Worldwide experience of homozygous familial hypercholesterolaemia: retrospective cohort study.

BACKGROUND: Homozygous familial hypercholesterolaemia (HoFH) is a rare inherited disorder resulting in extremely elevated low-density lipoprotein cholesterol levels and premature atherosclerotic cardiovascular disease (ASCVD). Current guidance about its management and prognosis stems from small studies, mostly from high-income countries. The objective of this study was to assess the clinical and genetic characteristics, as well as the impact, of current practice on health outcomes of HoFH patients globally. METHODS: The HoFH International Clinical Collaborators registry collected data on patients with a clinical, or genetic, or both, diagnosis of HoFH using a retrospective cohort study design. This trial is registered with ClinicalTrials.gov, NCT04815005. FINDINGS: Overall, 751 patients from 38 countries were included, with 565 (75%) reporting biallelic pathogenic variants. The median age of diagnosis was 12·0 years (IQR 5·5-27·0) years. Of the 751 patients, 389 (52%) were female and 362 (48%) were male. Race was reported for 527 patients; 338 (64%) patients were White, 121 (23%) were Asian, and 68 (13%) were Black or mixed race. The major manifestations of ASCVD or aortic stenosis were already present in 65 (9%) of patients at diagnosis of HoFH. Globally, pretreatment LDL cholesterol levels were 14·7 mmol/L (IQR 11·6-18·4). Among patients with detailed therapeutic information, 491 (92%) of 534 received statins, 342 (64%) of 534 received ezetimibe, and 243 (39%) of 621 received lipoprotein apheresis. On-treatment LDL cholesterol levels were lower in high-income countries (3·93 mmol/L, IQR 2·6-5·8) versus non-high-income countries (9·3 mmol/L, 6·7-12·7), with greater use of three or more lipid-lowering therapies (LLT; high-income 66% vs non-high-income 24%) and consequently more patients attaining guideline-recommended LDL cholesterol goals (high-income 21% vs non-high-income 3%). A first major adverse cardiovascular event occurred a decade earlier in non-high-income countries, at a median age of 24·5 years (IQR 17·0-34·5) versus 37·0 years (29·0-49·0) in high-income countries (adjusted hazard ratio 1·64, 95% CI 1·13-2·38). INTERPRETATION: Worldwide, patients with HoFH are diagnosed too late, undertreated, and at high premature ASCVD risk. Greater use of multi-LLT regimens is associated with lower LDL cholesterol levels and better outcomes. Significant global disparities exist in treatment regimens, control of LDL cholesterol levels, and cardiovascular event-free survival, which demands a critical re-evaluation of global health policy to reduce inequalities and improve outcomes for all patients with HoFH. FUNDING: Amsterdam University Medical Centers, Location Academic Medical Center; Perelman School of Medicine at the University of Pennsylvania; and European Atherosclerosis Society.

Novel PCSK9 (Proprotein Convertase Subtilisin Kexin Type 9) Variants in Patients With Familial Hypercholesterolemia From Cape Town.

OBJECTIVE: Familial hypercholesterolemia (FH) is characterized by elevated low-density lipoprotein-cholesterol and markedly increased cardiovascular risk. In patients with a genetic diagnosis, low-density lipoprotein receptor (LDLR) mutations account for >90% of cases, apolipoprotein B (APOB) mutations for ≈5% of cases, while proprotein convertase subtilisin kexin type 9 (PCSK9) gain of function mutations are rare (<1% of cases). We aimed to evaluate the functional impact of several novel PCSK9 variants in a cohort of patients with FH by genetic cascade screening and in vitro functionality assays. Approach and Results: Patients with clinically diagnosed FH underwent genetic analysis of LDLR, and if negative, sequential testing of APOB and PCSK9. We analyzed cosegregation of hypercholesterolemia with novel PCSK9 variants. Gain of function status was determined by in silico analyses and validated by in vitro functionality assays. Among 1055 persons with clinical FH, we identified nonsynonymous PCSK9 variants in 27 (2.6%) patients and 7 of these carried one of the 4 previously reported gain of function variants. In the remaining 20 patients with FH, we identified 7 novel PCSK9 variants. The G516V variant (c.1547G>T) was found in 5 index patients and cascade screening identified 15 additional carriers. Low-density lipoprotein-cholesterol levels were higher in these 15 carriers compared with the 27 noncarriers (236±73 versus 124±35 mg/dL; P<0.001). In vitro studies demonstrated the pathogenicity of the G516V variant. CONCLUSIONS: In our study, 1.14% of cases with clinical FH were clearly attributable to pathogenic variants in PCSK9. Pathogenicity is established beyond doubt for the G516V variant.

Taking One Step Back in Familial Hypercholesterolemia: STAP1 Does Not Alter Plasma LDL (Low-Density Lipoprotein) Cholesterol in Mice and Humans.

OBJECTIVE: STAP1, encoding for STAP1 (signal transducing adaptor family member 1), has been reported as a candidate gene associated with familial hypercholesterolemia. Unlike established familial hypercholesterolemia genes, expression of STAP1 is absent in liver but mainly observed in immune cells. In this study, we set out to validate STAP1 as a familial hypercholesterolemia gene. Approach and Results: A whole-body Stap1 knockout mouse model (Stap1-/-) was generated and characterized, without showing changes in plasma lipid levels compared with controls. In follow-up studies, bone marrow from Stap1-/- mice was transplanted to Ldlr-/- mice, which did not show significant changes in plasma lipid levels or atherosclerotic lesions. To functionally assess whether STAP1 expression in B cells can affect hepatic function, HepG2 cells were cocultured with peripheral blood mononuclear cells isolated from heterozygotes carriers of STAP1 variants and controls. The peripheral blood mononuclear cells from STAP1 variant carriers and controls showed similar LDLR mRNA and protein levels. Also, LDL (low-density lipoprotein) uptake by HepG2 cells did not differ upon coculturing with peripheral blood mononuclear cells isolated from either STAP1 variant carriers or controls. In addition, plasma lipid profiles of 39 carriers and 71 family controls showed no differences in plasma LDL cholesterol, HDL (high-density lipoprotein) cholesterol, triglycerides, and lipoprotein(a) levels. Similarly, B-cell populations did not differ in a group of 10 STAP1 variant carriers and 10 age- and sex-matched controls. Furthermore, recent data from the UK Biobank do not show association between STAP1 rare gene variants and LDL cholesterol. CONCLUSIONS: Our combined studies in mouse models and carriers of STAP1 variants indicate that STAP1 is not a familial hypercholesterolemia gene.

The clinical and molecular diversity of homozygous familial hypercholesterolemia in children: Results from the GeneTics of clinical homozygous hypercholesterolemia (GoTCHA) study.

BACKGROUND: Homozygous familial hypercholesterolemia (hoFH) is either diagnosed on the identification of pathogenic genetic variants in LDLR, APOB, or PCSK9 or by phenotypic parameters of which an extremely elevated LDL-C level >13 mmol/L (>500 mg/dL) is the most prominent hallmark. Little is known about the clinical spectrum in children with hoFH. OBJECTIVE: We set out to investigate the phenotypical spectrum of genetically defined hoFH in our pediatric cohort and evaluated how many pediatric patients, now classified as heterozygous, carry a second mutation, which would reclassify these patients as hoFH. METHODS: We analyzed the data of a total of 1903 children with molecularly proven FH. Subsequently we performed candidate gene sequencing in the cohort of heterozygous familial hypercholesterolemia children in whom the LDL-C level was above the lowest level measured in the pediatric patients with hoFH. RESULTS: Of our 13 hoFH children, 8 (62%) had LDL-C levels below the clinical hoFH criteria of 13 mmol/L (500 mg/dL). In the remaining 1890 patients with heterozygous familial hypercholesterolemia, 64 (3.4%) had LDL-C levels equal to or above the lowest LDL-C level in a patient with hoFH carrying 2 deleterious variants (8.36 mmol/L or 323.3 mg/dL). No additional pathogenic variants in LDLR and APOB were identified. In 2 related patients, a PCSK9 gain of function mutation was found. CONCLUSION: We show that LDL-C levels vary among pediatric patients with molecularly proven hoFH, and that most of these patients do not meet the clinical LDL-C criteria for hoFH. The levels overlap with LDL-C levels in true heterozygous patients. This warrants a critical reappraisal of the current LDL-C cutoffs for the phenotypic diagnosis of hoFH in children.

A Deep Intronic Variant in LDLR in Familial Hypercholesterolemia.

BACKGROUND: Familial hypercholesterolemia (FH) is an inherited disorder characterized by high plasma LDL-C (low-density lipoprotein-cholesterol) levels. The vast majority of FH patients carry a mutation in the coding region of LDLR, APOB, or PCSK9. We set out to identify the culprit genetic defect in a large family with clinical FH, in whom no mutations were identified in the coding regions of these FH genes. METHODS: Whole genome sequencing was performed in 5 affected and 4 unaffected individuals from a family with an unexplained autosomal dominant FH trait. The effect on splicing of the identified novel intronic LDLR mutation was ascertained by cDNA sequencing. The prevalence of the novel variant was assessed in 1 245 FH patients without an FH causing mutation identified by Sanger sequencing and in 2 154 patients referred for FH analysis by next-generation sequencing (covering the intronic region). RESULTS: A novel deep intronic variant in LDLR (c.2140+103G>T) was found to cosegregate with high LDL-C in 5 patients, but was not present in 4 unaffected family members. The variant was shown to result in a 97 nucleotides insertion leading to a frameshift and premature stop codon in exon 15 of LDLR. The prevalence of the intronic variant was 0.24% (3/1245) in a cohort of FH patients without a known FH causing mutation and 0.23% (5/2154) in a population of FH patients referred for analysis by next-generation sequencing. Cosegregation analysis of a second family showed full penetrance of the novel variant with the FH phenotype over 3 generations. CONCLUSIONS: The c.2140+103G>T mutation in LDLR is a novel intronic variant identified in FH that cosegregates with the FH phenotype. Our findings underline the need to analyze the intronic regions of LDLR in patients with FH, especially those in whom no mutation is found in the coding regions of LDLR, APOB, or PCSK9.

Achieved LDL cholesterol levels in patients with heterozygous familial hypercholesterolemia: A model that explores the efficacy of conventional and novel lipid-lowering therapy.

BACKGROUND: A large proportion of patients with heterozygous familial hypercholesterolemia (heFH) do not reach low-density lipoprotein cholesterol (LDL-c) levels advocated by international guidelines (<70 mg/dL or <100 mg/dL). OBJECTIVE: We set out to model which proportion of patients reach targets using conventional and novel therapies. METHODS: We performed a cross-sectional analysis in a large cohort of genetically identified heFH patients and calculated the proportion reaching treatment targets in four scenarios: (1) after 50% LDL-c reduction (representing maximal dose statin); (2) after 70% LDL-c reduction (maximal dose statin + ezetimibe); (3) additional 40% LDL-c reduction representing cholesteryl ester transfer protein inhibitor (CETPi); and (4) 60% LDL-c reduction (proprotein convertase subtilisin/kexin type 9 inhibitors [PCSK9i]), on top of scenario 2. We applied 100% adherence rates and literature-based adherence rates from 62% to 80%. RESULTS: We included 1,059 heFH patients with and 9,420 heFH patients without coronary heart disease (CHD). With maximal dose statin, 8.3% and 48.1% of patients with and without CHD would reach their recommended LDL-c targets, respectively. This increases to 54.3% and 93.2% when ezetimibe is added. Addition of CETPi increases these numbers to 95.7% and 99.7%, whereas adding PCSK9i would result in 99.8% and 100% goal attainment. Using literature-based adherence rates, these numbers decrease to 3.8% and 27.3% for maximal dose statin, 5.8% and 38.9% combined with ezetimibe, 31.4% and 81.2% when adding CETPi, and 40.3% and 87.1% for addition of PCSK9i. CONCLUSIONS: Less than 10% with and 50% of heFH patients without CHD would reach treatment targets with maximal dose statin, but this substantially increases on addition of ezetimibe, CETPi, or PCSK9i. However, considering recently published adherence data, this might be lower in real life, especially in heFH patients with CHD.

Alirocumab efficacy in patients with double heterozygous, compound heterozygous, or homozygous familial hypercholesterolemia.

BACKGROUND: Mutations in the genes for the low-density lipoprotein receptor (LDLR), apolipoprotein B, and proprotein convertase subtilisin/kexin type 9 have been reported to cause heterozygous and homozygous familial hypercholesterolemia (FH). OBJECTIVE: The objective is to examine the influence of double heterozygous, compound heterozygous, or homozygous mutations underlying FH on the efficacy of alirocumab. METHODS: Patients from 6 alirocumab trials with elevated low-density lipoprotein cholesterol (LDL-C) and FH diagnosis were sequenced for mutations in the LDLR, apolipoprotein B, proprotein convertase subtilisin/kexin type 9, LDLR adaptor protein 1 (LDLRAP1), and signal-transducing adaptor protein 1 genes. The efficacy of alirocumab was examined in patients who had double heterozygous, compound heterozygous, or homozygous mutations. RESULTS: Of 1191 patients sequenced, 20 patients were double heterozygotes (n = 7), compound heterozygotes (n = 10), or homozygotes (n = 3). Mean baseline LDL-C levels were similar between patients treated with alirocumab (n = 11; 198 mg/dL) vs placebo (n = 9; 189 mg/dL). All patients treated with alirocumab 75/150 or 150 mg every 2 weeks had an LDL-C reduction of ≥15% at either week 12 or 24. At week 12, 1 patient had an increase of 7.1% in LDL-C, whereas in others, LDL-C was reduced by 21.7% to 63.9% (corresponding to 39-114 mg/dL absolute reduction from baseline). At week 24, LDL-C was reduced in all patients by 8.8% to 65.1% (10-165 mg/dL absolute reduction from baseline). Alirocumab was generally well tolerated in the 6 trials. CONCLUSION: Clinically meaningful LDL-C-lowering activity was observed in patients receiving alirocumab who were double heterozygous, compound heterozygous, or homozygous for genes that are causative for FH.

PCSK9 inhibitors in clinical practice: Delivering on the promise?

BACKGROUND AND AIMS: In clinical trials, protein convertase subtilisin/kexin type 9 (PCSK9) inhibitors robustly lowered LDL-cholesterol (LDL-c) and had a favorable tolerability and safety profile. Based on these findings, PCSK9 inhibitors are incorporated in updates of clinical treatment guidelines. However, trial results do not necessarily predict the effectiveness under real-world conditions. The aim of the current study is to determine the efficacy and tolerability of PCSK9 inhibitors in routine outpatient care. METHODS: The cohort comprised all patients who were prescribed evolocumab or alirocumab at the outpatient clinic of a large university hospital in the Netherlands. Eligible patients required additional lipid-lowering despite maximally tolerated statin therapy and ezetimibe, or were statin intolerant. Data were systematically collected during routine outpatient visits. RESULTS: The study included 238 patients of whom 67.2% had familial hypercholesterolemia (FH) and 42.9% were statin intolerant. The mean LDL-c reduction was 55.0% from a baseline of 4.4 mmol/L. LDL-c goals were attained by 62.3% of patients. Side effects were reported by 15.5% of patients and 2.5% discontinued treatment. No meaningful differences in efficacy or tolerability were observed between patients with FH or statin intolerance, or across treatment regimens. CONCLUSIONS: The observed lipid reductions and side effects profile of PCSK9 inhibitors in a routine care setting were comparable to observations in clinical trials.

Prevention of cardiovascular disease in patients with familial hypercholesterolaemia: The role of PCSK9 inhibitors.

Familial hypercholesterolaemia is an autosomal dominant inherited disorder characterised by elevated low-density lipoprotein cholesterol levels and consequently an increased risk of atherosclerotic cardiovascular disease (ASCVD). Familial hypercholesterolaemia is relatively common, but is often underdiagnosed and undertreated. Cardiologists are likely to encounter many individuals with familial hypercholesterolaemia; however, patients presenting with premature ASCVD are rarely screened for familial hypercholesterolaemia and fasting lipid levels are infrequently documented. Given that individuals with familial hypercholesterolaemia and ASCVD are at a particularly high risk of subsequent cardiac events, this is a missed opportunity for preventive therapy. Furthermore, because there is a 50% chance that first-degree relatives of individuals with familial hypercholesterolaemia will also be affected by the disorder, the underdiagnosis of familial hypercholesterolaemia among patients with ASCVD is a barrier to cascade screening and the prevention of ASCVD in affected relatives. Targeted screening of patients with ASCVD is an effective strategy to identify new familial hypercholesterolaemia index cases. Statins are the standard treatment for individuals with familial hypercholesterolaemia; however, low-density lipoprotein cholesterol targets are not achieved in a large proportion of patients despite treatment. Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors have been shown to reduce low-density lipoprotein cholesterol levels considerably in individuals with familial hypercholesterolaemia who are concurrently receiving the maximal tolerated statin dose. The clinical benefit of PCSK9 inhibitors must, however, also be considered in terms of their cost-effectiveness. Increased awareness of familial hypercholesterolaemia is required among healthcare professionals, particularly cardiologists and primary care physicians, in order to start early preventive measures and to reduce the mortality and morbidity associated with familial hypercholesterolaemia and ASCVD.

Double-heterozygous autosomal dominant hypercholesterolemia: Clinical characterization of an underreported disease.

INTRODUCTION: Autosomal dominant hypercholesterolemia (ADH), characterized by high-plasma low-density lipoprotein cholesterol (LDL-C) levels and premature cardiovascular disease (CVD) risk, is caused by mutations in LDLR, APOB, and/or PCSK9. OBJECTIVE: To describe the clinical characteristics of "double-heterozygous carriers," with 2 mutations in 2 different ADH causing genes, that is, LDLR and APOB or LDLR and PCSK9. METHODS: Double heterozygotes were identified in the database of the national referral laboratory for DNA diagnostics of inherited dyslipidemias. We collected the medical data (comprising lipids and CVD events) from double heterozygotes and compared these with data from their heterozygous and unaffected relatives and homozygote/compound heterozygous LDLR mutation carriers, identified in a previously described cohort (n = 45). RESULTS: A total of 28 double heterozygotes (23 LDLR/APOB and 5 LDLR/PCSK9 mutation carriers) were identified. Off treatment, LDL-C levels were significantly higher in double heterozygotes (mean ± SD, 8.4 ± 2.8 mmol/L) compared with 28 heterozygous (5.6 ± 2.2) and 18 unaffected relatives (2.5 ± 1.1; P ≤ .01 for all comparisons) and significantly lower compared with homozygous/compound heterozygous LDLR mutation carriers (13.0 ± 5.1; P < .001). CONCLUSIONS: Double-heterozygous carriers of mutations in ADH genes express an intermediate phenotype compared with heterozygous and homozygous/compound heterozygous carriers and might well be misconceived to suffer from a severe form of heterozygous ADH. The molecular identification of double heterozygosity is of relevance from both a screening and an educational perspective.

New Approaches in Detection and Treatment of Familial Hypercholesterolemia.

Familial hypercholesterolemia (FH) is an autosomal dominant genetic disorder that clinically leads to increased low density lipoprotein-cholesterol (LDL-C) levels. As a consequence, FH patients are at high risk for cardiovascular disease (CVD). Mutations are found in genes coding for the LDLR, apoB, and PCSK9, although FH cannot be ruled out in the absence of a mutation in one of these genes. It is pivotal to diagnose FH at an early age, since lipid lowering results in a decreased risk of cardiovascular complications especially if initiated early, but unfortunately FH is largely underdiagnosed. While a number of clinical criteria are available, identification of a pathogenic mutation in any of the three aforementioned genes is seen by many as a way to establish a definitive diagnosis of FH. It should be remembered that clinical treatment is based on LDL-C levels and not solely on presence or absence of genetic mutations as LDL-C is what drives risk. Traditionally, mutation detection has been done by means of dideoxy sequencing. However, novel molecular testing methods are gradually being introduced. These next generation sequencing-based methods are likely to be applied on broader scale once their efficacy and effect on cost are being established. Statins are the first-line therapy of choice for FH patients as they have been proven to reduce CVD risk across a range of conditions including hypercholesterolemia (though not specifically tested in FH). However, in a significant proportion of FH patients LDL-C goals are not met, despite the use of maximal statin doses and additional lipid-lowering therapies. This underlines the need for additional therapies, and inhibition of PCSK9 and CETP is among the most promising new therapeutic options. In this review, we aim to provide an overview of the latest information about the definition, diagnosis, screening, and current and novel therapies for FH.