Enzyme replacement therapy and hematopoietic stem cell transplant: a new paradigm of treatment in Wolman disease

Twice weekly dosing with Sebelipase alfa (Kanuma®) rescues severely ill infants with Wolman disease

BACKGROUND

Sebelipase alfa (Kanuma®) is approved for patients with Wolman disease (WD) at a dosage of 3-5 mg/kg once weekly. Survival rates in the second of two clinical trials was greater, despite recruiting more severely ill patients, probably related to higher initial and maximal doses. We aimed to evaluate the effective pharmacokinetics and pharmacodynamics of Sebelipase alfa when administered to patients with severe WD at 5 mg/kg twice weekly, an intensive regimen which was not assessed in the trials.

METHODS

We recruited 3 patients receiving Sebelipase alfa 5 mg/kg twice weekly. We measured LAL activity in leukocytes and plasma oxysterol concentration in two patients and LAL activity in fibroblasts in one patient. Clinical follow up was also assessed.

RESULTS

Analyses of LAL activity and oxysterols demonstrate that there is short-lived enzyme activity post-dosing which is associated with the release of stored lipids. Clinical data demonstrate that 5 mg/kg twice weekly dosing is well tolerated and effective.

CONCLUSION

5 mg/kg twice weekly dosing with Sebelipase alfa rescues severely ill infants with WD by increasing substrate clearance. There is biologically relevant lipid accumulation in the 'trough' periods before the next dosing, even with this intensive regimen.

Hematopoietic Stem Cell Transplantation for Storage Disorders: Present Status

Storage disorders are a group of inborn errors of metabolism caused by the defective activity of lysosomal enzymes or transporters. All of these disorders have multisystem involvement with variable degrees of neurological features. Neurological manifestations are one of the most difficult aspects of treatment concerning these diseases. The available treatment modalities for some of these disorders include enzyme replacement therapy, substrate reduction therapy, hematopoietic stem cell transplantation (HSCT) and the upcoming gene therapies. As a one-time intervention, the economic feasibility of HSCT makes it an attractive option for treating these disorders, especially in lower and middle-income countries. Further, improvements in peri-transplantation medical care, better conditioning regimens and better supportive care have improved the outcomes of patients undergoing HSCT. In this review, we discuss the current evidence for HSCT in various storage disorders and its suitability as a mode of therapy for the developing world.

Hepatomegaly and Splenomegaly: An Approach to the Diagnosis of Lysosomal Storage Diseases

Clinical findings of hepatomegaly and splenomegaly, the abnormal enlargement of the liver and spleen, respectively, should prompt a broad differential diagnosis that includes metabolic, congestive, neoplastic, infectious, toxic, and inflammatory conditions. Among the metabolic diseases, lysosomal storage diseases (LSDs) are a group of rare and ultrarare conditions with a collective incidence of 1 in 5000 live births. LSDs are caused by genetic variants affecting the lysosomal enzymes, transporters, or integral membrane proteins. As a result, abnormal metabolites accumulate in the organelle, leading to dysfunction. Therapeutic advances, including early diagnosis and disease-targeted management, have improved the life expectancy and quality of life of people affected by certain LSDs. To access these new interventions, LSDs must be considered in patients presenting with hepatomegaly and splenomegaly throughout the lifespan. This review article navigates the diagnostic approach for individuals with hepatosplenomegaly particularly focusing on LSDs. We provide hints in the history, physical exam, laboratories, and imaging that may identify LSDs. Additionally, we discuss molecular testing, arguably the preferred confirmatory test (over biopsy), accompanied by enzymatic testing when feasible.

High-Dose ERT, Rituximab, and Early HSCT in an Infant with Wolman's Disease

Wolman's disease, a severe form of lysosomal acid lipase deficiency, leads to pathologic lipid accumulation in the liver and gut that, without treatment, is fatal in infancy. Although continued enzyme-replacement therapy (ERT) in combination with dietary fat restriction prolongs life, its therapeutic effect may wane over time. Allogeneic hematopoietic stem-cell transplantation (HSCT) offers a more definitive solution but carries a high risk of death. Here we describe an infant with Wolman's disease who received high-dose ERT, together with dietary fat restriction and rituximab-based B-cell depletion, as a bridge to early HSCT. At 32 months, the infant was independent of ERT and disease-free, with 100% donor chimerism in the peripheral blood.

Prevalence of p.G87V and p.Gln298=Variations in LIPA Gene Within Middle Eastern Population Living Around Los Angeles

Background: The LIPA gene encodes for lysosomal acid lipase (LAL), which catalyzes the hydrolysis of cholesterol esters and triglycerides. Variations in the LIPA gene impair LAL activity, predisposing patients to a rare metabolic disorder called LAL deficiency (LAL-D). The lack of functioning LAL promotes lipid accumulation and subsequent dyslipidemia, which can increase the likelihood of complications in both infants and adults. Although the worldwide prevalence is 1:500,000 births, the frequency in Mizrahi Jewish populations is projected to be as high as 1 in every 4200 births (Valles-Ayoub et al.) based on the LIPA p.G87V variant frequency among 162 individuals. Materials and Methods: This study was conducted to validate the previously reported prevalence of LAL-D in the Mizrahi Jewish population based on the pathogenic LIPA missense variants in exon 4 (c.260G>T; p.G87V) and exon 8 (c.894G>A; p.Gln298=) using a larger cohort of those with Middle Eastern ancestry living around Los Angeles. Among the 1184 individual samples sequenced, 660 self-reported as Mizrahi Jewish, while the remaining 524 came from other Middle Eastern groups labeled as "non-Jewish." Results: Of the 1184 samples, 22 alleles of the exon 4 variant were identified (1.85%), and 2 alleles of the exon 8 variant were identified (0.16%). For the exon 4 variant, 20 of 22 (90.9%) heterozygotes were Mizrahi Jewish, while 2 of 22 (9.09%) heterozygotes were "non-Jewish." For the exon 8 variant, 2 of 2 (100%) heterozygotes were Mizrahi Jewish. This suggests that the prevalence of LAL-D in this population is 1 in 900, which suggests that LAL-D may be 4.6% higher in the Mizrahi Jewish population in previous reports. Conclusion: These findings show increased prevalence of LIPA gene exon 4 variation p.G87V in the Middle East population when compared to the general population, indicating the need for prenatal screening in those of Mizrahi Jewish ancestry.

First LIPA Mutational Analysis in Egyptian Patients Reveals One Novel Variant: Wolman Disease

Lysosomal acid lipase (LAL) is a necessary enzyme for the hydrolysis of both triglycerides (TGs) and cholesteryl esters (CEs) in the lysosome. Deficiency of this enzyme encoded by the lipase A (LIPA) gene leads to LAL deficiency (LAL-D). A severe disease subtype of LAL-D is known as Wolman disease (WD), present with diarrhea, hepatosplenomegaly, and adrenal calcification. Untreated patients do not survive more than a year. The aim of this study was to assess the clinical and molecular characterizations of WD patients in Egypt. A total of seven patients (from five unrelated Egyptian families) were screened by targeted next-generation sequencing (NGS), and the co-segregation of causative variants was analyzed using Sanger sequencing. Furthermore, multiple in silico analyses were performed to assess the pathogenicity of the candidate variants. Overall, we identified three diseases causing variants harbored in the LIPA gene. One of these variants is a novel missense variant (NM_000235.4: c.1122 T > G; p. His374Gln), which was classified as a likely pathogenic variant. All variants were predicted to be disease causing using in silico analyses. Our findings expand the spectrum of variants involved in WD which may help to investigate phenotype-genotype correlation and assist genetic counseling. To the best of our knowledge, this is the first clinico-genetic study carried out on Egyptian patients affected with WD.

Recent insights into lysosomal acid lipase deficiency

Lysosomal acid lipase (LAL) is the sole enzyme known to degrade neutral lipids in the lysosome. Mutations in the LAL-encoding LIPA gene lead to rare lysosomal lipid storage disorders with complete or partial absence of LAL activity. This review discusses the consequences of defective LAL-mediated lipid hydrolysis on cellular lipid homeostasis, epidemiology, and clinical presentation. Early detection of LAL deficiency (LAL-D) is essential for disease management and survival. LAL-D must be considered in patients with dyslipidemia and elevated aminotransferase concentrations of unknown etiology. Enzyme replacement therapy, sometimes in combination with hematopoietic stem cell transplantation (HSCT), is currently the only therapy for LAL-D. New technologies based on mRNA and viral vector gene transfer are recent efforts to provide other effective therapeutic strategies.

Lysosomal Acid Lipase Deficiency: Genetics, Screening, and Preclinical Study

Lysosomal acid lipase (LAL) is a lysosomal enzyme essential for the degradation of cholesteryl esters through the endocytic pathway. Deficiency of the LAL enzyme encoded by the LIPA gene leads to LAL deficiency (LAL-D) (OMIM 278000), one of the lysosomal storage disorders involving 50-60 genes. Among the two disease subtypes, the severe disease subtype of LAL-D is known as Wolman disease, with typical manifestations involving hepatomegaly, splenomegaly, vomiting, diarrhea, and hematopoietic abnormalities, such as anemia. In contrast, the mild disease subtype of this disorder is known as cholesteryl ester storage disease, with hypercholesterolemia, hypertriglyceridemia, and high-density lipoprotein disappearance. The prevalence of LAL-D is rare, but several treatment options, including enzyme replacement therapy, are available. Accordingly, a number of screening methodologies have been developed for this disorder. This review summarizes the current discussion on LAL-D, covering genetics, screening, and the tertiary structure of human LAL enzyme and preclinical study for the future development of a novel therapy.

Lysosomal acid lipase deficiency: A rare inherited dyslipidemia but potential ubiquitous factor in the development of atherosclerosis and fatty liver disease

Lysosomal acid lipase (LAL), encoded by the gene LIPA, is the sole neutral lipid hydrolase in lysosomes, responsible for cleavage of cholesteryl esters and triglycerides into their component parts. Inherited forms of complete (Wolman Disease, WD) or partial LAL deficiency (cholesteryl ester storage disease, CESD) are fortunately rare. Recently, LAL has been identified as a cardiovascular risk gene in genome-wide association studies, though the directionality of risk conferred remains controversial. It has also been proposed that the low expression and activity of LAL in arterial smooth muscle cells (SMCs) that occurs inherently in nature is a likely determinant of the propensity of SMCs to form the majority of foam cells in atherosclerotic plaque. LAL also likely plays a potential role in fatty liver disease. This review highlights the nature of LAL gene mutations in WD and CESD, the association of LAL with prediction of cardiovascular risk from genome-wide association studies, the importance of relative LAL deficiency in SMC foam cells, and the need to further interrogate the pathophysiological impact and cell type-specific role of enhancing LAL activity as a novel treatment strategy to reduce the development and induce the regression of ischemic cardiovascular disease and fatty liver.

"Why them, why me, why us?" The experiences of parents of children with lysosomal acid lipase deficiency: an interpretative phenomenological analysis study

BACKGROUND

Lysosomal acid lipase deficiency (LALD) is an ultra-rare, inherited metabolic disease within the category of lysosomal storage disorders, affecting an infant's ability to metabolise cholesterol. Developments in treatment, including Enzyme Replacement Therapy, have proven successful, with some children living for a number of years with treatment, although the future still remains unknown. The aim of this study was to explore the lived experiences of parents of children with LALD.

MAIN TEXT

Participants were recruited from across the United Kingdom between 2020 and 2021. Eight parents (five mothers and three fathers) whose child had a confirmed diagnosis of LALD were interviewed. Data collected from the semi-structured interviews were audio-record, transcribed and analysed using Interpretative Phenomenological Analysis (IPA). Three superordinate and nine subordinate themes emerged from the data: (1) Uncertainty-a double-edged sword (plunged into an uncertain world, living life with worry and walking the tightrope of stability), (2) Powerless against a shared battle with LALD (a helpless parent, a joint battle, protection against distress and a vulnerable parent needing help) and 3) Accepting a life with LALD (coming to terms with a diagnosis of LALD and a hidden condition).

CONCLUSIONS

The findings of this study highlight that the diagnosis of LALD proves to be a very challenging and emotionally distressing time in parents' lives, with increased uncertainty about what the future will hold for their child. This study signified the importance of healthcare pathways and service provisions to support parents and their children throughout diagnosis and beyond.

Diagnosis, treatment, and follow-up of a case of Wolman disease with hemophagocytic lymphohistiocytosis

Wolman Disease (WD) is a severe multi-system metabolic disease due to lysosomal acid lipase (LAL) deficiency. We report on a WD infant who developed an unusual hemophagocytic lymphohistiocytosis (HLH) phenotype related to WD treated with sebelipase alfa. A male baby came to our attention at six months of life for respiratory insufficiency and sepsis, abdominal distension, severe hepatosplenomegaly, diarrhea, and severe growth retardation. HLH was diagnosed and treated with intravenous immunoglobulin, steroids, cyclosporine, broad-spectrum antimicrobial therapy, and finally with the anti-IL-6 drug tocilizumab. WD was suspected for the presence of adrenal calcifications and it was confirmed by LAL enzyme activity and by molecular analysis of LIPA. Plasma oxysterols cholestan-3β,5α,6β-triol (C-triol), and 7-ketocholesterol (7-KC) were markedly increased. Sebelipase alfa was started with progressive amelioration of biochemical and clinical features. The child died from sepsis, 2 months after sebelipase discontinuation requested by parents. Our case shows the importance of an early diagnosis of WD and confirms the difficulty to reach a diagnosis in the HLH phenotype. Sebelipase alpha is an effective treatment for LAL deficiency, also in children affected by WD. Further data are necessary to confirm the utility of measuring plasma c-triol as a biochemical marker of the disease.

Cholesterol metabolism: from lipidomics to immunology

Oxysterols, the oxidized forms of cholesterol or of its precursors, are formed in the first steps of cholesterol metabolism. Oxysterols have interested chemists, biologists, and physicians for many decades, but their exact biological relevance in vivo, other than as intermediates in bile acid biosynthesis, has long been debated. However, in the first quarter of this century, a role for side-chain oxysterols and their C-7 oxidized metabolites has been convincingly established in the immune system. 25-Hydroxycholesterol has been shown to be synthesized by macrophages in response to the activation of Toll-like receptors and to offer protection against microbial pathogens, whereas 7α,25-dihydroxycholesterol has been shown to act as a chemoattractant to lymphocytes expressing the G protein-coupled receptor Epstein-Barr virus-induced gene 2 and to be important in coordinating the action of B cells, T cells, and dendritic cells in secondary lymphoid tissue. There is a growing body of evidence that not only these two oxysterols but also many of their isomers are of importance to the proper function of the immune system. Here, we review recent findings related to the roles of oxysterols in immunology.