Barbara Sjouke

The PCSK9 decade.

PCSK9 proprotein convertase subtilisin/kexin type (PCSK9) is a crucial protein in LDL cholesterol (LDL-C) metabolism by virtue of its pivotal role in the degradation of the LDL receptor. In recent years, both in vitro and in vivo studies have greatly supplemented our understanding of the (patho)physiological role of PCSK9 in human biology. In the current review, we summarize studies published or in print before May 2012 concerning the physiological role of PCSK9 in cholesterol metabolism. Moreover, we briefly describe the clinical phenotypes encountered in carriers of mutations in the gene encoding PCSK9. As PCSK9 has emerged as a novel target for LDL-C lowering therapy, methods to inhibit PCSK9 will also be reviewed. Initial data from investigations of PCSK9 inhibition in humans are promising and indicate that PCSK9 inhibition may be a viable new therapeutic option for the treatment of dyslipidemia and associated cardiovascular diseases.

Exome Sequencing and Directed Clinical Phenotyping Diagnose Cholesterol Ester Storage Disease Presenting as Autosomal Recessive Hypercholesterolemia

Objective—Autosomal recessive hypercholesterolemia is a rare inherited disorder, characterized by extremely high total and low-density lipoprotein cholesterol levels, that has been previously linked to mutations in LDLRAP1. We identified a family with autosomal recessive hypercholesterolemia not explained by mutations in LDLRAP1 or other genes known to cause monogenic hypercholesterolemia. The aim of this study was to identify the molecular pathogenesis of autosomal recessive hypercholesterolemia in this family. Approach and Results—We used exome sequencing to assess all protein-coding regions of the genome in 3 family members and identified a homozygous exon 8 splice junction mutation (c.894G>A, also known as E8SJM) in LIPA that segregated with the diagnosis of hypercholesterolemia. Because homozygosity for mutations in LIPA is known to cause cholesterol ester storage disease, we performed directed follow-up phenotyping by noninvasively measuring hepatic cholesterol content. We observed abnormal hepatic accumulation of cholesterol in the homozygote individuals, supporting the diagnosis of cholesterol ester storage disease. Given previous suggestions of cardiovascular disease risk in heterozygous LIPA mutation carriers, we genotyped E8SJM in >27 000 individuals and found no association with plasma lipid levels or risk of myocardial infarction, confirming a true recessive mode of inheritance. Conclusions—By integrating observations from Mendelian and population genetics along with directed clinical phenotyping, we diagnosed clinically unapparent cholesterol ester storage disease in the affected individuals from this kindred and addressed an outstanding question about risk of cardiovascular disease in LIPA E8SJM heterozygous carriers.

Lipoprotein(a) and Risk of Coronary, Cerebrovascular, and Peripheral Artery Disease The EPIC-Norfolk Prospective Population Study

Objective—Although the association between circulating levels of lipoprotein(a) [Lp(a)] and risk of coronary artery disease (CAD) and stroke is well established, its role in risk of peripheral arterial disease (PAD) remains unclear. Here, we examine the association between Lp(a) levels and PAD in a large prospective cohort. To contextualize these findings, we also examined the association between Lp(a) levels and risk of stroke and CAD and studied the role of low-density lipoprotein as an effect modifier of Lp(a)-associated cardiovascular risk. Methods and Results—Lp(a) levels were measured in apparently healthy participants in the European Prospective Investigation of Cancer (EPIC)-Norfolk cohort. Cox regression was used to quantify the association between Lp(a) levels and risk of PAD, stroke, and CAD outcomes. During 212 981 person-years at risk, a total of 2365 CAD, 284 ischemic stroke, and 596 PAD events occurred in 18 720 participants. Lp(a) was associated with PAD and CAD outcomes but not with ischemic stroke (hazard ratio per 2.7-fold increase in Lp(a) of 1.37, 95% CI 1.25–1.50, 1.13, 95% CI 1.04–1.22 and 0.91, 95% CI 0.79–1.03, respectively). Low-density lipoprotein cholesterol levels did not modify these associations. Conclusion—Lp(a) levels were associated with future PAD and CAD events. The association between Lp(a) and cardiovascular disease was not modified by low-density lipoprotein cholesterol levels.

Eprotirome in patients with familial hypercholesterolaemia (the AKKA trial): a randomised, double-blind, placebo-controlled phase 3 study

BACKGROUND Eprotirome is a liver-selective thyroid hormone receptor agonist that has been shown to lower plasma LDL cholesterol concentrations in previous phase 1 and 2 studies of patients with dyslipidaemia. We aimed to assess the long-term safety and efficacy of 50 μg and 100 μg eprotirome in patients with familial hypercholesterolaemia. METHODS For this randomised, double-blind, placebo-controlled, parallel-group, phase 3 clinical trial, we enrolled patients between Oct 3, 2011, and Feb 14, 2012, at 53 sites in 11 countries in Europe, Africa, and south Asia. Patients were eligible for enrolment if they were aged 18 years or older, diagnosed with heterozygous familial hypercholesterolaemia, and had not reached target LDL cholesterol concentrations after at least 8 weeks of statin therapy with or without ezetimibe. We used a computer-generated randomisation sequence to allocate patients to one of three groups: 50 μg eprotirome, 100 μg eprotirome, or placebo. This trial was planned for 52-76 weeks, with primary efficacy analysis at 12 weeks, but it was prematurely terminated when another study found that eprotirome causes cartilage damage in dogs. Although it was impossible to meet the predefined study outcomes, we analysed changes in the concentrations of LDL cholesterol and other lipids, liver parameters, thyroid hormone concentrations, and adverse effects of treatment with eprotirome versus placebo at 6 weeks of treatment. Analysis was done in all patients who received 6 weeks of treatment. This study is registered with ClinicalTrials.gov, number NCT01410383. FINDINGS We enrolled 236 patients, randomly allocating 80 to receive placebo, 79 to receive 50 μg eprotirome, and 77 to receive 100 μg eprotirome. 69 patients reached the 6 week timepoint (23 given placebo, 24 given 50 μg eprotirome, and 22 given 100 μg eprotirome). Mean LDL cholesterol concentrations increased by 9% (95% CI -2 to 20) in the placebo group, decreased by 12% (-28 to 4%; p=0.0677 vs placebo) in the 50 μg eprotirome group, and decreased by 22% (-32 to -13%; p=0.0045 vs placebo) in the 100 μg eprotirome group. We noted statistically significant increases between both eprotirome groups and placebo in aspartate aminotransferase (AST; p<0.0001), alanine aminotransferase (ALT; p<0.0001), conjugated bilirubin (p=0.0006), and gamma-glutamyltranspeptidase (p<0.0001). Four patients had to discontinue or interrupt study treatment before trial termination due to AST increases between the upper limit of normal (ULN) and six times ULN, and ALT concentrations between three and seven times ULN. Although we detected no changes in serum concentrations of thyroid-stimulating hormone or free tri-iodothyronine, free tetra-iodothyronine decreased by 19% (23 to 16) in the 50 μg eprotirome group and 27% (30 to 23) in the 100 μg eprotirome group (p<0.0001 vs placebo for both groups). INTERPRETATION Our findings show that eprotirome can lower LDL cholesterol concentrations in patients with familial hypercholesterolaemia when added to conventional statin treatment with or without ezetimibe, but that it has the potential to induce liver injury. These findings, along with findings of cartilage damage in dogs, raise serious doubts about selective thyroid hormone mimetics as a therapeutic approach to lower LDL cholesterol concentrations. FUNDING Karo Bio AB.

Nonpharmacological Lipoprotein Apheresis Reduces Arterial Inflammation in Familial Hypercholesterolemia

BACKGROUND Patients with familial hypercholesterolemia (FH) are characterized by elevated atherogenic lipoprotein particles, predominantly low-density lipoprotein cholesterol (LDL-C), which is associated with accelerated atherogenesis and increased cardiovascular risk. OBJECTIVES This study used (18)F-fluorodeoxyglucose positron emission tomography ((18)FDG-PET) to investigate whether arterial inflammation is higher in patients with FH and, moreover, whether lipoprotein apheresis attenuates arterial wall inflammation in FH patients. METHODS In total, 38 subjects were recruited: 24 FH patients and 14 normolipidemic controls. All subjects underwent FDG-PET imaging at baseline. Twelve FH patients who met the criteria for lipoprotein apheresis underwent apheresis procedures followed by a second FDG-PET imaging 3 days (range 1 to 4 days) after apheresis. Subsequently, the target-to-background ratio (TBR) of FDG uptake within the arterial wall was assessed. RESULTS In FH patients, the mean arterial TBR was higher compared with healthy controls (2.12 ± 0.27 vs. 1.92 ± 0.19; p = 0.03). A significant correlation was observed between baseline arterial TBR and LDL-C (R = 0.37; p = 0.03) that remained significant after adjusting for statin use (β = 0.001; p = 0.02) and atherosclerosis risk factors (β = 0.001; p = 0.03). LDL-C levels were significantly reduced after lipoprotein apheresis (284 ± 118 mg/dl vs. 127 ± 50 mg/dl; p < 0.001). There was a significant reduction of arterial inflammation after lipoprotein apheresis (TBR: 2.05 ± 0.31 vs. 1.91 ± 0.33; p < 0.02). CONCLUSIONS The arterial wall of FH patients is characterized by increased inflammation, which is markedly reduced after lipoprotein apheresis. This lends support to a causal role of apoprotein B-containing lipoproteins in arterial wall inflammation and supports the concept that lipoprotein-lowering therapies may impart anti-inflammatory effects by reducing atherogenic lipoproteins.

Characterization of Autosomal Dominant Hypercholesterolemia Caused by PCSK9 Gain of Function Mutations and its Specific Treatment with Alirocumab, a PCSK9 Monoclonal Antibody

Background—Patients with PCSK9 gene gain of function (GOF) mutations have a rare form of autosomal dominant hypercholesterolemia. However, data examining their clinical characteristics and geographic distribution are lacking. Furthermore, no randomized treatment study in this population has been reported. Methods and Results—We compiled clinical characteristics of PCSK9 GOF mutation carriers in a multinational retrospective, cross-sectional, observational study. We then performed a randomized placebo-phase, double-blind study of alirocumab 150 mg administered subcutaneously every 2 weeks to 13 patients representing 4 different PCSK9 GOF mutations with low-density lipoprotein cholesterol (LDL-C) ≥70 mg/dL on their current lipid-lowering therapies at baseline. Observational study: among 164 patients, 16 different PCSK9 GOF mutations distributed throughout the gene were associated with varying severity of untreated LDL-C levels. Coronary artery disease was common (33%; average age of onset, 49.4 years), and untreated LDL-C concentrations were higher compared with matched carriers of mutations in the LDLR (n=2126) or apolipoprotein B (n=470) genes. Intervention study: in PCSK9 GOF mutation patients randomly assigned to receive alirocumab, mean percent reduction in LDL-C at 2 weeks was 62.5% (P<0.0001) from baseline, 53.7% compared with placebo-treated PCSK9 GOF mutation patients (P=0.0009; primary end point). After all subjects received 8 weeks of alirocumab treatment, LDL-C was reduced by 73% from baseline (P<0.0001). Conclusions—PCSK9 GOF mutation carriers have elevated LDL-C levels and are at high risk of premature cardiovascular disease. Alirocumab, a PCSK9 antibody, markedly lowers LDL-C levels and seems to be well tolerated in these patients. Clinical Trial Registration—URL: http://www.clinicaltrials.gov. Unique Identifier: NCT01604824.

Genetic variation in APOB, PCSK9, and ANGPTL3 in carriers of pathogenic autosomal dominant hypercholesterolemic mutations with unexpected low LDL-Cl Levels†

Autosomal Dominant Hypercholesterolemia (ADH) is caused by LDLR and APOB mutations. However, genetically diagnosed ADH patients do not always exhibit the expected hypercholesterolemic phenotype. Of 4,669 genetically diagnosed ADH patients, identified through the national identification screening program for ADH, 75 patients (1.6%) had LDL‐cholesterol (LDL‐C) levels below the 50th percentile for age and gender prior to lipid‐lowering therapy. The genes encoding APOB, PCSK9, and ANGPTL3 were sequenced in these subjects to address whether monogenic dominant loss‐of‐function mutations underlie this paradoxical phenotype. APOB mutations, resulting in truncated APOB, were found in five (6.7%) probands, reducing LDL‐C by 56%. Rare variants in PCSK9, and ANGPTL3 completely correcting the hypercholesterolemic phenotype were not found. The common variants p.N902N, c.3842+82T>A, p.D2312D, and p.E4181K in APOB, and c.1863+94A>G in PCSK9 were significantly more prevalent in our cohort compared to the general European population. Interestingly, 40% of our probands carried at least one minor allele for all four common APOB variants compared to 1.5% in the general European population. While we found a low prevalence of rare variants in our cohort, our data suggest that regions in proximity of the analyzed loci, and linked to specific common haplotypes, might harbor additional variants that correct an ADH phenotype. Hum Mutat 33:448–455, 2012.

Homozygous autosomal dominant hypercholesterolaemia: prevalence, diagnosis, and current and future treatment perspectives.

Purpose of review Homozygous autosomal dominant hypercholesterolemia (hoADH) is a rare genetic disorder caused by mutations in LDL receptor, apolipoprotein B, and/or proprotein convertase subtilisin-kexin type 9. Both the genetic mutations and the clinical phenotype vary largely among individual patients, but patients with hoADH are typically characterized by extremely elevated LDL-cholesterol (LDL-C) levels, and a very high-risk for premature cardiovascular disease. Current lipid-lowering therapies include bile acid sequestrants, statins, and ezetimibe. To further decrease LDL-C levels in hoADH, lipoprotein apheresis is recommended, but this therapy is not available in all countries. Recent findings Recently, the microsomal triglyceride transfer protein inhibitor lomitapide and the RNA antisense inhibitor of apolipoprotein B mipomersen were approved by the Food and Drug Administration/European Medicine Agency and the Food and Drug Administration, respectively. Several other LDL-C-lowering strategies and therapeutics targeting the HDL-C pathway are currently in the clinical stage of development. Summary Novel therapies have been introduced for LDL-C-lowering and innovative drug candidates for HDL-C modulation for the treatment of hoADH. Here, we review the current available literature on the prevalence, diagnosis, and therapeutic strategies for hoADH.

Vascular risk factors, vascular disease, lipids and lipid targets in patients with familial dysbetalipoproteinemia: A European cross- sectional study

BACKGROUND Familial dysbetalipoproteinemia (FD), also known as type III hyperlipoproteinemia, is a genetic dyslipidemia characterized by elevated very low density lipoprotein (VLDL) and chylomicron remnant particles that confers increased risk of cardiovascular disease (CVD). The objective of this study was to evaluate the prevalence of vascular risk factors, CVD, lipid values, treatment and lipid targets in patients with FD across Europe. METHODS This cross-sectional study was performed in 305 patients with FD from seven academic hospitals in four European countries. Information was collected from clinical records. RESULTS Patients mean (±standard deviation) age was 60.9±14.4 years, 201 (66%) were male, 69 (23%) had diabetes mellitus (DM) and 87 (29%) had a prior history of CVD. Mean body mass index was 28.5±5.0 kg/m2. Lipid-lowering medication was used by 227 (74%) patients (27% usual dose (theoretical low-density lipoprotein cholesterol (LDL-C) reduction≤40%) and 46% intensive dose (theoretical LDL-C reduction>40%)). Non high-density lipoprotein cholesterol (non-HDL-C) levels below treatment target (<3.3 mmol/L) were present in 123 (40%) patients and 163 patients (53%) had LDL-C levels below target (<2.5 mmol/L). No significant determinants were found for having non-HDL-C levels below target, while a prior history of CVD (OR 1.90, 95%CI 1.05-3.47) and presence of DM (OR 2.00, 95%CI 1.08-3.70) were associated with having LDL-C levels below treatment target. CONCLUSION The majority of FD patients had non-HDL-C levels above the treatment target of 3.3 mmol/L. Intensive dose lipid-lowering medication was used by only half of the patients, leaving them at increased cardiovascular risk.

Is mipomersen ready for clinical implementation? A transatlantic dilemma.

Purpose of review Mipomersen has been approved by the US Food and Drug Administration as an orphan drug for patients with homozygous familial hypercholesterolemia (HoFH). In contrast, the European Medicines Agency advised negatively on the use of mipomersen. In this review, we discuss the efficacy and safety considerations for this discrepancy. Recent findings On the basis of the results of clinical trials with mipomersen, safety concerns have been raised regarding cardiovascular risk reduction and development of hepatic steatosis. In addition, (long-term) tolerability concerns have been raised predominantly regarding injection site reactions. A pooled analysis of cardiovascular events in phase III trials with mipomersen did not provide evidence for either a positive or negative effect on cardiovascular disease. Although long-term studies with mipomersen are eagerly awaited, hepatic fat content appears to stabilize after 6–12 months notwithstanding continued mipomersen administration. Summary HoFH is a disease with an unmet medical need for new lipid-lowering therapies. On the basis of a mean 2.9 mmol/l LDL-cholesterol reduction, mipomersen is expected to reduce cardiovascular risk in HoFH. Available evidence suggests that the fat accumulation associated with this treatment differs from steatohepatitis, which is a progressive and damaging liver disease. No evidence is available suggesting that injection site reactions because of mipomersen treatment will result in safety issues.