Baseline characteristics of patients enrolled in the Canadian Fabry Disease Initiative

Independent Registries Are Cost-Effective Tools to Provide Mandatory Postauthorization Surveillance for Orphan Medicinal Products

OBJECTIVES

Orphan medicinal products (OMPs) often receive market authorization under conditions imposed by regulators for ongoing postauthorization surveillance (PAS) to answer questions that remain at the time of market entry. This surveillance may be provided through industry-funded registries (IFRs). Nevertheless, data in these registries may not be of sufficient quality to answer these questions and may not always be accessible for regulatory review. We propose that a mandatory independent registry is an efficient and cost-effective tool for PAS for OMPs.

METHODS

Using data from the Canadian Fabry Disease Initiative, we reviewed costs per unique patient from sites participating in both the independent national registry and IFRs for Fabry disease and compared data completeness from the Canadian Fabry Disease Initiative to that in published documents from IFRs.

RESULTS

The costs of data collection through the independent registry were 17% to 36% (depending on site) lower than costs to collect data in the IFRs, and completeness of data collected through the independent registry was higher than that through the IFRs. Data from the independent registry were reviewed annually to guide indications for publicly funded Fabry disease therapy. Even when enrollment ceased to be a requirement to receive therapy, 77% of patients continued to enroll in the registry, suggesting the structure was acceptable to patients.

CONCLUSIONS

Independent registries are cost-effective and efficient tools and should be mandated by regulatory agencies as the preferred tool for PAS for OMPs. Countries with publicly funded health systems should consider investment in registry infrastructure for OMPs.

Screening for Fabry Disease in patients with unexplained left ventricular hypertrophy

Fabry Disease (FD) is a systemic disorder that can result in cardiovascular, renal, and neurovascular disease leading to reduced life expectancy. FD should be considered in the differential of all patients with unexplained left ventricular hypertrophy (LVH). We therefore performed a prospective screening study in Edmonton and Hong Kong using Dried Blood Spot (DBS) testing on patients with undiagnosed LVH. Participants found to have unexplained LVH on echocardiography were invited to participate and subsequently subjected to DBS testing. DBS testing was used to measure α-galactosidase (α-GAL) enzyme activity and for mutation analysis of the α-galactosidase (GLA) gene, both of which are required to make a diagnosis of FD. DBS testing was performed as a screening tool on patients (n = 266) in Edmonton and Hong Kong, allowing for detection of five patients with FD (2% prevalence of FD) and one patient with hydroxychloroquine-induced phenocopy. Left ventricular mass index (LVMI) by GLA genotype showed a higher LVMI in patients with IVS4 + 919G > A mutations compared to those without the mutation. Two patients were initiated on ERT and hydroxychloroquine was discontinued in the patient with a phenocopy of FD. Overall, we detected FD in 2% of our screening cohort using DBS testing as an effective and easy to administer screening tool in patients with unexplained LVH. Utilizing DBS testing to screen for FD in patients with otherwise undiagnosed LVH is clinically important due to the availability of effective therapies and the value of cascade screening in extended families.

Registries for orphan drugs: generating evidence or marketing tools?

Independent disease registries for pre-and post-approval of novel treatments for rare diseases are increasingly important for healthcare professionals, patients, regulators and the pharmaceutical industry. Current registries for rare diseases to evaluate orphan drugs are mainly set up and owned by the pharmaceutical industry which leads to unacceptable conflicts of interest. To ensure independence from commercial interests, disease registries should be set up and maintained by healthcare professionals and patients. Public funding should be directed towards an early establishment of international registries for orphan diseases, ideally well before novel treatments are introduced. Regulatory bodies should insist on the use of data from independent disease registries rather than company driven, drug-oriented registries.

Therapeutic challenges in two adolescent male patients with Fabry disease and high antibody titres

Enzyme replacement therapy (ERT) has been shown to stabilize certain aspects of Fabry disease (FD). However, in some patients on ERT, high antibody titres have been documented, with limited clinical improvement in systemic manifestations and often with significant adverse drug reactions. We present two related adolescent males with a 4.5 kb GLA deletion, not amenable to chaperone therapy, leading to profound reduction in α-galactosidase A (α-gal A) enzyme activity. Over a 3-year period of ERT, increasing IgG antibody titres against α-gal A were noted. After starting ERT serial urine globotriaosylceramide (Gb₃) measurements showed an upward trend from 333 to 2260 μg/mmol creatinine for patient 1 and 1165 to 2260 μg/mmol creatinine for patient 2. Markedly increased levels of urine and plasma globotriaosylsphingosine (Lyso-Gb₃₎ analogues were also found. The patients experienced recurrent infusion-associated reactions necessitating premedication and prolonged infusion times. Over the 3-year period of ERT, the patients experienced continued malaise, gastrointestinal symptoms and neuropathic pain. In addition, they had increasing anxiety related to their disease and apparent lack of response to ERT which led to a decision to ultimately stop ERT. No other approved treatment options are currently available for these patients. It is possible that the rapid development of the high antidrug neutralizing antibody (ADA) titres is related to the large GLA deletion leading to virtually absent enzyme activity. It remains unclear if their symptomatology during the period of receiving ERT is related to lack of its efficacy, the rising ADA titres, or both. These two patients highlight the need for further research into the management of antidrug antibodies and additional therapeutic approaches for FD.

Synopsis

The development of very high antidrug antibody titres in response to ERT in two related adolescent males with FD highlight the need for other therapeutic options for patients in whom ERT or other currently approved therapies does not meet their treatment needs.

Longitudinal study on ocular manifestations in a cohort of patients with Fabry disease

Purpose

This study aims to assess the evolution of ocular manifestations in a cohort of Fabry patients.

Methods

This is a prospective observational study conducted from 2013 to 2017 (5 consecutive exams). All subjects underwent a comprehensive ocular examination including oriented case history, refraction, corneal topography, biomechanical corneal properties and pachometry assessments, aberrometry, anterior segment evaluation, double-frequency visual field (FDT), intra-ocular pressure, and ocular fundus. At baseline, 41 subjects enrolled but 9 dropped-out and 4 files were not kept for analysis (missing data). Remaining 28 subjects were classified into: Group 1 -hemizygotes (HMZ), all on enzyme replacement therapy (ERT) (N = 10); Group 2 -heterozygotes (HTZ) actively ERT-treated (N = 8), and Group 3 -HTZ not treated (N = 10).

Results

There is a high intra and inter-subjects variability. At baseline, prevalence of the ocular manifestations found is similar to published data: cornea verticillata (89.2%), conjunctival vessels tortuosity (85.7%), corneal haze (67.8%), retinal vessels tortuosity (64.2%), anterior cataract (39.2%) and posterior cataract (28.5%). Prevalence for new elements are found: upper lid vessels toricity (96.4%) and micro-aneurysms (42.8%). At the end, micro-aneurysms (+82%), posterior cataract (+75%) corneal haze (+21%) anterior cataract (+17%) and retinal vessels tortuosities (+4%) evolved in prevalence and severity despite the fact that 68% of the patients were on ERT. Treated heterozygotes evolved more than other groups (p>0.05).

Conclusion

ERT does not seem to halt the clinical evolution of several ocular manifestations. Longer observational time and objective grading systems may be required to fully confirm these findings.

Fabry disease: Detection of Alu-mediated exon duplication by NGS

Monogenetic diseases can be analyzed routinely by targeted DNA sequencing. If causative variants are not found, complementary methods like RNA sequencing or analysis of copy number variations by multiplex ligation-dependent probe amplification have to be considered. In the latter, especially exonic duplications or deletions can be detected, but the precise sites of mutations remain unclear. As we demonstrate in this casuistic report of Fabry disease, next-generation sequencing (NGS) of a long-range PCR product can identify the recombination site directly and illuminate the underlying molecular mechanism.

Comparison of Cardiac Magnetic Resonance Imaging and Echocardiography in Assessment of Left Ventricular Hypertrophy in Fabry Disease

BACKGROUND

Cardiac hypertrophy in Fabry disease can be assessed using the left ventricular mass index (LVMI) with either echocardiography (LVMI-ECHO) or magnetic resonance imaging (LVMI-CMR).

METHODS

A retrospective case series of patients with Fabry disease in Alberta involved a cross-sectional analysis of 32 patients and a longitudinal analysis of 14 of these patients with at least 4 serial CMR measurements.

RESULTS

The cross-sectional analysis showed the mean LVMI-ECHO was 97.8 ± 26.0 g/m², which was higher compared with LVMI-CMR at 81.1 ± 26.9 g/m² with a mean bias of 16.7 g/m² (P < 0.001). In the longitudinal analysis, LVMI-ECHO was higher, with an estimated marginal mean of 96.21 ± 6.13 (mean ± standard error of the mean [SEM]) compared with 71.18 ± 5.99 for LVMI-CMR (P < 0.01; generalized estimating equations). There was an association between an increase in LVMI-CMR over time with the presence of cardiac fibrosis, and patients treated with enzyme replacement therapy (ERT) had slower increases than those without therapy. LVMI-ECHO failed to detect these associations owing to the higher variability and tendency to overestimate the LVMI.

CONCLUSIONS

We propose the preferred method for measuring LVMI is CMR in patients with Fabry disease.

Agalsidase alfa versus agalsidase beta for the treatment of Fabry disease: an international cohort study

Background

Two recombinant enzymes (agalsidase alfa 0.2 mg/kg/every other week and agalsidase beta 1.0 mg/kg/every other week) have been registered for the treatment of Fabry disease (FD), at equal high costs. An independent international initiative compared clinical and biochemical outcomes of the two enzymes.

Methods

In this multicentre retrospective cohort study, clinical event rate, left ventricular mass index (LVMI), estimated glomerular filtration rate (eGFR), antibody formation and globotriaosylsphingosine (lysoGb3) levels were compared between patients with FD treated with agalsidase alfa and beta at their registered dose after correction for phenotype and sex.

Results

387 patients (192 women) were included, 248 patients received agalsidase alfa. Mean age at start of enzyme replacement therapy was 46 (±15) years. Propensity score matched analysis revealed a similar event rate for both enzymes (HR 0.96, P=0.87). The decrease in plasma lysoGb3 was more robust following treatment with agalsidase beta, specifically in men with classical FD (β: −18 nmol/L, P<0.001), persisting in the presence of antibodies. The risk to develop antibodies was higher for patients treated with agalsidase beta (OR 2.8, P=0.04). LVMI decreased in a higher proportion following the first year of agalsidase beta treatment (OR 2.27, P=0.03), while eGFR slopes were similar.

Conclusions

Treatment with agalsidase beta at higher dose compared with agalsidase alfa does not result in a difference in clinical events, which occurred especially in those with more advanced disease. A greater biochemical response, also in the presence of antibodies, and better reduction in left ventricular mass was observed with agalsidase beta.

Prevalence of Fabry Disease and Outcomes in Young Canadian Patients With Cryptogenic Ischemic Cerebrovascular Events

Background and Purpose—

Previous studies reported Fabry disease in 0% to 4% of young patients with cryptogenic ischemic stroke (IS). We sought to determine the prevalence of Fabry and outcomes among young Canadians with cryptogenic IS or transient ischemic attack (TIA).

Methods—

We prospectively enrolled individuals aged 18 to 55 with IS or speech or motor TIA, and no cause identified despite predetermined investigation. α-galactosidase-A gene was sequenced for Fabry diagnosis. National Institutes of Health Stroke Scale score was measured at presentation to quantify stroke severity. Modified Rankin Scale determined functional outcomes ≤7 days after presentation and 6 months later.

Results—

We enrolled 365 patients with IS and 32 with TIA. α-galactosidase-A sequencing identified a single carrier of a genetic variant of unknown significance (p.R118C) and no well-recognized pathogenic variants. Mean National Institutes of Health Stroke Scale score was 3.1. Proportion of patients with modified Rankin Scale of 0 to 2 was 70.7% at ≤7 days and 87.4% at 6 months. National Institutes of Health Stroke Scale score at presentation and diabetes mellitus predicted 6-month modified Rankin Scale. Thirteen patients experienced 5 recurrent IS and 9 TIA during follow-up. No patient died. Most patients (98.7%) returned home. Among previous workers, 43% had residual working limitations.

Conclusions—

In this Canadian cohort of patients with cryptogenic IS or TIA, the prevalence of Fabry was 0.3% if p.R118C variant is considered as pathogenic. This suggests that more cost-effective methods should be applied for diagnosis of Fabry rather than systematic genetic screening in this population. Overall, cryptogenic IS in young adults is associated with favorable outcomes.

Echocardiographic and clinical findings in patients with Fabry disease during long-term enzyme replacement therapy: a nationwide Danish cohort study

OBJECTIVES

In patients with Fabry disease (FD), left ventricular hypertrophy and arrhythmias are frequently observed and cardiac involvement is the leading cause of death. Long-term efficacy of enzyme replacement therapy (ERT) on cardiac involvement is unclear. We assessed and compared long-term progression of cardiac involvement according to ERT and non-ERT.

METHODS

We retrospectively assessed and compared long-term progression of cardiac involvement in adult patients with FD in the nationwide Danish cohort. We followed clinical signs, symptoms and findings by echocardiography, electrocardiography and Holter-monitoring.

RESULTS

We included 66 patients; 47 patients (27 women) received ERT (ERT group) and 19 patients (15 women) did not (non-ERT group). The groups were followed for a median of 8 [0-12] years and 6 [0-13] years, respectively. Comparison between ERT and non-ERT receiving patients by left ventricular mass (echocardiographic assessment) and Sokolow-Lyon voltage- and Cornell product criteria (electrocardiographic assessment) revealed no significant differences. In the ERT group, we observed no change in left ventricular mass but a decrease in Sokolow-Lyon voltage- and Cornell product criteria from baseline to follow-up; 30 mm [15-53] vs. 25 mm [3-44], p < 0.005 and 1710 mm·ms [480-3740] vs. 1520 mm·ms [550-5740], p < .05, respectively. There were no changes within the non-ERT group. During follow-up, cardiac symptoms and use of cardiovascular procedures and -medication increased significantly in the ERT group, whereas no differences were observed within the non-ERT group.

DISCUSSION

We raise concerns regarding the efficacy and benefit of ERT on cardiac involvement in Fabry disease and stress the need for further research.

Switch to agalsidase alfa after shortage of agalsidase beta in Fabry disease: a systematic review and meta-analysis of the literature

BACKGROUND

In 2009, the agalsidase beta shortage resulted in switching to agalsidase alfa treatment for many Fabry disease patients, offering the unique opportunity to compare the effects of the two drugs. Because single studies describing effects of switching on the disease course are limited and inconclusive, we performed a systematic review and meta-analysis of existing data.

METHODS

Relevant studies were identified in the PubMed, Cochrane, ISI Web, and SCOPUS databases from July 2009 to September 2015. The following parameters were analyzed: clinical events, changes in organ function or structure, disease-related symptoms, lyso-Gb3 plasma levels, and adverse effects.

CONCLUSIONS

The nine studies (217 patients) included in our systematic review showed only marginal differences in most of the evaluated parameters. Seven of these studies were included in the meta-analysis (176 patients). The pooled incidence rate of major adverse events was reported for five studies (150 patients) and was equal to 0.04 events per person-year. No significant change was observed after the shift in glomerular filtration rate, whereas left ventricular mass index, left ventricular posterior wall dimension, and ejection fraction were significantly reduced over time. Our data showed that the switch to agalsidase alfa was well tolerated and associated with stable clinical conditions.Genet Med 19 3, 275-282.

Tandem mass spectrometry multiplex analysis of methylated and non-methylated urinary Gb3 isoforms in Fabry disease patients

BACKGROUND

Fabry disease is a lysosomal storage disorder leading to the accumulation of glycosphingolipids in biological fluids and tissues. Globotriaosylceramide (Gb3) and globotriaosylsphingosine (lyso-Gb3) are currently used for Fabry screening and diagnosis. However, these biomarkers are not always increased in Fabry patients with residual enzyme activity. We recently identified 7 urinary methylated Gb3-related isoforms. The aims of this study were (1) to develop and validate a novel LC-MS/MS method for the relative quantification of methylated and non-methylated Gb3 isoforms normalized to creatinine, (2) to evaluate these biomarkers in Fabry patients and healthy controls, and (3) to assess correlations between biomarker urinary excretion with age, gender, treatment and genotype of patients.

METHODS

Urine samples from 150 Fabry patients and 95 healthy controls were analyzed. Samples were purified and injected in the tandem mass spectrometer working in positive electrospray ionization. Relative quantification was performed for 15 methylated and non-methylated Gb3 isoforms.

RESULTS

Significant correlations (p<0.001) were established between Gb3 isoform concentrations, gender and treatment. Five patients with the late-onset cardiac mutation p.N215S showed abnormal concentrations of methylated Gb3 isoforms compared to their non-methylated homologues.

CONCLUSIONS

Methylated Gb3 isoforms might be helpful urinary biomarkers for Fabry patients with late-onset cardiac variant mutations.

Toward a functional definition of a "rare disease" for regulatory authorities and funding agencies

BACKGROUND

The designation of a disease as "rare" is associated with some substantial benefits for companies involved in new drug development, including expedited review by regulatory authorities and relaxed criteria for reimbursement. How "rare disease" is defined therefore has major financial implications, both for pharmaceutical companies and for insurers or public drug reimbursement programs. All existing definitions are based, somewhat arbitrarily, on disease incidence or prevalence.

OBJECTIVES

What is proposed here is a functional definition of rare based on an assessment of the feasibility of measuring the efficacy of a new treatment in conventional randomized controlled trials, to inform regulatory authorities and funding agencies charged with assessing new therapies being considered for public funding.

METHODS

It involves a five-step process, involving significant negotiations between patient advocacy groups, pharmaceutical companies, physicians, and public drug reimbursement programs, designed to establish the feasibility of carrying out a randomized controlled trial with sufficient statistical power to show a clinically significant treatment effect.

RESULTS AND CONCLUSIONS

The steps are as follows: 1) identification of a specific disease, including appropriate genetic definition; 2) identification of clinically relevant outcomes to evaluate efficacy; 3) establishment of the inherent variability of measurements of clinically relevant outcomes; 4) calculation of the sample size required to assess the efficacy of a new treatment with acceptable statistical power; and 5) estimation of the difficulty of recruiting an adequate sample size given the estimated prevalence or incidence of the disorder in the population and the inclusion criteria to be used.

Outcomes of patients treated through the Canadian Fabry disease initiative

BACKGROUND

The Canadian Fabry disease initiative (CFDI) tracks outcomes of subjects with Fabry disease treated enzyme replacement therapy (ERT) given to subjects who meet evidence-based treatment guidelines and cardiovascular risk factor modification.

METHODS

We report 5 year follow-up data on 362 subjects for a composite endpoint (death, neurologic or cardiovascular events, development of end-stage renal disease or sustained increase in serum creatinine of 50% from baseline).

RESULTS

At enrollment, 86 subjects had previously received ERT (Cohort 1a) and 67 subjects were newly started (Cohort 1b) and randomized to agalsidase alfa or agalsidase beta. 209 subjects did not initially meet ERT criteria (Cohort 1c), 25 of whom met ERT criteria in follow-up and were moved to Cohort 1b (total N=178 ERT treated subjects). Use of supportive therapies such as aspirin (78%), renin-angiotensin blockade (59%), and statins (55%) was common in ERT treated subjects. In Cohort 1a, 32 subjects met the composite endpoint with 8 deaths. In Cohort 1b, 16 subjects met the composite endpoint with 1 death. Cohort 1b had fewer clinical events than Cohort 1a (p=0.039) suggesting that the treatment protocol was effective in targeting subjects at an earlier stage. 19.4% of Cohort 1b subjects on agalsidase alfa and 13.3% on agalsidase beta had a clinical event (p=0.57). 10 Cohort 1c subjects had clinical events, none of which would have been prevented by earlier use of ERT.

CONCLUSIONS

Cardiovascular risk factor modification and targeted use of ERT reduce the risk of adverse outcomes related to Fabry disease.

Vascular tortuosities of the upper eyelid: a new clinical finding in fabry patient screening

Purpose. To report a new clinical finding related to Fabry disease. Methods. Fabry subjects were enrolled in the study, matched for age and sex with healthy individuals as a control group. This is a prospective review of all upper lid pictures taken for every subject at their last visit. A 4-step grading scale is proposed to classify this new entity. Results. Group A (Fabry) comprised 16 males and 22 females, aged 40 (±14) years on average. Group B (control) comprised 7 males and 8 females, aged 37 (±12) Vessels tortuosity was identified on the external superior lid in 36 of the Fabry patients (94.7%), while none of the subjects in group B showed similar vessels tortuosity. In addition, microaneurysms (MAs) were found in 10/38 group A subjects while none in group B presented a similar finding. The differences are highly significant. Conclusion. This paper proposes that blood vessels tortuosity on the upper eyelid be recognized as a new clinical entity for inclusion among the classic ocular manifestations of Fabry's disease. Without evidence of any negative impact, it should be considered a benign sign contributing to evidence of suspected Fabry disease.

Canadian policy makers' views on pharmaceutical reimbursement contracts involving confidential discounts from drug manufacturers

Pharmaceutical policy makers are increasingly negotiating reimbursement contracts that include confidential price terms that may be affected by drug utilization volumes, patterns, or outcomes. Though such contracts may offer a variety of benefits, including the ability to tie payment to the actual performance of a product, they may also create potential policy challenges. Through telephone interviews about this type of contract, we studied the views of officials in nine of ten Canadian provinces. Use of reimbursement contracts involving confidential discounts is new in Canada and ideas about power and equity emerged as cross-cutting themes in our interviews. Though confidential rebates can lower prices and thereby increase coverage of new medicines, several policy makers felt they had little power in the decision to negotiate rebates. Study participants explained that the recent rise in the use of rebates had been driven by manufacturers' pricing tactics and precedent set by other jurisdictions. Several policy makers expressed concerns that confidential rebates could result in inter-jurisdictional inequities in drug pricing and coverage. Policy makers also noted un-insured and under-insured patients must pay inflated "list prices" even if rebates are negotiated by drug plans. The establishment of policies for disciplined negotiations, inter-jurisdictional cooperation, and provision of drug coverage for all citizens are potential solutions to the challenges created by this new pharmaceutical pricing paradigm.

Long term enzyme replacement therapy for Fabry disease: effectiveness on kidney, heart and brain

Background

Fabry disease is an X-linked lysosomal storage disorder caused by α-galactosidase A deficiency leading to renal, cardiac, cerebrovascular disease and premature death. Treatment with α-galactosidase A (enzyme replacement therapy, ERT) stabilises disease in some patients, but long term effectiveness is unclear.

Methods

Renal, cardiac, and cerebral outcomes were prospectively studied in males and females with Fabry disease treated with ERT. Additionally, the occurrence of major cardiac events, stroke, end-stage renal disease and death was compared to a natural history (NH) cohort meeting treatment criteria.

Results

Of 75 patients on ERT (median treatment duration 5.2 years, range 0.05-11.0), prospective follow-up was available for 57 adult patients (30 males) and 6 adolescents. Renal function declined in males (-3.4 ml/min/1.73 m² per year, SE 0.2; p < 0.001) despite ERT, but followed the normal course in females (-0.8 ml/min/1.73 m² per year, SE 0.3; p = 0.001). Cardiac mass increased during ERT in males (+ 1.2 gram/m^2.7, SE 0.3; p < 0.001), but remained stable in females (-0.3 gram/m^2.7 per year, SE 0.4; p = 0.52). ERT did not prevent the occurrence of cerebral white matter lesions. Comparison of ERT treated to untreated patients revealed that the odds to develop a first complication increased with age (OR 1.05 (95% CI: 1.0-1.1) per year, p = 0.012). For development of a first or second complication the odds declined with longer treatment duration (OR 0.81 (95% CI: 0.68-0.96) per year of ERT, p = 0.015;OR 0.52 (0.31-0.88), p = 0.014 respectively).

Conclusions

Long term ERT does not prevent disease progression, but the risk of developing a first or second complication declines with increasing treatment duration. ERT in advanced Fabry disease seems of doubtful benefit.

Cost-effectiveness of enzyme replacement therapy for Fabry disease

Background

The cost-effectiveness of enzyme replacement therapy (ERT) compared to standard medical care was evaluated in the Dutch cohort of patients with Fabry disease.

Methods

Cost-effectiveness analysis was performed using a life-time state-transition model. Transition probabilities, effectiveness data and costs were derived from retrospective data and prospective follow-up of the Dutch study cohort consisting of males and females aged 5–78 years. Intervention with ERT (either agalsidase alfa or agalsidase beta) was compared to the standard medical care. The main outcome measures were years without end organ damage (renal, cardiac en cerebrovascular complications), quality adjusted life years (QALYs), and costs.

Results

Over a 70 year lifetime, an untreated Fabry patient will generate 55.0 years free of end-organ damage (53.5 years in males, 56.9 years in females) and 48.6 QALYs (47.8 in males, 49.7 in females). Starting ERT in a symptomatic patient increases the number of years free of end-organ damage by 1.5 year (1.6 in males, 1.3 in females), while the number of QALYs gained increases by a similar amount (1.7 in males, 1.4 in females). The costs of ERT starting in the symptomatic stage are between €9 - €10 million (£ 7.9 - £ 8.8 million, $13.0- $14.5 million) during a patient’s lifetime. Consequently, the extra costs per additional year free of end-organ damage and the extra costs per additional QALY range from €5.5 - €7.5 million (£ 4.8 – £ 6.6 million, $ 8.0 – $ 10.8 million), undiscounted.

Conclusions

In symptomatic patients with Fabry disease, ERT has limited effect on quality of life and progression to end organ damage. The pharmaco-economic evaluation shows that this modest effectiveness drives the costs per QALY and the costs per year free of end-organ damage to millions of euros. Differentiation of patients who may benefit from ERT should be improved to enhance cost-effectiveness.

Enzyme replacement therapy in patients with Fabry disease: state of the art and review of the literature

Anderson-Fabry disease is an X-linked lysosomal storage disorder resulting from the deficiency of the hydrolytic enzyme alpha galactosidase A, with consequent accumulation of globotrioasoyl ceramide in cells and tissues of the body, resulting in a multi-system pathology including end organ failure. In the classical phenotype, cardiac failure, renal failure and stroke result in a reduced median life expectancy. The current causal treatment for Fabry disease is the enzyme replacement therapy (ERT): two different products, Replagal (agalsidase alfa) and Fabrazyme (agalsidase beta), have been commercially available in Europe for almost 10 years and they are both indicated for long-term treatment. In fact, clinical trials, observational studies and registry data have provided many evidences for safety and efficacy of ERT in improving symptoms of pain, gastrointestinal disturbances, hypohidrosis, left ventricular mass index, glomerular filtration rate and quality of life. Few data are available on comparison of the two treatments and on the clinical course of the disease. This article reviews the published evidence for clinical efficacy of the two available enzyme preparations.

Recommendations on reintroduction of agalsidase Beta for patients with fabry disease in europe, following a period of shortage

The interruption of the manufacturing process of agalsidase beta has led to a worldwide shortage of this drug. In the EU, nearly all patients initially reduced their agalsidase beta dose, and many of these switched to agalsidase alfa (Replagal Shire HGT). The clinical consequences of this period of drug shortage need to be further evaluated. A gradual increase of agalsidase beta supply is now expected. This implies that patients could resume or even commence agalsidase beta treatment. Guidance for prioritization of patients is needed to support equitable distribution of agalsidase beta to EU member states. To achieve this, in absence of level I clinical evidence, a draft consensus proposal was initiated and distributed. No full consensus was achieved, as there is disagreement regarding the indications for switching patients from agalsidase alfa to agalsidase beta. Some physicians support the concept that the 1.0 mg/kg EOW dose of agalsidase beta is more effective than agalsidase alfa at 0.2 mg/kg EOW, while others believe that at recommended dose, the preparations are equivalent. In light of these difficulties and the uncertainties with respect to supply of agalsidase beta, recommendations were agreed upon by a subgroup of physicians. These current recommendations focus on prioritization of criteria indicative of disease progression.

Qualitative Evaluation of the Canadian Fabry Disease Initiative

Background:

In late 2005, the federal and provincial governments responded to an increasing demand from physicians and their patients with Fabry disease for access to enzyme replacement therapy (ERT). This response took the form of a nationwide clinical research study, the Canadian Fabry Disease Initiative (CFDI). Patients who enrolled as participants in this longitudinal study received 1 of 2 ERT treatments. The present study used a qualitative evaluative approach to describe the perspectives of various key stakeholders regarding the CFDI and its potential as a model for providing access to expensive drugs for rare diseases.

Methods:

The CFDI was evaluated from the perspectives of 4 groups of key informants: patients, CFDI investigators, policy-makers and pharmaceutical manufacturers. The qualitative methods strategy used for the study involved semistructured interviews, a holistic-inductive design and content analysis.

Results:

Eighteen participants were interviewed. The study revealed that stakeholders held the following perceptions about the CFDI. The CFDI was created as a response to a drug reimbursement problem in Canada. Through specialist physicians, the CFDI has provided ERT to patients with Fabry disease across the country. The CFDI established a national database for collecting and monitoring the incidence of Fabry disease and information about ERT. The CFDI represented a collaborative effort among the various stakeholders (federal, provincial, pharmaceutical), but no stakeholder group thought that the CFDI was the correct response to the need for access to ERT. Finally, the CFDI can and should be redesigned, through modification of either its governing structure or its outcome goals.

Discussion:

The CFDI was a prototype for sharing the costs of expensive therapies for rare diseases. It has provided ERT to many patients with Fabry disease for several years. However, it was poorly designed to meet its outcome goals and has been unable to provide therapy to all individuals with the disease. Therefore, many stakeholders saw this initiative as an inappropriate solution.

Conclusions:

The CFDI has not met the expectations of key informant groups and some modifications may be necessary. A registry study might better accomplish the CFDI's original goals of providing access to treatment, gathering data and monitoring patients' progress.

Diagnostic dilemma: a young woman with Fabry disease symptoms, no family history, and a "sequencing cryptic" α-galactosidase a large deletion

Fabry disease, an X-linked lysosomal storage disorder, results from the deficient activity of α-galactosidase A (α-Gal A). In affected males, the clinical diagnosis is confirmed by the markedly decreased α-Gal A activity. However, in female heterozygotes, the α-Gal A activity can range from low to normal due to random X-chromosomal inactivation, and diagnostic confirmation requires identification of the family's α-Gal A gene mutation. In a young female who had occasional acroparesthesias, corneal opacities, and 15 to 50% of the lower limit of normal leukocyte α-Gal A activity, α-Gal A sequencing in two expert laboratories did not identify a confirmatory mutation, presenting a diagnostic dilemma. A renal biopsy proved diagnostic and renewed efforts to detect an α-Gal A mutation. Subsequent gene dosage analyses identified a large α-Gal A deletion confirming her heterozygosity, and she was started on enzyme replacement therapy. Thus, gene dosage analyses can detect large deletions (>50bp) in suspect heterozygotes for X-linked and autosomal dominant diseases that are "sequencing cryptic," resolving molecular diagnostic dilemmas.

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

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

Detection of large gene rearrangements in X-linked genes by dosage analysis: identification of novel α-galactosidase A (GLA) deletions causing Fabry disease

For most Mendelian disorders, targeted genome sequencing is an effective method to detect causative mutations. However, sequencing PCR-amplified exonic regions and their intronic boundaries can miss large deletions or duplications and mutations that lead to PCR failures in autosomal dominant disorders and in heterozygote detection for X-linked diseases. Here, a method is described for detecting large (>50 bp) deletions/duplications in the X-linked α-galactosidase A (GLA) gene, which cause Fabry disease. Briefly, multiplex PCR mixtures were designed to amplify each GLA exon and an unrelated internal control exon to normalize GLA exonic amplicon peak heights. For each normalized GLA amplicon, the normal control female to male peak-height ratios were 1.8 to 2.2 (expected 2.0), whereas the expected ratios for deletions or duplications would be ∼1.0 or 3.0, respectively. Using this method, three novel deletions, c.369+3_547+954del4096insT, c.194+2049_369+773del2619insCG, and c.207_369+651del814ins231, were detected in unrelated women with signs and/or symptoms suggestive of Fabry disease, but no "sequencing-detectable" mutations. The deletions were confirmed by sequencing their respective GLA RT-PCR products. This method can identify gene rearrangements that may be cryptic to genomic DNA sequencing and can be readily adapted to other X-linked or autosomal dominant genes.

Update on role of agalsidase alfa in management of Fabry disease

Fabry disease (FD) is an X-linked lysosomal storage disorder that affects both men and women. The manifestations of this heterogeneous disease are multisystemic and progressive. Prior to the development of enzyme replacement therapy, the management and treatment for Fabry disease was largely nonspecific and supportive. Because enzyme replacement therapy became commercially available in 2001, a variety of clinical benefits in Fabry patients have been consistently reported, including improved renal pathology and cardiac function, and reduced severity of neuropathic pain and improved pain-related quality of life. This update focuses on published data on the efficacy and tolerability of enzyme replacement therapy with agalsidase alfa, and gives a brief overview on some of the outstanding management issues in the treatment of this complex disease.

Enzyme replacement therapy for Fabry disease: some answers but more questions

Fabry disease (FD) is a multisystem, X-linked disorder of glycosphingolipid metabolism caused by enzyme deficiency of α-galactosidase A. Affected patients have symptoms including acroparesthesias, angiokeratomas, and hypohidrosis. More serious manifestations include debilitating pain and gastrointestinal symptoms, proteinuria and gradual deterioration of renal function leading to end-stage renal disease, hypertrophic cardiomyopathy, and stroke. Heterozygous females may have symptoms as severe as males with the classic phenotype. Before 2001, treatment of patients with FD was supportive. The successful development of enzyme replacement therapy (ERT) has been a great advancement in the treatment of patients with FD and can stabilize renal function and cardiac size, as well as improve pain and quality of life of patients with FD. In this review, we have provided a critical appraisal of the literature on the effects of ERT for FD. This analysis shows that data available on the treatment of FD are often derived from studies which are not controlled, rely on surrogate markers, and are of insufficient power to detect differences on hard clinical endpoints. Further studies of higher quality are needed to answer the questions that remain concerning the efficacy of ERT for FD.

Effects of enzyme replacement therapy in Fabry disease--a comprehensive review of the medical literature

Enzyme replacement therapy with α-galactosidase A has been used to treat Fabry disease since 2001. This article reviews the published evidence for clinical efficacy of the two available enzyme preparations. We focused on heart, kidney, and nervous system manifestations, which impact both quality of life and overall prognosis. A literature search was undertaken to identify prospective open or randomized controlled trials of enzyme replacement therapy in patients with Fabry disease published since 2001. To date, no definitive conclusion can be drawn from studies that have directly compared therapeutic responses between the two commercially available enzyme preparations. Significant clinical benefits of enzyme replacement therapy have been demonstrated, mainly in patients at an early phase of the disease, with beneficial effects on heart, kidneys, pain, and quality of life in treated patients. Incidence of antibodies against agalsidase alfa and agalsidase beta observed during major clinical studies suggests a greater antigenic response to agalsidase beta. Further studies are required to confirm the long-term clinical benefits of enzyme replacement therapy. More studies with female patients are needed as are investigations of early initiation of enzyme replacement therapy to determine the optimal time to start treatment to prevent irreversible organ damage. The value of adjunctive and supportive therapies should also be rigorously analyzed.

Fabry disease

Fabry disease (FD) is a progressive, X-linked inherited disorder of glycosphingolipid metabolism due to deficient or absent lysosomal α-galactosidase A activity. FD is pan-ethnic and the reported annual incidence of 1 in 100,000 may underestimate the true prevalence of the disease. Classically affected hemizygous males, with no residual α-galactosidase A activity may display all the characteristic neurological (pain), cutaneous (angiokeratoma), renal (proteinuria, kidney failure), cardiovascular (cardiomyopathy, arrhythmia), cochleo-vestibular and cerebrovascular (transient ischemic attacks, strokes) signs of the disease while heterozygous females have symptoms ranging from very mild to severe. Deficient activity of lysosomal α-galactosidase A results in progressive accumulation of globotriaosylceramide within lysosomes, believed to trigger a cascade of cellular events. Demonstration of marked α-galactosidase A deficiency is the definitive method for the diagnosis of hemizygous males. Enzyme analysis may occasionnally help to detect heterozygotes but is often inconclusive due to random X-chromosomal inactivation so that molecular testing (genotyping) of females is mandatory. In childhood, other possible causes of pain such as rheumatoid arthritis and 'growing pains' must be ruled out. In adulthood, multiple sclerosis is sometimes considered. Prenatal diagnosis, available by determination of enzyme activity or DNA testing in chorionic villi or cultured amniotic cells is, for ethical reasons, only considered in male fetuses. Pre-implantation diagnosis is possible. The existence of atypical variants and the availability of a specific therapy singularly complicate genetic counseling. A disease-specific therapeutic option - enzyme replacement therapy using recombinant human α-galactosidase A - has been recently introduced and its long term outcome is currently still being investigated. Conventional management consists of pain relief with analgesic drugs, nephroprotection (angiotensin converting enzyme inhibitors and angiotensin receptors blockers) and antiarrhythmic agents, whereas dialysis or renal transplantation are available for patients experiencing end-stage renal failure. With age, progressive damage to vital organ systems develops and at some point, organs may start to fail in functioning. End-stage renal disease and life-threatening cardiovascular or cerebrovascular complications limit life-expectancy of untreated males and females with reductions of 20 and 10 years, respectively, as compared to the general population. While there is increasing evidence that long-term enzyme therapy can halt disease progression, the importance of adjunctive therapies should be emphasized and the possibility of developing an oral therapy drives research forward into active site specific chaperones.

Agalsidase alfa for enzyme-replacement therapy in Fabry disease

Fabry disease is an X-linked lysosomal storage disorder that is caused by a deficiency in the enzyme α-galactosidase A. Manifestations emerge during childhood, including neuropathic pain, hypohidrosis and gastrointestinal problems. Major organ involvement typically occurs during adulthood and includes progressive kidney dysfunction, cardiomyopathy and valve disease, and stroke. Enzyme-replacement therapy with agalsidase alfa has been available since 2001 and is associated with clinical benefit in adult men and women, as well as in children, with Fabry disease. The responses to agalsidase alfa include reduction in the severity of neuropathic pain, stabilization of kidney function and reduction in left ventricular mass in patients with baseline left ventricular hypertrophy. Several issues, including when to initiate treatment and whether long-term treatment will extend survival, remain to be answered. This article covers the clinical development of agalsidase alfa and the postmarketing reports of its safety and effectiveness.