Ineffective Subtilisin/Kexin Type 9 (PCSK9) Inhibitors Monotherapy in Dyslipidemia with Low-Density Lipoprotein Cholesterol (LDL-C) Receptor Abnormalities: A Report of 2 Cases

Research on Hepatocyte Regulation of PCSK9-LDLR and Its Related Drug Targets

The prevalence of hyperlipidemia has increased significantly due to genetic, dietary, nutritional and pharmacological factors, and has become one of the most common pathological conditions in humans. Hyperlipidemia can lead to a range of diseases such as atherosclerosis, stroke, coronary heart disease, myocardial infarction, diabetes, and kidney failure, etc. High circulating low-density lipoprotein cholesterol (LDL-C) is one of the causes of hyperlipidemia. LDL-C in the blood binds to LDL receptor (LDLR) and regulates cholesterol homeostasis through endocytosis. In contrast, proprotein convertase subtilisin/kexin type 9 (PCSK9) mediates LDLR degradation via the intracellular and extracellular pathways, leading to hyperlipidemia. Targeting PCSK9-synthesizing transcription factors and downstream molecules are important for development of new lipid-lowering drugs. Clinical trials regarding PCSK9 inhibitors have demonstrated a reduction in atherosclerotic cardiovascular disease events. The purpose of this review was to explore the target and mechanism of intracellular and extracellular pathways in degradation of LDLR and related drugs by PCSK9 in order to open up a new pathway for the development of new lipid-lowering drugs.

Association of low-density lipoprotein-cholesterol with all-cause and cause-specific mortality

AIMS

To explore the association between low-density lipoprotein-cholesterol (LDL-C) and all-cause and cause-specific mortality based on a prospective cohort study.

METHODS

Among 10850 individuals enrolled from National Health and Nutrition Examination Survey (NHANES) 1999-2014, 1355 (12.5%) died after an average follow-up of 5.7 years. Cox proportional regression models were used to determine the association between LDL-C with the risk of mortality.

RESULTS

The level of LDL-C was L-shaped associated with the risk of all-cause mortality, namely a low level was related to an increased mortality risk. The level of LDL-C associated with the lowest risk of all-cause mortality was 124 mg/dL (3.2 mmol/L) in the overall population, and 134 mg/dL (3.4 mmol/L) in individuals not receiving lipid lowering treatment. Compared with participants with LDL-C of 110-134 mg/dL (2.8-3.5 mmol/L), the multivariable adjusted hazard ratio was 1.18 (95% confidence interval 1.01 to 1.38) for individuals with the lowest quartile for all-cause mortality. In participants with coronary heart diseases, the conclusion was similar but the critical point was lower.

CONCLUSIONS

We found that low levels of LDL-C increased the risk of all-cause mortality, and the lowest risk of all-cause mortality for LDL-C concentration was 124 mg/dL (3.2 mmol/L). Our results provide a reasonable range of LDL-C when to initiate a statin therapy in clinical practice.

Mechanisms of unusual response to lipid-lowering therapy: PCSK9 inhibition

The efficacy of proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition has broadened lipid-lowering therapy thus providing decreased risk in atherosclerotic cardiovascular disease. Unfortunately, the widespread use of PCSK9 inhibitors (PCSK9i), ie, monoclonal antibodies, has led to the findings of unusual responsiveness, ie, a phenomenon defined as an LDL-C reduction of <30% vs the average LDL-C reduction efficacy of 50-60%. This unusual responsiveness to PCSK9i is attributable to several factors, ie, lack of adherence, impaired absorption, poor distribution or early elimination as well as abnormal effects of PCSK9i in the presence of anti-antibodies or mutations in PCSK9 and LDLR. Unexpectedly increased lipoprotein (Lp)(a) also appear to contribute to the unusual responsiveness scenario. Identification of these responses and mechanisms underlying them are essential for effective management of LDL-C and cardiovascular risk. In this review, we describe plausible reasons underlying this phenomenon supported by findings of clinical trials. We also elaborate on the need for education and regular follow-up to improve adherence. Collectively, the review provides a summary of the past, present, and future of mechanisms and countermeasures revolving around unusual responses to PCSK9i therapy.

PCSK9 inhibitors revisited: Effectiveness and safety of PCSK9 inhibitors in a real-life Spanish cohort

INTRODUCTION

Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) have emerged as a therapeutic option for patients with hypercholesterolemia who do not attain low-density lipoprotein cholesterol (LDL-C) goals and/or are intolerant to other lipid-lowering drugs. Our aim was to analyze the effectiveness and safety of PCSK9i in routine clinical practice and factors related to poor outcomes.

MATERIALS AND METHODS

We conducted an ambispective study in 115 patients who recieved alirocumab or evolocumab, in a tertiary level hospital. From February 2017 to April 2020, patients were recruited and followed up for a median of 20.4 months. The main outcomes were relative reduction in LDL-C, percentage of patients achieving the therapeutic goals established by 2016 ESC/EAS guidelines, incidence of major cardiovascular events (MACEs) and drug-related adverse events (ADRs).

RESULTS

The median LDL-C achieved was 57.0 mg/dL (relative reduction of 59.9% from baseline, p< 0.001). After adjusting for confounders, smaller LDL-C reductions were related to female sex, absence of concomitant lipid-lowering therapy and treatment with alirocumab. Overall, 84.6% of the patients achieved the therapeutic goals. During follow-up, 7 MACEs were detected. ADRs, generally considered mild, affected 38.1% of the participants (mainly mialgias and arthralgias) and triggered discontinuations in 8.7% of cases.

CONCLUSIONS

PCSK9i are effective and safe, although certain factors may influence their effectiveness. Interestingly, our results suggest that alirocumab and evolocumab may not be therapeutic equivalents, as initially suggested.

Real-World Efficacy of Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitors (PCSK9i) in Heterozygous Familial Hypercholesterolemia Patients Referred for Lipoprotein Apheresis

BACKGROUND A small proportion of familial hypercholesterolemia (FH) patients can adequately control this condition, although achieving the recommended targets for low-density lipoprotein cholesterol (LDL-c) levels remains a challenge. Proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) are new and potent lipid-lowering drugs. However, there is scarce literature on real-world data about their use in patients with FH. MATERIAL AND METHODS We examined the reduction in LDL-c levels from the baseline, after PCSK9i initiation in heterozygous familial hypercholesterolemia patients referred for lipoprotein apheresis in our regional lipid clinic. The study was conducted from March 2018 to September 2019, the period immediately after PCSK9i reimbursement was available in France. PCSK9i was added on top of the patients' maximal tolerated lipid-lowering regimens. RESULTS The study had 123 patients with heterozygous FH. The mean age of the patients was 59±11 years. The mean baseline LDL-c for all the participants was 277±78 mg/dl. It was 283±81 mg/dl in the PCSK9i monotherapy group (n=83), 247±68 mg/dl in the PCSK9i plus ezetimibe group (n=12), and 264±78 mg/dl in the PCSK9i plus statin and ezetimibe group (n=28). The mean decrease observed in the LDL-c level from baseline was 136±70 mg/dl (n=123), 125±60 mg/dl (n=83), 103±77 mg/dl (n=12), and 175±70 mg/dl (n=28), respectively. CONCLUSIONS An overall reduction of 49.1% from the baseline LDL-c was observed in the heterozygous FH population after PCSK9i initiation in a real-world experience. The group treated with PCSK9i ezetimibe plus statin showed further reduction of their LDL-c levels with a better responder rate, achieving the target 50% reduction in LDL-c from the baseline.