Withdrawal of enzyme replacement therapy in Gaucher's disease

Although enzyme replacement therapy is safe and effective in ameliorating the signs and symptoms of Gaucher's disease, some patients have withdrawn from treatment. The purpose of this study was to evaluate the response to withdrawal and to discuss the implications for patients currently on unaltered therapy regimens since the advent of treatment. Fifteen patients, who had been treated with enzyme replacement for 5-56 months and then withdrew for 8-47 months, were assessed for changes in haematological parameters and in liver and spleen index volume. Despite non-uniformity of duration of on and off periods, degree of organomegaly, anaemia and thrombocytopenia, most patients did not revert to respective baseline values in most parameters after withdrawal. None of the patients suffered exacerbation of bone involvement or had new or aggravated pulmonary hypertension. Adult patients with stable Gaucher's disease may be withdrawn from therapy for circumscribed periods without forfeiting most gains accrued during enzyme therapy. Therefore, stopping and restarting may be considered in some patients. Alternatively, maintenance at reduced dosage and/or frequency may be appropriate in some adult patients who are stable or non-responsive after the first years of enzyme therapy. This caveat does not apply to children.     

Recombinant methionyl human leptin therapy in replacement doses improves insulin resistance and metabolic profile in patients with lipoatrophy and metabolic syndrome induced by the highly active antiretroviral therapy

CONTEXT: Highly active antiretroviral therapy (HAART) for HIV-1 infection has been associated with a metabolic syndrome characterized by insulin resistance, hyperlipidemia, and redistribution of body fat (lipodystrophy). A subset of patients with predominant lipoatrophy has low levels of the adipocyte-secreted hormone leptin. OBJECTIVE: The objective of the study was to assess whether administration of recombinant methionyl human leptin (r-metHuLeptin) improves insulin resistance and other metabolic abnormalities in HIV+ leptin-deficient subjects with HAART-induced lipoatrophy. DESIGN, SETTING, PATIENTS, AND INTERVENTION: We conducted a randomized, placebo-controlled, double-blinded, crossover study from 2002 to 2004 in seven HIV+ men with HAART-induced lipoatrophy, serum leptin level less than 3 ng/ml, and fasting triglyceride level greater than 300 mg/dl, who were administered placebo for 2 months before or after administration of r-metHuLeptin at physiological doses for an additional 2 months. MAIN OUTCOME MEASURES: Insulin resistance, lipid levels, inflammatory markers, body composition, and HIV control were measured. RESULTS: Compared with placebo, r-metHuLeptin therapy improved fasting insulin levels, insulin resistance (as expressed by the homeostasis model assessment index and an insulin suppression test), and high-density lipoprotein. Body weight and fat mass decreased on r-metHuLeptin, mainly due to a decrease in truncal fat but not peripheral fat or lean body mass. r-metHuLeptin was well tolerated, and HIV control was not adversely affected. CONCLUSIONS: r-metHuLeptin replacement at physiological doses in HIV+ leptin-deficient patients with HAART-induced lipoatrophy improves insulin resistance, high-density lipoprotein, and truncal fat mass. Future larger and more long-term studies in HAART-induced lipoatrophy, including patients with more severe metabolic abnormalities, are warranted to evaluate the physiological and potentially therapeutic role of r-metHuLeptin for this condition and to fully clarify the underlying mechanisms of action.     

Efficacy of enzyme replacement therapy in Fabry disease

Enzyme replacement therapy has recently been introduced to treat Fabry disease, a rare X-linked lysosomal storage disorder. The disease occurs due to deficient activity of alpha-galactosidase A, leading to progressive accumulation of globotriaosylceramide in multiple organs and tissues. Renal, cardiac and cerebrovascular manifestations of the disease result in premature death in both hemizygous males and heterozygous females. This paper outlines the clinical signs, symptoms and diagnosis of Fabry disease, and the development of the two available enzyme replacement therapies -- agalsidase alfa and agalsidase beta. Agalsidase alfa and agalsidase beta are produced in a human cell line and in Chinese hamster ovary cells, respectively, resulting in products with the same amino acid sequence as the native human enzyme, but with different patterns of glycosylation. Correct post-translational glycosylation is important in terms of the pharmacokinetics, biodistribution, clinical efficacy and tolerability of genetically engineered protein therapeutics. Differences in glycosylation, which may affect immunogenicity and mannose-6-phosphate receptor-mediated cellular internalisation of administered enzyme, possibly account for the differences in dosing, clinical effects and safety profiles reported for agalsidase alfa and agalsidase beta.     

Imaging of enzyme replacement therapy using PET

Direct enzyme replacement therapy (ERT) has been introduced as a means to treat a number of rare, complex genetic conditions associated with lysosomal dysfunction. Gaucher disease was the first for which this therapy was applied and remains the prototypical example. Although ERT using recombinant lysosomal enzymes has been shown to be effective in altering the clinical course of Gaucher disease, Fabry disease, Hurler syndrome, Hunter syndrome, Maroteaux-Lamy syndrome, and Pompe disease, the recalcitrance of certain disease manifestations underscores important unanswered questions related to dosing regimes, tissue half-life of the recombinant enzyme and the ability of intravenously administered enzyme to reach critical sites of known disease pathology. We have developed an innovative method for tagging acid β-glucocerebrosidase (GCase), the recombinant enzyme formulated in Cerezyme® used to treat Gaucher disease, using an ¹⁸F-labeled substrate analogue that becomes trapped within the active site of the enzyme. Using micro-PET we show that the tissue distribution of injected enzyme can be imaged in a murine model and that the PET data correlate with tissue ¹⁸F counts. Further we show that PET imaging readily monitors pharmacokinetic changes effected by receptor blocking. The ability to ¹⁸F-label GCase to monitor the enzyme distribution and tissue half-life in vivo by PET provides a powerful research tool with an immediate clinical application to Gaucher disease and a clear path for application to other ERTs.     

Hematopoietic stem cell transplantation improves the high incidence of neutralizing allo-antibodies observed in Hurler's syndrome after pharmacological enzyme replacement therapy

Background Mucopolysaccharidosis type I is caused by deficiency of α-L-iduronidase. Currently available treatment options include an allogeneic hematopoietic stem cell transplant and enzyme replacement therapy. Exogenous enzyme therapy appears promising but the benefits may be attenuated, at least in some patients, by the development of an immune response to the delivered enzyme. The incidence and impact of alloimmune responses in these patients remain unknown. DESIGN AND METHODS: We developed an immunoglobulin G enzyme-linked immunosorbent assay as well as in vitro catalytic enzyme inhibition and cellular uptake inhibition assays and quantified enzyme inhibition by allo-antibodies. We determined the impact of these antibodies in eight patients who received enzyme therapy before and during hematopoietic stem cell transplantation. In addition, 20 patients who had previously received an allogeneic stem cell transplant were tested to evaluate this treatment as an immune tolerance induction mechanism. RESULTS: High titer immune responses were seen in 87.5% (7/8) patients following exposure to α-L-iduronidase. These patients exhibited catalytic enzyme inhibition (5/8), uptake inhibition of catalytically active enzyme (6/8) or both (4/8). High antibody titers generally preceded elevation of previously described biomarkers of disease progression. The median time to development of immune tolerance was 101 days (range, 26-137) after transplantation. All 20 patients, including those with mixed chimerism (22%), tested 1 year after transplantation were tolerized despite normal enzyme levels. Conclusions We found a high incidence of neutralizing antibodies in patients with mucopolysaccharidosis type I treated with enzyme replacement therapy. We also found that allogeneic hematopoietic stem cell transplantation was an effective and rapid immune tolerance induction strategy.     

Prosthetic valve thrombosis after initiation of hormone replacement therapy

The complications of hormone replacement therapy (HRT) related to hypercoagulability are well known. However, there have been no cases of prosthetic valve thrombosis reported in the literature in conjunction with HRT. The present report discusses a case of acute mitral prosthetic valve thrombosis associated with the initiation of HRT. Because hypercoagulability is usually associated with significant morbidity and mortality, caution should be exercised in the management of patients with prosthetic valve thrombosis receiving HRT.     

Thrombocytosis associated with enzyme replacement therapy in Gaucher disease

We describe a patient with an intact spleen and moderately severe symptoms of Gaucher disease in whom, after initiation of (low-dose) enzyme replacement therapy (ERT), thrombocytosis (720 x 10(9)/l) was documented. Checking the International Gaucher Registry database revealed that this patient is the only nonsplenectomized patient of more than 1,000 treated patients to experience ERT-induced thrombocytosis. Platelet counts dropped immediately after the discontinuation of ERT.     

Effect of enzyme replacement therapy on gammopathies in Gaucher disease

Chronic antigenic stimulation by the abnormal lipid storage has been postulated to be the mechanism underlying anecdotal reports of monoclonal and polyclonal gammopathies as well as an increased incidence of multiple myeloma in patients with Gaucher disease of all ages. With the advent of specific enzyme therapy, it has been possible to ascertain whether signs and symptoms associated with Gaucher disease are true features of the disorder by virtue of their responsiveness to treatment. The purpose of this study was to assess the incidence of polyclonal and monoclonal gammopathies in a large cohort of patients and the effect of enzyme treatment. All adult patients whose records of immunoglobulin levels were available at presentation or at the advent of enzyme replacement therapy (ERT), and who had been followed for 2 years or receiving ERT for at least 2 years, respectively, and for whom there were also immunoglobulin levels at their most recent follow-up, were included in the study. The incidence of polyclonal gammopathies ranged between 14% and 25% among treated and untreated patients. There were statistically significant percentage decreases per year of enzyme therapy in polyclonal but not monoclonal (1% of all patients) gammopathies. Among enzyme-treated patients, there was no statistically significant difference among patients with regard to spleen status or relative to other parameters of disease severity, hepatitis status, age or gender. This study represents the largest database of gammopathies among patients with Gaucher disease from a large referral clinic. Because there was no correlation of abnormal immunoglobulin levels with disease severity, etiology may not be related to lipid accumulation per se but perhaps reflects a secondary, enzyme-sensitive process, whereas monoclonal gammopathies remain unaffected.     

Erythropoietin regulates metabolic response in mice via receptor expression in adipose tissue,brain, and bone

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Combined hormone replacement therapy improves endothelial function in healthy postmenopausal women

OBJECTIVES: Large scale epidemiological studies suggest that hormone replacement therapy (HRT) reduces cardiovascular events in postmenopausal women. Improvement in endothelial function may contribute to this protective effect. DESIGN: In a prospective, double blind study, 61 healthy postmenopausal women were randomized to receive either oral continuous combined HRT [oestradiol 2 mg and norethisterone acetate (NETA) 1 mg per day] or placebo. Endothelial function, assessed by flow-mediated vasodilation (FMD) of the brachial artery and expression of soluble endothelial cell adhesion molecules (CAM) were determined before, after 3 and 6 months of therapy. RESULTS: The FMD was significantly improved in women on combined HRT (from 5.97% to 10.94% after 3 months and to 10.58% after 6 months; both P < 0.01 versus baseline values) and did not change in the placebo group (6.92% at baseline, 5.86% after 3 and 6.26% after 6 months). After 3 months of combined HRT, significant decreases of 24.6% for E-selectin and 13.9% for intercellular adhesion molecule-1 (ICAM-1) were observed (both P < 0.01 versus baseline values) and were sustained after 6 months of therapy, whilst no differences emerged in the placebo group. CONCLUSIONS: Oestradiol and norethisterone acetate improve endothelial function by both enhancing FMD and reducing the levels of soluble E-selectin and ICAM-1 in healthy postmenopausal women.     

Limitations of enzyme replacement therapy: Current and future

Summary Orphan drug legislation passed in the USA in 1983 and in Europe in 1999 has encouraged biotechnology companies to develop treatments for diseases that the industry previously ignored because they affect only small numbers of people and promised only limited profitability. Incentives, exclusivity and the freedom to charge sufficient to cover development costs has led to a niche market, and patients with lysosomal storage disorders have been one of the main beneficiaries of these developments. The recombinant production of highly purified enzymes that are modified to improve tissue targeting has been a direct result of this legislation. The spectacular clinical and financial success of Cerezyme (and previously Ceredase, Genzyme) for the treatment of Gaucher disease has led to the development of enzyme replacement treatment(s) for Fabry disease and mucopolysaccharidoses types I and VI. A number of other enzyme replacement therapies are at an earlier stage in development and the next 12 months could see the launch of therapies for mucopolysaccharidosis type II and Pompe disease. Like all medical treatments, this approach has some limitations. Not all patients are suitable for treatment, some organs and tissues are corrected more readily than others, and there are problems with gauging efficacy in these highly variable disorders. Finally, the therapies are expensive, limiting access to patients from those countries that are able to afford expensive health care. Presented at the 42nd Annual Meeting of the SSIEM, Paris, 6–9 September 2005 Competing interests: None declared     

Modulation of the gut microbiota by metformin improves metabolic profiles in aged obese mice

The gut microbiota is a contributing factor in obesity-related metabolic disorders. The effect of metformin on the gut microbiota has been reported; however, the relationship between the gut microbiota and the mechanism of action of metformin in elderly individuals is unclear. In this study, the effect of metformin on the gut microbiota was investigated in aged obese mice. The abundance of the genera Akkermansia, Bacteroides, Butyricimonas, and Parabacteroides was significantly increased by metformin in mice fed a high-fat diet. Metformin treatment decreased the expression of IL-1β and IL-6 in epididymal fat, which was correlated with the abundance of various bacterial genera. In addition, both fecal microbiota transplantation from metformin-treated mice and extracellular vesicles of Akkermansia muciniphila improved the body weight and lipid profiles of the mice. Our findings suggest that modulation of the gut microbiota by metformin results in metabolic improvements in aged mice, and that these effects are associated with inflammatory immune responses.     

Timing of initiation of enzyme replacement therapy after diagnosis of type 1 Gaucher disease: effect on incidence of avascular necrosis

Data from the International Collaborative Gaucher Group Gaucher Registry were analysed to assess the relationship between enzyme replacement therapy with imiglucerase (ERT) and incidence of avascular necrosis (AVN) in type 1 Gaucher disease (GD1), and to determine whether the time interval between diagnosis and initiation of ERT influences the incidence rate of AVN. All patients with GD1 enrolled in the Gaucher Registry who received ERT and did not report AVN prior to starting therapy ( n  = 2700) were included. The incidence rate of AVN following initiation of ERT was determined. An incidence rate of AVN of 13·8 per 1000 person-years was observed in patients receiving ERT. Patients who initiated ERT within 2 years of diagnosis had an incidence rate of 8·1 per 1000 person-years; patients who started ERT ≥2 years after diagnosis had an incidence rate of 16·6 per 1000 person-years. The adjusted incidence rate ratio was 0·59 [95% confidence interval (CI) 0·36–0·96, P  = 0·0343]. Splenectomy was an independent risk factor for AVN (adjusted incidence rate ratio 2·23, 95% CI 1·61–3·08, P  < 0·0001). In conclusion, the risk of AVN was reduced among patients who initiated ERT within 2 years of diagnosis, compared to initiating treatment ≥2 years after diagnosis. A higher risk of AVN was observed among patients who had previously undergone splenectomy.