Enzyme therapy for the treatment of type 1 Gaucher disease: clinical outcomes and dose – response relationships

Intra-monocyte Pharmacokinetics of Imiglucerase Supports a Possible Personalized Management of Gaucher Disease Type 1

BACKGROUND AND OBJECTIVES

Intravenous imiglucerase enzyme replacement therapy for Gaucher disease type 1 administered every 2 weeks is at variance with the imiglucerase plasma half-life of a few minutes. We hypothesized that studying the pharmacokinetics of imiglucerase in blood Gaucher disease type 1 monocytes would be more relevant for understanding enzyme replacement therapy responses.

METHODS

Glucocerebrosidase intra-monocyte activity was studied by flow cytometry. The pharmacokinetics of imiglucerase was analyzed using a population-pharmacokinetic model from a cohort of 31 patients with Gaucher disease type 1 who either started or were receiving long-term treatment with imiglucerase.

RESULTS

A pharmacokinetic analysis of imiglucerase showed a two-compartment model with a high peak followed by a two-phase exponential decay (fast phase half-life: 0.36 days; slow phase half-life: 9.7 days) leading to a median 1.4-fold increase in glucocerebrosidase intra-monocyte activity from the pre-treatment activity (p = 0.04). In patients receiving long-term treatment, for whom the imiglucerase dose per infusion was chosen on the basis of disease aggressiveness/response, imiglucerase clearance correlated with the administered dose. However, the residual glucocerebrosidase intra-monocyte activity value was dose independent, suggesting that the maintenance of imiglucerase residual activity is patient specific. Endogenous pre-treatment glucocerebrosidase intra-monocyte activity was the most informative single parameter for distinguishing patients without (n = 10) and with a clinical indication (n = 17) for starting enzyme replacement therapy (area under the receiver operating characteristic curve: 0.912; 95% confidence interval 0.8-1; p < 0.001), as confirmed also by a factorial analysis of mixed data.

CONCLUSION

This study provides novel pharmacokinetic data that support current imiglucerase administration regimens and suggests the existence of a glucocerebrosidase activity threshold related to Gaucher disease type 1 aggressiveness. These findings can potentially improve Gaucher disease type 1 management algorithms and clinical decision making.

Biochemical and imaging parameters in acid sphingomyelinase deficiency: Potential utility as biomarkers

Acid Sphingomyelinase Deficiency (ASMD), or Niemann-Pick type A/B disease, is a rare lipid storage disorder leading to accumulation of sphingomyelin and its precursors primarily in macrophages. The disease has a broad phenotypic spectrum ranging from a fatal infantile form with severe neurological involvement (the infantile neurovisceral type) to a primarily visceral form with different degrees of pulmonary, liver, spleen and skeletal involvement (the chronic visceral type). With the upcoming possibility of treatment with enzyme replacement therapy, the need for biomarkers that predict or reflect disease progression has increased. Biomarkers should be validated for their use as surrogate markers of clinically relevant endpoints. In this review, clinically important endpoints as well as biochemical and imaging markers of ASMD are discussed and potential new biomarkers are identified. We suggest as the most promising biomarkers that may function as surrogate endpoints in the future: diffusion capacity measured by spirometry, spleen volume, platelet count, low-density lipoprotein cholesterol, liver fibrosis measured with a fibroscan, lysosphingomyelin and walked distance in six minutes. Currently, no biomarkers have been validated. Several plasma markers of lipid-laden cells, fibrosis or inflammation are of high potential as biomarkers and deserve further study. Based upon current guidelines for biomarkers, recommendations for the validation process are provided.

Evaluation of neopterin as a biomarker for the monitoring of Gaucher disease patients

OBJECTIVES

Biomarker research is an important area of investigation in Gaucher disease, caused by an inherited deficiency of a lysosomal enzyme, glucocerebrosidase. We evaluated the usefulness of neopterin, as a novel biomarker reflecting chronic inflammation and immune system activation in Gaucher disease and analysed its evolution in response to enzyme replacement therapy (ERT).

METHODS

Circulating plasma neopterin levels in 31 patients with non-neuronopathic Gaucher disease were measured before and after the onset of ERT and were compared with those of 18 healthy controls. Plasma chitotriosidase activity was also monitored, as a reference biomarker, against which we evaluated the evolution of neopterin.

RESULTS

Neopterin levels were significantly increased in treatment-naïve patients (mean 11.90 ± 5.82 nM) compared with controls (6.63 ± 5.59 nM, Mann-Whitney U test P = 0.001), but returned to normal levels (6.92 ± 4.66 nM) following ERT. Investigating the diagnostic value of neopterin by receiver operating characteristic analysis, we found a cut-off value of 7.613 nM that corresponds to an area under the curve of 0.780 and indicates a good discrimination capacity, with a sensitivity of 0.774 and a specificity of 0.778.

DISCUSSION

Our results suggest that measurement of circulating neopterin may be considered as a novel test for the confirmation of diagnosis and monitoring of the efficacy of therapeutic intervention in Gaucher disease. Plasma neopterin levels reflect the global accumulation and activation of Gaucher cells and the extent of chronic immune activation in this disorder.

CONCLUSION

Neopterin may be an alternative storage cell biomarker in Gaucher disease, especially in chitotriosidase-deficient patients.

Activities of genes controlling sphingolipid metabolism in human fibroblasts treated with flavonoids

Natural flavonoids such as genistein, kaempferol and daidzein were previously found to be able to reduce efficiency of glycosaminoglycan synthesis in cells of patients suffering from mucopolysaccharidoses, inherited metabolic diseases with often brain disease symptoms. This feature was employed to test these compounds as potential drugs for treatment other neuronopathic lysosomal storage disorders, in which errors in sphingolipid metabolism occur. In this report, on the basis of DNA microarray analyses and quantitative real time PCR experiments, we present evidence that these compounds modify expression of genes coding for enzymes required for metabolism of sphingolipids in human dermal fibroblasts (HDFa). Expression of several genes involved in sphingolipid synthesis was impaired by tested flavonoids. Therefore, it is tempting to speculate that they may be considered as potential drugs in treatment of LSD, in which accumulation of sphingolipids, especially glycosphingolipids, occurs. Nevertheless, further studies on more advances models are required to test this hypothesis and to assess a therapeutic potential for flavonoids in this group of metabolic brain diseases.

Evaluation of disease burden and response to treatment in adults with type 1 Gaucher disease using a validated disease severity scoring system (DS3)

BACKGROUND

GD1-DS3 is an integrated assessment of type 1 Gaucher disease (GD1) burden based on bone, hematologic and visceral domains. We investigated this disease severity scoring system (DS3) methodology for initial assessment, long-term follow-up and evaluation of treatment responses.

METHODS

We enrolled 133 treated adult GD1 patients. Baseline DS3 scores were calculated near the initial treatment date and patients stratified by severity as marked (DS3 6.00-19.00), moderate (DS3 3.00-5.99), mild (DS3 < 3.00). Follow-up scores were calculated annually. Minimal clinically important improvement (MCII), is defined as ΔDS3 of -3.1.

RESULTS

PATIENT CHARACTERISTICS

N370S was the most common allele (118 patients had at least one), 52 were N370S/N370S (48/52 were Ashkenazi Jews), N370S/L444P was the most common genotype among non-Jews. Median age of treatment: 45 years; median follow-up: 14 years. Baseline DS3 scores: Patients with marked disease (N = 58; median 7.84) were least likely to be N370S homozygous (19 %) and most likely to have had splenectomy (53 %), early age at diagnosis (median 18 years) and major pre-treatment bone pathology (76 %). Among patients with moderate disease (N = 53; median 4.33), 49 % were N370S/N370S, 15.1 % had splenectomy and 17 % had major bone disease. Median age at diagnosis: 32 years. No patient with mild disease (N = 22; median 2.4) had splenectomy or major skeletal disease. Median age at diagnosis: 40 years. 68 % were N370S homozygous. Response to treatment: Health-state transitions occurred primarily during the early treatment years. At Year 5, among 48 evaluable patients with marked baseline disease, eight were unchanged in severity status whereas 40 had MCII of varying degrees with 11 scored as mild. Among 42 evaluable moderate patients, none worsened, 16 remained moderate and 26 improved to mild. Among 16 evaluable mild patients, 14 remained so and 2 had DS3 scores in the low moderate range.

CONCLUSIONS

DS3 is effective for assessing disease burden in GD1 and for monitoring response. ERT was associated with MCII in DS3 scores in patients with high severity. Nevertheless, despite better DS3 scores with treatment, GD1 patients especially those with splenectomy and pre-treatment bone pathology, continued to have bone complications.

Macrophage-derived soluble CD163 level in young patients with Gaucher disease: relation to phenotypes, disease severity and complications

OBJECTIVES

Bone and lung involvement are two major causes of morbidity in Gaucher disease (GD). The soluble form of CD163 (sCD163) is a valuable diagnostic biomarker for monitoring diseases with increased macrophage activation. We determined sCD163 levels in 30 children and adolescence with GD compared with 30 healthy controls and assessed the relation to phenotypes, disease severity and complications.

METHODS

Thirty GD patients (10 had type 1 and 20 had type 3) were studied stressing on skeletal, pulmonary or neurological manifestations, enzyme replacement therapy (ERT), hematological profile, plasma chitotriosidase activity, D-dimer and sCD163. Liver and spleen volumes and bone mineral density (BMD) were assessed.

RESULTS

sCD163 levels were markedly elevated in patients compared with controls. D-dimer, chitotriosidase activity and sCD163 levels were significantly increased in type 3 GD patients compared with type 1. sCD163 was significantly elevated in GD patients with dysphagia, developmental delay, pulmonary hypertension risk or abnormal BMD (osteopenia/osteoporosis) than those without. GD patients receiving ERT every 2weeks had lower levels than those under ERT for more than 2weeks. sCD163 was positively correlated with age, disease duration, severity score index, D-dimer and chitotriosidase activity. The cutoff value of sCD163 at 9400ng/mL could differentiate GD patients with and without pulmonary hypertension risk with a sensitivity of 90% and specificity of 95%.

CONCLUSIONS

sCD163 is a biomarker for the clinical assessment of macrophage proliferation and activity that would help in risk prediction of bone and lung involvement and monitoring treatment response.

Value of plasma chitotriosidase to assess non-neuronopathic Gaucher disease severity and progression in the era of enzyme replacement therapy

Gaucher disease (GD) is caused by deficiency of the enzyme glucocerebrosidase catalysing the regular lysosomal degradation of glucosylceramide. In the common non-neuropathic variant of GD, glucosylceramide-laden macrophages (Gaucher cells) accumulate in various tissues. Gaucher cells secrete chitotriosidase, an active chitinase, resulting in increased plasma chitotriosidase levels, which can be sensitively monitored by an enzyme activity assay. Plasma chitotriosidase is a rough estimate of body burden of Gaucher cells. Non-neuronopathic GD is presently treated by enzyme replacement therapy (ERT) and substrate reduction therapy (SRT). We addressed the question whether plasma chitotriosidase acts as (predictive) marker of clinical manifestations in non-neuronopathic GD patients receiving treatment. Reductions in plasma chitotriosidase during therapy correlated with corrections in liver and spleen volumes and showed positive trends with improvements in haemoglobin and platelet count and bone marrow composition. The occurrence of long-term complications and associated conditions such as multiple myeloma, bone complications, Parkinson's disease, hepatocellular carcinoma and pulmonary hypertension positively correlated with the plasma chitotriosidase level pre-therapy, the average plasma chitotriosidase during 3 years of ERT and the residual plasma chitotriosidase after 2 years of ERT. In summary, plasma chitotriosidase is a valuable marker in the assessment and follow-up of GD patients.

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.

Glucosylsphingosine is a highly sensitive and specific biomarker for primary diagnostic and follow-up monitoring in Gaucher disease in a non-Jewish, Caucasian cohort of Gaucher disease patients

Background

Gaucher disease (GD) is the most common lysosomal storage disorder (LSD). Based on a deficient β-glucocerebrosidase it leads to an accumulation of glucosylceramide. Standard diagnostic procedures include measurement of enzyme activity, genetic testing as well as analysis of chitotriosidase and CCL18/PARC as biomarkers. Even though chitotriosidase is the most well-established biomarker in GD, it is not specific for GD. Furthermore, it may be false negative in a significant percentage of GD patients due to mutation. Additionally, chitotriosidase reflects the changes in the course of the disease belatedly. This further enhances the need for a reliable biomarker, especially for the monitoring of the disease and the impact of potential treatments.

Methodology

Here, we evaluated the sensitivity and specificity of the previously reported biomarker Glucosylsphingosine with regard to different control groups (healthy control vs. GD carriers vs. other LSDs).

Findings

Only GD patients displayed elevated levels of Glucosylsphingosine higher than 12 ng/ml whereas the comparison controls groups revealed concentrations below the pathological cut-off, verifying the specificity of Glucosylsphingosine as a biomarker for GD. In addition, we evaluated the biomarker before and during enzyme replacement therapy (ERT) in 19 patients, demonstrating a decrease in Glucosylsphingosine over time with the most pronounced reduction within the first 6 months of ERT. Furthermore, our data reveals a correlation between the medical consequence of specific mutations and Glucosylsphingosine.

Interpretation

In summary, Glucosylsphingosine is a very promising, reliable and specific biomarker for GD.

Gauchers disease--a reappraisal of hematopoietic stem cell transplantation

Hematopoietic stem cell transplantation (HSCT), first performed in 1984, was the first treatment approach for Gaucher's disease (GD) which had curative intent. The early successes in HSCT were soon eclipsed by the introduction of a highly effective enzyme replacement therapy (ERT), which has remained the single most widely used treatment. Experience with HSCT is limited to about 50 reported cases, mainly performed in the last century, with an overall survival around 85%. HSCT typically achieves complete correction of visceral and bony changes and can fully stabilize neurological features in otherwise progressive type II and III GD. ERT, in contrast, is completely safe and effective, but is limited by cost, incomplete resolution of visceral, hematological, and bony features in some patients, and lack of neurological correction in type II and III disease. In this review, we summarize and compare HSCT and ERT. With 20 years of experience of ERT, its limitations as well as its advantages are now well delineated. Meanwhile progress in HSCT over the last decade suggests that transplantation would today represent a very safe curative approach for GD offering one time complete correction of the disease, contrasting with the lifelong need for ERT with its associated expense and dependence on sophisticated drug manufacture. Additionally, unlike ERT, HSCT can be beneficial for neurological forms of GD. We conclude that the time has come to re-evaluate HSCT in selected patients with GD where ERT is less likely to fully eradicate symptoms of the disease.

Therapeutic approaches to bone pathology in Gaucher disease: past, present and future

Enzyme replacement therapy (ERT) is effective for the treatment of the systemic manifestations of Gaucher disease (GD) and can have a significant impact on skeletal manifestations. Bone involvement is broad and can occur in otherwise clinically asymptomatic individuals. The heterogeneity in GD-related bone disease may implicate multiple pathological processes such as disruption of coordinated bone cell activity, in addition to the physical impact of Gaucher cells causing vascular occlusion. Accumulated data suggests that earlier treatment initiation decreases skeletal complications and that bone disease may require a longer duration of treatment and higher dose than is necessary for organ involvement and hematopoietic manifestations. However, in some patients, bone manifestations persist and even worsen despite ERT, regardless of dose or duration of treatment. Treating skeletal disease should be considered of equal importance as treating visceral and hematologic manifestations. When treatment decisions involve multiple enzyme preparations and other therapeutic modalities such small molecules, the choice should be tailored on an individual basis with continuing evaluation.

D-dimer assay in Egyptian patients with Gaucher disease: correlation with bone and lung involvement

Gaucher disease is the most frequent lysosomal storage disorder. Bone and lung involvement are two major causes of morbidity in this disease. D-dimer is a reliable indicator of active microvascular thrombosis, even in patients without overt hypercoagulation. This study aimed to assess D-dimer levels in Gaucher disease, correlating this marker to clinical characteristics and radiological parameters to investigate its role as a potential predictor for the occurrence and severity of skeletal and pulmonary manifestations. The study population consisted of 56 Egyptian patients with Gaucher disease, 36 had type 1 Gaucher disease (64.3%) and 20 had type 3 Gaucher disease (35.7%). Thirty healthy individuals were enrolled as a control group. D-dimer levels were significantly higher in all patients with Gaucher disease compared with controls (P < 0.001). Patients with type 3 showed significantly higher D-dimer concentrations compared with type 1 (P < 0.001). Pulmonary involvement was present in a significant proportion among type 3 Gaucher patients (P < 0.05), whereas bone changes were present in a higher percentage in type 1 compared with type 3 Gaucher patients. D-dimers were significantly higher in patients with abnormal MRI findings of the long bones and in those with ground glass appearance on high-resolution computerized tomography of the chest compared with patients with normal radiology (P < 0.001). Splenectomized patients displayed significantly higher D-dimer levels compared with nonsplenectomized patients (P < 0.001). Our results suggest that D-dimer is significantly elevated in Gaucher disease, particularly type 3, and may be considered as a potential marker of risk prediction of bone and lung involvement that could be used to monitor treatment response.

Priority setting for orphan drugs: an international comparison

OBJECTIVES

To describe the process of priority setting for two orphan drugs - Cerezyme and Fabrazyme - in Canada, Australia and Israel, in order to understand and improve the process based on stakeholder perspectives.

METHODS

We conducted qualitative case studies of how three independent drug advisory committees made decisions relating to the funding of Cerezyme and Fabrazyme. Interviews were conducted with 22 informants, including committee members, patient groups and industry representatives.

RESULTS

(1) DESCRIPTION: Orphan drugs reimbursement recommendations by expert panels were based on clinical evidence, cost and cost-effectiveness analysis. (2) EVALUATION: Committee members expressed an overall preference for the current drug review process used by their own committee, but were concerned with the fairness of the process particularly for orphan drugs. Other informants suggested the inclusion of other relevant values (e.g. lack of alternative treatments) in order to improve the priority setting process. Some patient groups suggested the use of an alternative funding mechanism for orphan drugs.

CONCLUSIONS

Priority setting for drugs is not solely a technical process (involving cost-effective analysis, evidence-based medicine, etc.). Understanding the process by which reimbursement decisions are made for orphan drugs may help improve the system for future orphan drugs.

Lysosomal storage diseases as differential diagnosis of hepatosplenomegaly

In adults, elevated transaminases and hepatomegaly, often mild, with moderate to massive idiopathic splenomegaly might hint to a lysosomal storage disease (LSD). In most of these cases, hepatosplenomegaly does not eventually lead to cirrhosis, hepatocellular carcinoma or cholestasis. Nevertheless, the hepatic clinical findings might be the incentive for the patient to present at the physician's office. Many of the currently known >50 lysosomal storage diseases might manifest in liver: out of these, the most important ones in adults are: Gaucher disease, cholesterol ester storage disease (CESD) and the Niemann-Pick diseases. An increase of plasma chitotriosidase should alert the physician for the presence of an LSD. For Gaucher's disease, enzyme supplementation and substrate deprivation constitute effective therapeutic options. Fabry's disease, the most prevalent lysosomal storage disease, does usually not affect the liver, but causes painful episodes of hands' or feet pain (acroparesthesias), left ventricular hypertrophy, renal failure, early stroke and decreased life expectancy. The emerging advent of effective therapeutic options and the cumulative prevalence of lysosomal storage diseases urge the hepatologist to add these diagnostic pathways to the clinical repertoire.

Comparative therapeutic effects of velaglucerase alfa and imiglucerase in a Gaucher disease mouse model

Gaucher disease type 1 is caused by the defective activity of the lysosomal enzyme, acid β-glucosidase (GCase). Regular infusions of purified recombinant GCase are the standard of care for reversing hematologic, hepatic, splenic, and bony manifestations. Here, similar in vitro enzymatic properties, and in vivo pharmacokinetics and pharmacodynamics (PK/PD) and therapeutic efficacy of GCase were found with two human GCases, recombinant GCase (CHO cell, imiglucerase, Imig) and gene-activated GCase (human fibrosarcoma cells, velaglucerase alfa, Vela), in a Gaucher mouse, D409V/null. About 80+% of either enzyme localized to the liver interstitial cells and <5% was recovered in spleens and lungs after bolus i.v. injections. Glucosylceramide (GC) levels and storage cell numbers were reduced in a dose (5, 15 or 60 U/kg/wk) dependent manner in livers (60–95%) and in spleens (∼10–30%). Compared to Vela, Imig (60 U/kg/wk) had lesser effects at reducing hepatic GC (p = 0.0199) by 4 wks; this difference disappeared by 8 wks when nearly WT levels were achieved by Imig. Anti-GCase IgG was detected in GCase treated mice at 60 U/kg/wk, and IgE mediated acute hypersensitivity and death occurred after several injections of 60 U/kg/wk (21% with Vela and 34% with Imig). The responses of GC levels and storage cell numbers in Vela- and Imig-treated Gaucher mice at various doses provide a backdrop for clinical applications and decisions.