Proprotein Convertase Subtilisin/kexin Type 9 mAbs Research Articles

Proprotein convertase subtilisin/kexin type 9-inhibition across different patient populations.

Monoclonal antibodies (mAb) targeting proprotein convertase subtilisin/kexin type 9 (PCSK9) have been established in cardiovascular risk prevention. The purpose of this review is to summarize the effects of PCSK9 inhibitors across different patient populations. Long-term data on the use of evolocumab and alirocumab shows persisting low- density lipoprotein cholesterol (LDL-C) lowering and good tolerability. PCSK9 inhibitors are effective and safe in both sexes, in pediatric patients as well as in the elderly. Initiation of PCSK9 mAb during acute myocardial infarction is safe and leads to beneficial morphological plaque changes. The PCSK9 inhibitors evolocumab, alirocumab and inclisiran lower LDL-C in patients with heterozygous familial hypercholesterolemia (FH), while the response of patients with homozygous FH is heterogeneous. New areas of application beyond lipid lowering are currently investigated. PCSK9 inhibitors are safe, well tolerated, and effective in primary and secondary prevention in a wide range of patient populations.

Optimal follow-up schedule for patients taking PCSK9 monoclonal antibodies in a health system: Analysis of specialty pharmacy clinical interventions.

In an effort to expedite the publication of articles, AJHP is posting manuscripts online as soon as possible after acceptance. Accepted manuscripts have been peer-reviewed and copyedited, but are posted online before technical formatting and author proofing. These manuscripts are not the final version of record and will be replaced with the final article (formatted per AJHP style and proofed by the authors) at a later time. The objective of this study was to determine if and when it is clinically appropriate to consider a reduction in the frequency of health-system specialty pharmacy (HSSP) clinical pharmacist assessments for patients taking a proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibody (mAb) after they are deemed clinically stable on therapy. A single-center, retrospective, observational study of adult patients on PCSK9 mAb therapy enrolled in the University of Rochester Specialty Pharmacy Cardiology Patient Management Program was performed between October 24, 2016, and April 30, 2022. The primary outcome was the number of clinical pharmacist interventions per interval within the baseline 12 months compared to 12-month intervals for up to 72 months after initiation of PCSK9 mAb therapy. A total of 368 patients on PCSK9 mAb therapy were included in the study. A significantly lower percentage of patients had more than 2 interventions during the 12- to 24-month interval (24.3%) as compared to the baseline 12-month interval (80.2%) (P < 0.001); this represented a 70% reduction in the chance of a patient requiring more than 2 interventions (relative risk, 0.30; 95% CI, 0.24-0.38). A similar trend was demonstrated in the 24- to 36-month and 36- to 48-month intervals when compared to the first year of therapy. The most commonly documented clinical pharmacist interventions were the categories of safety (29.2%), effectiveness (28.4%), and adherence (19.9%). Patients beyond 1 year of PCSK9 mAb therapy required less clinical pharmacist interventions. Therefore, stable patients receiving a PCSK9 mAb may be considered for less frequent clinical assessments to allow for HSSP growth to nontraditional clinical areas.

Small-interfering RNA targeting proprotein convertase subtilisin/kexin type 9 might promote fatty liver disease and hepatocellular carcinoma through upregulation of CD36.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to low-density lipoprotein (LDL) receptor and fatty acid translocase CD36, inducing lysosomal degradation of these two receptors in the liver cells. Both monoclonal antibody (mAb) and small-interfering RNA (siRNA) targeting PCSK9 have been designed for treatment of familial hypercholesterolemia recently, with elevating LDL receptors on the liver cell surface and increasing LDL uptake as the main beneficial mechanism. However, given that the binding domains of PCSK9 for LDL receptor and CD36 are different, and PCSK9 mAb only attacks the domain for LDL receptor, CD36 expression remains partially controlled under PCSK9 mAb treatment. In contrast, PCSK9 siRNA brings on complete loss of PCSK9, resulting in overexpression of CD36. Based on the fact that CD36 is a key factor in the pathogenesis of non-alcoholic fatty liver disease (NAFLD) and subsequent hepatocellular carcinoma (HCC), the risk of developing NAFLD and HCC on long-term use of PCSK9 siRNA is thus raised as a hypothesis. Additionally, because CD36 is also involved in the promotion of malignant diseases other than HCC, such as acute myeloid leukemia, gastric cancer, breast cancer, and colorectal cancer, the speculative danger of flourishing these malignancies by PCSK9 siRNA is discussed as well.

Composition and distribution of lipoproteins after evolocumab in familial dysbetalipoproteinemia: A randomized controlled trial

Proprotein convertase subtilisin kexin type 9 (PCSK9) monoclonal antibodies (mAbs) reduce fasting and post fat load cholesterol in non-HDL and intermediate density lipoprotein (IDL) in familial dysbetalipoproteinemia (FD). However, the effect of PCSK9 mAbs on the distribution and composition of atherogenic lipoproteins in patients with FD is unknown. To evaluate the effect of the PCSK9 mAb evolocumab added to standard lipid-lowering therapy in patients with FD on fasting and post fat load lipoprotein distribution and composition. Randomized placebo-controlled double-blind crossover trial comparing evolocumab (140 mg subcutaneous every 2 weeks) with placebo during two 12-week treatment periods. Patients received an oral fat load at the start and end of each treatment period. Apolipoproteins (apo) were measured with ultracentrifugation, gradient gel electrophoresis, retinyl palmitate and SDS-PAGE. PCSK9 mAbs significantly reduced particle number of all atherogenic lipoproteins, with a stronger effect on smaller lipoproteins than on larger lipoproteins (e.g. IDL-apoB 49%, 95%confidence interval (CI) 41-59 and very low-density lipoprotein (VLDL)-apoB 33%, 95%CI 16-50). Furthermore, PCSK9 mAbs lowered cholesterol more than triglyceride (TG) in VLDL, IDL and low-density lipoprotein (LDL) (e.g. VLDL-C 48%, 95%CI 29-63%; and VLDL-TG 20%, 95%CI 6.3-41%). PCSK9 mAbs did not affect the post fat load response of chylomicrons. PCSK9 mAbs added to standard lipid-lowering therapy in FD patients significantly reduced lipoprotein particle number, in particular the smaller and more cholesterol-rich lipoproteins (i.e. IDL and LDL). PCSK9 mAbs did not affect chylomicron metabolism. It seems likely that the observed effects are achieved by increased hepatic lipoprotein clearance, but the specific working mechanism of PCSK9 mAbs in FD patients remains to be elucidated.

LDL lowering effect of PCSK9 inhibition is reduced in women.

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a key regulator of plasma low-density lipoprotein cholesterol (LDL-C) concentration, and its inhibition reduces the risk of atherosclerotic cardiovascular disease (ASCVD). We aimed to assess the sex-differential effect of either pharmacological or genetic inhibition of PCSK9 on LDL-C levels. We meta-analyzed six real-life studies (1216 men and 641 women) that investigated the effects of PCSK9 monoclonal antibodies (mAbs) on LDL-C reduction in men and women. Despite higher LDL-C levels in women at baseline [mean difference (MD)=17.4mg/dL, P<0.0001, women = 175mg/dL vs. men = 152mg/dL], the LDL-C reduction under PCSK9 mAb treatment was significantly greater in men (MD=7.6mg/dL, 95% confidence interval: 2.7-12.4, P=0.002) than in women.We tested the sex-related association of the loss-of-function variant PCSK9-R46L with LDL-C plasma levels in 382 813 individuals (219 301 women and 163 512 men) free of lipid-lowering drugs from the UK Biobank general population cohort. The magnitude of LDL-C reduction was larger in men than in women (mean LDL-C difference: -35mg/dL vs. -26mg/dL, when comparing homozygous carriers with non-carriers in men and women, respectively). The relationship between PCSK9-R46L and LDL-C was significantly dependent on sex (P for interaction=7.2e-04). These results demonstrate by complementary approaches that the decrease in LDL-C mediated by PCSK9 inhibition is slightly, but significantly, less marked in women than in men. These data reinforce the need for specific studies to develop sex-specific recommendations for the management of ASCVD in women.

Latest clinical evidence about the effect of PCSK9 monoclonal antibodies in patients with familial hypercholesterolaemia: an updated meta-analysis.

Familial hypercholesterolaemia (FH) is the most common autosomal genetic disease of cholesterol metabolism disorder. Proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibody (mAb) is a new target lipid-regulating drug related to cholesterol metabolism that has been developed in recent years. The reported rate of reduction varies widely, and comprehensive assessments of efficacy and safety are lacking. Therefore, we conducted this study to investigate the clinical effect of PCSK9 mAbs in patients with familial hypercholesterolaemia to provide a theoretical reference for clinical practice. We analysed the clinical data of patients, including the percentage change in LDL-C and the incidence rates of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs), from selected articles. Weighted mean differences (WMDs), risk ratios (RRs), and 95% confidence intervals (95% CIs) were calculated to compare the endpoints. The results showed that, compared with placebo, the PCSK9 mAb reduced the percentage change in LDL-C in FH patients (WMD = -45.52, 95% CI: -49.70 to -41.34, I2 = 99.6%). In addition, there was no significant difference between the experimental and placebo groups in the incidence of TEAEs (RR = 1.03, 95% CI: 0.97 to 1.10, I2 = 19.1%) and SAEs (RR = 1.02, 95% CI: 0.72 to 1.44, I2 = 0.0%). Overall, PSCK9 mAbs are an effective and safe method of LDL-C reduction in patients with FH.

PCSK9 Biology and Its Role in Atherothrombosis.

It is now about 20 years since the first case of a gain-of-function mutation involving the as-yet-unknown actor in cholesterol homeostasis, proprotein convertase subtilisin/kexin type 9 (PCSK9), was described. It was soon clear that this protein would have been of huge scientific and clinical value as a therapeutic strategy for dyslipidemia and atherosclerosis-associated cardiovascular disease (CVD) management. Indeed, PCSK9 is a serine protease belonging to the proprotein convertase family, mainly produced by the liver, and essential for metabolism of LDL particles by inhibiting LDL receptor (LDLR) recirculation to the cell surface with the consequent upregulation of LDLR-dependent LDL-C levels. Beyond its effects on LDL metabolism, several studies revealed the existence of additional roles of PCSK9 in different stages of atherosclerosis, also for its ability to target other members of the LDLR family. PCSK9 from plasma and vascular cells can contribute to the development of atherosclerotic plaque and thrombosis by promoting platelet activation, leukocyte recruitment and clot formation, also through mechanisms not related to systemic lipid changes. These results further supported the value for the potential cardiovascular benefits of therapies based on PCSK9 inhibition. Actually, the passive immunization with anti-PCSK9 antibodies, evolocumab and alirocumab, is shown to be effective in dramatically reducing the LDL-C levels and attenuating CVD. While monoclonal antibodies sequester circulating PCSK9, inclisiran, a small interfering RNA, is a new drug that inhibits PCSK9 synthesis with the important advantage, compared with PCSK9 mAbs, to preserve its pharmacodynamic effects when administrated every 6 months. Here, we will focus on the major understandings related to PCSK9, from its discovery to its role in lipoprotein metabolism, involvement in atherothrombosis and a brief excursus on approved current therapies used to inhibit its action.

Enhancing the value of PCSK9 monoclonal antibodies by identifying patients most likely to benefit. A consensus statement from the National Lipid Association

Acquisition costs and cost-effectiveness have limited access and recommendations to use proprotein convertase subtilisin/kexin type 9 (PCSK9)–inhibiting monoclonal antibodies (mAbs). Recently, prices were reduced by 60% for alirocumab and evolocumab. This statement systematically reviewed subgroup analyses from statin and PCSK9 mAb trials to identify higher risk groups for which PCSK9 mAbs at the new price could be considered a reasonable (<US$100,000 per quality adjusted life year [QALY]) or high (<US$50,000 per QALY) value. In patients at extremely high risk, with a high burden of athersclerotic cardiovascular disease (ASCVD) or ASCVD with multiple poorly controlled or adverse risk factors, PCSK9 mAbs can provide reasonable value when low-density lipoprotein cholesterol (LDL-C) is ≥70 mg/dL. In patients at very high risk (ASCVD without peripheral arterial disease and lower levels of poorly controlled risk factors), PCSK9 mAbs provide a reasonable value when LDL-C levels are ≥100 mg/dL. High-risk patients (less-extensive ASCVD with well-controlled risk factors) may experience reasonable value when LDL-C levels are ≥130 mg/dL. Patients with heterozygous familial hypercholesterolemia or severe hypercholesterolemia with untreated LDL-C levels ≥220 mg/dL also should experience reasonable or high value from PCSK9 mAbs when LDL-C is ≥100 mg/dL for primary prevention and ≥70 mg/dL for secondary prevention.

Potential utility of the SAFEHEART risk equation for rationalising the use of PCSK9 monoclonal antibodies in adults with heterozygous familial hypercholesterolemia

Background and aimsPatients with familial hypercholesterolaemia (FH) may require proprotein convertase subtilisin/kexin-type 9 (PCSK9) mAb as add-on therapy to achieve LDL-cholesterol (LDL-C) goals. However, the current cost of these therapies means that choosing suitable patients is based on consensus or clinical judgement rather than a quantitative risk assessment. We used the SAFEHEART Risk Equation (RE) to estimate the number needed to treat (NNT) at different risk thresholds and baseline LDL-C to identify those FH patients more likely to derive the greatest benefit from PCSK9 mAb. MethodsFive-year event rates were calculated using the SAFEHEART-RE for every patient, overall and across LDL-C strata. A 60% reduction of LDL-C after theoretical treatment with PCSK9 mAb was assumed. Individual absolute risk simulating the effects of PCSK9 inhibition was calculated using the SAFEHEART-RE and, in a similar way, by using the Cholesterol Treatment Trialists’ (CTT) Collaboration criteria. Absolute risk reduction and NNTs were calculated. ResultsOf the total SAFEHEART population, 2,153 were FH cases aged 18 years or older, on maximum tolerated lipid lowering treatment. NNTs were dependent of both baseline predicted risk and baseline LDL-C level ranging from 44 to 17 for those with 5-year risk of ≥1 to ≥5. The smallest NNT (12) was observed among those with 5-year risk of ≥5% and LDL-C ≥160 mg/dl. Using the CTT criteria produced similar results. ConclusionsThe SAFEHEART-RE may provide a useful quantitative tool for rationalising the selection of FH patients who might derive greater absolute benefits from PCSK9 mAb.

Vaccines Targeting PCSK9: A Promising Alternative to Passive Immunization with Monoclonal Antibodies in the Management of Hyperlipidaemia?

Hypercholesterolaemia is frequently observed in patients with cardiovascular diseases (CVD) and is associated with increased mortality. Statin treatment has been the standard of care for reducing low-density lipoprotein cholesterol (LDL-C) to improve cardiovascular outcomes. However, statins have limited effects in some patients and may be discontinued due to adverse effects resulting in LDL-C above target levels. The proprotein convertase subtilisin kexin type 9 (PCSK9) is a pivotal regulator in the LDL-C metabolism by degrading the LDL-C receptor on hepatocytes. Inhibition of PCSK9 by monoclonal antibodies (mAb) significantly lowers LDL-C levels and is considered to reduce the likelihood of adverse cardiac events. However, such treatment regimens are not cost-effective, and require frequent administrations at high doses that may be associated with side effects and poor drug adherence. Furthermore, it has been shown that these PCSK9 medicines may trigger the formation of antidrug antibodies followed by a significant attenuation of the LDL-C-lowering effect. Active vaccination inducing high-affinity antibodies against PCSK9 with less frequent administration intervals may be a novel promising therapeutic approach to overcome the drawback of passive immunization with PCSK9 mAb. However there is a paucity of available clinical safety and efficacy data. This article discusses challenges in the development of PCSK9 vaccines and their potential therapeutic benefits by reviewing clinical studies that evaluated the safety and efficacy of PCSK9 mAb.

Identifying Patients for Nonstatin Therapy.

Statins are first-line therapy for reducing atherosclerotic cardiovascular disease (ASCVD) risk. Some patients remain at high ASCVD risk despite maximizing statin therapy. Ezetimibe and proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies (mAbs) have been shown to reduce ASCVD events in randomized trials and may be of benefit in selected high-risk patients with cardiovascular disease (CVD) or familial hypercholesterolemia (FH). Number-needed-to-treat (NNT) to prevent one ASCVD event can help identify groups of patients who may gain a net benefit from added nonstatin therapy. Patient groups with NNTs <25 (in whom PCSK9 mAbs may approach cost effectiveness with discounting) include extremely high-risk patients (those with CVD with FH, polyvascular disease, or recurrent ASCVD events) with lowdensity lipoprotein cholesterol (LDL-C) levels ≥70 mg/dL, very high-risk patients (those with CVD with diabetes [and no polyvascular disease], chronic kidney disease, or acute coronary syndromes, or CVD or FH with poorly controlled risk factors) with LDL-C levels ≥100 mg/dL, and high-risk patients (those with CVD or FH with well-controlled risk factors) with LDL-C ≥130 mg/dL. Ezetimibe, which is generic in the United States, is reasonable for patient groups with NNTs <30, the level considered reasonable by most patients. This includes extremely high-risk patients with LDL-C levels ≥130 mg/dL, or very high-risk patients with LDL-C ≥190 mg/dL. All guidelines recommend statin therapy for the prevention of ASCVD.

PCSK9 in context: A contemporary review of an important biological target for the prevention and treatment of atherosclerotic cardiovascular disease.

The identification of the critical role of proprotein convertase subtilisin/kexin type 9 (PCSK9) has rapidly led to the development of PCSK9 inhibition with monoclonal antibodies (mAbs). PCSK9 mAbs are already in limited clinical use and are the subject of major cardiovascular outcomes trials, which, if universally positive, could see much wider clinical application of these agents. Patients with familial hypercholesterolaemia are the most obvious candidates for these drugs, but other patients with elevated cardiovascular risk, statin intolerance or hyperlipoproteinaemia(a) may also benefit. PCSK9 mAbs, administered once or twice monthly, reduce LDL cholesterol levels by 50% to 70%, and appear to be safe and acceptable to patients over at least 2 years of treatment; however, treatment-emergent adverse effects are not always identified in clinical trials, as well-evidenced by statin myopathy. Inclisiran is a promising RNA-based therapy that promotes the degradation of PCSK9 mRNA transcripts and has similar efficacy to mAbs, but with a much longer duration of action. The cost-effectiveness and long-term safety of therapies targeted at inhibiting PCSK9 remain to be demonstrated if they are to be used widely in coronary prevention.

Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) and Its Inhibitors: a Review of Physiology, Biology, and Clinical Data.

Atherosclerotic cardiovascular disease (ASCVD) remains the number one killer in the western world. Low-density lipoprotein cholesterol (LDL-C) reduction with statins and ezetimibe has been shown to reduce the risk of cardiovascular events. Now, proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies (mabs) are available for high-risk individuals with ASCVD or familial hypercholesterolemia on maximally tolerated statin therapy but requiring greater LDL-C reduction. PCSK9 mab outcome trial results from the Further Cardiovascular Outcomes Research with PCSK9 Inhibitions in Subjects with Elevated Risk (FOURIER) study, which was presented at the American College of Cardiology in March 2017, which demonstrated a decrease of 15% in primary and 20% secondary end points over a 2-year period [1••]. These results firmly demonstrated additional benefit beyond maximally tolerated statin therapy in high-risk individuals. Thus, management of LDL-C will soon become more complex, as a new class of medication is added to our standard armamentarium. This review explores the discovery of PCSK9, its biology and physiology, and the development of the PCSK9 mabs.

Bococizumab for the treatment of hypercholesterolaemia

ABSTRACTIntroduction: Low-density lipoprotein cholesterol (LDL-C) remains a well-established risk factor for cardiovascular disease (CVD). LDL-C levels are considered primary targets of therapy. A new series of systemic biomolecules, the monoclonal antibodies (mAbs) of proprotein convertase subtilisin/kexin type 9 (PCSK9), have a higher activity in reducing LDL-C.Areas covered: The authors critically review the current evidence on the efficacy and safety of bococizumab, a humanized mAb against PCSK9, which was surprisingly discontinued in November 2016. The pharmacokinetic profile and the biological features of bococizumab vs others mAbs are also discussed. As of now, in adjunct to diet, alirocumab and evolocumab are the only approved PCSK9 mAbs for the treatment of adult patients with severe clinical atherosclerotic CVD already at maximally-tolerated statin therapy and require additional LDL-C lowering.Expert opinion: Although discontinued, data from a phase 2b trial show the effectiveness of bococizumab...

Abstract 401: Hypercholesterolemia Induces Pro-Inflammatory Changes in Monocytes Which Are Reversed by PCSK9 Antibody Treatment

Aims: Migration of monocytes into the arterial wall contributes to arterial inflammation and atherosclerosis progression. Since elevated LDL levels have been associated with activation of monocytes, intensive LDL lowering may reverse these pro-inflammatory changes. Subjects with elevated LDL levels are currently treated with statins, which are also described to have pleiotropic effects. Using proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies which selectively reduce LDL we studied the impact of LDL lowering on monocyte phenotype and function in patients with familial hypercholesterolemia (FH). Methods and Results: We assessed monocyte phenotype and function using flow cytometry for a broad range of monocyte-relevant markers and a trans-endothelial migration assay in FH patients (n=22: LDL-C 6.8±1.9mmol/L) and healthy controls (n=18, LDL-C 2.9±0.8mmol/L). Interestingly, monocyte chemokine receptor (CCR) 2 expression was approximately 3-fold increased in FH patients compared with controls (ΔMFI 605±214 vs 236±155 P &lt;0.001). CCR2 expression correlated significantly with plasma LDL-C levels (r=0.709) and positively associated with intracellular lipid accumulation. Monocytes from FH patients also displayed enhanced migratory capacity ex vivo. After 24 weeks of PCSK9 monoclonal antibody treatment (n=17), plasma LDL-C was reduced by 49% (from 6.7±1.3 mmol/L to 3.4±1.3 mmol/L P &lt;0.001), which coincided with reduced monocyte intracellular lipid accumulation and suppressed CCR2 expression (ΔMFI: baseline 607±209, post PCSK9 mAbs: 207±180, P &lt;0.001). Functional relevance was substantiated by the reversal of enhanced migratory capacity of monocytes following PCSK9 monoclonal antibody therapy. All changes were comparable in subjects who were treated with statins (n=14: LDL-C 2.8±0.6mmol/L) indicating that the anti-inflammatory effects were mainly mediated through LDL lowering. Conclusions: Elevated LDL levels in FH induce pro-inflammatory changes in monocytes, which is dampened by PCSK9 monoclonal antibody therapy. LDL lowering was paralleled by reduced intracellular lipid accumulation, suggesting that LDL lowering itself is associated with anti-inflammatory effects on circulating monocytes.

Advances in dyslipidemia management for prevention of atherosclerosis: PCSK9 monoclonal antibody therapy and beyond.

In 2003, select families with familial hypercholesterolemia were first identified to have gain-of-function mutations for proprotein convertase subtilisin kexin type 9 (PCSK9) followed, in 2006, by the identification of those with lifelong low levels of LDL-C and lowered atherosclerotic cardiovascular disease (ASCVD) risk who had loss-of-function PCSK9 mutations. These discoveries led to the rapid development of PSCK9-targeted monoclonal antibody (PCSK9 mAb) therapies and, in 2015, 2 'fully-humanized' PCSK9 mAbs (alirocumab and evolocumab) were marketed in the United States, Europe, and other countries. In a wide range of high risk patients, with and without ASCVD, these PCSK9 mAbs, as once or twice monthly subcutaneous injections, potently reduce LDL-C 50-65% beyond levels achieved by maximally tolerated statin therapy; approximately one-third of patients achieve LDL-C levels <25 mg/dL. In the US, PCSK9 mAb therapy has current limited indications for persons with ASCVD or familial hypercholesterolemia requiring additional LDL-C reduction beyond maximally tolerated statin therapy. The first of the ASCVD outcomes-driven trials, the FOURIER trial has very recently shown in over 27,000 subjects randomized to evolocumab or placebo on top of moderate or high intensity statin therapy, a 15% risk reduction in the primary and 20% reduction in the secondary outcome over 2.2 years of treatment. Also of interest in patients with coronary artery disease on statin therapies, once-monthly evolocumab treatment, for only 76 weeks, resulted in significant plaque atheroma volume regression, as assessed by serial intravascular ultrasonography imaging, in approximately two-thirds of treated patients. Finally, in development is a highly durable RNA interference therapeutic inhibitor of PCSK9 synthesis which from a single dosage has been shown to maintain, for 6 months, a 75% reduction in PCSK9 levels and 50% reductions in LDL-C levels. The potential role of this vaccination-like product, as well as currently available PCSK9 mAb therapies, represents significant therapeutic advances to address ASCVD residual risk.

A New Approach to PCSK9 Therapeutics.

PCSK9 inhibition is an effective therapy to reduce LDL cholesterol (LDL-C) and cardiovascular events. A recent study shows that one or two doses of inclisiran, a long-acting synthetic small-interfering RNA (siRNA) that selectively targets hepatic PCSK9, causes a sustained reduction of plasma LDL-C for up to 6 months. Pending further studies of safety and efficacy, this may represent an important addition to the armamentarium for inhibiting PCSK9.

PCSK9 monoclonal antibodies reverse the pro-inflammatory profile of monocytes in familial hypercholesterolaemia.

Migration of monocytes into the arterial wall contributes to arterial inflammation and atherosclerosis progression. Since elevated low-density lipoprotein cholesterol (LDL-C) levels have been associated with activation of plasma monocytes, intensive LDL-C lowering may reverse these pro-inflammatory changes. Using proprotein convertase subtilisin/kexin type 9 (PCSK9) monoclonal antibodies (mAbs) which selectively reduce LDL-C, we studied the impact of LDL-C lowering on monocyte phenotype and function in patients with familial hypercholesterolaemia (FH) not using statins due to statin-associated muscle symptoms. We assessed monocyte phenotype and function using flow cytometry and a trans-endothelial migration assay in FH patients (n = 22: LDL 6.8 ± 1.9 mmol/L) and healthy controls (n = 18, LDL 2.9 ± 0.8 mmol/L). Monocyte chemokine receptor (CCR) 2 expression was approximaterly three-fold higher in FH patients compared with controls. C-C chemokine receptor type 2 (CCR2) expression correlated significantly with plasma LDL-C levels (r = 0.709) and was positively associated with intracellular lipid accumulation. Monocytes from FH patients also displayed enhanced migratory capacity ex vivo. After 24 weeks of PCSK9 mAb treatment (n = 17), plasma LDL-C was reduced by 49%, which coincided with reduced intracellular lipid accumulation and reduced CCR2 expression. Functional relevance was substantiated by the reversal of enhanced migratory capacity of monocytes following PCSK9 mAb therapy. Monocytes of FH patients have a pro-inflammatory phenotype, which is dampened by LDL-C lowering by PCSK9 mAb therapy. LDL-C lowering was paralleled by reduced intracellular lipid accumulation, suggesting that LDL-C lowering itself is associated with anti-inflammatory effects on circulating monocytes.

The complexity of lipoprotein (a) lowering by PCSK9 monoclonal antibodies.

Since 2012, clinical trials dedicated to proprotein convertase subtilisin kexin type9 (PCSK9) inhibition with monoclonal antibodies (mAbs) have unambiguously demonstrated robust reductions not only in low-density lipoprotein (LDL) cholesterol (LDL-C) but also in lipoprotein (a) [Lp(a)] levels. The scientific literature published prior to those studies did not provide any evidence for a link between PCSK9 and Lp(a) metabolism. More recent investigations, either invitro or invivo, have attempted to unravel the mechanism(s) by which PCSK9 mAbs reduce circulating Lp(a) levels, with some showing a specific implication of the LDL receptor (LDLR) in Lp(a) clearance whereas others found no significant role for the LDLR in that process. This elusive pathway appears clearly distinct from that of the widely prescribed statins that also enhance LDLR function but do not lower circulating Lp (a) levels in humans. So how does PCSK9 inhibition with mAbs reduce Lp(a)? This still remains to be established.

Bococizumab for the treatment of hypercholesterolaemia

ABSTRACTIntroduction: Low-density lipoprotein cholesterol (LDL-C) remains a well-established risk factor for cardiovascular disease (CVD). LDL-C levels are considered primary targets of therapy. A new series of systemic biomolecules, the monoclonal antibodies (mAbs) of proprotein convertase subtilisin/kexin type 9 (PCSK9), have a higher activity in reducing LDL-C.Areas covered: The authors critically review the current evidence on the efficacy and safety of bococizumab, a humanized mAb against PCSK9, which was surprisingly discontinued in November 2016. The pharmacokinetic profile and the biological features of bococizumab vs others mAbs are also discussed. As of now, in adjunct to diet, alirocumab and evolocumab are the only approved PCSK9 mAbs for the treatment of adult patients with severe clinical atherosclerotic CVD already at maximally-tolerated statin therapy and require additional LDL-C lowering.Expert opinion: Although discontinued, data from a phase 2b trial show the effectiveness of bococizumab in lowering LDL-C in a similar way to the two available PCSK9 antagonists. However, some peculiar biological characteristics of bococizumab may explain the attenuation of LDL-C lowering over time, as well as a higher rate of immunogenicity and of injection-site reactions.