PCSK9 Antibody-based Treatment Strategies for Patients With Statin Intolerance

PCSK9 Inhibitors and Infection-Related Adverse Events: A Pharmacovigilance Study Using the World Health Organization VigiBase

AIMS

Protein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) are novel lipid-lowering agents used in patients with cardiovascular disease. Despite reassuring safety data from pivotal trials, increasing evidence from real-world studies suggests that PCSK9i increase the risk of bacterial and viral infections. Therefore, this study aimed to identify signals of infection-related adverse events (AEs) associated with PCSK9i.

METHODS

We performed an observational pharmacovigilance study using the World Health Organization's VigiBase, recorded up to December 2022. We included individual case safety reports (ICSRs) of PCSK9 inhibitors, alirocumab and evolocumab, and compared them with those of other drugs. Infection-related ICSRs were retrieved from the Medical Dictionary for Regulatory Activities System Organ Class 'infections and infestations.'

RESULTS

Among 114,293 reports (258,099 drug-AE pairs) related to PCSK9 inhibitors, 54% included female patients, 41% included patients aged ≥65 years, and 82% included patients who received evolocumab. Additionally, beyond AEs recognized by regulatory authorities, organ infections such as influenza (reporting odds ratio [ROR] 2.89, 95% confidence interval [CI] 2.74-3.05), gastric infections (ROR 2.47, 95% CI 1.63-3.75), and kidney infections (ROR 1.36, 95% CI 1.06-1.73) were observed. Sensitivity analysis indicated a heightened risk of infection-related AEs associated with PCSK9i regardless of the specific drug type.

CONCLUSIONS

In addition to the labelled respiratory infections, six infection-related symptoms in the gastrointestinal, urinary, and renal organs were identified. Our findings support the need for systematic surveillance of infections among PCSK9i users.

The First Report of a Real-World Experience With a PCSK9 Inhibitor in a Large Familial Hyperlipidemia and Very-High-Risk Middle Eastern Population

PURPOSE

Evolocumab, a monoclonal inhibitor of proprotein convertase subtilisin/kexin 9, has been shown to reduce proatherogenic lipoproteins in patients with or without familial hypercholesterolemia (FH), diabetes mellitus, or atherosclerotic cardiovascular disease (ASCVD). We explored the safety profile and clinical effectiveness of evolocumab in an outpatient population of Emirati individuals with FH diagnosed per Dutch Lipid Clinic Network criteria, previous ASCVD, or statin intolerance.

METHODS

This study was a retrospective review of patients initiating evolocumab treatment for any indication at Imperial College London Diabetes Centre between 2017 and 2020. All individuals followed up for at least 90 days or with at least one lipid panel postinitiation were included. Participants were subclassified into primary prevention (no previous ASCVD event, n = 81) and secondary prevention (any prior clinical ASCVD event, n = 102) groups.

FINDINGS

Evolocumab was initiated in 183 individuals (mean [SD] age, 51.5 [12.4] years; 51% male); 108 (59%) had a clinical or genetic FH diagnosis, and 70.5% had diabetes mellitus. Statin intolerance was a treatment indication in 60 (32.8%) individuals. At 90 days, substantial reductions in serum LDL-C, triglycerides (TG), and total cholesterol:HDL-C (TC:HDL-C) were observed in both the primary and secondary prevention groups, and both FH and non-FH individuals. In the primary prevention group, median (interquartile range) reduction in LDL-C was 43.7% (10.8%; 63.0%); TG, 15.0% (7.2%; 35.3%); and TC:HDL-C, 31.5% (11.1%; 46.0%). In the secondary prevention group, median (interquartile range) reduction in LDL-C was 48.3% (22%; 70%); TG, 19.6% (1.2%; 32.5%); and TC:HDL-C, 32.6% (14.6%; 46.3%) (all, P < 0.0001). American College of Cardiology/American Heart Association LDL-C targets were consistently achieved in 114 (62.3%) patients during a follow-up of 359 (79-639) days. Nonattainment of the LDL-C target was attributed to nonadherence in 36 (52.2%) patients and discontinuation of treatment in 14 (20.3%) patients. Evolocumab was discontinued in 4 patients because of adverse events.

IMPLICATIONS

This study is the first from the Middle East and North Africa region that reports the real-world efficacy of evolocumab in a mixed risk population of individuals with FH and other non-FH indications. Clinically meaningful and sustained reductions in LDL-C, TG, and cholesterol ratios were observed after evolocumab initiation. Few adverse events were reported in this predominantly Arabic population, consistent with previous safety reports for evolocumab. Notable strengths of this study include a relatively large cohort, patient heterogeneity and high retention, and a minimum follow-up of 1 year. Despite these strengths, the study has some limitations, including the selection bias due to the retrospective design and absence of comparative group. (Clin Ther. 2022;44:XXX-XXX) © 2022 Elsevier HS Journals, Inc.

The Multifaceted Biology of PCSK9

This article reviews the discovery of PCSK9, its structure-function characteristics, and its presently known and proposed novel biological functions. The major critical function of PCSK9 deduced from human and mouse studies, as well as cellular and structural analyses, is its role in increasing the levels of circulating low-density lipoprotein (LDL)-cholesterol (LDLc), via its ability to enhance the sorting and escort of the cell surface LDL receptor (LDLR) to lysosomes. This implicates the binding of the catalytic domain of PCSK9 to the EGF-A domain of the LDLR. This also requires the presence of the C-terminal Cys/His-rich domain, its binding to the secreted cytosolic cyclase associated protein 1, and possibly another membrane-bound "protein X". Curiously, in PCSK9-deficient mice, an alternative to the downregulation of the surface levels of the LDLR by PCSK9 is taking place in the liver of female mice in a 17β-estradiol-dependent manner by still an unknown mechanism. Recent studies have extended our understanding of the biological functions of PCSK9, namely its implication in septic shock, vascular inflammation, viral infections (Dengue; SARS-CoV-2) or immune checkpoint modulation in cancer via the regulation of the cell surface levels of the T-cell receptor and MHC-I, which govern the antitumoral activity of CD8+ T cells. Because PCSK9 inhibition may be advantageous in these processes, the availability of injectable safe PCSK9 inhibitors that reduces by 50% to 60% LDLc above the effect of statins is highly valuable. Indeed, injectable PCSK9 monoclonal antibody or small interfering RNA could be added to current immunotherapies in cancer/metastasis.