Profile of eliglustat tartrate in the management of Gaucher disease

Lysosomal Dysfunction: Connecting the Dots in the Landscape of Human Diseases

Lysosomes are the main organelles responsible for the degradation of macromolecules in eukaryotic cells. Beyond their fundamental role in degradation, lysosomes are involved in different physiological processes such as autophagy, nutrient sensing, and intracellular signaling. In some circumstances, lysosomal abnormalities underlie several human pathologies with different etiologies known as known as lysosomal storage disorders (LSDs). These disorders can result from deficiencies in primary lysosomal enzymes, dysfunction of lysosomal enzyme activators, alterations in modifiers that impact lysosomal function, or changes in membrane-associated proteins, among other factors. The clinical phenotype observed in affected patients hinges on the type and location of the accumulating substrate, influenced by genetic mutations and residual enzyme activity. In this context, the scientific community is dedicated to exploring potential therapeutic approaches, striving not only to extend lifespan but also to enhance the overall quality of life for individuals afflicted with LSDs. This review provides insights into lysosomal dysfunction from a molecular perspective, particularly in the context of human diseases, and highlights recent advancements and breakthroughs in this field.

Massive Splenomegaly with Pancytopenia in an Adult: Gaucher's Disease

INTRODUCTION

Gaucher's disease (GD) is a rare lysosomal storage disease. It is characterized by the deposition of glucocerebroside in cells of the macrophage-monocyte system. GD presents a broad clinical expression, including hematologic abnormalities (such as pancytopenia), massive hepatosplenomegaly, diffuse infiltrative pulmonary disease, renal involvement in the form of nephropathy and glomerulonephritis, skeletal involvement in the form of bone pain, bony infarct, osteopenia, and pathological fracture. Based on the presence or absence of neurologic involvement, it is differentiated into type 1, type 2, and type 3. Gaucher's disease type 1 is the most common form, having the nonneuropathic form and carrying autosomal recessive traits. Gaucher's disease affects all racial and ethnic groups, while type 1 GD is most prevalent among Ashkenazi Jews.

CASE PRESENTATION

A 20-year-old female was admitted to the medicine department with complaints of generalized weakness and easy fatigability, menorrhagia, and a dragging sensation in the abdomen. On clinical evaluation, she had bone marrow failure syndrome features along with massive splenomegaly. Later, she was confirmed with Gaucher disease type 1 disease by clinical and investigation (low β-glucosidase level) evaluation.

CONCLUSION

This case emphasizes keeping a differential diagnosis of glycogen storage disorder while evaluating a case of unexplained pancytopenia with massive splenomegaly in adulthood for an extended period. Currently, enzyme replacement therapy and substrate reduction therapy are the mainstay therapeutic options for GD.

Assessment of Target Engagement in a First-in-Human Trial with Sinbaglustat, an Iminosugar to Treat Lysosomal Storage Disorders

In this first-in-human study, the tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of single and multiple oral doses of sinbaglustat, a dual inhibitor of glucosylceramide synthase (GCS) and non-lysosomal glucosyl ceramidase (GBA2), were investigated in healthy subjects. The single-ascending dose (SAD) and multiple-ascending dose (MAD) studies were randomized, double-blind, and placebo-controlled. Single doses from 10 to 2,000 mg in men and multiple doses from 30 to 1,000 mg twice daily for 7 days in male and female subjects were investigated. Tolerability, PK, and PD data were collected up to 3 days after (last) treatment administration and analyzed descriptively. Sinbaglustat was well-tolerated in the SAD and MAD studies, however, at the highest dose of the MAD, three of the four female subjects presented a similar pattern of general symptoms. In all cohorts, sinbaglustat was rapidly absorbed. Thereafter, plasma concentrations decreased biphasically. In the MAD study, steady-state conditions were reached on Day 2 without accumulation. During sinbaglustat treatment, plasma concentrations of glucosylceramide (GlcCer), lactosylceramide, and globotriaosylceramide decreased in a dose-dependent manner, reflecting GCS inhibition. The more complex the glycosphingolipid, the more time was required to elicit PD changes. After treatment stop, GlcCer levels returned to baseline and increased above baseline at lowest doses, probably due to the higher potency of sinbaglustat on GBA2 compared to GCS. Overall, sinbaglustat was welltolerated up to the highest tested doses. The PK profile is compatible with b.i.d. dosing. Sinbaglustat demonstrated target engagement in the periphery for GCS and GBA2.

Therapeutic advances in Fabry disease: The future awaits

Fabry disease (FD) is an X-linked disorder caused by mutations in GLA gene responsible for coding of the lysosomal enzyme alpha-galactosidase A(α-GAL). The resultant accumulation of globotriaosylceramide (Gb-3) leads to multisystemic disease including progressive chronic kidney disease, hypertrophic cardiomyopathy, stroke, angiokeratomas and corneal whorls. Current treatments include enzyme replacement therapy (ERT), along with recent advent of chaperone therapy. ERT has not shown to have dramatic improvement in outcomes for all organ systems, with benefit mostly seen in kidney disease and reduction in left ventricular hypertrophy. ERT, however, is associated with formation of anti-drug antibodies and requirement of long-term venous access, while chaperone therapy can only be used in amenable mutations. A multitude of therapies are now under investigation in various phases of clinical trials. These include pegylated form of α-GAL (pegunigalsidase alpha), gene therapy (both in-vivo and ex-vivo methods), mRNA therapy (inducing production of α-GAL) and substrate reduction therapy (inhibitors of glucosylceramide synthase leading to reduction of Gb-3). This review encapsulates literature pertaining to current and investigational therapies for FD.

White vitreous opacities in five patients with Gaucher disease type 3

Fundal abnormalities, including preretinal and retinal changes, are a rare finding in patients with the autosomal recessive lysosomal storage disorder Gaucher disease, most often described in patients with the chronic neuronopathic form (type 3). We evaluated whether these ophthalmological findings correlated with other manifestations of type 3 Gaucher disease. Reviewing the records of 40 patients with type 3 Gaucher disease, we identified five with white vitreous opacities and reviewed their clinical course in depth. Each of the patients described decreased visual acuity and "floaters" obstructing their vision. The development and/or progression of these fluffy-appearing white opacities in each patient were tracked longitudinally in the context of their neurological and other clinical findings. It was noted that all five patients shared genotype p.L483P/p.L483P (L444P/L444P) and had significant neurological, oculomotor and bone involvement and two had undergone splenectomy. Enzyme replacement therapy with recombinant glucocerebrosidase did not prevent the development or progression of these ocular opacities. Since preretinal findings, in addition to other neuro-ophthalmological findings, can be a feature of Gaucher disease, it is recommended that patients be monitored by regular eye examinations.

Glucosylceramide synthase inhibition with lucerastat lowers globotriaosylceramide and lysosome staining in cultured fibroblasts from Fabry patients with different mutation types

Fabry disease is an X-linked lysosomal storage disorder caused by mutations in the GLA gene coding for α-galactosidase A (α-GalA). The deleterious mutations lead to accumulation of α-GalA substrates, including globotriaosylceramide (Gb3) and globotriaosylsphingosine. Progressive glycolipid storage results in cellular dysfunction, leading to organ damage and clinical disease, i.e. neuropathic pain, impaired renal function and cardiomyopathy. Many Fabry patients are treated by bi-weekly intravenous infusions of replacement enzyme. While the only available oral therapy is an α-GalA chaperone, which is indicated for a limited number of patients with specific 'amenable' mutations. Lucerastat is an orally bioavailable inhibitor of glucosylceramide synthase (GCS) that is in late stage clinical development for Fabry disease. Here we investigated the ability of lucerastat to lower Gb3, globotriaosylsphingosine and lysosomal staining in cultured fibroblasts from 15 different Fabry patients. Patients' cells included 13 different pathogenic variants, with 13 cell lines harboring GLA mutations associated with the classic disease phenotype. Lucerastat dose dependently reduced Gb3 in all cell lines. For 13 cell lines the Gb3 data could be fit to an IC50 curve, giving a median IC50 [interquartile range (IQR)] = 11 μM (8.2-18); the median percent reduction (IQR) in Gb3 was 77% (70-83). Lucerastat treatment also dose dependently reduced LysoTracker Red staining of acidic compartments. Lucerastat's effects in the cell lines were compared to those with current treatments-agalsidase alfa and migalastat. Consequently, the GCS inhibitor lucerastat provides a viable mechanism to reduce Gb3 accumulation and lysosome volume, suitable for all Fabry patients regardless of genotype.

Lucerastat, an Iminosugar for Substrate Reduction Therapy: Tolerability, Pharmacodynamics, and Pharmacokinetics in Patients With Fabry Disease on Enzyme Replacement

Lucerastat is a glucosylceramide synthase inhibitor aimed at reducing production of glycosphingolipids (GSLs), including those accumulating in Fabry disease. The safety, tolerability, pharmacodynamics, and pharmacokinetics of oral lucerastat were evaluated in an exploratory study in patients with Fabry disease. In this single-center, open-label, randomized study, 10 patients received lucerastat 1,000 mg b.i.d. for 12 weeks in addition to enzyme replacement therapy (ERT; the lucerastat group). Four patients with Fabry disease received ERT only. Eight patients reported 17 adverse events (AEs) in the lucerastat group. No clinically relevant safety abnormalities were observed. The mean (SD) levels of the plasma GSLs, glucosylceramide, lactosylceramide, and globotriaosylceramide, were significantly decreased from baseline in the lucerastat group (-49.0% (16.5%), -32.7% (13.0%), and -55.0% (10.4%), respectively). Lucerastat 1,000 mg b.i.d. was well tolerated in patients with Fabry disease over 12 weeks. A marked decrease in plasma GSLs was observed, suggesting clinical potential for lucerastat in patients with Fabry disease.

Clinical characteristics of adult patients with inborn errors of metabolism in Spain: A review of 500 cases from university hospitals

Patients with inborn errors of metabolism (IEMs) have become an emerging and challenging group in the adult healthcare system whose needs should be known in order to implement appropriate policies and to adapt adult clinical departments. We aimed to analyze the clinical characteristics of adult patients with IEMs who attend the most important Spanish hospitals caring for these conditions. A cohort study was conducted in 500 patients, categorized by metabolic subtype according to pathophysiological classification. The most prevalent group of IEMs was amino acid disorders, with 108 (21.6%) patients diagnosed with phenylketonuria. Lysosomal storage disorders were the second group, in which 32 (6.4%) and 25 (5%) patients had Fabry disease and Gaucher disease respectively. The great clinical heterogeneity, the significant delay in diagnosis after symptom onset, the existence of some degree of physical dependence in a great number of patients, the need for a multidisciplinary and coordinated approach, and the lack of specific drug treatment are common features in this group of conditions.

Early manifestations of type 1 Gaucher disease in presymptomatic children diagnosed after parental carrier screening

PURPOSE

The overall published experience with pediatric type 1 Gaucher disease (GD1) has been based on ascertainment through clinical presentation of the disease. We describe the longitudinal follow-up in a presymptomatic pediatric cohort.

METHODS

The cohort includes children diagnosed with GD1, either prenatally or postnatally by molecular genetic testing, and followed for clinical care at our center from 1998 to 2016. All patients' parents were GBA mutation carriers identified through carrier screening programs. Longitudinal clinical, laboratory, and imaging data were obtained through chart review.

RESULTS

Thirty-eight patients aged 1-18 years (mean at last visit 6.9 ± 4.1 years) were followed, including 32 p.N409S homozygotes and 6 p.N409S/p.R535H compound heterozygotes. At the last evaluation, a minority had hematological (5%), bone (15%), or linear growth (19%) issues. Only 12% had splenomegaly and 74% had moderate hepatomegaly. Chitotriosidase activity varied widely (6-5,640 nmol/hour/ml) and generally increased with age. Pediatric Gaucher severity scores (GSS) remained stable and within the mild-disease range for most (95%). Treatment for progressive disease during this period was recommended for four children.

CONCLUSION

Most children with the p.N409S/p.N409S and p.N409S/p.R535H GD1 genotypes have minimal disease manifestations and progression during childhood and can be monitored using limited assessments. Those with other mutations may require additional monitoring. These data are valuable for newborn screening and counseling.Genet Med advance online publication 13 October 2016.

Disease models for the development of therapies for lysosomal storage diseases

Lysosomal storage diseases (LSDs) are a group of rare diseases in which the function of the lysosome is disrupted by the accumulation of macromolecules. The complexity underlying the pathogenesis of LSDs and the small, often pediatric, population of patients make the development of therapies for these diseases challenging. Current treatments are only available for a small subset of LSDs and have not been effective at treating neurological symptoms. Disease-relevant cellular and animal models with high clinical predictability are critical for the discovery and development of new treatments for LSDs. In this paper, we review how LSD patient primary cells and induced pluripotent stem cell-derived cellular models are providing novel assay systems in which phenotypes are more similar to those of the human LSD physiology. Furthermore, larger animal disease models are providing additional tools for evaluation of the efficacy of drug candidates. Early predictors of efficacy and better understanding of disease biology can significantly affect the translational process by focusing efforts on those therapies with the higher probability of success, thus decreasing overall time and cost spent in clinical development and increasing the overall positive outcomes in clinical trials.