Recent advances in developing PCSK9 inhibitors for lipid-lowering therapy

Inhibition of PCSK9: A Promising Enhancer for Anti-PD-1/PD-L1 Immunotherapy

Immune checkpoint therapy, such as programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) blockade, has achieved remarkable results in treating various tumors. However, most cancer patients show a low response rate to PD-1/PD-L1 blockade, especially those with microsatellite stable/mismatch repair-proficient colorectal cancer subtypes, which indicates an urgent need for new approaches to augment the efficacy of PD-1/PD-L1 blockade. Cholesterol metabolism, which involves generating multifunctional metabolites and essential membrane components, is also instrumental in tumor development. In recent years, inhibiting proprotein convertase subtilisin/kexin type 9 (PCSK9), a serine proteinase that regulates cholesterol metabolism, has been demonstrated to be a method enhancing the antitumor effect of PD-1/PD-L1 blockade to some extent. Mechanistically, PCSK9 inhibition can maintain the recycling of major histocompatibility protein class I, promote low-density lipoprotein receptor-mediated T-cell receptor recycling and signaling, and modulate the tumor microenvironment (TME) by affecting the infiltration and exclusion of immune cells. These mechanisms increase the quantity and enhance the antineoplastic effect of cytotoxic T lymphocyte, the main functional immune cells involved in anti-PD-1/PD-L1 immunotherapy, in the TME. Therefore, combining PCSK9 inhibition therapy with anti-PD-1/PD-L1 immunotherapy may provide a novel option for improving antitumor effects and may constitute a promising research direction. This review concentrates on the relationship between PCSK9 and cholesterol metabolism, systematically discusses how PCSK9 inhibition potentiates PD-1/PD-L1 blockade for cancer treatment, and highlights the research directions in this field.

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.

Computational Design, Synthesis, and Biological Evaluation of Diimidazole Analogues Endowed with Dual PCSK9/HMG-CoAR-Inhibiting Activity

Proprotein convertase subtilisin/kexin 9 (PCSK9) is responsible for the degradation of the hepatic low-density lipoprotein receptor (LDLR), which regulates circulating cholesterol levels. Consequently, the PCSK9 inhibition is a valuable therapeutic approach for the treatment of hypercholesterolemia and cardiovascular diseases. In our studies, we discovered Rim13, a polyimidazole derivative reducing the protein-protein interaction between PCSK9 and LDLR with an IC₅₀ of 1.6 μM. The computational design led to the optimization of the shape of the PCSK9/ligand complementarity, enabling the discovery of potent diimidazole derivatives. In fact, carrying out biological assays to fully characterize the cholesterol-lowering activity of the new analogues and using both biochemical and cellular techniques, compound Dim16 displayed improved PCSK9 inhibitory activity (IC₅₀ 0.9 nM). Interestingly, similar to other lupin-derived peptides and their synthetic analogues, some compounds in this series showed dual hypocholesterolemic activity since some of them complementarily inhibited the 3-hydroxy-3-methylglutaryl coenzyme A reductase.

Advancing targeted protein degradation for metabolic diseases therapy

The development and application of traditional drugs represented by small molecule chemical drugs and biological agents, especially inhibitors, have become the mainstream drug development. In recent years, targeted protein degradation (TPD) technology has become one of the most promising methods to remove specific disease-related proteins using cell self-destruction mechanisms. Many different TPD strategies are emerging based on the ubiquitin-proteasome system (UPS) and the autophagy-lysosomal pathway (ALP), including but not limited to proteolysis-targeting chimeras (PROTAC), molecular glues (MG), lysosome targeting chimeras (LYTAC), chaperone-mediated autophagy (CMA)-targeting chimeras, autophagy-targeting chimera (AUTAC), autophagosome-tethering compound (ATTEC), and autophagy-targeting chimera (AUTOTAC). The advent of targeted degradation technology can change most protein targets in human cells from undruggable to druggable, greatly expanding the therapeutic prospect of refractory diseases such as metabolic syndrome. Here, we summarize the latest progress of major TPD technologies, especially in metabolic syndrome and look forward to providing new insights for drug discovery.

Clearance of plasma PCSK9 via the asialoglycoprotein receptor mediated by heterobifunctional ligands

Proprotein convertase subtilisin/kexin type 9 (PCSK9) regulates plasma low-density lipoprotein cholesterol (LDL-C) levels by promoting the degradation of hepatic LDL receptors (LDLRs). Current therapeutic approaches use antibodies that disrupt PCSK9 binding to LDLR to reduce circulating LDL-C concentrations or siRNA that reduces PCSK9 synthesis and thereby levels in circulation. Recent reports describe small molecules that, like therapeutic antibodies, interfere with PCSK9 binding to LDLR. We report an alternative approach to decrease circulating PCSK9 levels by accelerating PCSK9 clearance and degradation using heterobifunctional molecules that simultaneously bind to PCSK9 and the asialoglycoprotein receptor (ASGPR). Various formats, including bispecific antibodies, antibody-small molecule conjugates, and heterobifunctional small molecules, demonstrate binding in vitro and accelerated PCSK9 clearance in vivo. These molecules showcase a new approach to PCSK9 inhibition, targeted plasma protein degradation (TPPD), and demonstrate the feasibility of heterobifunctional small molecule ligands to accelerate the clearance and degradation of pathogenic proteins in circulation.

[Lipid lowering: new agents and new concepts]

Low-density lipoprotein (LDL) cholesterol (LDL-C) is a causal risk factor for cardiovascular complications. A target value is set according to risk, guideline-based and individual basis. We now have the means to lower LDL‑C levels to ranges that are even associated with plaque volume regression. Moreover, lipid treatment is an example of how pharmacotherapy has evolved from classical selective inhibition of enzymes by drugs (e.g. statins) to targeted neutralization of proteins by antibodies. The reduction of atherogenic lipoproteins by specific inhibition or reduction of mRNA of target proteins, e.g. PCSK‑9, ANGPLT3, ApoC-III or Apo (a), and possibly one day by vaccination or even CRISP-based gene therapy will in the long term lead to new concepts in the treatment and prevention of dyslipidemia and cardiovascular complications. The cumulative exposure of atherogenic lipoproteins to the vessel wall is determined by the time-averaged LDL‑C level. This essentially depends on patient adherence and prescribed treatment intensity by physicians. Therefore, it is likely that treatment adherence influences the cumulative benefit of treatment. Accordingly, the new therapeutic strategies mentioned above with presumably higher adherence rates could help to optimize cardiovascular prevention. Early and effective LDL‑C lowering could drastically reduce the incidence of cardiovascular complications in the long term and help to maintain the health of our patients.

RNA-based therapy in the management of lipid disorders: a review

This review focuses on antisense oligonucleotides and small interfering ribonucleic acid therapies approved or under development for the management of lipid disorders. Recent advances in RNA-based therapeutics allow tissue-specific targeting improving safety. Multiple potential target proteins have been identified and RNA-based therapeutics have the potential to significantly improve outcomes for patients with or at risk for atherosclerotic cardiovascular disease. The advantages of RNA-based lipid modifying therapies include the ability to reduce the concentration of almost any target protein highly selectively, allowing for more precise control of metabolic pathways than can often be achieved with small molecule-based drugs. RNA-based lipid modifying therapies also make it possible to reduce the expression of target proteins for which there are no small molecule inhibitors. RNA-based therapies can also reduce pill burden as their administration schedule typically varies from weekly to twice yearly injections. The safety profile of most current RNA-based lipid therapies is acceptable but adverse events associated with various therapies targeting lipid pathways have included injection site reactions, inflammatory reactions, hepatic steatosis and thrombocytopenia. While the body of evidence for these therapies is expanding, clinical experience with these therapies is currently limited in duration and the results of long-term studies are eagerly awaited.

Efficacy and safety of Qushi Huayu granule for hyperlipidemia: study protocol for a randomized, double-blind, placebo-controlled trial

Background

Hyperlipidemia has become a common chronic disease worldwide in recent years. Studies have shown that hyperlipidemia patients, especially those with a high level of serum low-density lipoprotein cholesterol (LDL-C), have a significantly higher prevalence of atherosclerosis, leading to coronary heart disease. Previous basic experiments and clinical studies have shown that Qushi Huayu granules (QSHY) reduce blood lipids in patients with non-alcoholic fatty liver disease (NAFLD) accompanied by hyperlipidemia. However, the clinical efficacy of QSHY in patients with hyperlipidemia is still lacking. This study aims to investigate the effect and safety of QSHY for hyperlipidemia.

Methods

This is a randomized, double-blind, placebo-controlled trial. A total of 210 participants will be enrolled and randomized into the QSHY or placebo granules groups in equal proportions, who will receive treatment for 24 weeks. The primary outcome will be the change in LDL-C from baseline to week 12. Secondary outcomes will be changes in other serum lipids markers, life quality measuring health surveys, and traditional Chinese medicine (TCM) pattern scale. All related tests will be measured at baseline, week 12, and week 24 after enrollment. Adverse events and the safety of intervention will be monitored and evaluated.

Discussion

We designed a clinical trial of hyperlipidemia management with QSHY, a TCM prescription. The results of this trial will present the efficacy and safety of QSHY in patients with hyperlipidemia.

Trial registration

Chinese Clinical Trial Registry ChiCTR2000034125. Registered on June 25, 2019

A Series of Novel, Highly Potent, and Orally Bioavailable Next-Generation Tricyclic Peptide PCSK9 Inhibitors

Proprotein convertase subtilisin-like/kexin type 9 (PCSK9) is a key regulator of plasma LDL-cholesterol (LDL-C) and a clinically validated target for the treatment of hypercholesterolemia and coronary artery disease. Starting from second-generation lead structures such as 2, we were able to refine these structures to obtain extremely potent bi- and tricyclic PCSK9 inhibitor peptides. Optimized molecules such as 44 demonstrated sufficient oral bioavailability to maintain therapeutic levels in rats and cynomolgus monkeys after dosing with an enabled formulation. We demonstrated target engagement and LDL lowering in cynomolgus monkeys essentially identical to those observed with the clinically approved, parenterally dosed antibodies. These molecules represent the first report of highly potent and orally bioavailable macrocyclic peptide PCSK9 inhibitors with overall profiles favorable for potential development as once-daily oral lipid-lowering agents. In this manuscript, we detail the design criteria and multiparameter optimization of this novel series of PCSK9 inhibitors.

Finding inhibitors for PCSK9 using computational methods

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is one of the key targets for atherosclerosis drug development as its binding with low-density lipoprotein receptor leads to atherosclerosis. The protein-ligand interaction helps to understand the actual mechanism for the pharmacological action. This research aims to discover the best inhibitory candidates targeting PCSK9. To start with, reported ACE inhibitors were incorporated into pharmacophore designing using PharmaGist to produce pharmacophore models. Selected models were later screened against the ZINC database using ZINCPHARMER to define potential drug candidates that were docked with the target protein to understand their interactions. Molecular docking revealed the top 10 drug candidates against PCSK9, with binding energies ranging from -9.8 kcal·mol^-1 to -8.2 kcal·mol^-1, which were analyzed for their pharmacokinetic properties and oral bioavailability. Some compounds were identified as plant-derived compounds like (S)-canadine, hesperetin or labetalol (an antihypertensive drug). Molecular dynamics results showed that these substances formed stable protein-ligand complexes. (S)-canadine-PCSK9 complex was the most stable with the lowest RMSD. It was concluded that (S)-canadine may act as a potential inhibitor against atherosclerosis for the development of new PCSK9 inhibitory drugs in future in vitro research.

Potent Lys Patch-Containing Stapled Peptides Targeting PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9), identified as a regulator of low-density lipoprotein receptor (LDLR), plays a major role in cardiovascular diseases (CVD). Recently, Pep2-8, a small peptide with discrete three-dimensional structure, was found to inhibit the PCSK9/LDLR interaction. In this paper, we describe the modification of this peptide using stapled peptide and SIP technologies. Their combination yielded potent compounds such as 18 that potently inhibited the binding of PCSK9 to LDLR (K_D = 6 ± 1 nM) and restored in vitro LDL uptake by HepG2 cells in the presence of PCSK9 (EC₅₀ = 175 ± 40 nM). The three-dimensional structures of key peptides were extensively studied by circular dichroism and nuclear magnetic resonance, and molecular dynamics simulations allowed us to compare their binding mode to tentatively rationalize structure-activity relationships (SAR).

New PCSK9 inhibitor miR-552-3p reduces LDL-C via enhancing LDLR in high fat diet-fed mice

PCSK9 has emerged as a promising new therapeutic target for hyperlipidemia. The efficacy of PCSK9 siRNA in clinic trials clues the feasibility of exploring more PCSK9 inhibitors based on genetic inhibition in the treatment of hyperlipidemia. MicroRNAs (miRNAs) as a class of endogenous non-coding small RNAs can regulate genes at transcriptional and/or translational level. Here, we screened miRNAs from the prediction of TargetScan database with possible inhibitory activities in PCSK9 protein level via AlphaLISA and Western blotting, in which miR-552-3p was selected out for its strongest inhibitory effect. MiR-552-3p could bind to the 3' untranslated region (3'-UTR) of PCSK9 to inhibit translation and interact with the promoter of PCSK9 to suppress transcription. Further in vitro and in vivo experiments proved the effects of miR-552-3p on PCSK9 and downstream effectors: it could increase LDLR protein level, promote LDL-C uptake in HepG2 cells and lower serum LDL-C in high fat diet (HFD)-fed mice. In conclusion, our findings firstly identified miR-552-3p as a new PCSK9 inhibitor with the dual-inhibition mechanism, which suggested the possible application of miR-552-3p in the treatment of hyperlipidemia.

Small interfering RNA to proprotein convertase subtilisin/kexin type 9: transforming LDL-cholesterol-lowering strategies

PURPOSE OF REVIEW

Proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibition is a new strategy to reduce LDL cholesterol (LDL-C), that is currently pursued by mAbs. A promising novel approach to target PCSK9 is using small interfering RNAs to inhibit hepatic PCSK9 synthesis. The first small interfering RNA developed for this purpose is inclisiran. Here, we review its clinical trial data and potential impact on patient management.

RECENT FINDINGS

Inclisiran achieves sustained, additional 50% LDL-C reduction in patients receiving background statin therapy. Resulting LDL-C changes can be maintained by an infrequent dosing regimen with twice per year injections, that appear safe and well tolerated. Thus far, inclisiran has been studied in patients with established cardiovascular disease, high-risk primary prevention and in patients with familial hypercholesterolemia.

SUMMARY

High and very high-risk individuals may benefit from the additional LDL-C-lowering effect of inclisiran when added to current lipid-lowering therapies. Furthermore, the simple dosing regimen may improve the convenience for users and facilitate patient adherence to therapy. The safety and convenience of inclisiran may offer new opportunities for population health.

Metabolic Syndrome and Skin Diseases

The increasing prevalence of Metabolic syndrome (MetS) is a worldwide health problem, and the association between MetS and skin diseases has recently attracted growing attention. In this review, we summarize the associations between MetS and skin diseases, such as psoriasis, acne vulgaris, hidradenitis suppurativa, androgenetic alopecia, acanthosis nigricans, and atopic dermatitis. To discuss the potential common mechanisms underlying MetS and skin diseases, we focus on insulin signaling and insulin resistance, as well as chronic inflammation including adipokines and proinflammatory cytokines related to molecular mechanisms. A better understanding of the relationship between MetS and skin diseases contributes to early diagnosis and prevention, as well as providing clues for developing novel therapeutic strategies.