phenotypes. Median age at MPS I diagnosis was earlier in the ROW than Latin America for all phenotypes, and age at first treatment for Hurler and Hurler-Scheie patients was also earlier in the ROW. Hurler patients in Latin America showed a gap of 3.1 years between median ages of diagnosis and first treatment compared to only 0.5 years in the ROW. Treatment allocation in Latin America compared to ROW was as follows: enzyme replacement therapy (ERT) only, 80 vs. 45%; hematopoietic stem cell transplantation (HSCT) only, 0.9 vs. 27%; both ERT and HSCT, 0 vs. 16%; and neither treatment, 19 vs. 13%.

CONCLUSION

These data highlight important differences in MPS I patients between Latin America and ROW in terms of phenotypic distribution, clinical manifestations, and treatment practices.

Laronidase replacement therapy improves myocardial function in mucopolysaccharidosis I

We assessed whether laronidase (recombinant human α-L-iduronidase) replacement therapy could improve left ventricular (LV) myocardial function in a 49-year-old woman with mucopolysaccharidosis I (MPS I) and valvular heart disease. After 6 months of laronidase treatment, the concentration of urinary uron acid decreased by 78.8%. Hepatosplenomegaly improved and LV weight decreased by 19.6%. LV ejection fraction assessed by two-dimensional echocardiogram did not change after laronidase treatment. However, in two-dimensional ultrasound speckle tracking imaging method, LV myocardial longitudinal strain (shortening ratio) increased from -13.2 to -17.4%. LV myocardial radial strain (thickening ratio) increased from 26.6 to 83.4%. LV myocardial torsion increased from +6 to +18°. These indexes of myocardial function were normalized after laronidase treatment. Thus, our findings were a first report that laronidase treatment had a beneficial effect on LV myocardial function in an adult patient with MPS I.

Combined Hurler and Sanfilippo syndrome in a sibling pair

The mucopolysaccharidoses (MPS) are lysosomal storage disorders caused by defects in the enzymes involved in the degradation of glycosaminoglycans. Hurler syndrome (MPS I) and Sanfilippo syndrome (MPS III) are among the more common diseases in the group, each occurring with an incidence of approximately 1 in 100,000. We present a case of siblings, born of a consanguineous union, affected with both MPS I and MPS IIIa. The diagnoses were confirmed with fibroblast enzyme assays and sequence analysis of the genes, which identified homozygous mutations in IDUA and SGSH. We discuss their clinical features and course and examine the psychosocial aspects of their case, specifically, the decision-making process that the medical team and family faced regarding treatment with enzyme replacement therapy.

Ethical issues related to the access to orphan drugs in Brazil: the case of mucopolysaccharidosis type I

BACKGROUND/AIMS

Mucopolysaccharidosis type I (MPS I) is a rare lysosomal storage disorder treated with bone marrow transplantation or enzyme replacement therapy with laronidase, a high-cost orphan drug. Laronidase was approved by the US Food and Drug Administration and the European Medicines Agency in 2003 and by the Brazilian National Health Surveillance Agency in 2005. Many Brazilian MPS I patients have been receiving laronidase despite the absence of a governmental policy regulating access to the drug. Epidemiological and treatment data concerning MPS I are scarce. This study aims to present a demographic profile of Brazilian patients with MPS I, describe the routes of access to laronidase in Brazil, and discuss associated ethical issues relating to public funding of orphan drugs.

METHODS

In this cross-sectional observational study, data were collected nationwide between January and September 2008 from physicians, public institutions and non-governmental organisations involved with diagnosis and treatment of MPS I, using two data collection instruments specifically designed for this purpose.

RESULTS

The minimum prevalence of MPS I in Brazil was estimated at 1/2,700,000. Most patients (69.8%) were younger than 15 years; 60 (88.2%) received laronidase. The most common route of access to the drug was through lawsuits (86.6%).

CONCLUSIONS

In Brazil, MPS I is predominantly a paediatric illness. Even though the cost of laronidase treatment is not officially covered by the Brazilian government, most MPS I patients receive the drug, usually through litigation. This gives rise to major ethical conflicts concerning drug access in a low-resource context. The Brazilian health policy framework lacks evidence-based clinical protocols for the distribution of orphan drugs.

Sudden vision loss in a mucopolysaccharidosis I patient receiving enzyme replacement therapy

A 25-year-old female was referred for short stature and joint deformities. Except for previous corneal transplantation, her medical history was unremarkable. Initial physical examination revealed the presence of a coarse facies, short neck, kyphosis, restricted joint movements and deformities, and cardiac murmur besides a normal intellect. Urine glycosaminoglycan levels were high, and blood enzyme assay indicated significantly low alpha-L-iduronidase levels. Mucopolysaccharidosis I (MPS I) was diagnosed and prompted the onset of enzyme replacement therapy (ERT), which significantly improved articular complaints, while cardiac pathology remained stable. At the eighteenth month of ERT, sudden vision loss developed. She spontaneously recovered her vision in a month. MPS I is a progressive disease, in which tissue accummulation of heparan and dermatan sulphate result from defective activity or lack of alpha-L-iduronidase. ERT in MPS I usually presents favourable outcomes or at least stabilization of symptoms. This present case qualifies as the first report ofa MPS I patient developing sudden vision loss under ERT. We suggest that further research studies are warranted for defining the efficiency and possible limitations of ERT.

Early versus late treatment of spinal cord compression with long-term intrathecal enzyme replacement therapy in canine mucopolysaccharidosis type I

Enzyme replacement therapy (ERT) with intravenous recombinant human alpha-l-iduronidase (IV rhIDU) is a treatment for patients with mucopolysaccharidosis I (MPS I). Spinal cord compression develops in MPS I patients due in part to dural and leptomeningeal thickening from accumulated glycosaminoglycans (GAG). We tested long-term and every 3-month intrathecal (IT) and weekly IV rhIDU in MPS I dogs age 12-15months (Adult) and MPS I pups age 2-23days (Early) to determine whether spinal cord compression could be reversed, stabilized, or prevented. Five treatment groups of MPS I dogs were evaluated (n=4 per group): IT+IV Adult, IV Adult, IT + IV Early, 0.58mg/kg IV Early and 1.57mg/kg IV Early. IT + IV rhIDU (Adult and Early) led to very high iduronidase levels in cervical, thoracic, and lumber spinal meninges (3600-29,000% of normal), while IV rhIDU alone (Adult and Early) led to levels that were 8.2-176% of normal. GAG storage was significantly reduced from untreated levels in spinal meninges of IT + IV Early (p<.001), IT+IV Adult (p=.001), 0.58mg/kg IV Early (p=.002) and 1.57mg/kg IV Early (p<.001) treatment groups. Treatment of dogs shortly after birth with IT+IV rhIDU (IT + IV Early) led to normal to near-normal GAG levels in the meninges and histologic absence of storage vacuoles. Lysosomal storage was reduced in spinal anterior horn cells in 1.57mg/kg IV Early and IT + IV Early animals. All dogs in IT + IV Adult and IV Adult groups had compression of their spinal cord at 12-15months of age determined by magnetic resonance imaging and was due to protrusion of spinal disks into the canal. Cord compression developed in 3 of 4 dogs in the 0.58mg/kg IV Early group; 2 of 3 dogs in the IT + IV Early group; and 0 of 4 dogs in the 1.57mg/kg IV Early group by 12-18months of age. IT + IV rhIDU was more effective than IV rhIDU alone for treatment of meningeal storage, and it prevented meningeal GAG accumulation when begun early. High-dose IV rhIDU from birth (1.57mg/kg weekly) appeared to prevent cord compression due to protrusion of spinal disks.

Cognitive and neuroradiological improvement in three patients with attenuated MPS I treated by laronidase

Stem cell transplantation is not appropriate first-line treatment for attenuated phenotypes of mucopolysaccharidosis type I (MPS I). In three patients with attenuated MPSA I treated by laronidase, Patients 2 and 3 displayed significant cognitive improvement within 2years; Patients 1 and 3 displayed improvement on MRI scans of the brain.

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

The aims of the study were to assess the effectiveness of enzyme replacement therapy (ERT) with laronidase on the range of motion (ROM) of upper extremities and influence on activities of daily living (ADLs) of patients with mucopolysaccharidosis type I (MPS I). The ROM of 17 patients with MPS I was followed from the first year of life until the introduction of ERT and after 52-208 weeks of treatment. In all patients (group 1, n = 10), passive ROM was assessed. In patients with Hurler/Scheie or Scheie phenotype (group 2, n = 7) both passive and active ROM, as well as daily life activities, were evaluated. Passive and active ROM was measured by a goniometer, while a health assessment questionnaire was used to assess activities of daily living. The data since the first months of life until the beginning of treatment were obtained by retrospective review of patients' charts. Restriction in ROM of the upper extremities of patients with MPS I was observed from the first year of life. These limitations intensified and became more severe with the patients' age, making patients' self-care more difficult or even impossible. Introduction of ERT led to slower progression of symptoms, especially in the passive range of motion in all patients. Additionally, patients with normal mental development, or only slightly delayed (group 2), who underwent active physical rehabilitation (including mobilisation of nerve system, passive techniques for joint mobility, active gymnastics for muscle power, as well as massage and the training of families for therapy at home) showed improvement in active movement followed by enhanced self-care.

Anthropometric data of 14 patients with mucopolysaccharidosis I: retrospective analysis and efficacy of recombinant human alpha-L-iduronidase (laronidase)

OBJECTIVES

Our goal was to evaluate growth patterns in terms of body height, weight, head and chest circumference in patients with mucopolysaccharidosis type I (MPS I) without treatment and after enzyme replacement therapy (ERT) with alpha-l-iduronidase (laronidase).

PATIENTS AND METHODS

Anthropometric features of 14 patients with MPS I were followed from birth until the introduction of ERT (group 1-1st year of life, group 2 3rd year of life), after 52-260 weeks of ERT and periodically during treatment. The data since birth until beginning of treatment was obtained by retrospective review of patients' charts. Patients received intravenous laronidase at 100 U/kg (0.58 mg/kg) weekly for 52-260 weeks.

RESULTS

Patients from group 1 (n=7) and group 2 (n=7) had similar characteristics at the time of birth but showed significant difference when compared with healthy population. Growth patterns were associated significantly with the MPS I at birth. After 96-260 weeks of ERT, patients receiving laronidase (group 1) compared with group 2 did not show statistically significant improvement.

CONCLUSIONS

Anthropometric features of patients with MPS I significantly differ from the healthy population. Children with MPS I grew considerably slower, and differences between healthy and affected children increased with age. In studied patients with MPS I, laronidase did not appear to alter the growth patterns.

[The development of cognitive functions in children with Hurler phenotype mucopolysaccharidosis type I on enzyme replacement therapy with laronidase]

INTRODUCTION

Mucopolysaccharidosis type I (MPS I) Hurler syndrome, Hurler/Scheie i Scheie is a metabolic disorder manifesting in early childhood, and characterized by the accumulation of mucopolysaccharides (glycosaminoglycans - GAG) in the cells, blood, and connective tissues. Eventually, this causes damage to cells and organs, leading to progressive impairment of the child's physical abilities, organ function, and mental development. Treatment with enzyme replacement therapy (ERT) alleviates many symptoms of the disease, however, there is no evidence indicating that ERT is effective in the prevention of nervous system degradation.

THE AIM OF THE STUDY

The current study seeks to assess the development of cognitive functions in ERT-treated children with Hurler syndrome.

MATERIAL AND METHODS

The analysis covers 8 children suffering from MPS type I (7 boys and 1 girl), aged from 9.8 months to 12.7 months at the beginning of the study. All were on enzymatic treatment for the first year of life. The level of intellectual development was measured using the Psyche Cattell Infant's Intelligence Scale.

RESULTS

Children with MPS type I achieved significantly lower IQ scores compared to the reference group of healthy children. Qualitative analyses revealed that the acquisition of skills and new cognitive functions is very slow in children with MPS type I.

CONCLUSIONS

1. Among children with MPS type I, there was a measurable decrease in IQ associated with advancing age. 2. In spite of lower IQ, the acquisition of new abilities does occur, but the pace of that development is slower than that expected for the child's age. 3. The study reveals the need for functional diagnosis of development, in order to assess the progress made by the child.

Scheie syndrome: enzyme replacement therapy does not prevent progression of cervical myelopathy due to spinal cord compression

Hurler-Scheie syndrome is caused by alpha-l-iduronidase deficiency. Enzyme replacement therapy (ERT) can improve physical capacity and reduces organomegaly. However, the effect on bradytrophic connective tissue is limited. As intravenously administered enzyme cannot cross the blood-brain barrier, the therapy of choice for the more severe Hurler syndrome is haematopoietic stem cell transplantation (HCT). In the more attenuated Scheie syndrome, neurological impairment is less severe; therefore, ERT may be appropriate to treat these patients. Information on long-term outcome in Scheie patients undergoing ERT is scarce. We report a 38-year-old female Scheie patient who has been on ERT for 8 years. While non-neurological symptoms improved, she developed paresthesias in her hands and feet and progressive pain in her legs. Somatosensory evoked potentials were abnormal, suggesting dysfunction of the dorsal funiculus and lemniscus medialis. After 6 years of ERT, a spinal MRI showed dural thickening at the upper cervical spine. These soft-tissue deposits are presumably due to the accumulation of mucopolysaccharides. Intramedullary hyperintensities at the level of C1/2 revealed cervical myelopathy. An MRI before the start of ERT had shown milder spinal lesions. Cystic lesions in the white matter of the centrum semiovale due to dilated Virchow-Robin spaces were essentially unchanged compared with the MRI scan before ERT. Decompression of the spinal cord resulted in clinical improvement. In an adult patient with Scheie syndrome, ERT failed to prevent progression of cervical myelopathy. Clinical significance of cerebral changes is unclear. Whether early HCT or intrathecal ERT could have prevented these lesions remains speculative.

Postmortem studies on a patient with mucopolysaccharidosis type I: histopathological findings after one year of enzyme replacement therapy

Deficiency of lysosomal α-L-iduronidase results in systemic accumulation of glycosaminoglycans (GAGs). Cardiac lesions due to accumulation of GAGs include hypertrophic cardiomyopathy, valvular insufficiency/stenosis, and coronary artery stenosis due to intimal proliferation. Cardiac dysfunction is one of the most common causes of death in patients with mucopolysaccharidosis type I (MPS I). Enzyme replacement therapy (ERT) with laronidase has shown clear effects in reduction of hepatomegaly and it has been unclear whether ERT could improve or prevent the cardiac lesions. Postmortem findings in a 3 1/2-year-old boy diagnosed with MPS I at age 2 years are described. He received ERT with laronidase at 100 U/kg/week for one year. He suddenly developed cardiorespiratory failure and died the next day after C2-3 spinal surgery for instability. Postmortem examination showed hypertrophic cardiomyopathy, severe aortic valve and mitral valve thickening with shortened chordae, and endocardial fibroelastosis. Histology of the cardiac tissue revealed increased perivascular and interstitial connective tissue in the myocardium and intimal thickening causing stenosis in the cardiac vessels. Electron-microscopic (EM) studies of the thickened endocardium revealed numerous histiocytes with enlarged lysosomes. EM examination of the liver and the cardiac muscle revealed no accumulation of GAGs. ERT with laronidase showed clear effects in removing GAGs from the liver and the cardiac muscle. However, it did not show a clear effect on the thickened endocardium, myocardial perivascular and interstitial connective tissue or intimal thickening in the epicardial vessels.

Enzyme replacement therapy in 12 patients with MPS I-H/S with homozygous p.Leu490Pro mutation

We describe a cohort of 14 Hurler-Scheie patients homozygous for the p.Leu490Pro missense mutation in the alpha-L-iduronidase gene. Now based in the UK, they are all of Pakistani/Kashmiri descent; 64% were female; 11/14 (79%) had a sibling or cousin with MPS I and the parents are consanguineous in all cases. The median age at diagnosis was 1.8 years (range from antenatal diagnosis to 16.5 years). Twelve were on ERT with recombinant human alpha-L-iduronidase (IDUA; Laronidase, Genzyme) for a median duration of 22.5 months (range 2-71 months) and median age at commencement of ERT was 8.6 years (range 0.4-23.1 years). There was clear improvement in the size of liver and spleen as well as reduction in urine glycosaminoglycans (GAGs). The mean (range) urine GAG levels in mg/mmol creatinine were 63.4 (28.9-105.6), 28.3 (10.9-41.4), 22.8 (12.1-43.1), 15.7 (9.2-24.8) and 16.3 (10.1-21.0) at commencement, 3 months post ERT, 6 months post ERT, 12 months post ERT and 24 months post ERT, respectively. Effects on growth were not clear as there does not seem to be an obvious trend of increase or decrease in height after commencement of ERT and this seems to be the case regardless of the age at which ERT was started.

Successful treatment of severe heart failure in an infant with Hurler syndrome

Hurler syndrome (MPS IH) is the most severe form of mucopolysaccharidosis type I. It is caused by deficiency or absence of the enzyme alpha-L-iduronidase. Cardiac involvement includes cardiomyopathy and valve and coronary pathology. Cardiomyopathy causing symptoms in an infant with MPS IH carries a very poor prognosis. We describe a previously healthy 10-week-old boy who was admitted to hospital critically ill with severe heart failure. Echocardiography on admission showed severe dilatation of the left ventricle and moderate insufficiency of the left-sided cardiac valves. Accumulation of heparan sulfate and dermatan sulfate substrates in the urine and leukocyte analysis confirmed the diagnosis of MPS IH. Enzyme replacement therapy (ERT) with intravenous laronidase at a standard dosage of 100 U/kg weekly was started soon after. This improved the child's general clinical wellbeing dramatically. His cardiac function improved steadily over a period of months. Stem cell transplantation from cord blood is not available in Norway and he underwent successful transplantation from an unrelated bone marrow donor at the age of 11 months. ERT was stopped four months later. At the age of 26 months his heart function is close to normal and he is currently on no medication. This report highlights three important clinical issues: (1) MPS IH must be considered in infants with cardiomyopathy; (2) early ERT may have a significant impact on short-term outcome in children less than 18 months old with severe cardiomyopathy; (3) our report confirms that patients in poor condition benefit from ERT before stem cell transplantation.

Pre-stem cell transplantation enzyme replacement therapy in Hurler syndrome does not lead to significant antibody formation or delayed recovery of the endogenous enzyme post-transplant: a case report

Combined enzyme replacement therapy (ERT) and stem cell transplant (SCT) were done for a two year old boy with severe Hurler syndrome(HS) with the aim to decrease transplant related complications. He tolerated both the procedures well without any major complications. Urine glycosaminoglycans (GAGs) decreased post-transplant and child has improved clinically and neurologically. Insignificant titers of the anti-iduronidase antibodies which developed post-transplant did not affect the transplant outcome or the endogenous recovery of the alpha-L-iduronidase enzyme.

Enzyme replacement therapy in two patients with an advanced severe (Hurler) phenotype of mucopolysaccharidosis I

Although offered, two of our Hurler patients (OMIM 607014) had not undergone bone marrow transplantation at an early stage of their disease. Rapid disease progression had resulted in a range of signs and symptoms representative of advanced neurodegeneration and debilitating somatic Hurler disease. As general palliative care had only little impact on the burden of disease, laronidase (Aldurazyme) treatment was introduced in an attempt to alleviate somatic symptoms and to improve the quality of their lives. Therapeutic benefits from enzyme replacement therapy included improvements in general physical condition and mood, as well as normalisation of the sleep patterns, disappearance of sleep apnoea syndrome and reduction of hepatosplenomegaly. Improvements in the joint mobility were mainly limited to the wrists and hips. In addition, improvements in cardiac function, stool habits, visual acuity, corneal clouding and hearing were observed in one or both patients. Irreversible skeletal changes did not deteriorate. The neurological outcome of these patients is likely not influenced as laronidase is believed not to pass the blood-brain barrier. Therefore, the decision to initiate this therapy in transplant-naïve Hurler patients with an advanced stage of the disease should be taken after careful consideration.

CONCLUSION

We are of the opinion that the option of enzyme therapy should not be excluded in severely affected Hurler patients who cannot undergo bone marrow transplantation. Stabilization or amelioration of somatic disease and improvement of the quality of their lives should be embraced as therapeutic goals.

Intrathecal enzyme replacement therapy: successful treatment of brain disease via the cerebrospinal fluid

Treatment of brain disease with recombinant proteins is difficult due to the blood-brain barrier. As an alternative to direct injections into the brain, we studied whether application of high concentrations of therapeutic enzymes via intrathecal (IT) injections could successfully drive uptake across the ependyma to treat brain disease. We studied IT enzyme replacement therapy with recombinant human iduronidase (rhIDU) in canine mucopolysaccharidosis I (MPS I, Hurler syndrome), a lysosomal storage disorder with brain and meningeal involvement. Monthly or quarterly IT treatment regimens with rhIDU achieved supranormal iduronidase enzyme levels in the brain, spinal cord, and spinal meninges. All regimens normalized total brain glycosaminoglycan (GAG) storage and reduced spinal meningeal GAG storage by 58-70%. The improvement in GAG storage levels persisted three months after the final IT dose. The successful use of enzyme therapy via the CSF represents a potentially useful approach for lysosomal storage disorders.

[Overview of enzyme replacement therapy in mucopolysaccharidosis]

Mucopolysaccharidosis are rare, multisystemic and progressive diseases with an extremely various clinical spectrum. For the type I, II and VI mucopolysaccharidosis, enzyme replacement therapy is available. In these three diseases, enzyme replacement therapy induces a reduction in urinary glycosaminoglycanes excretion and on improvement in functional tests, 6 minutes walk test, pulmonary function test and range of motion.

A follow-up study of MPS I patients treated with laronidase enzyme replacement therapy for 6 years

Recombinant human alpha-L-iduronidase (Aldurazyme, laronidase) was approved as an enzyme replacement therapy for patients with the lysosomal storage disorder, mucopolysaccharidosis I (MPS I). In order to assess the long-term safety and efficacy of laronidase therapy, 5 of 10 patients in the original laronidase Phase 1/2 clinical trial were re-evaluated after 6 years of treatment. Lysosomal storage was further improved at 6 years (urinary glycosaminoglycans (GAG) excretion decreased 76%; mean liver size at 1.84% of body weight). Shoulder maximum range of motion was maintained or further increased and reached a mean 33.2 (R) and 25.0 (L) degrees gained in flexion and 34.0 (R) and 27.3 (L) degrees gained in extension. Sleep apnea was decreased in four of five patients and the airway size index improved. Cardiac disease evaluations showed no progression to heart failure or cor pulmonale but pre-existing significant valve disease did progress in some patients. Substantial growth was observed for the pre-pubertal patients, with a gain of 33 cm (27%) in height and a gain of 31 kg in weight (105%). In general, the evaluated patients reported an improved ability to perform normal activities of daily living. Overall these data represent the first evidence that laronidase can stabilize or reverse many aspects of MPS I disease during long-term therapy and that early treatment prior to the development of substantial cardiac and skeletal disease may lead to better outcomes.

Outcome after three years of laronidase enzyme replacement therapy in a patient with Hurler syndrome

Enzyme replacement therapy (ERT) with laronidase, recombinant alpha-L-iduronidase, for mucopolysaccharidosis type I (MPS I) has been clinically available since April 2003. Pre-approval studies were performed on patients with the more attenuated forms of MPS I, Hurler-Scheie and Scheie syndromes. The clinical efficacy of laronidase on the severe form of MPS I, Hurler syndrome, is not well known. We present a patient with Hurler syndrome who has been treated with laronidase for 3 years. Clinically, the patient demonstrated improvement in urinary glycosaminoglycan (GAG) levels and hepatomegaly, but continued to experience decline in respiratory status, musculoskeletal and spinal involvement, and developmental skills. Overall, the benefit of ERT with laronidase in advanced Hurler syndrome appeared to be minimal in this patient.

A systematic review of the clinical effectiveness and cost-effectiveness of enzyme replacement therapies for Fabry's disease and mucopolysaccharidosis type 1

OBJECTIVES

To determine the clinical effectiveness and cost-effectiveness of the administration of intravenous enzyme replacement therapy (ERT) to symptomatic patients for the prevention of long-term damage and symptoms in Fabry's disease and in mucopolysaccharidosis type 1 (MPS1).

DATA SOURCES

Electronic databases from inception up to mid-2004. Contact with clinical experts.

REVIEW METHODS

Relevant studies were identified and assessed using recommended quality criteria.

RESULTS

The results suggested beneficial effects of ERT for Fabry's disease on measures of pain, cardiovascular function and some end-points reflecting neurosensory function. Renal function appeared to be stabilised by ERT. At present there are no utility-related health-related quality of life data on which to assess the relative health gain of ERT in MPS1. In order to be able to demonstrate the full extent of health gain from treatment, it was necessary to review the natural history of untreated patients in each disease in order to try to estimate the health loss prevented. The published information for Fabry's disease tallied with descriptions of a multi-system, life-threatening disorder particularly involving kidney, heart and brain with individual patients exhibiting many manifestations. The fragmentary information reviewed in 16 studies relevant to the natural history of MPS1 did not generate a coherent picture of disease progression and could provide little added value to published narrative reviews. For Fabry's disease, the mean cost per patient (50 kg) treated is around pounds sterling 85,000 per annum in England and Wales. The cost per patient varies considerably by dose. No published evidence reporting an economic evaluation of ERT for Fabry's disease was identified by this review. A dynamic decision model was constructed based on a birth cohort of male patients who are followed up until death. Owing to lack of information reported in the literature, many assumptions had to be applied. The key assumptions were that ERT returns patients to full health and a normal life expectancy. As far as possible, all assumptions favoured rather than detracted from the value of ERT. ERT was assumed to restore patients to full health in the base case. The estimated incremental cost-effectiveness ratio (ICER) in the base case was pounds sterling 252,000 per QALY (agalsidase beta). Univariate sensitivity analysis around the key assumptions produced ICERs ranging from pounds sterling 602,000 to pounds sterling 241,000. The base case unit cost of ERT was taken as pounds sterling 65.1/mg based on the cost of agalsidase beta. The unit cost would have had to be reduced to pounds sterling 9 to obtain an ICER of pounds sterling 30,000 per QALY. For MPS1, the mean cost per child patient (20 kg) treated is approximately pounds sterling 95,000 and an adult (70 kg) around pounds sterling 335,000 per annum in England and Wales. The cost per patient varies considerably by dose. There is no published evidence reporting an economic evaluation of ERT for MPS1 and no study was identified that reported the quality of life of MPS1 patients within a utility format. Furthermore, no or minimal information of the severity and rate of change of clinical manifestations of disease or the impact of ERT on these factors was identified. Information on the effect of ERT on mortality is also lacking owing to the relatively short time that the treatment has been available. Given this lack of data, it was not possible to develop a cost-effectiveness model of ERT treatment for MPS1 as the model would consist almost completely of assumptions based on no published evidence, leading to an incremental cost per QALY result that would be meaningless.

CONCLUSIONS

Although ERT for treating the 'average' patient with Fabry's disease exceeds the normal upper threshold for cost-effectiveness seen in NHS policy decisions by over sixfold, and the value for MPS1 is likely to be of a similar order of magnitude, clinicians and the manufacturers argue that, as the disease is classified as an orphan disease under European Union legislation, it has special status, and the NHS has no option but to provide ERT. More information is required before the generalisability of the findings can be determined. Although data from the UK have been used wherever possible, this was very thin indeed. Nonetheless, even large errors in assumptions made will not reduce the ICER to anywhere near the upper level of treatments usually considered cost-effective. In order to overcome limited evidence on the natural history of the disease and the clinical effectiveness of the intervention, the establishment of disease-specific data registries is suggested to facilitate the process of technology assessment and improving patient care. These registries should attempt to include all affected patients in the UK, and collect longitudinal patient level data on clinically relevant problems, interventions received and quality of life in a utility format.

Cardiac findings after enzyme replacement therapy for mucopolysaccharidosis type I

Mucopolysaccharidosis type I is a lethal autosomal recessive storage disease caused by a deficiency of lysosomal alpha-L-iduronidase and the consequent systemic accumulation of glycosaminoglycan. Cardiomyopathy and valvar insufficiency occur as glycosaminoglycan accumulates in the myocardium, expands the spongiosa of cardiac valves, and proliferates within the myointima of the epicardial coronary arteries. Congestive heart failure and death occur within the first decade of life in the most severe cases. Allogeneic hematopoietic stem cell transplantation, used in severe forms of the disease, markedly prolongs survival, alleviates ventricular hypertrophy, and preserves cardiac function, but cardiac valves continue to thicken and valvular insufficiency progresses. Enzyme replacement therapy with human recombinant alpha-L-iduronidase has been proposed as an alternativee therapy for patients with mucopolysaccharidosis type I in whom the risk/benefit ratio of hematopoietic stem cell transplantation seems unfavorable. The investigators report the cardiac findings in a small series of 5 children with mucopolysaccharidosis type I who received enzyme replacement therapy for as long as 7 years. No deaths occurred during treatment. Left ventricular hypertrophy, which was present before therapy, resolved in all cases, and myocardial function remained normal. In contrast, the mitral and aortic valves remained thickened and, in some instances, developed progressive thickening and regurgitation. In conclusion, long-term enzyme replacement therapy has some clear benefits for the myocardium, but the cardiac valves appear unresponsive, and the ultimate effect on the coronary vasculature is unknown.

Impact of 144 weeks of laronidase therapy on body functions, endurance and general well-being in a Hurler-Scheie patient

The quality of life of a Hurler-Scheie patient who experienced improvement in several organ functions and regained mobility after 144 weeks of laronidase enzyme replacement therapy is described.

Haematopoietic cell transplantation (HCT) in combination with enzyme replacement therapy (ERT) in patients with Hurler syndrome

Hurler syndrome (MPS 1H) is the severe form of mucopolysaccharidosis type 1 (MPS 1). Haematopoietic cell transplantation (HCT) is the treatment of choice, but carries a high incidence of graft failure and morbidity. The use of enzyme replacement therapy (ERT) might improve the clinical signs and symptoms before HCT, resulting in less transplantation-related complications. Moreover, clearance of glycosaminoglycans (GAG's) from the bone marrow might improve engraftment. Twenty-two patients with MPS 1H received one or more HCT procedures in combination with ERT. One patient with severe cardiomyopathy improved significantly after ERT. All children were in a relatively good clinical condition before HCT. Of patients 59, 82 and 86% were alive and engrafted after one, two and three HCT procedures, respectively. Two patients died after repetitive HCT. No serious ERT-infusion-related toxicity occurred. ERT with HCT was well tolerated. Neither a positive nor a negative effect on the number of patients who are alive and engrafted after receiving ERT before HCT as compared to a historic cohort was noted. However, patients in a poor clinical condition before HCT might benefit from ERT.