Cessation of enzyme replacement therapy in Gaucher disease

Advancements in Viral Gene Therapy for Gaucher Disease

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

Discontinuation of enzyme replacement therapy in Fabry disease in the Dutch cohort

Fabry disease (FD) is a progressive, multi-organ, lysosomal storage disease. Enzyme replacement therapy (ERT) is available for the treatment of the disease. While the reasons to initiate ERT have been frequently discussed, discontinuation of ERT is rarely reported. In this paper we describe our experiences with stopping ERT in FD. From 1999 through 2015, twenty-one patients discontinued ERT. These patients were generally older and more severely affected in comparison those who continued ERT. The reason to discontinue ERT switched from death or terminal illness in the first years towards treatment failure in more recent years. Three cases are described in more detail. We conclude that discontinuation of ERT should or may be considered in subgroups of FD patients although further studies on the effectiveness of ERT in subgroups of patients and the course of the disease after discontinuation of ERT are needed.

Long-term treatment outcomes in Gaucher disease

Following the treatment of the first Gaucher disease patient with enzyme replacement therapy (ERT), it was clear that ERT had the potential to be transformative with dramatic improvements in systemic manifestations of the disease within 2 years. Following over 20 years existence of the International Collaborative Gaucher Group Gaucher Registry and evidence from ∼6000 patients, the long-term effects of therapy have been documented. It has been shown that ERT can result in improvements in all clinical and laboratory parameters of nonneuronopathic disease. However, different aspects of the disease, such as hematologic parameters, organ volumes and bone disease do not necessarily respond to therapy at the same rate or to the same extent, and this has had major implications for disease monitoring and for the establishment of therapeutic goals for ERT. Response may be affected by factors such as the timing of therapy initiation, the presence of irreversible complications such as osteonecrosis, and by enzyme dose. It is also apparent that ERT has no impact on neurological aspects of disease and highlights the need for additional or alternative treatment strategies able to meet the needs of patients with neuronopathic disease.

Impact of imiglucerase supply constraint on the therapeutic management and course of disease in French patients with Gaucher disease type 1

Background

In 2009, a worldwide supply constraint of imiglucerase led to treatment modifications or interruptions for patients with Gaucher disease (GD) type 1. In France, joint treatment recommendations were issued to protect the most vulnerable patients. This observational study evaluated the impact of imiglucerase treatment modifications on the clinical and biological course of GD.

Methods

Retrospective data on patients’ characteristics, treatment, clinical and biological parameters from 01 June 2009 to 31 October 2010 were collected during a single visit.

Results

Ninety-nine GD1 patients, aged 7–84 years, were included (median age 47 years); 10 were children. Patients experienced a median of 4 different treatment modifications. Median change from pre-supply constraint dose (92 U/kg/4-weeks) was −69, −51, −29 and −60 U/kg/4-weeks at 3, 6, 9 and 12 months after first modification, respectively, with imiglucerase discontinuation reported for 70%, 47%, 29% and 55% of patients at these timepoints. Replacement with another ERT was reported for 35 patients. Results show a statistically significant decrease in hemoglobin (−0.8 g/L/month) and platelets (−5905.10³/mm³/month) and an increase in chitotriosidase (+537 nmol/mL/h/month) and angiotensin-converting enzyme (+4 IU/L/month) in the subgroup of 61 patients who discontinued treatment for at least 3 months; this magnitude of change was not seen in the subgroup (32 patients) treated with reduced imiglucerase for at least 3 consecutive months. GD-related events were spontaneously reported by the study investigators for 39% of the whole study population, including asthenia/fatigue (8%), bone infarction and bone pain (4% each), and hepatomegaly (3%). A Kaplan-Meier estimate of the probability for a patient to present a bone, hematological or visceral event during the constraint was 37% for patients who discontinued the treatment and 10% for patients treated with a reduced imiglucerase dose.

Conclusion

The release of recommendations and individuals’ close follow-up allowed satisfactory management of patients during the imiglucerase supply constraint in France. This study suggests that during this period, lowering the dose of imiglucerase had less impact on the outcomes of patients than interrupting treatment. However, general effects (such as fatigue, bone pain) reported in some patients, emphasize the importance of maintaining appropriate individualized dosing.

The European Gaucher Alliance: a survey of member patient organisations' activities, healthcare environments and concerns

Background

The European Gaucher Alliance (EGA) was established in 1994 and constituted in 2008 as an umbrella group supporting patient organisations for Gaucher disease. Every two years, the EGA conducts a questionnaire survey of member associations to help develop its priorities and annual work programme. Results of the latest survey are presented.

Methods

Between June 2012 and April 2013, the 36 members and associate members of the EGA were asked to complete a questionnaire detailing membership numbers, disease specific treatments used by patients, means of access to treatment, availability of treatment centres and home infusions, sources of support for patients with Gaucher disease, patient organisations’ activities, collaborations, funding sources and any issues of concern. Questionnaires completed in 2012 were revised in January 2013 and responses analysed between July and September 2013.

Results

Thirty three members returned data on one or more questions. Findings identified inequalities in access to treatment both within and between members’ countries. Three of 27 countries, for which data were available, relied totally on humanitarian aid for treatment and 6% of untreated patients in 20 countries were untreated because of funding issues, a situation many feared would worsen with deteriorating economic climates. Access to treatment and reimbursement represented 45% of members’ concerns, while 35% related to access to specialist treatment centres, home infusions and doctors with expertise in Gaucher disease. Member associations’ main activities centred on patient support (59% of responses) and raising awareness of Gaucher disease and patients’ needs amongst the medical community, government and healthcare decision makers and the general public (34% of responses). Twenty one (78% of respondents) indicated they were the only source of help for Gaucher disease patients in their country. For many, activities were constrained by funds; two members had no external funding source. Activities were maximised through collaboration with other patient organisations and umbrella organisations for rare diseases.

Conclusion

The survey provided a ‘snapshot’ of the situation for patients and families affected by Gaucher disease, helping the EGA direct its activities into areas of greatest need.

Evaluation of miglustat as maintenance therapy after enzyme therapy in adults with stable type 1 Gaucher disease: a prospective, open-label non-inferiority study

Background

Previous studies have provided equivocal data on the use of miglustat as maintenance therapy in Gaucher disease type 1. We report findings from a clinical trial evaluating the effects of miglustat treatment in patients with stable type 1 Gaucher disease after enzyme therapy.

Methods

Adult type 1 Gaucher disease patients stabilized during at least 3 years of previous enzyme therapy were included in this 2-year, prospective, open-label non-inferiority study. The primary endpoint was percent change from baseline in liver volume. Secondary endpoints included changes in spleen volume, hemoglobin concentration and platelet count.

Results

Forty-two patients were enrolled (mean±SD age, 45.1±12.7 years; previous enzyme therapy duration 9.5±4.0 years). Median (range) exposure to miglustat 100 mg t.i.d. was 658 (3–765) days. Twenty-one patients discontinued treatment prematurely; 13 due to adverse events, principally gastrointestinal. The upper 95% confidence limit of mean percent change in liver volume from baseline to end of treatment was below the non-inferiority margin of 10% (–1.1%; 95%CI −6.0, 3.9%). Mean (95%CI) changes in spleen volume, hemoglobin concentration and platelet count were 102 (24,180) mL, –0.95 (−1.38, –0.53) g/dL and −44.1 (–57.6, –30.7) ×10⁹/L, respectively.

Conclusions

The primary efficacy endpoint was met; overall there was no change in liver volume during 24 months of miglustat therapy. Several patients showed a gradual deterioration in some disease manifestations, suggesting that miglustat could maintain clinical stability, but not in all patients. Miglustat demonstrated a predictable profile of safety and tolerability that was consistent with that reported in previous clinical trials and experience in clinical practice.

Trial registration

Clinicaltrials.gov identifier NCT00319046

Effect of rapid cessation of enzyme replacement therapy: a report of 5 cases and a review of the literature

Enzyme replacement therapy (ERT) is a treatment modality available for several of the lysosomal storage diseases including mucopolysaccharidosis type II (MPS II). We report a series of patients with MPS II (n = 5, age range at the start of ERT 11-21 years, median 15 years) and the effects of ERT cessation (range 2-8 months, median 3 months) on their clinical status. Additionally, we review previously published cases. In our series, a worsening of the patients' clinical status was observed. Symptoms after ERT discontinuation included recurrent respiratory infections (severe pneumonia) with respiratory insufficiency (80%), difficulty with walking/standing (60%), increased joint stiffness (40%), but also decreased hematological parameters (40%), renal insufficiency (40%) and death (20%). The literature review confirms that the beneficial clinical effects of ERT are soon lost if treatment is discontinued in MPS I and Pompe patients.

CONCLUSIONS

1. Rapid cessation of ERT results not only in the loss of the beneficial effects, but in a significant worsening of the patient's clinical status. 2. Decisions about the introduction of ERT, especially in patients severely affected, should be made carefully. 3. Once started, it is essential to keep an adequate administration schedule of ERT to maintain the clinical benefits of enzyme therapy.

Did the temporary shortage in supply of imiglucerase have clinical consequences? Retrospective observational study on 34 italian Gaucher type I patients

Background. Enzyme Replacement Therapy (ERT) is the standard of care in Gaucher disease. The effects of withdrawal or reduced doses are debated, thus a retrospective cohort study was conducted to investigate clinical and laboratory differences in 34 Gaucher type 1 patients experiencing an ERT dosage reduction after the forced temporary imiglucerase shortage in 2009. Methods. Haemoglobin concentration, leukocytes and platelets counts, and chitotriosidase activity were assessed at baseline and after 6 and 12 months (t0, t6, t12), while bone pain, energy, work or school performance, concentration, memory and social life every 3 months. Results. The cohort was made up of 18 males and 16 females (medians: age 41.8 years, therapy duration 14.1 years, dosage reduction 35.5%). Haemoglobin, leukocytes and platelets remained substantially stable, while chitotriosidase activity showed an increase, especially after t6. Age, splenectomy or genotype were not associated with laboratory parameters changes, except for a significant median increase of chitotriosidase activity in non-splenectomised patients after 12 months (p = 0.01). At 3, 6, 9 and 12 months, more than 50% patients reported at least one problem in subjective well-being (56%, 65%, 70%, 58%, respectively), while bone pain occurred or worsened in 13/33, 13/32, 7/28 and 5/26 patients, respectively. No bone crises were reported. Conclusions. Drug reduction did not induce substantial modification in the laboratory values but seems to have influenced the well-being perception of some Gaucher patients. Thus, bone pain, general health and quality of life should be carefully monitored during ERT reductions.

Mucopolysaccharidosis type II in females and response to enzyme replacement therapy

Mucopolysaccharidosis type II (MPS II, Hunter syndrome) is an X-linked lysosomal storage disease caused by a deficiency of iduronate-2-sulfatase (IDS). Two affected girls with moderate and severe forms of MPS II with normal karyotypes and increased urinary dermatan sulphate and heparin sulphate excretion and marked deficiencies of IDS activity are reported. Molecular studies showed that case 1 has a heterozygous mutation c.1568A > G (p.Y523C) associated with almost totally skewed inactivation of the normal maternal X chromosome, and case 2 has a heterozygous deletion that includes exons 1-4 of IDS (minimal deletion range c.1-103_184del). The multi-exon deletion correlated with early onset of the disease and severe phenotype with intellectual disability, whereas the missense mutation was associated with moderate developmental delay. Although genotype-phenotype correlation in MPS II is difficult, gene deletions seem to correlate with more severe clinical manifestation of the disease. Enzyme replacement therapy (ERT) in these two females resulted in disease stabilization in both.

Biomarkers for osteonecrosis in Gaucher disease

INTRODUCTION

The search for surrogate biomarkers of osteonecrosis, a disabling complication of Gaucher disease, has intensified in the last decade. Biomarkers that predict osteonecrosis and monitor the effectiveness of therapies would improve clinical practice and enrich the molecular exploration of this disorder.

AREAS COVERED

Here we discuss advances in biomarker research with special reference to those biomarkers associated with Gaucher disease and investigated in the context of enzyme therapy. Much progress has been made in the diversification of treatment for the condition and several biomarker molecules, which may ultimately improve risk assessment for osteonecrosis, have been identified.

EXPERT OPINION

The discovery of prospective biomarkers of osteonecrosis such as CCL18/PARC, CXCL8/IL-8, CCL5/RANTES, CCL3/MIP-1α, CCL4/MIP-1β, particularly during recurrent episodes occurring despite enzyme treatment, has the potential radically to change practices in the management of Gaucher disease and should improve therapeutic monitoring and prognostic evaluation. Ultimately, exploration of this field will provide the basis for a refined mechanistic understanding of pathogenesis.

How I treat Gaucher disease

This review presents a cohesive approach to treating patients with Gaucher disease. The spectrum of the clinical presentation of the disease is broad, yet heretofore there was only one disease-specific treatment. In the past 2 years, a global shortage of this product has resulted in reassessment of the “one enzyme–one disease–one therapy” mantra. It has also showcased the multiple levels that engage the patient, the treating physician, and the third-party insurer in providing adequate treatment to all symptomatic patients. The key points summarizing the way I manage my patients include accurate enzymatic diagnosis with mutation analysis (for some prognostication and better carrier detection in the family), a detailed follow-up every 6-12 months (with an option to see consultants and attention to comorbidities), and initiation of enzyme replacement therapy according to symptoms or deterioration in clinically significant features or both. I do not treat patients with very mild disease, but I consider presymptomatic therapy for patients at risk, including young women with poor obstetric history. I prefer the minimal-effective dose rather than the maximally tolerated dose, and when the difference between high-dose and lower-dose regimens is (merely statistically significant but) clinically meaningless, minimizing the burden on society by advocating less-expensive treatments is ethically justified.

Evaluation of Spanish Gaucher disease patients after a 6-month imiglucerase shortage

Recently, an acute restriction of imiglucerase has occurred as a result of viral contamination and manufacturing problems. A position statement from the European Working Group for Gaucher Disease and European Gaucher Alliance established a set of key recommendations for identifying and monitoring at-risk patients. In Spain, a profile of the shortage situation was obtained through follow-up of patients with Gaucher disease (GD) and compliance with the therapy recommendations. Here we describe a group of patients, with modified doses of imiglucerase, during the shortage. Fifty adult GD1 patients (25 males/25 females), previously on ERT, were analysed before and after the 6-month shortage. The mean age was 45.3 ± 15.3 years (range: 18-84). The mean Severity Score Index at diagnosis was 8.7 ± 3.8 (range: 3-19); 20% of patients were splenectomized; and 78% had bone disease. During the shortage, 23 patients (46%) discontinued therapy; as complications in this group only one patient suffered a bone crisis and another anaemia (Hb <10.0 g/dL). The mean reduction of haemoglobin level (-2.7%) and platelet counts (-5.4%) were non-significant. Chitotriosidase (CT) activity was increased 135% (p<0.03) and CCL18/PARC 8.2% (p<0.08) in this group. Imiglucerase was reduced by 50% in 17 patients (34%) in this group, seven patients (41.0%) suffered bone pain, three of them true bone crisis and four (23.5%) required support therapy. The mean reduction of haemoglobin (-2.8%) and platelet counts (-10.7%), CT activity was increased 48.2% (p<0.03) and no changes were observed in CCL18/PARC concentration. In both groups no significant changes in visceral size were observed. In 3 patients (6%), imiglucerase was reduced 75% and 7 patients (14%) needed to switch to another ERT (4 patients) or miglustat (3 patients) due to a restart of symptomatic disease. In Spain the 6 first months shortage of imiglucerase have produced a 20% incidence of bone pain, one case of anaemia, and a significant increase in CT activity. Fourteen percent of patients had to switch to another therapy. No significant changes in blood counts, visceral volumes and CCL18/PARC concentration were observed.

Force majeure: therapeutic measures in response to restricted supply of imiglucerase (Cerezyme) for patients with Gaucher disease

Gaucher disease is the first lysosomal disorder for which clinically effective enzyme replacement therapy has been introduced. Lifelong treatment with imiglucerase, the recombinant glucocerebrosidase manufactured by the Genzyme Corporation (MA, USA), is administered intravenously - usually at biweekly intervals. An acute shortage of imiglucerase (to 20% of prior global supply) has occurred as a result of viral contamination of the production facility; production was halted, and a full supply of imiglucerase is not anticipated until January 2010. An urgent meeting of physicians, researchers, and patients was convened through the agency of the European Working Group for Gaucher Disease; this was instigated by patients internationally represented by the European Gaucher Alliance. Here we present a position statement based on the findings of the group, with key recommendations about identification and monitoring of at-risk patients threatened by the abrupt withdrawal of treatment, the equitable distribution of residual imiglucerase - and access to alternative treatments including those that have completed phase III clinical trials but have not yet been licensed.

Review of the safety and efficacy of imiglucerase treatment of Gaucher disease

Most patients who suffer from symptomatic Gaucher disease will benefit from enzyme replacement therapy (ERT) with imiglucerase. The safety profile is excellent, only a small percentage of those exposed developing antibodies; similarly, very few patients require pre-medication for allergic reactions. Within 3 to 5 years of imiglucerase therapy, best documented at doses of 30 to 60 units/kg/infusion, hepatosplenomegaly can be expected to be reduced so that the liver volume will be maintained at 1 to 1.5 times normal (30% to 40% reduction from advent of ERT) and spleen volume to </= 2 to 8 times normal (50% to 60% reduction from advent of ERT). For anemic and thrombocytopenic patients, with 2 to 5 years of imiglucerase, hemoglobin levels are expected to be >/= 11 g/dL for women and children and >/= 12 g/dL for men; and platelet counts in patients with an intact spleen, depending on the baseline value, should approximately be doubled. Bone crises and bone pain but not irreversible skeletal damage will improve in most patients. Nonetheless, some features and some symptomatic patients apparently do not respond equally well and/or perhaps inadequately. The benefit for patients with the neuronopathic forms is primarily in improved visceral and hematological signs and symptoms. There are still several unresolved issues, the high per-unit cost being an important one, which have spurred the development of biosimilar enzymes as well as chaperone therapies currently in clinical trials.

Review of the safety and efficacy of imiglucerase treatment of Gaucher disease

Most patients who suffer from symptomatic Gaucher disease will benefit from enzyme replacement therapy (ERT) with imiglucerase. The safety profile is excellent, only a small percentage of those exposed developing antibodies; similarly, very few patients require pre-medication for allergic reactions. Within 3 to 5 years of imiglucerase therapy, best documented at doses of 30 to 60 units/kg/infusion, hepatosplenomegaly can be expected to be reduced so that the liver volume will be maintained at 1 to 1.5 times normal (30% to 40% reduction from advent of ERT) and spleen volume to </= 2 to 8 times normal (50% to 60% reduction from advent of ERT). For anemic and thrombocytopenic patients, with 2 to 5 years of imiglucerase, hemoglobin levels are expected to be >/= 11 g/dL for women and children and >/= 12 g/dL for men; and platelet counts in patients with an intact spleen, depending on the baseline value, should approximately be doubled. Bone crises and bone pain but not irreversible skeletal damage will improve in most patients. Nonetheless, some features and some symptomatic patients apparently do not respond equally well and/or perhaps inadequately. The benefit for patients with the neuronopathic forms is primarily in improved visceral and hematological signs and symptoms. There are still several unresolved issues, the high per-unit cost being an important one, which have spurred the development of biosimilar enzymes as well as chaperone therapies currently in clinical trials.

Eight-year clinical outcomes of long-term enzyme replacement therapy for 884 children with Gaucher disease type 1

OBJECTIVE

The goal was to analyze the clinical responses to enzyme replacement therapy with alglucerase or imiglucerase in a large international cohort of children with Gaucher disease type 1.

METHODS

Anonymized data from 884 children in the International Collaborative Gaucher Group Gaucher Registry were analyzed to determine the effects of long-term enzyme replacement therapy with alglucerase or imiglucerase on hematologic and visceral manifestations, linear growth, and skeletal disease. The parameters measured were hemoglobin levels, platelet counts, spleen and liver volumes, z scores for height and bone mineral density, and reports of bone pain and bone crises.

RESULTS

The median height z score for the study population was -1.4 at baseline. After 8 years of treatment, the median height approximated the median value for the normal population. Anemia, although not severe, was present in >50% of patients at baseline and resolved for all patients after 8 years of treatment. More than 50% of patients had platelet counts of <100000 platelets per mm3 at baseline, but >95% had platelet counts above this level after 8 years of treatment. Liver and spleen volumes decreased over 8 years of treatment. The mean bone mineral density z score was -0.34 at baseline, and values normalized within 6.6 years of treatment. Seventeen percent of patients reported a bone crisis before treatment and in the first 2 years of treatment, but no bone crises were reported after 2 years of enzyme replacement therapy. Few patients (2.5%) without bone crises before enzyme replacement therapy had a crisis after the start of treatment.

CONCLUSIONS

These longitudinal data quantitate the benefits of continuous enzyme replacement therapy with alglucerase/imiglucerase for children with Gaucher disease type 1. Within 8 years of enzyme replacement therapy, most clinical parameters studied became normal or nearly normal.

Clinical consequences of interrupting enzyme replacement therapy in children with type 1 Gaucher disease

OBJECTIVE

To document the effects of interrupting enzyme replacement therapy (ERT) for at least 1 year in a group of children with type 1 Gaucher disease.

STUDY DESIGN

All children with type 1 Gaucher disease who were treated at 2 pediatric centers and who were required to suspend ERT for at least 1 year were studied before, during, and after treatment interruption. Hemoglobin and platelet levels, organomegaly, growth, and bone manifestations were monitored.

RESULTS

Five of 32 children experienced treatment interruptions. Before ERT, all children had splenomegaly, 4 children had hepatomegaly, 4 children had growth retardation, 3 children had skeletal manifestations, 3 children had thrombocytopenia, and 1 child had anemia. After 1 to 7 years of ERT, all children were growing normally, none had skeletal manifestations, organomegaly had decreased or disappeared, and hematologic features had improved. After 15 to 36 months of ERT interruption, splenomegaly recurred or worsened in all children, hepatomegaly and hematologic features recurred or worsened in 4 children, serious bone manifestations developed in 4 children, and 3 children experienced growth retardation. After at least 11 months of resumed ERT in 4 children, 2 had hepatomegaly, 2 had splenomegaly, and all had persistent skeletal manifestations.

CONCLUSION

Interruption of ERT in children with type 1 Gaucher disease should be avoided because it can cause recurrent organomegaly, growth delays, and skeletal manifestations that do not resolve after treatment reinstatement.

National health budgets for expensive orphan drugs: Gaucher disease in Israel as a model

Drugs for orphan diseases are often disproportionately costly, although the patient population is by definition small. In Israel, with a high percentage of Ashkenazi Jews and therefore many patients with Gaucher disease, the expense of enzyme replacement therapy for all patients would be prohibitive. For this reason, with approval of enzyme replacement therapy in Israel, the low-dose regimen (30 U/kg/month), less than one quarter of the manufacturer's original recommended dosage, was instituted as the starting regimen. A Gaucher Committee of medical experts under the auspices of the Ministry of Health determines eligibility for enzyme replacement therapy based on criteria of disease severity. At the advent of 2006, 184 patients in Israel receive enzyme replacement therapy, about one third of all known Israeli patients with Gaucher disease. The national budget provides capitation for each patient to each Sick Fund via a health care basket for severe/expensive treatments. After nearly nine years, the benefits of these innovations include availability of budget for patients requiring enzyme replacement therapy, evidence-based data that low dose is safe and effective, and that untreated mildly affected patients generally continue a benign disease trajectory, but if necessary, have recourse to enzyme replacement therapy, that is, patient care is never compromised. Questionnaires of satisfaction with this system highlight good outcome scores. For countries with limited resources, the use of an impartial committee of experts is recommended, as is long-term surveillance of all patients; maintenance protocols or even drug vacations as enzyme-treated patients approach normalization of disease parameters should be considered.

Lysosomal storage diseases: natural history and ethical and economic aspects

Potential treatment for lysosomal diseases now includes enzyme replacement therapy, substrate reduction therapy, and chaperone therapy. The first two of these have been implemented commercially, and the spectrum of diseases that are now treatable has expanded from Gaucher disease to include several other disorders. Treatment of these diseases is extremely costly. We explore some of the reasons for the high cost and discuss how, by proper selection of patients and appropriate dosing, the economic burden on society of treating these disease may be ameliorated, at least in part. However, the cost of treating rare diseases is a growing problem that society needs to address.

A questionnaire study for 128 patients with Gaucher disease

Gaucher disease is an uncommon autosomal recessive disorder characterized by lysosomal storage of glucosyl ceramide, a material released during cell degradation. Patients with Gaucher disease often have significant hematologic, bone structural, and visceral problems which sometimes greatly affect their health and life style. Based on some extraordinary scientific discoveries over the past 45 years, a treatment system has evolved which consists of administration of an enzyme, which destroys the lysosome-stored material and to some extent restores the patients to good health. There are still some problems for these patients; however, and the purpose of the study is to define some of the clinical, sociologic, and psychologic problems with a specially designed questionnaire. Questionnaire data was collected for 128 patients from two institutions with complete anonymity, and the information compared against data from a National Health Interview Survey. The results show that many of the patients still have fairly extensive problems, which could possibly be helped by some alterations in treatment protocols.

Therapeutic goals in the treatment of Gaucher disease

Gaucher disease, the most common lysosomal storage disorder, is a heterogeneous multisystem condition. Patients with non-neuronopathic (type 1) Gaucher disease may suffer from hepatomegaly, splenomegaly, thrombocytopenia, bleeding tendencies, anemia, hypermetabolism, skeletal pathology, growth retardation, pulmonary disease, and decreased quality of life. Enzyme replacement therapy (ERT) with mannose-terminated glucocerebrosidase reverses or ameliorates many of the manifestations of type 1 Gaucher disease. However, the variable disease pattern and severity, and the uncertain manner of progression, render the decision to initiate ERT difficult. Thus, implementation of treatment and evaluation of the therapeutic response must be tailored to the individual patient. To obtain an evidence-based consensus on contemporary therapeutic goals, an international panel of physicians with extensive clinical experience in Gaucher disease met to review the extant literature on its treatment. The panel adopted an integrated system-based approach to arrive at a comprehensive guide to individualized management. Here we establish goals of treatment in Gaucher disease and propose a comprehensive schedule of monitoring of all relevant aspects to confirm the achievement, maintenance, and continuity of the therapeutic response.

Substrate reduction therapy: miglustat as a remedy for symptomatic patients with Gaucher disease type 1

Gaucher disease (GD) is an inborn error of glycosphingolipid metabolism, associated with multisystemic manifestations resulting from the lysosomal accumulation of an incompletely degraded material (glucosylceramide) within cells of monocyte/macrophage lineage. In the majority of GD patients with non-neurological involvement (type 1), the clinical features are dominated by haematological, visceral (hepatic and splenic) and skeletal complications. Infrequently, cardiopulmonary involvement may develop and lead to major morbidity. Investigations of substrate turnover within cellular compartments, such as the lysosome, indicate that progressive tissue storage occurs when the activity of the responsible hydrolytic enzyme declines. Thus, the provision of functional enzyme to deficient cells is a straightforward means of achieving metabolic correction. Conversely, the concentration of stored substrate within cells bearing particular affected enzymes (i.e., expressing residual activity) may be controlled by a reduction of the 'load'. This means that metabolic homeostasis can also be restored by restricting the amount of substrate presented to disease cells to a level that can be hydrolysed by the existing enzyme activity. Proof-of-concept for both approaches has been demonstrated through enzyme replacement therapy using alglucerase/imiglucerase and more recently, substrate reduction therapy by miglustat. Enzyme replacement therapy is proven to be safe and effective in the treatment of GD type 1, establishing imiglucerase as the current standard of care. The experience with substrate reduction therapy, specifically miglustat, is limited but encouraging. This review is an attempt to examine the potential role of this latter approach in light of current patient management. The consideration of miglustat as a therapeutic option requires the appropriate selection of patients (amongst those unwilling or unsuitable to receive enzyme replacement therapy), a definition of the therapeutic objectives and monitoring not only for response but potential adverse effects.