Fabry disease in a large Nova Scotia kindred: carrier detection using leucocyte alpha-galactosidase activity and an NcoI polymorphism detected by an alpha-galactosidase cDNA clone

The Safety of Agalsidase Alfa Enzyme Replacement Therapy in Canadian Patients with Fabry Disease Following Implementation of a Bioreactor Process

Background and Objective

Fabry disease, an X-linked lysosomal storage disorder characterized by absent or reduced alpha-galactosidase activity, is a lifelong disease that impairs patients’ quality of life. Patients with Fabry disease have a considerably shortened lifespan, with mortality being mainly due to renal failure, cardiovascular disease, or cerebrovascular disease. Enzyme replacement therapy with agalsidase alfa has been shown to attenuate the renal, cardiovascular, and neuropathic disease progression associated with Fabry disease. The objective of this study was to investigate the safety of a new animal component-free version of agalsidase alfa.

Methods

A phase III/IV, open-label, single-arm, multicenter safety study was conducted in Canadian patients with Fabry disease between August 2011 and September 2017 as a regulatory requirement to assess the safety of agalsidase alfa produced using an animal component-free bioreactor process. Eligible patients had a documented diagnosis of Fabry disease and satisfied current Canadian guidelines for receiving enzyme replacement therapy for Fabry disease. Following treatment with animal component-free bioreactor-processed agalsidase alfa, treatment-emergent adverse events were monitored, and post hoc analyses of infusion-related reactions by antidrug antibody and neutralizing antibody statuses were conducted. The data were analyzed using descriptive statistics.

Results

A total of 167 patients (mean [standard deviation] age, 48.9 [14.8] years), including six pediatric patients (< 18 years of age), received at least one full or partial infusion of agalsidase alfa animal component-free. Fewer than 5% of treatment-emergent adverse events (212/4446) observed in 40 patients were reported as infusion-related reactions. Antidrug antibody and neutralizing antibody status did not affect the proportion of patients with infusion-related reactions. No clinically significant changes in vital signs were observed in patients over the course of the study.

Conclusions

Long-term treatment with bioreactor-produced agalsidase alfa animal component-free did not reveal new safety signals in this population of Canadian patients with Fabry disease. The treatment-emergent adverse event profile was consistent with the clinical manifestations of the disease and the known safety profile of roller bottle-produced agalsidase alfa.

Clinical Trial Registration

ClinicalTrials.gov identifier NCT01298141.

Gene therapy for Fabry disease: Progress, challenges, and outlooks on gene-editing

Gene therapy is the delivery of a therapeutic gene for endogenous cellular expression with the goal of rescuing a disease phenotype. It has been used to treat an increasing number of human diseases with many strategies proving safe and efficacious in clinical trials. Gene delivery may be viral or non-viral, performed in vivo or ex vivo, and relies on gene integration or transient expression; all of these techniques have been applied to the treatment of Fabry disease. Fabry disease is a genetic disorder of the α-galactosidase A gene, GLA, that causes an accumulation of glycosphingolipids in cells leading to cardiac, renal and cerebrovascular damage and eventually death. Currently, there are no curative treatments available, and the therapies that are used have significant drawbacks. These treatment concerns have led to the advent of gene therapies for Fabry disease. The first Fabry patients to receive gene therapy were treated with recombinant lentivirus targeting their hematopoietic stem/progenitor cells. Adeno-associated virus treatments have also begun. Alternatively, the field of gene-editing is a new and rapidly growing field. Gene-editing has been used to repair disease-causing mutations or insert genes into cellular DNA. These techniques have the potential to be applied to the treatment of Fabry disease provided the concerns of gene-editing technology, such as safety and efficiency, were addressed. This review focuses on the current state of gene therapy as it is being developed for Fabry disease, including progresses and challenges as well as an overview of gene-editing and how it may be applied to correct Fabry disease-causing mutations in the future.

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.

Cardiomyopathies and Genetic Testing in Heart Failure: Role in Defining Phenotype-Targeted Approaches and Management

Cardiomyopathies represent an important cause of heart failure, often affecting young individuals, and have important implications for relatives. Genetic testing for cardiomyopathies is an established care pathway in contemporary cardiology practice. The primary cardiomyopathies where genetic testing is indicated are hypertrophic, dilated, arrhythmogenic, and restrictive cardiomyopathies, with left ventricular noncompaction as a variant phenotype. Early identification and initiation of therapies in patients with inherited cardiomyopathies allow for targeting asymptomatic and presymptomatic patients in stages A and B of the American College of Cardiology/American Heart Association classification of heart failure. The current approach for genetic testing uses gene panel-based testing with the ability to extend to whole-exome and whole-genome sequencing in rare instances. The central components of genetic testing include defining the genetic basis of the diagnosis, providing prognostic information, and the ability to screen and risk-stratify relatives. Genetic testing for cardiomyopathies should be coordinated by a multidisciplinary team including adult and pediatric cardiologists, genetic counsellors, and geneticists, with access to expertise in cardiac imaging and electrophysiology. A pragmatic approach for addressing genetic variants of uncertain significance is important. In this review, we highlight the indications for genetic testing in the various cardiomyopathies, the value of early diagnosis and treatment, family screening, and the care process involved in genetic counselling and testing.

Retinal Vein Occlusion in a Woman with Heterozygous Fabry's Disease

Fabry's disease is associated with high incidence of thrombosis in hemizygous males and heterozygous females. We describe a woman with Fabry's disease who developed hemi-central retinal vein occlusion during the follow-up. The vein occlusion showed a fulminant course ending with a painful blind eye within a short period. Fabry's disease should be considered in the differential diagnosis of the vascular occlusive disorders especially in young patients.

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.

Treatment perspectives for the lysosomal storage diseases

BACKGROUND

The therapy of the lysosomal storage diseases (LSDs) was developed by supplying adequate amounts of the needed enzyme to affected individuals. This approach in Gaucher disease provided a prototype for the basic and clinical sciences, and the economic foundation for other ultra-orphan diseases.

OBJECTIVE

Using the success of enzyme therapy for Gaucher disease, the challenges are highlighted for alternative bioproduction systems, and substrate reduction and molecular chaperone approaches for treatment of Gaucher disease and other ultra-orphan diseases.

METHODS

Literature review provided insight into the current status of enzyme therapies for LSDs, the proposed mechanisms of alternative approaches to therapy, and the obstacles in a competitive marketplace for treatment of ultra-rare diseases.

RESULTS/CONCLUSIONS

These developments are placed in the contexts of finding rare patients with LSDs, their marked phenotypic spectrum, potential markets, and new orphan drug costs. The confluence of these challenges has led to a competitive environment with the potential for multiple, alternative, expensive treatments for orphan diseases.

Psychiatric findings in four female carriers of Fabry disease

Anderson-Fabry disease (AFD) is an X-linked recessive disorder of glycosphingolipid metabolism. Most female carriers are clinically symptomatic; however, psychiatric diagnoses have not been reported in this population. We describe four female carriers of AFD disease who met DSM-IV criteria for major depression. All cases had a score above 26 on the Hamilton Rating Scale for Depression, indicating severe depression. This was independent of the severity or number of symptoms of AFD disease. Excessive guilt, fatigue, occupational difficulty, suicidal ideation and depressed mood were findings in all cases. In conclusion, the common presence of depression in carriers of AFD implies the need for a multidisciplinary approach, including psychiatry, in management of these patients. Further studies are recommended to establish the etiology of psychiatric complications, as well as the incidence and the response to pharmacotherapy and psychotherapy.

Membrane anchoring and surface distribution of glycohydrolases of human erythrocyte membranes

The membrane anchoring of the following glycohydrolases of human erythrocyte plasma membranes was investigated: alpha- and beta-D-glucosidase, alpha- and beta-D-galactosidase, beta-D-glucuronidase, N-acetyl-beta-D-glucosaminidase, alpha-D-mannosidase, and alpha-L-fucosidase. Optimized fluorimetric methods for the assay of these enzymes were set up. Treatment of the ghost preparation with 1.0 mol/l (optimal concentration) NaCl caused release ranging from 4.2% of alpha-D-glucosidase to 70% of beta-D-galactosidase; treatment with 0.4% (optimal concentration) Triton X-100 liberated 5.1% of beta-D-galactosidase to 89% of alpha-D-glucosidase; treatment with 1.75% (optimal concentration) octylglucoside yielded solubilization from 6.3% of beta-D-galactosidase to 85% of alpha-D-glucosidase. Treatment with phosphoinositide-specific phospholipase C caused no liberation of any of the studied glycohydrolases. These results are consistent with the notion that the above glycohydrolases are differently anchored or associated with the erythrocyte plasma membrane, and provide the methodological basis for inspecting the occurrence of these enzymes in different membrane microdomains.

Linkage disequilibrium mapping of the Nova Scotia variant of Niemann-Pick disease

Niemann-Pick type D (NPD) disease is a severe degenerative disorder of the nervous system characterized by the accumulation of tissue cholesterol and sphingomyelin. Because of a founder effect, it is unusually common in southwestern Nova Scotia, Canada. We have confirmed that almost all patients from 20 affected sibships descended on both sides from a small group of Acadians who settled in this region in about the year 1767. Previously using classic linkage analysis of this large kindred, we defined the critical gene region to a 13-cM chromosome segment between D18S869 and D18S66. Seven ESTs have been positioned within this interval. Carstea et al. (Niemann Pick C disease gene: homology to mediators of cholesterol homeostasis. Science 1997: 277: 232-235) recently demonstrated that one of these ESTs is the Niemann-Pick type C (NPCI) gene, the gene disrupted in most patients with NPC disease, and we have shown that a G3097-->T mutation in the NPC1 gene is also responsible for NPD. Here we report the development of five new polymorphic microsatellite markers and the testing for complete linkage disequilibrium in our single large NPD kindred that allowed us to reduce the NPD critical region to a 1-cM (1.3-1.6 Mb) interval between D18S1398 and D18S1108. In contrast, Carstea et al., using classic linkage analysis, required more than 18 unrelated NPC families to reduce the NPC1 critical region to a 5-cM interval. Our work supports the finding that NPD is an allelic variant of NPC1, and illustrates the power of large kindreds, which are common in Atlantic Canada and other relatively isolated areas, for gene mapping and identification.

Detection of a R173W mutation in the porphobilinogen deaminase gene in the Nova Scotian "foreign Protestant" population with acute intermittent porphyria: a founder effect

OBJECTIVES

Acute intermittent porphyria (AIP) is caused by mutations in the porphobilinogen deaminase (PBGD) gene that disrupt the function of the enzyme. Many mutations that lead to decreased PBGD activity have been described. An Arg to Trp substitution at codon 173 (CGG-->TGG in exon 10) and designated R173W, which leads to a CRIM-negative phenotype, has been reported in Swedish, Finnish, Scottish, and South African kindreds, and in a Nova Scotian proband with fatal AIP. In this work, we investigated the presence of this mutation in a Nova Scotian patient population presenting with AIP.

DESIGN AND METHODS

Single-strand conformation polymorphism analysis and DNA sequencing by TA cloning and Sanger's dideoxy chain termination method, were used to confirm the maternal transmission of this mutation to the proband. The mutation also eliminates an Ncil (also Mspl) endonuclease restriction site, which allows for detection of the mutant allele by polymerase chain reaction amplification and restriction enzyme digestion.

RESULTS

The family of the Nova Scotian proband and four other AIP kindreds showed the presence of the same mutation. These five families are descendants of German, Swiss, and French immigrants historically known as the "Foreign Protestants," who were recruited to Nova Scotia in the 1750s.

CONCLUSION

In all these families, descent from one couple that settled in Nova Scotia in 1751 has been identified by genealogy research, consistent with a founder effect within this population. This is the first identified mutation in PBGD causing AIP that has been linked to a founder effect in descendants of an immigrant population to North America, and which could be traced to such a distant background, similar to the South African variegate porphyria mutation.

Metachromatic leucodystrophy in three families from Nova Scotia, Canada: a recurring mutation in the arylsulphatase A gene

Metachromatic leucodystrophy (MLD) is a lysosomal storage disease resulting from a deficiency of arylsulphatase A. We have identified a child with infantile onset MLD who is homozygous for an A212V mutation, a mutation previously reported but not further characterised. We have introduced this mutation into an arylsulphatase A expression vector by site directed mutagenesis. Transient expression of this mutant plasmid in COS cells yields very low levels of arylsulphatase A activity consistent with the patient's phenotype. The arylsulphatase A pseudodeficiency also segregates in this family causing difficulty in interpreting enzyme levels in the absence of DNA data. Two other patients from the same province, also carrying the A212V allele, have juvenile and adult onset MLD and are heterozygous for P426L ("A" allele) and I179S alleles respectively, known late onset alleles.

Molecular basis of Fabry disease: mutations and polymorphisms in the human alpha-galactosidase A gene

Fabry disease, an X-linked inborn error of glycosphingolipid catabolism, results from mutations in the alpha-galactosidase A gene at Xq22.1. Studies of the mutations in unrelated Fabry families have identified a variety of lesions indicating the molecular genetic heterogeneity underlying the disease. Forty-nine different mutations have been described including five partial gene deletions, one partial gene duplication, nine small deletions and insertions, three splice junction consensus site alterations, and 31 coding region single base substitutions. Most mutations resulted in the classical disease phenotype; however, five missense mutations were detected in atypical hemizygotes who were asymptomatic or had symptoms confined to the heart, including N215S, which was described in three unrelated atypical males. Most mutations were confined to a single pedigree with the exception of N215S, R227Q, R227X, R342Q, and R342X, which were each found in several unrelated families. Five of the 14 coding region CpG dinucleotides were sites of point mutations including the CpGs in codons 227 and 342, which were each mutated in both orientations. The identification of the mutation in a given Fabry family permits precise prenatal diagnosis and heterozygote detection of other family members with this X-linked recessive disease. Studies of additional Fabry families will provide information on the nature and frequency of the mutations causing this disease as well as potential insights into the structure/function relationships of this lysosomal hydrolase.

Sequence variations in the first exon of alpha-galactosidase A

The alpha-galactosidase A gene (GALA), which is deficient in males with Anderson-Fabry disease, is shown to be remarkably polymorphic in the 5' untranslated region. GALA contains seven exons. The first exon contains 60 bp of 5' untranslated sequence before the methionine initiation codon. Single strand conformation polymorphism (SSCP) screening has shown three polymorphic variants from the published sequence within the 60 base pairs. The sequence changes involved are C to T at -10, G to A at -12 (which removes an MspI site), and G to A at -30 (which removes a SacII site). The combined frequency of these is 10%. A further insertion-deletion polymorphism is detected by SSCP of a 400 bp fragment including exon 3. Both polymorphisms can be easily detected using small polyacrylamide gels and ethidium bromide staining. Nine of 20 women were informative for one of these polymorphisms and this simple SSCP analysis should be of great assistance in family studies of Anderson-Fabry disease. Such a high level of polymorphism has not been previously reported in the 5' untranslated region of a human gene and is unusual in any such short stretch of DNA.