Homozygous Familial Hypercholesterolemia (HoFH) in Saudi Arabia and Two Cases of Lomitapide Use in a Real-World Setting

Lomitapide: A Medication Use Evaluation and a Formulary Perspective

Introduction

Lomitapide is approved for lowering low-density lipoprotein cholesterol (LDL-C) in homozygous familial hypercholesterolemia, which is a rare genetic disorder. The evidence regarding its safety and efficacy from a small clinical trial requires further validation for effectiveness and safety in the real world. This study aimed to use institutional data on the effectiveness and safety of lomitapide to assist in formulating a perspective on adding it to the formulary.

Methods

This was a retrospective review of patients who were actively prescribed lomitapide at King Abdulaziz Medical City, Riyadh, Saudi Arabia, from 2019 to 2022. Data collection included demographics, confirmed gene mutation results, duration of lomitapide therapy, baseline, on-treatment, last LDL-C levels, percent reduction in LDL-C after 1-3 months of therapy (whichever was first available), other LDL-C lowering therapies used, liver function tests, adverse effects, and compliance.

Results

Eight adult patients were included in the review, with a mean age of 25.5 years. Approximately 75% were female, and the duration of treatment with lomitapide ranged from 9 months to 3 years. None of the patients were on continuous LDL apheresis. The mean baseline LDL-C at presentation to our facility was 17.2 mmol/L (range, 11.78-21.97 mmol/L), the mean percent drop in LDL-C with lomitapide was 34.1% (range, 0%-87%), gastrointestinal disturbances were documented in 50% of the patients, and no cases of severe liver toxicities or increase in liver enzymes were seen.

Conclusions

In our cohort of adult patients, lomitapide showed an overall modest reduction in LDL-C, with no cases of increase in liver enzymes and documented intolerance, indicating that most patients were likely noncompliant. This review revealed important considerations when reimbursing expensive medications for rare diseases. Real-world evidence in real-time can support healthcare systems in price negotiations and reaching mutual agreements that can eventually improve patient access to care.

Modern approaches to the management of homozygous familial hypercholesterolemia in the Middle East and North Africa

Homozygous familial hypercholesterolaemia (HoFH) is a severe form of FH in which inheritance of two defective or null mutations in genes associated with metabolism of low-density lipoprotein cholesterol (LDL-C) results in extremely high LDL-C, premature atherosclerotic cardiovascular disease (ASCVD) and mortality. Treatment of HoFH comprises a multi-modal approach of statins, ezetimibe, lipoprotein apheresis; and inhibitors of proprotein convertase subtilisin/kexin type, angiopoietin-like protein 3 (ANGPTL3) and microsomal triglyceride transfer protein. These treatments are generally costly, and patients also often require treatment for ASCVD consequent to HoFH. Therefore, in the interests of both economics and preservation of life, disease prevention via genetic screening and counselling is rapidly becoming a key element in the overall management of HoFH. Guidelines are available to assist diagnosis and treatment of HoFH; however, while advancements have been made in the management of the disease, there has been little systematic attention paid to prevention. Additionally, the Middle East/North Africa (MENA) region has a higher prevalence of HoFH than most other regions - chiefly due to consanguinity. This has led to the establishment of regional lipid clinics and awareness programs that have thrown education and awareness of HoFH into sharp focus. Incorporation of principles of prevention, education, awareness, and data from real-world use of existing therapeutics will significantly enhance the effectiveness of future guidelines for the management of HoFH, particularly in the MENA region.

Identification and functional characterization of two rare LDLR stop gain variants (p.C231* and p.R744*) in Saudi familial hypercholesterolemia patients

BACKGROUND

Familial hypercholesterolemia (FH) is a globally underdiagnosed inherited metabolic disorder. Owing to limited published data from Arab world, this study was conducted with the aim of identifying the genetic and molecular basis of FH in highly consanguineous Saudi population.

METHODS

We performed clinical screening, biochemical profiling, whole exome sequencing and variant segregation analysis of two Saudi FH families. Additionally, 500 normolipic individuals were screened to ensure the absence of FH variant in general Saudi population. Functional characterization of FH variants on secondary structure characteristics of RNA and protein molecules was performed using different bioinformatics modelling approaches.

RESULTS

WES analysis identified two independent rare LDLR gene stop gain variants (p.C231* and p.R744*) consistent to the clinical presentation of FH patients from two different families. RNAfold analysis has shown that both variants were predicted to disturb the free energy dynamics of LDLR mRNA molecule and destabilize its folding pattern and function. PSIPRED based structural modelling analysis has suggested that both variants bring drastic changes disturbing the secondary structural elements of LDLR molecule. The p.C231* and p.R744* variants are responsible for partial or no protein product, thus they are class 1 variants causing loss of function (LoF) LDLR variants.

CONCLUSIONS

This study highlights the effectiveness of the WES, sanger sequencing, and computational analysis in expanding FH variant spectrum in culturally distinct populations like Saudi Arabia. Genetic testing of FH patients is very essential in better clinical diagnosis, screening, treatment, and management and prevention of cardiovascular disease burden in the society.

Novel LDLR Variant in Familial Hypercholesterolemia: NGS-Based Identification, In Silico Characterization, and Pharmacogenetic Insights

BACKGROUND

Familial Hypercholesterolemia (FH) is a hereditary condition that causes a rise in blood cholesterol throughout a person's life. FH can result in myocardial infarction and even sudden death if not treated. FH is thought to be caused mainly by variants in the gene for the low-density lipoprotein receptor (LDLR). This study aimed to investigate the genetic variants in FH patients, verify their pathogenicity, and comprehend the relationships between genotype and phenotype. Also, review studies assessed the relationship between the LDLR null variants and the reaction to lipid-lowering therapy.

METHODS

The study utilised high-throughput next-generation sequencing for genetic screening of FH-associated genes and capillary sequencing for cascade screening. Furthermore, bioinformatic analysis was employed to describe the pathogenic effects of the revealed novel variant on the structural features of the corresponding RNA molecule.

RESULTS

We studied the clinical signs of hypercholesterolemia in a Saudi family with three generations of FH. We discovered a novel frameshift variant (c.666_670dup, p.(Asp224Alafs*43) in the LDLR and a known single nucleotide variant (c.9835A > G, p.(Ser3279Gly) in the APOB gene. It is thought that the LDLR variant causes a protein to be prematurely truncated, likely through nonsense-mediated protein decay. The LDLR variant is strongly predicted to be pathogenic in accordance with ACMG guidelines and co-segregated with the FH clinical characteristics of the family. This LDLR variant exhibited severe clinical FH phenotypes and was restricted to the LDLR protein's ligand-binding domain. According to computational functional characterization, this LDLR variant was predicted to change the free energy dynamics of the RNA molecule, thereby affecting its stability. This frameshift variant is thought to eliminate important functional domains in LDLR that are required for receptor recycling and LDL particle binding. We provide insight into how FH patients with a null variant in the LDLR gene respond to lipid-lowering therapy.

CONCLUSIONS

The findings expand the range of FH variants and assist coronary artery disease preventive efforts by improving diagnosis, understanding the genotype-phenotype relationship, prognosis, and personalised therapy for patients with FH.

Efficacy and Safety of Lomitapide in Homozygous Familial Hypercholesterolaemia: A Systematic Review

Background

Homozygous familial hypercholesterolaemia (HoFH) patients have little or no low-density lipoprotein receptor (LDLR) function. HMG-CoA (3-hydroxy-3-methyl glutaryl coenzyme A) reductase inhibitors (statins) and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have limited lipid-lowering effects, therefore, there is an urgent need to develop new HoFH treatments. In 2012, the US Food and Drug Administration (FDA) approved the administration of lomitapide for lowering low-density lipoprotein cholesterol (LDL-C) levels. However, lomitapide is associated with various gastrointestinal disorders, elevated hepatic alanine aminotransferase (ALT) levels and other adverse reactions, thus, its long-term efficacy and safety in pediatrics and adults should be evaluated. A systematic review conducted in 2017 reported the efficacy and safety of lomitapide in Family hypercholesterolaemia (FH) patients. In this systematic review, we elucidate on the efficacy and safety of lomitapide in HoFH patients.

Methods

A search was conducted in PubMed, Embase, Web of Science and Cochrane library databases to identify valid studies involving lomitapide-treated HoFH patients published before 11th August 2021.

Results

A total of 18 clinical studies involving 120 lomitapide-treated HoFH patients were identified. Lomitapide significantly suppressed LDL-C levels in HoFH patients. Clinical manifestations for lomitapide in children were comparable to those in adults. The most common adverse events were gastrointestinal disturbances and elevated ALT levels. However, most patients tolerated the treatment-associated adverse reactions. Low-fat diets and drug dose adjustments were appropriate measures for controlling the treatment-associated adverse reactions.

Conclusions

In pediatric and adult HoFH patients, lomitapide significantly suppresses LDL-C levels, therefore, it is an important option for HoFH treatment. The most common adverse events of lomitapide treatment include gastrointestinal disorders and elevated hepatic ALT levels. Despite the limitations, lomitapide is feasible for long-term treatment of HoFH patients, with dietary and safety monitoring.

Registration Number in PROSPERO

CRD42021284425.

Pharmacogenomics Variability of Lipid-Lowering Therapies in Familial Hypercholesterolemia

The exponential expansion of genomic data coupled with the lack of appropriate clinical categorization of the variants is posing a major challenge to conventional medications for many common and rare diseases. To narrow this gap and achieve the goals of personalized medicine, a collaborative effort should be made to characterize the genomic variants functionally and clinically with a massive global genomic sequencing of "healthy" subjects from several ethnicities. Familial-based clustered diseases with homogenous genetic backgrounds are amongst the most beneficial tools to help address this challenge. This review will discuss the diagnosis, management, and clinical monitoring of familial hypercholesterolemia patients from a wide angle to cover both the genetic mutations underlying the phenotype, and the pharmacogenomic traits unveiled by the conventional and novel therapeutic approaches. Achieving a drug-related interactive genomic map will potentially benefit populations at risk across the globe who suffer from dyslipidemia.

Saudi Familial Hypercholesterolemia Patients With Rare LDLR Stop Gain Variant Showed Variable Clinical Phenotype and Resistance to Multiple Drug Regimen

Familial hypercholesterolemia (FH), a well-known lipid disease caused by inherited genetic defects in cholesterol uptake and metabolism is underdiagnosed in many countries including Saudi Arabia. The present study aims to identify the molecular basis of severe clinical manifestations of FH patients from unrelated Saudi consanguineous families. Two Saudi families with multiple FH patients fulfilling the combined FH diagnostic criteria of Simon Broome Register, and the Dutch Lipid Clinic Network (DLCN) were recruited. LipidSeq, a targeted resequencing panel for monogenic dyslipidemias, was used to identify causative pathogenic mutation in these two families and in 92 unrelated FH cases. Twelve FH patients from two unrelated families were sharing a very rare, pathogenic and founder LDLR stop gain mutation i.e., c.2027delG (p.Gly676Alafs^*33) in both the homozygous or heterozygous states, but not in unrelated patients. Based on the variant zygosity, a marked phenotypic heterogeneity in terms of LDL-C levels, clinical presentations and resistance to anti-lipid treatment regimen (ACE inhibitors, β-blockers, ezetimibe, statins) of the FH patients was observed. This loss-of-function mutation is predicted to alter the free energy dynamics of the transcribed RNA, leading to its instability. Protein structural mapping has predicted that this non-sense mutation eliminates key functional domains in LDLR, which are essential for the receptor recycling and LDL particle binding. In conclusion, by combining genetics and structural bioinformatics approaches, this study identified and characterized a very rare FH causative LDLR pathogenic variant determining both clinical presentation and resistance to anti-lipid drug treatment.