Pre-Clinical Evaluation of the Nanoliposomal antiPCSK9 Vaccine in Healthy Non-Human Primates

Immunotherapy and vaccine-based approaches for atherosclerosis prevention: a systematic review study

INTRODUCTION

Cardiovascular disease is a major global health issue, and atherosclerosis is a leading cause of cardiovascular conditions. Traditional approaches for managing atherosclerosis have limitations, creating a need for alternative preventive strategies such as vaccines.

METHODS

The authors conducted a systematic review following Cochrane Handbook and PRISMA guidelines. They searched multiple databases for studies on preventive vaccines against atherosclerosis, including clinical trials and experimental models. The search period was from 1950 to August 2024.

RESULTS

After screening and evaluation, 47 studies were included in the systematic review. The studies investigated various vaccine candidates and immunization strategies. Vaccination goals involve targeting proteins that are found in higher quantities in individuals with atherosclerosis, such as oxidized low-density lipoprotein (LDL), apolipoprotein B-100, proprotein convertase subtilisin/kexin type-9 serine protease (PCSK9), cholesteryl ester transfer protein (CETP), and heat shock proteins HSP60 and HSP65. The review highlights the potential of vaccines in preventing atherosclerosis by targeting specific antigens, modulating lipoprotein metabolism, and enhancing immune responses. Promising approaches included PCSK9 inhibitors, virus-like particle (VLP)-based vaccines, and gene-editing techniques. Monoclonal antibodies like alirocumab, designed to inhibit PCSK9, were also effective in reducing LDL cholesterol levels.

CONCLUSION

This systematic review provides insights into the progress, challenges, and future directions of preventive vaccine research against atherosclerosis. The findings support the development of effective vaccines to complement existing preventive strategies and reduce the global burden of cardiovascular diseases.

CLINICAL TRIAL NUMBER

It is not applicable.

Evaluating the effect of the antiPCSK9 vaccine on systemic inflammation and oxidative stress in an experimental mouse model

BACKGROUND

To investigate whether the antiPCSK9 vaccine can affect the CRP and oxidative stress (OS) during acute systemic inflammation.

METHODS

Male albino mice were randomly divided into three groups: non-treated mice (the sham group), treated with a nonspecific stimulator of the immune response - Freund's complete adjuvant (CFA; the CFA group), and vaccinated mice treated with CFA (the vaccine group). The vaccine group was subcutaneously immunized with the antiPCSK9 formulation, 4 × in bi-weekly intervals. To induce inflammation, all mice were subjected to the CFA challenge after the vaccination plan. The hsCRP level and OS status were evaluated by a mouse CRP ELISA kit and the pro-oxidant antioxidant balance (PAB) assay, respectively.

RESULTS

The vaccine induced a high-titter IgG antiPCSK9 antibody, which was accompanied with a significant PCSK9 reduction (-24.7% and -28.5% compared with the sham and CFA group, respectively), and the inhibition of PCSK9/LDLR interaction (-27.8% and -29.4%, respectively). hsCRP was significantly increased in the vaccine and CFA groups by 225% and 274% respectively, when compared with the sham group; however, it was non-significantly decreased (-18%; p = 0.520) in the vaccine group in comparison with the CFA group. The PAB values indicated that OS was significantly increased in the CFA group (by 72.7%) and the vaccine group (by 76%) when compared to the sham group; however, there was no significant difference in the PAB values between the vaccine and CFA groups.

CONCLUSION

The antiPCSK9 vaccine failed to significantly reduce the serum hs-CRP and OS induced in the CFA-challenged albino mice.

Non-rodent Models of Atherosclerosis: Repurposing of Existing Drugs and Search for Novel Treatment Strategies

Atherosclerosis and associated cardiovascular diseases are the leading causes of illness and mortality worldwide. The development of atherosclerosis is a complex process involving oxidative stress, surplus lipid deposition and retention, endothelial dysfunction, and chronic inflammation. Developing novel anti-atherogenic and repurposing existing drugs requires the use of suitable animal models to characterise the fundamental mechanisms underlying atherosclerosis initiation and progression and to evaluate potential therapeutic effects. Commonly used rodent models, however, are not always appropriate, and other models may be required to translate these discoveries into valuable preventive and treatment agents for human applications. Recent advances in gene-editing tools for large animals have allowed the creation of animals that develop atherosclerosis faster and more similarly to humans in terms of lesion localisation and histopathology. In this review, we discuss the major advantages and drawbacks of the main non-rodent animal models of atherosclerosis, particularly rabbits, pigs, zebrafish, and non-human primates. Moreover, we review the application of recently invented novel therapeutic methods and agents, and repurposed existing drugs (such as antidiabetic and anticancer) for atherosclerosis treatment, the efficacy of which is verified on non-rodent animal models of atherosclerosis. In total, the proper selection of a suitable animal model of atherosclerosis facilitates reproducible and rigorous translational research in repurposing of existing drugs, discovering new therapeutic strategies, and validating novel anti-atherosclerotic drugs.

Vaccination as a Promising Approach in Cardiovascular Risk Mitigation: Are We Ready to Embrace a Vaccine Strategy?

Cardiovascular disease (CVD) remains a leading global health concern, with atherosclerosis being its principal cause. Standard CVD treatments primarily focus on mitigating cardiovascular (CV) risk factors through lifestyle changes and cholesterol-lowering therapies. As atherosclerosis is marked by chronic arterial inflammation, the innate and adaptive immune systems play vital roles in its progression, either exacerbating or alleviating disease development. This intricate interplay positions the immune system as a compelling therapeutic target. Consequently, immunomodulatory strategies have gained increasing attention, though none have yet reached widespread clinical adoption. Safety concerns, particularly the suppression of host immune defenses, remain a significant barrier to the clinical application of anti-inflammatory therapies. Recent decades have revealed the significant role of adaptive immune responses to plaque-associated autoantigens in atherogenesis, opening new perspectives for targeted immunological interventions. Preclinical models indicate that vaccines targeting specific atherosclerosis-related autoantigens can slow disease progression while preserving systemic immune function. In this context, numerous experimental studies have advanced the understanding of vaccine development by exploring diverse targeting pathways. Key strategies include passive immunization using naturally occurring immunoglobulin G (IgG) antibodies and active immunization targeting low-density lipoprotein cholesterol (LDL-C) and apolipoproteins, such as apolipoprotein B100 (ApoB100) and apolipoprotein CIII (ApoCIII). Other approaches involve vaccine formulations aimed at proteins that regulate lipoprotein metabolism, including proprotein convertase subtilisin/kexin type 9 (PCSK9), cholesteryl ester transfer protein (CETP), and angiopoietin-like protein 3 (ANGPTL3). Furthermore, the literature highlights the potential for developing non-lipid-related vaccines, with key targets including heat shock proteins (HSPs), interleukins (ILs), angiotensin III (Ang III), and a disintegrin and metalloproteinase with thrombospondin motifs 7 (ADAMTS-7). However, translating these promising findings into safe and effective clinical therapies presents substantial challenges. This review provides a critical evaluation of current anti-atherosclerotic vaccination strategies, examines their proposed mechanisms of action, and discusses key challenges that need to be overcome to enable clinical translation.

The Emerging Role of PCSK9 in the Pathogenesis of Alzheimer's Disease: A Possible Target for the Disease Treatment

Alzheimer's disease (AD) is a multifactorial neurodegenerative disease mainly caused by β-amyloid (Aβ) accumulation in the brain. Among the several factors that may concur to AD development, elevated cholesterol levels and brain cholesterol dyshomeostasis have been recognized to play a relevant role. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protein primarily known to regulate plasma low-density lipoproteins (LDLs) rich in cholesterol and to be one of the main causes of familial hypercholesterolemia. In addition to that, PCSK9 is also recognized to carry out diverse important activities in the brain, including control of neuronal differentiation, apoptosis, and, importantly, LDL receptors functionality. Moreover, PCSK9 appeared to be directly involved in some of the principal processes responsible for AD development, such as inflammation, oxidative stress, and Aβ deposition. On these bases, PCSK9 management might represent a promising approach for AD treatment. The purpose of this review is to elucidate the role of PCSK9, whether or not cholesterol-related, in AD pathogenesis and to give an updated overview of the most innovative therapeutic strategies developed so far to counteract the pleiotropic activities of both humoral and brain PCSK9, focusing in particular on their potentiality for AD management.

Recent advances of self-assembled nanoparticles in the diagnosis and treatment of atherosclerosis

Atherosclerosis remains a significant global health challenge, with its related conditions as the leading cause of death, underscoring the urgent need for enhanced diagnostic and therapeutic approaches. Recently, self-assembled nanoparticles (SANPs) have shown remarkable promise in treating atherosclerosis, attributed to their superior bioavailability, biodegradability, biocompatibility, and ease of functional modification. Numerous SANP variants, such as DNA origami, metal-organic frameworks (MOFs), nanozymes, peptide-based nanoparticles, and self-assembled prodrug nanoparticles, have been engineered, extending their utility in targeted drug delivery and imaging. Advances in fabrication technologies, including microfluidic techniques, allow for precise and scalable SANP production, while innovative nanoparticle designs-such as stimuli-responsive and carrier-free variants-enhance pharmacokinetic properties. The deployment of SANPs in atherosclerosis has introduced a range of diagnostic and therapeutic solutions, from non-invasive imaging and stimuli-responsive drug delivery to vaccination, theranostics, and biosensing. This review consolidates the recent progress in SANP applications for atherosclerosis, emphasizing their transformative potential in disease management.

PCSK9-directed therapies: an update

PURPOSE OF REVIEW

Two large cardiovascular outcomes trials of monoclonal antibodies against proprotein convertase subtilisin/kexin type 9 (PCSK9) demonstrated that therapeutic inhibition of extracellular PCSK9 markedly reduces LDL cholesterol concentration and cardiovascular risk. Several novel strategies to inhibit PCSK9 function are in development. Different mechanisms of action may determine specific properties with potential relevance for patient care.

RECENT FINDINGS

For the monoclonal antibodies evolocumab und alirocumab as first-generation PCSK9 inhibitors, follow-up data of up to 8 years of exposure complement the information on efficacy and safety available from outcome trials. For the small-interfering RNA inclisiran as second-generation PCSK9 inhibitor, several phase III trials have been published and a cardiovascular outcome trial has completed recruitment and is ongoing. Third-generation PCSK9 inhibitors encompass, among others, orally available drugs such as MK-0616 and the fusion protein lerodalcibep. Additional strategies to inhibit PCSK9 include vaccination and gene editing.

SUMMARY

Long-term inhibition of PCSK9 with monoclonal antibodies is safe and conveys sustained cardiovascular benefit. Novel strategies to inhibit PCSK9 function such as orally available drugs, RNA targeting, and one-time treatment with gene editing may further enhance the therapeutic armamentarium and enable novel preventive strategies.

Role of Treg cell subsets in cardiovascular disease pathogenesis and potential therapeutic targets

In the genesis and progression of cardiovascular diseases involving both innate and adaptive immune responses, inflammation plays a pivotal and dual role. Studies in experimental animals indicate that certain immune responses are protective, while others exacerbate the disease. T-helper (Th) 1 cell immune responses are recognized as key drivers of inflammatory progression in cardiovascular diseases. Consequently, the CD4+CD25+FOXP3+ regulatory T cells (Tregs) are gaining increasing attention for their roles in inflammation and immune regulation. Given the critical role of Tregs in maintaining immune-inflammatory balance and homeostasis, abnormalities in their generation or function might lead to aberrant immune responses, thereby initiating pathological changes. Numerous preclinical studies and clinical trials have unveiled the central role of Tregs in cardiovascular diseases, such as atherosclerosis. Here, we review the roles and mechanisms of Treg subsets in cardiovascular conditions like atherosclerosis, hypertension, myocardial infarction and remodeling, myocarditis, dilated cardiomyopathy, and heart failure. While the precise molecular mechanisms of Tregs in cardiac protection remain elusive, therapeutic strategies targeting Tregs present a promising new direction for the prevention and treatment of cardiovascular diseases.

Whether and Why Do We Need a Vaccine Against Atherosclerosis? Can We Expect It Anytime Soon?

PURPOSE OF REVIEW

Atherosclerotic cardiovascular disease (ASCVD) is a leading cause of premature death. Lipid disorders, particularly elevated serum low-density lipoprotein cholesterol (LDL-C), contribute significantly to ASCVD. The risk of developing ASCVD is influenced by the duration of exposure to elevated LDL-C concentrations (cholesterol-years concept). Implementing lipid-lowering treatments based on the principles of "the earlier the better," "the lower the better," and "the longer the better" has been shown to reduce cardiovascular risk and significantly extend lifespan. Despite the availability of numerous lipid-lowering drugs, achieving satisfactory control of lipid disorders remains very challenging. Therefore, there is a need for novel approaches to improve treatment adherence.

RECENT FINDINGS

One promising solution under investigation is the development of an anti-PCSK9 vaccine, which could be administered annually to provide long-term control over LDL-C concentrations. Experimental studies and the sole clinical trial conducted thus far have demonstrated that the anti-PCSK9 vaccine induces a durable immune response associated with lipid-lowering and anti-atherosclerotic effects. Furthermore, it has exhibited good tolerability and a satisfactory safety profile. However, we still need data from phase 2, 3, and cardiovascular outcome trial to confirm its safety and efficacy and add value in the armamentarium of available and perspective lipid-lowering drugs. This article highlights the significance of developing an anti-PCSK9 vaccine and provides an overview of the current knowledge on various anti-PCSK9 vaccines.

Novel and Emerging LDL-C Lowering Strategies: A New Era of Dyslipidemia Management

Atherosclerotic cardiovascular disease (ASCVD) represents a major global health challenge, significantly contributing to mortality rates. This chronic inflammatory condition affecting blood vessels is intricately linked to hypercholesterolemia, with elevated levels of low-density lipoprotein cholesterol (LDL-C) recognized as a central and modifiable risk factor. The effectiveness of lipid-lowering therapy (LLT) in mitigating ASCVD risk is well established, with studies revealing a substantial reduction in major ischemic events correlating with LDL-C reduction. While statins, often combined with ezetimibe, remain fundamental in dyslipidemia management, a significant proportion of patients on statin therapy continue to experience cardiovascular events. Recent pharmacological advancements, driven by a deeper understanding of atherogenesis, have unveiled novel therapeutic targets and potent drugs. Notably, agents like bempedoic acid and proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors (evolocumab, alirocumab, inclisiran) have emerged as effective options to intensify LLT and achieve LDL-C goals, addressing limitations associated with statins, such as myopathy. Molecular insights into alternative pathways have spurred the investigation of emerging agents, offering promising perspectives for novel medications with efficacy comparable to established treatments, associated with advantages in cost and administration. This review provides a comprehensive overview of the evolving landscape of lipid-lowering strategies, highlighting the progress made in addressing ASCVD risk and the potential of upcoming therapies to further optimize cardiovascular prevention.

Novel therapeutic targets and emerging treatments for atherosclerotic cardiovascular disease

Atherosclerotic cardiovascular disease (ASCVD) is the leading cause of morbidity and mortality worldwide. Even with excellent control of low-density lipoprotein cholesterol (LDL-C) levels, adverse cardiovascular events remain a significant clinical problem worldwide, including among those without any traditional ASCVD risk factors. It is necessary to identify novel sources of residual risk and to develop targeted strategies that address them. Lipoprotein(a) has become increasingly recognized as a new cardiovascular risk determinant. Large-scale clinical trials have also signalled the potential additive cardiovascular benefits of decreasing triglycerides beyond lowering LDL-C levels. Since CANTOS (Anti-inflammatory Therapy with Canakinumab for Atherosclerotic Disease) demonstrated that antibodies against interleukin-1β may decrease recurrent cardiovascular events in secondary prevention, various anti-inflammatory medications used for rheumatic conditions and new monoclonal antibody therapeutics have undergone rigorous evaluation. These data build towards a paradigm shift in secondary ASCVD prevention, underscoring the value of targeting multiple biological pathways in the management of both lipid levels and systemic inflammation. Evolving knowledge of the immune system, and the gut microbiota may result in opportunities for modifying previously unrecognized sources of residual inflammatory risk. This review provides an overview of novel therapeutic targets for ASCVD and emerging treatments with a focus on mechanisms, efficacy, and safety.

New Biological Therapies for Low-Density Lipoprotein Cholesterol

Depressed low-density lipoprotein cholesterol concentration protects against atherosclerotic cardiovascular disease. Natural hypocholesterolemia states can have a monogenic etiology, caused by pathogenic loss of function variants in the PCSK9, ANGPTL3, MTTP, or APOB genes. In this focused review, we discuss development and clinical use of several new therapeutics that inhibit these gene products to target elevated levels of low-density lipoprotein cholesterol. In particular, inhibitors of proprotein convertase subtilisin kexin type 9 (PCSK9) have notably affected clinical practice, followed recently by inhibition of angiopoietin-like 3 (ANGPTL3). Currently used in the clinic are alirocumab and evolocumab, two anti-PCSK9 monoclonal antibodies, inclisiran, a small interfering RNA that prevents PCSK9 translation, evinacumab, an anti-ANGPTL3 monoclonal antibody, and lomitapide, a small-molecule inhibitor of microsomal triglyceride transfer protein. Additional therapies are in preclinical or clinical trial stages of development. These consist of other monoclonal antibodies, antisense oligonucleotides, small-molecule inhibitors, mimetic peptides, adnectins, vaccines, and gene-editing therapies. Vaccines and gene-editing therapies in particular hold great potential to confer active long-term attenuation or provide single-treatment life-long knock-down of PCSK9 or ANGPTL3 activity. Biologic therapies inspired by monogenic hypocholesterolemia states are becoming valuable tools to help protect against atherosclerotic cardiovascular disease.

A virus-like particle-based bivalent PCSK9 vaccine lowers LDL-cholesterol levels in non-human primates

Elevated low-density lipoprotein cholesterol (LDL-C) is an important risk factor in the development of atherosclerotic cardiovascular disease (ASCVD). Inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9), a negative regulator of LDL-C metabolism, have emerged as promising approaches for reducing elevated LDL-C levels. Here, we evaluated the cholesterol-lowering efficacy of virus-like particle (VLP) based vaccines that target epitopes found within the LDL receptor (LDL-R) binding domain of PCSK9. In both mice and non-human primates, a bivalent VLP vaccine targeting two distinct epitopes on PCSK9 elicited strong and durable antibody responses and lowered cholesterol levels. In macaques, a VLP vaccine targeting a single PCSK9 epitope was only effective at lowering LDL-C levels in combination with statins, whereas immunization with the bivalent vaccine lowered LDL-C without requiring statin co-administration. These data highlight the efficacy of an alternative, vaccine-based approach for lowering LDL-C.

Development of liposomal contrast agent with high iodine concentration and minimal effect on renal function

Purpose

The use of contrast media is essential to achieve high accuracy in diagnostic imaging. Iodine contrast media, one of these contrast media, has nephrotoxicity as a side effect. Therefore, the development of iodine contrast media that can reduce nephrotoxicity is expected. Since liposomes are generally adjustable in size (100-300 nm) and are not filtered by the renal glomerulus, we hypothesized that iodine contrast media could be encapsulated in liposomes and administered to avoid the nephrotoxicity of iodine contrast media. The aim of this study is to develop an iomeprol-containing liposome (IPL) agent with high iodine concentration and to investigate the effect of intravenous administration of IPL on renal function in a rat model with chronic kidney injury.

Materials and methods

IPLs were prepared by encapsulating an iomeprol (400mgI/mL) solution in liposomes by a kneading method using a rotation-revolution mixer. Radiodensities of iomeprol and IPL were measured. IPL or iopamidol at normal dose (0.74 g I/kg) or high dose (3.7 g I/kg) was administered to healthy and 5/6-nephrectomized rats (n = 3-6). Serum creatinine (sCr) and histopathological change of tubular epithelial cells were evaluated after injection.

Results

The iodine concentration of IPL was 220.7 mgI/mL, equivalent to 55.2% of the iodine concentration of iomeprol. The CT values of IPL was 4731.6 ± 53.2 HU, 59.04% that of iomeprol. The ratios of change in sCr in 5/6-nephrectomized rats that received high-dose iopamidol were 0.73, which were significantly higher than that in 5/6-nephrectomized rats that received high-dose IPL (-0.03) (p = 0.006). Change in foamy degeneration of tubular epithelial cells was confirmed in 5/6-nephrectomized rats that received high-dose iopamidol than that in the sham control group and healthy rats that received normal dose iopamiron (p = 0.016, p = 0.032, respectively). Foamy degeneration of tubular epitherial cells was rarely observed in the IPL injection group.

Conclusions

We developed new liposomal contrast agents that have high iodine concentration and minimal effect on renal function.

Two decades of vaccine development against atherosclerosis

Atherosclerosis is an immune-mediated chronic inflammatory disease that leads to the development of fatty plaques in the arterial walls, ultimately increasing the risk of thrombosis, stroke, and myocardial infarction. The immune response in this complex disease is both atheroprotective and pro-atherogenic, involving both innate and adaptive immunity. Current treatments include the adjustment of lifestyle factors, cholesterol-lowering drugs such as statins, and immunotherapy, whereas vaccine development has received comparatively little attention. In this review, we discuss the potential of antigen-specific vaccination as a preventative approach based on more than 20 years of research and innovation. Vaccination targets include proteins that are more abundant in atherosclerotic patients, such as oxidized low-density lipoprotein (LDL), apolipoprotein B-100, proprotein convertase subtilisin/kexin type-9 serine protease (PCSK9), cholesteryl ester transfer protein (CETP), and heat shock proteins HSP60 and HSP65. Immunization with such proteins or their peptide epitopes has been shown to induce T-cell activation, produce antigen-specific antibodies, reduce the size of atherosclerotic lesions, and/or reduce serum cholesterol levels. Vaccination against atherosclerosis therefore offers a new strategy to address the burden on healthcare systems caused by cardiovascular disease, the leading cause of death worldwide.

A Virus-like particle-based bivalent PCSK9 vaccine lowers LDL-cholesterol levels in Non-Human Primates

Elevated low-density lipoprotein cholesterol (LDL-C) is an important risk factor in the development of atherosclerotic cardiovascular disease (ASCVD). Inhibitors of proprotein convertase subtilisin/kexin type 9 (PCSK9), a negative regulator of LDL-C metabolism, have emerged as promising approaches for reducing elevated LDL-C levels. Here, we evaluated the cholesterol lowering efficacy of virus-like particle (VLP) based vaccines that target epitopes found within the LDL receptor (LDL-R) binding domain of PCSK9. In both mice and non-human primates, a bivalent VLP vaccine targeting two distinct epitopes on PCSK9 elicited strong and durable antibody responses and lowered cholesterol levels. In macaques, a VLP vaccine targeting a single PCSK9 epitope was only effective at lowering LDL-C levels in combination with statins, whereas immunization with the bivalent vaccine lowered LDL-C without requiring statin co-administration. These data highlight the efficacy of an alternative, vaccine-based approach for lowering LDL-C.

The effect of PCSK9 immunization on the hepatic level of microRNAs associated with the PCSK9/LDLR pathway

INTRODUCTION

MicroRNAs (miRNAs) are a class of gene expression epigenetic regulators that play roles in regulating genes involved in cholesterol homeostasis, including low-density lipoprotein receptor (LDLR) and PCSK9; therefore, miRNAs have been suggested as potential therapeutic targets for treating cardiometabolic disorders. Thus, the present study aimed to assess the effect of immunotherapy with the PCSK9 peptide vaccine on the hepatic expression levels of microRNAs associated with the LDLR pathway, including miRNA-27a, miRNA-30c, and miRNA-191, in normal vaccinated mice.

MATERIAL AND METHODS

PCSK9 immunogenic peptide and 0.4% alum adjuvant were mixed at a 1 : 1 ratio and used as a vaccine formulation. Male albino mice were randomly assigned to the vaccine or control group. Mice in the vaccine group were injected four times at two-week intervals with a PCSK9 peptide vaccine, and mice in the control group were injected with phosphate-buffered saline (PBS). Animal livers were sampled 2 weeks after the last injection to assess miRNA expression levels. The hepatic expression levels of miRNA-27a, miRNA-30c, and miRNA-191 were evaluated by SYBR Green real-time PCR, quantified by a comparative (2- Δ Δ CT) method (fold change (FC)) and normalized to U6 small nuclear RNA (U6snRNA) expression as an internal control.

RESULTS

The hepatic expression level of miRNA-27a was significantly lower in mice following immunotherapy with the PCSK9 peptide vaccine compared to the control group (FC: 0.731 ±0.1, p = 0.027). Also, there was a borderline significantly lower hepatic expression level of miRNA-30c in the vaccinated group compared to the control (FC: 0.569 ±0.1, p = 0.078). However, no significant differences were found in the hepatic expression level of miRNA-191 between the two studied groups (FC: 0.852 ±0.1, p = 0.343).

CONCLUSIONS

According to the findings, the PCSK9 peptide vaccine could effectively reduce the hepatic expression level of miRNA-27a and may be helpful in the management of LDL-C level and atherosclerosis, which may be mediated through the LDLR pathway.

A cVLP-Based Vaccine Displaying Full-Length PCSK9 Elicits a Higher Reduction in Plasma PCSK9 Than Similar Peptide-Based cVLP Vaccines

Administration of PCSK9-specific monoclonal antibodies, as well as peptide-based PCSK9 vaccines, can lower plasma LDL cholesterol by blocking PCSK9. However, these treatments also cause an increase in plasma PCSK9 levels, presumably due to the formation of immune complexes. Here, we utilize a versatile capsid virus-like particle (cVLP)-based vaccine platform to deliver both full-length (FL) PCSK9 and PCSK9-derived peptide antigens, to investigate whether induction of a broader polyclonal anti-PCSK9 antibody response would mediate more efficient clearance of plasma PCSK9. This head-to-head immunization study reveals a significantly increased capacity of the FL PCSK9 cVLP vaccine to opsonize and clear plasma PCSK9. These findings may have implications for the design of PCSK9 and other vaccines that should effectively mediate opsonization and immune clearance of target antigens.

PCSK9 in Liver Cancers at the Crossroads between Lipid Metabolism and Immunity

Metabolic rewiring and defective immune responses are considered to be the main driving forces sustaining cell growth and oncogenesis in many cancers. The atypical enzyme, proprotein convertase subtilisin/kexin type 9 (PCSK9), is produced by the liver in large amounts and plays a major role in lipid metabolism via the control of the low density lipoprotein receptor (LDLR) and other cell surface receptors. In this context, many clinical studies have clearly demonstrated the high efficacy of PCSK9 inhibitors in treating hyperlipidemia and cardiovascular diseases. Recent data implicated PCSK9 in the degradation of major histocompatibility complex I (MHC-I) receptors and the immune system as well as in other physiological activities. This review highlights the complex crosstalk between PCSK9, lipid metabolism and immunosuppression and underlines the latest advances in understanding the involvement of this convertase in other critical functions. We present a comprehensive assessment of the different strategies targeting PCSK9 and show how these approaches could be extended to future therapeutic options to treat cancers with a main focus on the liver.

The role of PCSK9 in NAFLD/NASH and therapeutic implications of PCSK9 inhibition

INTRODUCTION

There are inconsistent findings regarding the effect of lipid-lowering agents on nonalcoholic fatty liver disease (NAFLD). Proprotein Convertase Subtilisin/Kexin type 9 (PCSK9) is an important player in cholesterol homeostasis and intracellular lipogenesis, and PCSK9 inhibitors (PCSK9-i) have been found to be efficient for pharmacological management of hyperlipidemia.

AREAS COVERED

Whether PCSK9 (itself) or PCSK9-i affects NAFLD is still disputed. To address this question, we review published preclinical and clinical studies providing evidence for the role of PCSK9 in and the effect of PCSK9-I on the development and pathogenesis of NAFLD.

EXPERT OPINION

The current evidence from a landscape of preclinical and clinical studies examining the role of PCSK9 in NAFLD shows controversial results. Preclinical studies indicate that PCSK9 associates with NAFLD and nonalcoholic steatohepatitis (NASH) progression in opposite directions. In humans, it has been concluded that the severity of hepatic steatosis affects the correlation between circulating PCSK9 and liver fat content in humans, with a possible impact of circulating PCSK9 in the early stages of NAFLD, but not in the late stages. However, data from clinical trials with PCSK9-i reassure to the safety of these agents, although real-life long-term evidence is needed.

PCSK9 Inhibition: From Current Advances to Evolving Future

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secretory serine protease synthesized primarily by the liver. It mainly promotes the degradation of low-density lipoprotein receptor (LDL-R) by binding LDL-R, reducing low-density lipoprotein cholesterol (LDL-C) clearance. In addition to regulating LDL-R, PCSK9 inhibitors can also bind Toll-like receptors (TLRs), scavenger receptor B (SR-B/CD36), low-density lipoprotein receptor-related protein 1 (LRP1), apolipoprotein E receptor-2 (ApoER2) and very-low-density lipoprotein receptor (VLDL-R) reducing the lipoprotein concentration and slowing thrombosis. In addition to cardiovascular diseases, PCSK9 is also used in pancreatic cancer, sepsis, and Parkinson’s disease. Currently marketed PCSK9 inhibitors include alirocumab, evolocumab, and inclisiran, as well as small molecules, nucleic acid drugs, and vaccines under development. This review systematically summarized the application, preclinical studies, safety, mechanism of action, and latest research progress of PCSK9 inhibitors, aiming to provide ideas for the drug research and development and the clinical application of PCSK9 in cardiovascular diseases and expand its application in other diseases.

mRNA Display Reaches for the Clinic with New PCSK9 Inhibitor

Merck & Co. recently reported one of the first mRNA display-derived clinical candidates in a bioavailable inhibitor of proprotein convertase subtilisin/kexin type 9 (PCSK9). Herein, we discuss the chemical and pharmacological challenges surmounted in bringing this compound to trials and the current outlook for mRNA display-based therapeutic development.

New Therapeutic Approaches in Treatment of Dyslipidaemia—A Narrative Review

Dyslipidaemia is a well-known risk factor for the development of cardiovascular disease, a leading cause of morbidity and mortality in developed countries. As a consequence, the medical community has been dealing with this problem for decades, and traditional statin therapy remains the cornerstone therapeutic approach. However, clinical trials have observed remarkable results for a few agents effective in the treatment of elevated serum lipid levels. Ezetimibe showed good but limited results when used in combination with statins. Bempedoic acid has been thoroughly studied in multiple clinical trials, with a reduction in LDL cholesterol by approximately 15%. The first approved monoclonal antibodies for the treatment of dyslipidaemia, PCSK9 inhibitors, are currently used as second-line treatment for patients with unregulated lipid levels on statin or statin combination therapy. A new siRNA molecule, inclisiran, demonstrates great potential, particularly concerning compliance, as it is administered twice yearly and pelacarsen, an antisense oligonucleotide that targets lipoprotein(a) and lowers its levels. Volanesorsen is the first drug that was designed to target chylomicrons and lower triglyceride levels, and olezarsen, the next in-line chylomicron lowering agent, is currently being researched. The newest possibilities for the treatment of dyslipidaemia are ANGPTL3 inhibitors with evinacumab, already approved by the FDA, and EMA for the treatment of familial hypercholesterolemia. This article provides a short summary of new agents currently used or being developed for lipid lowering treatment.

PCSK9 inhibition-based therapeutic approaches: an immunotherapy perspective

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors (PCSK9-I) are novel therapeutic tools to decrease cardiovascular risk. These agents work by lowering the low-density lipoprotein cholesterol (LDL-C) in hypercholesterolemic patients who are statin resistant/intolerant. Current clinically approved and investigational PCSK9-I act generally by blocking PCSK9 activity in the plasma or suppressing its expression or secretion by hepatocytes. The most widely investigated method is the disruption of PCSK9/LDL receptor (LDLR) interaction by fully-humanized monoclonal antibodies (mAbs), evolocumab and alirocumab, which have been approved for the therapy of hypercholesterolemia and atherosclerotic cardiovascular disease (CVD). Besides, a small interfering RNA called inclisiran, which specifically suppresses PCSK9 expression in hepatocytes, is as effective as mAbs but with administration twice a year. Because of the high costs of such therapeutic approaches, several other PCSK9-I have been surveyed, including peptide-based anti-PCSK9 vaccines and small oral anti-PCSK9 molecules, which are under investigation in preclinical and phase I clinical studies. Interestingly, anti-PCSK9 vaccination has been found to serve as a more widely feasible and more cost-effective therapeutic tool over mAb PCSK9-I for managing hypercholesterolemia. The present review will discuss LDL-lowering and cardioprotective effects of PCSK9-I, mainly immunotherapy-based inhibitors including mAbs and vaccines, in preclinical and clinical studies.

Impact of PCSK9 Immunization on Glycemic Indices in Diabetic Rats

METHODS

To prepare the anti-PCSK9 vaccine, a peptide construct called Immunogenic Fused PCSK9-Tetanus (IFPT) was linked to the surface of nanoliposome carriers. Healthy rats received four subcutaneous injections of the vaccine at biweekly intervals. Two weeks after the last vaccination, anti-PCSK9 antibody titers, PCSK9 targeting, and inhibition of PCSK9-low-density lipoprotein receptor (LDLR) interaction were evaluated. After verification of antibody generation, the immunized rats were intraperitoneally treated with a single dose (45 mg/kg) of streptozotocin (STZ) to induce diabetes mellitus. The levels of fasting blood glucose (FBG) were measured, and the oral glucose tolerance test (OGTT) as well as the insulin tolerance test (ITT) were carried out to assess glycemic status. At the end of the study, the total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglyceride, and high-density lipoprotein cholesterol concentrations were assayed. Histopathology examination of the liver and pancreas was also performed using the hematoxylin-eosin staining method.

RESULTS

The prepared nanoliposomal vaccine could strongly induce anti-PCSK9 antibodies in the vaccinated rats. Within one week following the STZ injection, the FBG level was lower in the vaccinated group vs. diabetic control group (49% (-171.7 ± 35 mg/dL, p < 0.001)). In the OGTT, the injected rats showed improved glucose tolerance as reflected by the reduction of blood glucose levels over 180 min, compared with the diabetic controls. Moreover, the ITT demonstrated that, after the insulin injection, blood glucose concentration declined by 49.3% in the vaccinated group vs. diabetic control group. Expectedly, the vaccinated rats exhibited lower (-26.65%, p = 0.03) plasma LDL-C levels compared with the diabetic controls. Histopathology examination of pancreas tissue demonstrated that the pancreatic islets of the vaccinated rats had a slight decline in the population of β-cells and few α-cells. Normal liver histology was also observed in the vaccinated rats.

CONCLUSION

PCSK9 inhibition through the liposomal IFPT vaccine can improve the glucose and insulin tolerance impairments as well as the lipid profile in diabetes.