Increased FH-Risk-Score and Diabetes Are Cardiovascular Risk Equivalents in Heterozygous Familial Hypercholesterolemia.

BACKGROUND: Familial hypercholesterolemia (FH) is a genetic condition causing premature atherosclerotic cardiovascular disease (ASCVD). It is well established that patients with FH should be treated with statin therapy. However, there exists discordance concerning low-density lipoprotein cholesterol-lowering goals in the management of these patients between different guidelines worldwide. The objective was to compare the 10-year ASCVD risk of different subgroups of patients with and without FH including those with diabetes or a history of ASCVD and patients with FH within different FH-Risk-Score categories. METHODS: This multinational observational study used data from 3 different prospective cohorts. A total of 3383 FH and 6917 non-FH controls matched for age and sex were included (104 363 person-years of follow-up). The 10-year incident ASCVD risk was assessed using Kaplan-Meier estimates, whereas the relative risk was estimated using Cox proportional hazards regression models. RESULTS: FH patients with a high (score >20%) FH-Risk-Score (hazard ratio, 8.45 [95% CI, 6.69-10.67]; P<0.0001), FH patients with diabetes (hazard ratio, 7.67 [95% CI, 4.82-12.21]; P<0.0001), and non-FH patients with ASCVD (hazard ratio, 6.78 [95% CI, 5.45-8.42]; P<0.0001) had a significantly higher incident ASCVD risk over 10 years than the reference group (non-FH without ASCVD or diabetes). The observed 10-year risks in these groups were 32.1%, 30.8%, 30.0%, and 5.1%, respectively. The 10-year ASCVD risk associated with both FH and ASCVD was extremely high (observed risk of 50.7%; hazard ratio, 14.53 [95% CI, 12.14-17.38]; P<0.0001). CONCLUSIONS: This study strongly suggests that the observed risk of FH patients with diabetes, history of ASCVD, and FH-Risk-Score >20% is as high or higher than non-FH individuals with a history of ASCVD. More aggressive management should be recommended for these patients.

Efficacy and Safety of an Investigational Single-Course CRISPR Base-Editing Therapy Targeting PCSK9 in Nonhuman Primate and Mouse Models.

BACKGROUND: VERVE-101 is an investigational in vivo CRISPR base-editing medicine designed to alter a single DNA base in the PCSK9 gene, permanently turn off hepatic protein production, and thereby durably lower low-density lipoprotein cholesterol. We test the efficacy, durability, tolerability, and potential for germline editing of VERVE-101 in studies of nonhuman primates and a murine F1 progeny study. METHODS: Cynomolgus monkeys were given a single intravenous infusion of a vehicle control (n=10) or VERVE-101 at a dose of 0.75 mg/kg (n=4) or 1.5 mg/kg (n=22) with subsequent follow-up up to 476 days. Two studies assessed the potential for germline editing, including sequencing sperm samples from sexually mature male nonhuman primates treated with VERVE-101 and genotyping offspring from female mice treated with the murine surrogate of VERVE-101 (VERVE-101mu). RESULTS: Liver biopsies 14 days after dosing noted mean PCSK9 editing of 46% and 70% in monkeys treated with VERVE-101 at 0.75 and 1.5 mg/kg, respectively. This translated into mean reductions in blood PCSK9 (proprotein convertase subtilisin/kexin type 9) of 67% and 83% and reductions of low-density lipoprotein cholesterol of 49% and 69% at the 0.75 and 1.5 mg/kg doses, respectively, assessed as time-weighted average change from baseline between day 28 and up to 476 days after dosing. Liver safety monitoring noted a transient rise in alanine aminotransferase and aspartate aminotransferase concentrations after infusion that fully resolved by day 14 with no accompanying change in total bilirubin. In a subset of monkeys necropsied 1 year after dosing, no findings related to VERVE-101 were identified on macroscopic and histopathologic assessment of the liver and other organs. In the study to assess potential germline editing of male nonhuman primates, sperm samples collected after VERVE-101 dosing showed no evidence of PCSK9 editing. Among 436 offspring of female mice treated with a saturating dose of VERVE-101mu, the PCSK9 edit was transmitted in 0 of 436 animals. CONCLUSIONS: VERVE-101 was well tolerated in nonhuman primates and led to 83% lower blood PCSK9 protein and 69% lower low-density lipoprotein cholesterol with durable effects up to 476 days after dosing. These results have supported the initiation of a first-in-human clinical trial in patients with heterozygous familial hypercholesterolemia and atherosclerotic cardiovascular disease.

Subtyping Severe Hypercholesterolemia by Genetic Determinant to Stratify Risk of Coronary Artery Disease.

BACKGROUND: Severe hypercholesterolemia, defined as LDL (low-density lipoprotein) cholesterol (LDL-C) measurement ≥190 mg/dL, is associated with increased risk for coronary artery disease (CAD). Causes of severe hypercholesterolemia include monogenic familial hypercholesterolemia, polygenic hypercholesterolemia, elevated lipoprotein(a) [Lp(a)] hypercholesteremia, polygenic hypercholesterolemia with elevated Lp(a) (two-hit), or nongenetic hypercholesterolemia. The added value of using a genetics approach to stratifying risk of incident CAD among those with severe hypercholesterolemia versus using LDL-C levels alone for risk stratification is not known. METHODS: To determine whether risk stratification by genetic cause provided better 10-year incident CAD risk stratification than LDL-C level, a retrospective cohort study comparing incident CAD risk among severe hypercholesterolemia subtypes (genetic and nongenetic causes) was performed among 130 091 UK Biobank participants. Analyses were limited to unrelated, White British or Irish participants with available exome sequencing data. Participants with cardiovascular disease at baseline were excluded from analyses of incident CAD. RESULTS: Of 130 091 individuals, 68 416 (52.6%) were women, and the mean (SD) age was 56.7 (8.0) years. Of the cohort, 9.0% met severe hypercholesterolemia criteria. Participants with LDL-C between 210 and 229 mg/dL and LDL-C ≥230 mg/dL showed modest increases in incident CAD risk relative to those with LDL-C between 190 and 209 mg/dL (210-229 mg/dL: hazard ratio [HR], 1.3 [95% CI, 1.1-1.7]; ≥230 mg/dL: HR, 1.3 [95% CI, 1.0-1.7]). In contrast, when risk was stratified by genetic subtype, monogenic familial hypercholesterolemia, elevated Lp(a), and two-hit hypercholesterolemia subtypes had increased rates of incident CAD relative to the nongenetic hypercholesterolemia subtype (monogenic familial hypercholesterolemia: HR, 2.3 [95% CI, 1.4-4.0]; elevated Lp(a): HR, 1.5 [95% CI, 1.2-2.0]; two-hit: HR, 1.9 [95% CI, 1.4-2.6]), while polygenic hypercholesterolemia did not. CONCLUSIONS: Genetics-based subtyping for monogenic familial hypercholesterolemia and Lp(a) in those with severe hypercholesterolemia provided better stratification of 10-year incident CAD risk than LDL-C-based stratification.

Prevalence of FH-Causing Variants and Impact on LDL-C Concentration in European, South Asian, and African Ancestry Groups of the UK Biobank-Brief Report.

BACKGROUND: Familial hypercholesterolemia (FH) is a monogenic disease that causes high low-density lipoprotein cholesterol (LDL-C) and higher risk of premature coronary heart disease. The prevalence of FH-causing variants and their association with LDL-C in non-European populations remains largely unknown. Using DNA diagnosis in a population-based cohort, we aimed to estimate the prevalence of FH across 3 major ancestry groups in the United Kingdom. METHODS: Principal component analysis was used to distinguish genetic ancestry in UK Biobank participants. Whole exome sequencing data were analyzed to provide a genetic diagnosis of FH. LDL-C concentrations were adjusted for statin use. RESULTS: Principal component analysis distinguished 140 439 European, 4067 South Asian, and 3906 African participants with lipid and whole exome sequencing data. There were significant differences between the 3 groups, including total and LDL-C concentrations, and prevalence and incidence of coronary heart disease. We identified 488, 18, and 15 participants of European, South Asian, and African ancestry carrying a likely pathogenic or pathogenic FH-variant. No statistical difference in the prevalence of an FH-causing variant was observed: 1 out of 288 (95% CI, 1/316-1/264) in European, 1 out of 260 (95% CI, 1/526-1/173) in African, and 1 out of 226 (95% CI, 1/419-1/155) in South Asian. Carriers of an FH-causing variant had significantly higher LDL-C concentration than noncarriers in every ancestry group. There was no difference in median (statin-use adjusted) LDL-C concentration in FH-variant carriers depending on their ancestry background. Self-reported statin use was nonsignificantly highest in FH-variant carriers of South Asian ancestry (55.6%), followed by African (40.0%) and European (33.8%; P=0.15). CONCLUSIONS: The prevalence of FH-causing variants in the UK Biobank is similar across the ancestry groups analyzed. Despite overall differences in lipid concentrations, FH-variant carriers across the 3 ancestry groups had similar LDL-C levels. In all ancestry groups, the proportion of FH-variant carriers treated with lipid-lowering therapy should be improved to reduce future risk of premature coronary heart disease.

No effect of omega-3 polyunsaturated fatty acid supplementation on inflammatory markers in familial hypercholesterolemia: a randomized crossover trial.

Individuals with familial hypercholesterolemia (FH) have increased cardiovascular risk despite lipid-lowering therapy, and additional therapy is warranted. Omega-3 polyunsaturated fatty acid (n-3 PUFA) supplements have demonstrated an effect on cardiovascular endpoints in some clinical trials. Platelet-modifying and anti-inflammatory properties are among the proposed beneficial effects of n-3 PUFA. We investigated the effect of a high-dose n-3 PUFA supplement on platelet function and inflammatory markers in FH subjects. We performed a randomized, double-blind trial with a crossover design. Inclusion criteria were genetically verified heterozygous FH, stable disease, statin treatment >12 months, and age 18-75 years. Trial participants were allocated to two treatment periods in random order. The treatment periods (three months each) were separated by a three-month washout period. N-3 PUFA (1840 mg eicosapentaenoic acid and 1520 mg docosahexaenoic acid) and placebo (olive oil) were administered in four capsules daily. Endpoints were platelet function and inflammatory markers, assessed by platelet function analyzer, soluble markers P-selectin, vascular cell adhesion molecule (VCAM) and intercellular adhesion molecule (ICAM), 27 cytokines, and hematological parameters. Thirty-four heterozygous FH individuals completed the trial. No treatment effect (p = 0.93) from n-3 PUFA on the platelet function analyzer was found (2 s, 95% CI [-13, 6]). In our FH population, n-3 PUFA did not influence the levels of P-selectin (-2.0, 95% CI [-5.0, 2.0], p = 0.41), VCAM (0, 95% CI [-14.2, 14.2], p > 0.99), ICAM (-27.0, 95% CI [-70.1, 16.5]; p = 0.21), cytokine levels, or hematological parameters. In statin-treated FH individuals, high dose n-3 PUFA supplement did not affect platelet function and inflammatory markers.Trial registration number: EUDRACTNR 2012-000505-68; ClinicalTrials.gov NCT01813006HighlightsTrial studying the effect of omega-3 fatty acids supplements in familial hypercholesterolemia.High-dose omega-3 fatty acids supplements had no impact on platelet function.Cytokine levels were unchanged after three months of omega-3 fatty acid supplementation.No effect of omega-3 fatty acids on C-reactive protein was observed.

Familial Hypercholesterolemia-Risk-Score: A New Score Predicting Cardiovascular Events and Cardiovascular Mortality in Familial Hypercholesterolemia.

Objective: Familial hypercholesterolemia (FH) is associated with a high risk of premature atherosclerotic cardiovascular disease (ASCVD). However, this risk is highly heterogeneous and current risk prediction algorithms for FH suffer from limitations. The primary objective of this study was to develop a score predicting incident ASCVD events over 10 years in a large multinational FH cohort. The secondary objective was to investigate the prediction of major adverse cardiovascular events and cardiovascular mortality using this score. Approach and Results: We prospectively followed 3881 patients with adult heterozygous FH with no prior history of ASCVD (32 361 person-years of follow-up) from 5 registries in Europe and North America. The FH-Risk-Score incorporates 7 clinical variables: sex, age, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, hypertension, smoking, and lipoprotein (a) (Lp(a)) with a Harrell C-index for 10-year ASCVD event of 0.75, which was superior to the SAFEHEART-RE (Spanish Familial Hypercholesterolemia Cohort; 0.69). Subjects with an elevated FH-Risk-Score had decreases in 10-year ASCVD-free survival, 10-year major adverse cardiovascular event-free survival, and 30-year survival for CV mortality compared with the low-risk group, with hazard ratios of 5.52 (3.94-7.73), 4.64 (2.66-8.11), and 10.73 (2.51-45.79), respectively. The FH-Risk-Score showed a similar performance in subjects with and without an FH-causing mutation. Conclusions: The FH-Risk-Score is a stronger predictor of future ASCVD than the SAFEHEART-RE and was developed in FH subjects with no prior cardiovascular event. Furthermore, the FH-Risk-Score is the first score to predict CV death and could offer personalized cardiovascular risk assessment and treatment for patients with FH. Future studies are required to validate the FH-Risk-Score in different ethnic groups.

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.

Cascade Screening for Familial Hypercholesterolemia in South Africa: The Wits FIND-FH Program.

OBJECTIVE: Due to gene founder effects, familial hypercholesterolemia (FH) has a prevalence of ≈1:80 in populations of Afrikaner ancestry and is a major contributor to premature atherosclerotic cardiovascular disease in South Africans of Jewish and Indian descent. No systematic program exists to identify these families. Furthermore, information regarding FH prevalence in Black Africans is sparse. The Wits FIND-FH program was initiated in late 2016 to address these issues. Approach and Results: Based on index subjects with definite or probable FH, first-degree relatives were contacted, informed consent obtained, and targeted medical history, physical examination, and blood samples collected. In patients with likely FH using the Simon Broome criteria, DNA analysis for LDLR (low-density lipoprotein receptor), APOB (apolipoprotein B), PCSK9 (proprotein convertase subtilisin/kexin type 9), and LDLRAP1 (LDLR adaptor protein 1) variants was analyzed by next-generation sequencing. Of the initial 700 subjects screened of whom 295 (42%) were index cases, 479 (68.4%) were clinically diagnosed with probable or definite FH. Genetic analysis confirmed 285 of 479 (59.5%) as having variants consistent with FH. Three subjects met the clinical diagnosis for homozygous FH, but DNA analysis revealed a further 34 patients, including 4 Black African subjects, with ≥2 FH-causing variants. CONCLUSIONS: Using phenotype cascade screening, the Wits FIND-FH program has screened an average of 30 subjects monthly of whom 68% had a clinical diagnosis of FH with ≈60% genetically confirmed. The program is identifying a small but growing number of Black South Africans with FH. Interestingly, 37 subjects (7.7%) who underwent DNA testing were found to have ≥2 FH-causing variants.

PCSK9: From Basic Science Discoveries to Clinical Trials.

Unknown 15 years ago, PCSK9 (proprotein convertase subtilisin/kexin type 9) is now common parlance among scientists and clinicians interested in prevention and treatment of atherosclerotic cardiovascular disease. What makes this story so special is not its recent discovery nor the fact that it uncovered previously unknown biology but rather that these important scientific insights have been translated into an effective medical therapy in record time. Indeed, the translation of this discovery to novel therapeutic serves as one of the best examples of how genetic insights can be leveraged into intelligent target drug discovery. The PCSK9 saga is unfolding quickly but is far from complete. Here, we review major scientific understandings as they relate to the role of PCSK9 in lipoprotein metabolism and atherosclerotic cardiovascular disease and the impact that therapies designed to inhibit its action are having in the clinical setting.

Risk of Ischemic Stroke and Total Cerebrovascular Disease in Familial Hypercholesterolemia: A Register Study From Norway.

Background and Purpose- Familial hypercholesterolemia (FH) is a common autosomal dominant disease leading to increased level of serum LDL (low-density lipoprotein) cholesterol and risk of coronary heart disease. Whether FH increases the risk of cerebrovascular disease, including ischemic stroke, is debated. Accordingly, we studied the incidence of cerebrovascular disease in a cohort of people with genetically verified FH compared with the entire Norwegian population and examined whether people in this cohort with previous cohort had increased risk of cerebrovascular disease. Methods- Incidence rates of hospitalization for cerebrovascular disease (among 3144 people with FH) and ischemic stroke (among 3166 people with FH) were estimated by linkage of FH people to Cardiovascular Disease in Norway-a nationwide database of cardiovascular disease hospitalizations (2001-2009). We calculated standardized incidence ratios and used Cox regression to estimate hazard ratios. Results- A total of 46 cases (19 women and 27 men) of cerebrovascular disease were observed in the cohort of people with FH, with no increased risk of cerebrovascular disease compared with the general population (standardized incidence ratio, 1.0; 95% CI, 0.8-1.4). Total number of ischemic strokes in the cohort of people with FH was 26 (9 women and 17 men), with no increased risk compared with the general population (standardized incidence ratio, 1.0; 95% CI, 0.7-1.5). Prior coronary heart disease significantly increased cerebrovascular disease risk in women (hazard ratio, 3.29; 95% CI, 1.20-9.00) but not in men (hazard ratio, 1.03; 95% CI, 0.45-2.37; Pinteraction=0.04). Conclusions- In a large cohort of genetically verified FH, risks of cerebrovascular disease and ischemic stroke were not increased compared with the total Norwegian population.

Relationship Between Total Serum Bilirubin Levels and Carotid and Femoral Atherosclerosis in Familial Dyslipidemia.

OBJECTIVE: Bilirubin is a potent antioxidant that has been inversely related to cardiovascular disease. There is little information on serum total bilirubin (TB) in relation to atherosclerosis in familial dyslipidemia. We assessed the association between TB and carotid and femoral atherosclerosis in this high-risk group. APPROACH AND RESULTS: We evaluated 464 individuals with familial dyslipidemia (56% men; median age, 48 years), 322 with familial hypercholesterolemia, and 142 with familial combined hyperlipidemia. Carotid and femoral arteries were imaged bilaterally with a standardized ultrasonographic protocol. Mean and maximum intima-media thickness and plaque presence (≥1.2 mm) and height were recorded. Cross-sectional associations between TB and atherosclerosis variables were investigated in multivariable-adjusted models, including lipid values and hypolipidemic drug use. Inflammatory markers (C-reactive protein, total leukocyte count, and lipoprotein[a]) were also determined. Increasing TB levels were associated with decreasing intima-media thickness of all carotid segments (P<0.05, all). TB also related to carotid plaque, present in 78% of individuals, and to plaque burden (≥3 plaques), with odds ratios (95% confidence interval) 0.59 (0.36-0.98) and 0.57 (0.34-0.96) for each increase of 0.5 mg in TB, respectively. Findings were confirmed in a validation cohort of 177 subjects with nonfamilial dyslipidemia. Only the familial combined hyperlipidemia group, with higher inflammation-related markers, showed an inverse association between TB and femoral plaque height (ß=-0.183; P=0.030). CONCLUSIONS: TB was inversely and independently associated with carotid plaque burden in familial and nonfamilial dyslipidemia. These findings support the use of TB as a biomarker of atherosclerosis in this high-risk group.

Prevalence of Familial Hypercholesterolemia in the 1999 to 2012 United States National Health and Nutrition Examination Surveys (NHANES).

BACKGROUND: The prevalence of familial hypercholesterolemia (FH) is commonly reported as 1 in 500. European reports suggest a higher prevalence; the US FH prevalence is unknown. METHODS AND RESULTS: The 1999 to 2012 National Health and Nutrition Examination Survey (NHANES) participants ≥20 years of age (n=36 949) were analyzed to estimate the prevalence of FH with available Dutch Lipid Clinic criteria, including low-density lipoprotein cholesterol and personal and family history of premature atherosclerotic cardiovascular disease. Prevalence and confidence intervals of probable/definite FH were calculated for the overall population and by age, sex, obesity status (body mass index ≥30 kg/m(2)), and race/ethnicity. Results were extrapolated to the 210 million US adults ≥20 years of age. The estimated overall US prevalence of probable/definite FH was 0.40% (95% confidence interval, 0.32-0.48) or 1 in 250 (95% confidence interval, 1 in 311 to 209), suggesting that 834 500 US adults have FH. Prevalence varied by age, being least common in 20 to 29 year olds (0.06%, 1 in 1557) and most common in 60 to 69 year olds (0.85%, 1 in 118). FH prevalence was similar in men and women (0.40%, 1 in 250) but varied by race/ethnicity (whites: 0.40%, 1 in 249; blacks: 0.47%, 1 in 211; Mexican Americans: 0.24%, 1 in 414; other races: 0.29%, 1 in 343). More obese participants qualified as probable/definite FH (0.58%, 1 in 172) than nonobese (0.31%, 1 in 325). CONCLUSIONS: FH, defined with Dutch Lipid Clinic criteria available in NHANES, affects 1 in 250 US adults. Variations in prevalence by age and obesity status suggest that clinical criteria may not be sufficient to estimate FH prevalence.

Carotid intima-media thickness in children with familial hypercholesterolemia.

RATIONALE: Familial hypercholesterolemia (FH) predisposes patients to premature cardiovascular disease, with the process of atherosclerosis initiated in early childhood. OBJECTIVE: As part of an ongoing trial to assess the efficacy and safety of rosuvastatin in children with FH aged 6 to 17 years, we report the differences in carotid intima-media thickness (cIMT) at baseline between children with FH and their unaffected siblings. METHODS AND RESULTS: B-mode ultrasound measurements of the carotid artery were made in 196 children with FH and 64 of their siblings. Mean (±SE) cIMT in children with FH was significantly greater than that of unaffected siblings (0.398±0.052 versus 0.377±0.045 mm; P<0.001). A significantly greater cIMT value was observed before the age of 8 years. Multivariable analyses showed that age, male sex, and presence of FH were independent predictors of cIMT. CONCLUSIONS: The difference in mean cIMT between children with FH and their unaffected siblings may be significant as early as age 8 years. This study confirms the need for early cholesterol lowering in this high-risk population. These patients participating in a carefully monitored study will help assess the long-term efficacy on cIMT and safety of statin therapy in young children.

PCSK9: a key modulator of cardiovascular health.

Since the discovery of proprotein convertase subtilisin kexin 9 (PCSK9) in 2003, this PC has attracted a lot of attention from the scientific community and pharmaceutical companies. Secreted into the plasma by the liver, the proteinase K-like serine protease PCSK9 binds the low-density lipoprotein (LDL) receptor at the surface of hepatocytes, thereby preventing its recycling and enhancing its degradation in endosomes/lysosomes, resulting in reduced LDL-cholesterol clearance. Surprisingly, in a nonenzymatic fashion, PCSK9 enhances the intracellular degradation of all its target proteins. Rare gain-of-function PCSK9 variants lead to higher levels of LDL-cholesterol and increased risk of cardiovascular disease; more common loss-of-function PCSK9 variants are associated with reductions in both LDL-cholesterol and risk of cardiovascular disease. It took 9 years to elaborate powerful new PCSK9-based therapeutic approaches to reduce circulating levels of LDL-cholesterol. Presently, PCSK9 monoclonal antibodies that inhibit its function on the LDL receptor are evaluated in phase III clinical trials. This review will address the biochemical, genetic, and clinical aspects associated with PCSK9's biology and pathophysiology in cells, rodent and human, with emphasis on the clinical benefits of silencing the expression/activity of PCSK9 as a new modality in the treatment of hypercholesterolemia and associated pathologies.

AAV vectors expressing LDLR gain-of-function variants demonstrate increased efficacy in mouse models of familial hypercholesterolemia.

RATIONALE: Familial hypercholesterolemia is a genetic disorder that arises because of loss-of-function mutations in the low-density lipoprotein receptor (LDLR) and homozygous familial hypercholesterolemia is a candidate for gene therapy using adeno-associated viral vectors. Proprotein convertase subtilisin/kexin type 9 (PCSK9) and inducible degrader of LDLR (IDOL) negatively regulate LDLR protein and could dampen adeno-associated viral vector encoded LDLR expression. OBJECTIVE: We sought to create vectors expressing gain-of-function human LDLR variants that are resistant to degradation by human PCSK9 (hPCSK9) and IDOL and thereby enhance hepatic LDLR protein abundance and plasma LDL cholesterol reduction. METHODS AND RESULTS: Amino acid substitutions were introduced into the coding sequence of human LDLR cDNA to reduce interaction with hPCSK9 and human IDOL. A panel of mutant human LDLRs was initially screened in vitro for escape from PCSK9. The variant human LDLR-L318D was further evaluated using a mouse model of homozygous familial hypercholesterolemia lacking endogenous LDLR and apolipoprotein B mRNA editing enzyme catalytic, APOBEC-1 (double knockout). Administration of wild-type human LDLR to double knockout mice, expressing hPCSK9, led to diminished LDLR activity. However, LDLR-L318D was resistant to hPCSK9-mediated degradation and effectively reduced cholesterol levels. Similarly, the LDLR-K809R\C818A construct avoided human IDOL regulation and achieved stable reductions in serum cholesterol. An adeno-associated viral vector serotype 8.LDLR-L318D\K809R\C818A vector that carried all 3 amino acid substitutions conferred partial resistance to both hPCSK9- and human IDOL-mediated degradation. CONCLUSIONS: Amino acid substitutions in the human LDLR confer partial resistance to PCSK9 and IDOL regulatory pathways with improved reduction in cholesterol levels and improve on a potential gene therapeutic approach to treat homozygous familial hypercholesterolemia subjects.

Mipomersen, an antisense oligonucleotide to apolipoprotein B-100, reduces lipoprotein(a) in various populations with hypercholesterolemia: results of 4 phase III trials.

OBJECTIVE: Lp(a) is an independent, causal, genetic risk factor for cardiovascular disease and aortic stenosis. Current pharmacological lipid-lowering therapies do not optimally lower Lp(a), particularly in patients with familial hypercholesterolemia (FH). APPROACH AND RESULTS: In 4 phase III trials, 382 patients on maximally tolerated lipid-lowering therapy were randomized 2:1 to weekly subcutaneous mipomersen 200 mg (n=256) or placebo (n=126) for 26 weeks. Populations included homozygous FH, heterozygous FH with concomitant coronary artery disease (CAD), severe hypercholesterolemia, and hypercholesterolemia at high risk for CAD. Lp(a) was measured 8× between baseline and week 28 inclusive. Of the 382 patients, 57% and 44% had baseline Lp(a) levels >30 and >50 mg/dL, respectively. In the pooled analysis, the mean percent decrease (median, interquartile range in Lp(a) at 28 weeks was significantly greater in the mipomersen group compared with placebo (-26.4 [-42.8, -5.4] versus -0.0 [-10.7, 15.3]; P<0.001). In the mipomersen group in patients with Lp(a) levels >30 or >50 mg/dL, attainment of Lp(a) values ≤30 or ≤50 mg/dL was most frequent in homozygous FH and severe hypercholesterolemia patients. In the combined groups, modest correlations were present between percent change in apolipoprotein B-100 and Lp(a) (r=0.43; P<0.001) and low-density lipoprotein cholesterol and Lp(a) (r=0.36; P<0.001) plasma levels. CONCLUSIONS: Mipomersen consistently and effectively reduced Lp(a) levels in patients with a variety of lipid abnormalities and cardiovascular risk. Modest correlations were present between apolipoprotein B-100 and Lp(a) lowering but the mechanistic relevance mediating Lp(a) reduction is currently unknown.

Real-world effectiveness of monoclonal antibody inhibitors of PCSK9 in patients with heterozygous familial hypercholesterolemia: A retrospective cohort study.

BACKGROUND: Heterozygous familial hypercholesterolemia (HeFH) is a genetic condition that is associated with a high risk of atherosclerotic cardiovascular disease (ASCVD) due to elevated lipid levels. Proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibody inhibitors have been shown to reduce low-density lipoprotein cholesterol (LDL-C) substantially. This study aimed to assess the real-world effectiveness of PCSK9 inhibitor therapy among patients with HeFH. METHODS: Retrospective cohort study of patients with probable or definite HeFH on a PCSK9 inhibitor at a specialized lipid clinic between 2015 and 2022. The primary objective was the proportion of patients who attained a ≥50% reduction in LDL-C after 12 months of treatment. RESULTS: In total, 141 patients were screened and 95 were included. Mean age was 63 years, 51% were female, and mean baseline LDL-C level was 4.0 mmol/L (155 mg/dL). A majority of patients (60%) had statin intolerance, and 73% were on ezetimibe. The most common PCSK9 inhibitor was evolocumab (94%). Overall, 74% of patients achieved a ≥50% reduction in LDL-C after 12 months of therapy. Mean LDL-C concentration decreased to 1.7 mmol/L (66 mg/dL) (approximately 59% reduction from baseline) after 12 months of follow-up but increased to 1.9 mmol/L (73 mg/dL) after ≥24 months of follow-up. Similar trends were observed in non-high-density lipoprotein cholesterol and apolipoprotein B. Lipoprotein(a) was significantly reduced by 45% over 12 months. Twelve percent of patients permanently discontinued therapy. Barriers to PCSK9i use were mostly related to cost. CONCLUSIONS: In a real-world cohort of HeFH patients, most of which were intolerant to statins, a high majority were able to achieve a ≥50% reduction in LDL-C after 12 months of PCSK9 inhibitor therapy (mean reduction of approximately 59%), which is similar to clinical trial data of patients with ASCVD. A significant reduction in non-high-density lipoprotein cholesterol, apolipoprotein B, and lipoprotein(a) were also observed.