Lowering serum lipids via PCSK9-targeting drugs: current advances and future perspectives

Identification of 4-amino-2-Pyridones as new potent PCSK9 inhibitors: From phenotypic hit discovery to in vivo tolerability

Among the strategies to overcome the underperformance of statins in cardiovascular diseases (CVDs), the development of drugs targeting the Proprotein Convertase Subtilisin-like Kexin type 9 (PCSK9) is considered one of the most promising. However, only anti-PCSK9 biological drugs have been approved to date, and orally available small-molecules for the treatment of hypercholesterolemic conditions are still missing on the market. In the present work, we describe the application of a phenotypic approach to the identification and optimization of 4-amino-2-pyridone derivatives as a new chemotype with anti-PCSK9 activity. Starting from an in-house collection of compounds, functional assays on HepG2 cells followed by a chemistry-driven hit optimization campaign, led to the potent anti-PCSK9 candidate 5c. This compound, at 5 μM, totally blocked PCSK9 secretion from HepG2 cells, significantly increased LDL receptor (LDLR) expression, and acted cooperatively with simvastatin by reducing its induction of PCSK9 expression. Finally, compound 5c also proved to be well tolerated in C57BL/6J mice at the tested concentration (40 mg/kg) with no sign of toxicity or behavior modifications.

Variability in Plasma Lipids Between Intensive Statin Therapy and Conventional-Dose Statins Combined with Ezetimibe Therapy in Patients with Coronary Atherosclerosis Disease

Dyslipidemia has been widely recognized as a significant risk factor for coronary atherosclerosis disease (CAD). In fact, lipid variability has emerged as a more reliable predictor of cardiovascular events. In this study, we aimed to examine the variability in plasma lipids under two different lipid-lowering regimens (intensive statin therapy versus the combination of conventional-dose statins with ezetimibe). In total, we have retrospectively examined 1275 patients with CAD from January 2009 to April 2019 and divided them into two groups: intensive statin group and conventional-dose statins combined with ezetimibe group. All patients were followed up for at least 1 year. Lipid variability was verified by standard deviation (SD), coefficient of variation (CV), and variability independent of mean (VIM) triple methods. Multiple linear regression and subgroup analyses were performed. In the overall participants, the mean age was 62.3 ± 10.4 years old, and 72.8% were male. Multivariate linear regression analysis indicated that the intensive statin group had lower variability in terms of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and non-high-density lipoprotein cholesterol (non-HDL-C) in all SD, CV, and VIM triple methods than statins combined with ezetimibe group (P for all <0.05). Similar results were established in the subgroup analyses based on atorvastatin or rosuvastatin, diabetes mellitus or not, and hypertension or not (P for all < 0.05). Thus, we can conclude that intensive statin therapy could contribute in lowering lipid variability than conventional-dose statins combined with ezetimibe therapy among patients with CAD.

Hepatic fibrosis 2022: Unmet needs and a blueprint for the future

Steady progress over four decades toward understanding the pathogenesis and clinical consequences of hepatic fibrosis has led to the expectation of effective antifibrotic drugs, yet none has been approved. Thus, an assessment of the field is timely, to clarify priorities and accelerate progress. Here, we highlight the successes to date but, more importantly, identify gaps and unmet needs, both experimentally and clinically. These include the need to better define cell-cell interactions and etiology-specific elements of fibrogenesis and their link to disease-specific drivers of portal hypertension. Success in treating viral hepatitis has revealed the remarkable capacity of the liver to degrade scar in reversing fibrosis, yet we know little of the mechanisms underlying this response. Thus, there is an exigent need to clarify the cellular and molecular mechanisms of fibrosis regression in order for therapeutics to mimic the liver's endogenous capacity. Better refined and more predictive in vitro and animal models will hasten drug development. From a clinical perspective, current diagnostics are improving but not always biologically plausible or sufficiently accurate to supplant biopsy. More urgently, digital pathology methods that leverage machine learning and artificial intelligence must be validated in order to capture more prognostic information from liver biopsies and better quantify the response to therapies. For more refined treatment of NASH, orthogonal approaches that integrate genetic, clinical, and pathological data sets may yield treatments for specific subphenotypes of the disease. Collectively, these and other advances will strengthen and streamline clinical trials and better link histologic responses to clinical outcomes.

Generation of a Novel High-Affinity Antibody Binding to PCSK9 Catalytic Domain with Slow Dissociation Rate by CDR-Grafting, Alanine Scanning and Saturated Site-Directed Mutagenesis for Favorably Treating Hypercholesterolemia

Inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) has become an attractive therapeutic strategy for lowering low-density lipoprotein cholesterol (LDL-C). In this study, a novel high affinity humanized IgG1 mAb (named h5E12-L230G) targeting the catalytic domain of human PCSK9 (hPCSK9) was generated by using CDR-grafting, alanine-scanning mutagenesis, and saturated site-directed mutagenesis. The heavy-chain constant region of h5E12-L230G was modified to eliminate the cytotoxic effector functions and mitigate the heterogeneity. The biolayer interferometry (BLI) binding assay and molecular docking study revealed that h5E12-L230G binds to the catalytic domain of hPCSK9 with nanomolar affinity (K_D = 1.72 nM) and an extremely slow dissociation rate (k_off, 4.84 × 10⁻⁵ s⁻¹), which interprets its quite low binding energy (−54.97 kcal/mol) with hPCSK9. Additionally, h5E12-L230G elevated the levels of LDLR and enhanced the LDL-C uptake in HepG2 cells, as well as reducing the serum LDL-C and total cholesterol (TC) levels in hyperlipidemic mouse model with high potency comparable to the positive control alirocumab. Our data indicate that h5E12-L230G is a high-affinity anti-PCSK9 antibody candidate with an extremely slow dissociation rate for favorably treating hypercholesterolemia and relevant cardiovascular diseases.

New dammarane-type glycosides from Gynostemma pentaphyllum and their lipid-lowering activity

Gynostemma pentaphyllum (Thunb.) Makino has a long history as food and diary supplement in China. At present, there are some products for hyperlipidemia in the market, including G. pentaphyllum tea, healthy wine and healthy food. In order to discover proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, fourteen new triterpenoid saponins named gypenoside LXXXVIII-CI (1-14) along with six known compounds (15-20) were isolated from G. pentaphyllum. Their structures were elucidated by means of various spectroscopic techniques. Eight isolates were evaluated the inhibitory effect on PCSK9 in HepG2 cells. The results showed that three dammarane-type glycosides (2, 3, 15) remarkably reduced PCSK9 expression at 10 μM concentration. These findings suggested that G. pentaphyllum was worthy of further investigation to find small molecule PCSK9 inhibitors and facilitate their utilization as functional food ingredients.

Single-Strand DNA-Like Oligonucleotide Aptamer Against Proprotein Convertase Subtilisin/Kexin 9 Using CE-SELEX: PCSK9 Targeting Selection

BACKGROUND

Proprotein convertase subtilisin/kexin 9 (PCSK9) serves a key regulatory function in the metabolism of low-density lipoprotein (LDL)-cholesterol (LDL-C) through interaction with the LDL receptor (LDLR) followed by its destruction that results in the elevation of the plasma levels of LDL-C. The aims of the present study were to separate and select a number of single-stranded DNA (ssDNA) aptamers against PCSK9 from a library pool (n > 10¹²) followed by their characterization.

METHODS

The aptamers obtained from the DNA-PCSK9 complexes which presented the highest affinity against PCSK9 were separated and selected using capillary electrophoresis evolution of ligands by exponential enrichment (CE-SELEX). The selected aptamers were amplified and cloned into a T/A vector. The plasmids from the positive clones were extracted and sequenced. The Mfold web server was used to predict the secondary structure of the aptamers.

RESULTS

Following three rounds of CE-SELEX, the identified anti-PCSK9 ssDNA aptamers, namely aptamer 1 (AP-1) and aptamer 2 (AP-2), presented half maximal inhibitory concentrations of 325 and 327 nM, lowest dissociation constants of 294 and 323 nM, and most negative Gibbs free energy values of - 9.17 and - 8.28 kcal/mol, respectively.

CONCLUSION

The results indicated that the selected aptamers (AP-1 and AP-2) induced potent inhibitory effects against PCSK9. Further in vivo studies demand to find out AP-1 and AP-2 aptamers as suitable candidates, instead of antibodies, for using in therapeutic purposes in patients with hypercholesterolemia and cardiovascular disease.

Impact of Lowering Low-Density Lipoprotein Cholesterol with Contemporary Lipid-Lowering Medicines on Cognitive Function: A Systematic Review and Meta-Analysis

PURPOSE

To evaluate the potential association between the lowering of low-density lipoprotein cholesterol (LDL-C) with contemporary lipid-lowering medicines and cognitive function.

METHODS

Randomized controlled trials (RCTs) in databases including PubMed, Embase, and the Web of Science and all databases in the Cochrane Library and ClinicalTrials.gov were collected from inception to January 1, 2020. The cognitive function of patients receiving proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitors, statins and ezetimibe was evaluated using meta-analysis.

RESULTS

A total of 2910 studies were obtained from databases and other sources. Thirty-three studies were selected by screening, including 11 studies on alirocumab, 9 studies on evolocumab, 11 studies on statins and 2 studies on ezetimibe. In our study, a total of 128,691 patients with no cognitive impairment were divided into an intervention group (66,330 patients) and a control group (62,361 patients). The data were subjected to a random-effects model or a fixed-effects model for meta-analysis. The contemporary lipid-lowering medicines significantly reduced LDL-C in terms of both percentage (WMD: -45.06%, 95% CI -50.12% to -40.00%, P < 0.001) and absolute value (WMD: -64.01 mg/dL, 95% CI -72.25 to -55.78, P < 0.001). Compared with the control group, patients receiving treatment with contemporary lipid-lowering medicines did not show a significant difference in the rate of neurocognitive disorder (RR: 1.02, 95% CI 0.90 to 1.16, I² = 0.0%, p = 0.696). Subgroup analysis was performed according to the intervention and LDL-C stratification. The result of this subgroup analysis was consistent with the main findings. Regarding global cognitive performance, no difference in major cognition was found among the pooled data (SMD: 0.02, 95% CI -0.01 to 0.04, P = 0.002), except for psychomotor speed (SMD: 0.09, 95% CI 0.02 to 0.16, P = 0.0024).

CONCLUSIONS

Contemporary lipid-lowering medicines were not associated with cognitive impairment in RCTs. A low LDL-C level did not influence the incidence of cognitive disorder or global cognitive performance.

Relationship between Lipoprotein (a) and cognitive function - Results from the Berlin Aging Study II

It has been suggested that an age-related loss of cognitive function might be driven by atherosclerotic effects associated with altered lipid patterns. However, the relationship between Lipoprotein (a) [Lp(a)] and healthy cognitive aging has not yet been sufficiently investigated. For the current analysis we used the cross-sectional data of 1,380 Berlin Aging Study II (BASE-II) participants aged 60 years and older (52.2% women, mean age 68 ± 4 years). We employed the Consortium to Establish a Registry for Alzheimer's Disease (CERAD)-Plus test battery to establish latent factors representing continuous measures of domain specific cognitive functions. Regression models adjusted for APOE genotypes, lipid parameters and other risk factors for cognitive impairment were applied to assess the association between Lp(a) and performance in specific cognitive domains. Men within the lowest Lp(a)-quintile showed better cognitive performance in the cognitive domain executive functions and processing speed (p = 0.027). No significant results were observed in women. The results of the current analysis of predominantly healthy BASE-II participants point towards an association between low Lp(a) concentrations and better cognitive performance. However, evidence for this relationship resulting from the current analysis and the employment of a differentiated cognitive assessment is rather weak.

PCSK9: A new participant in lipophagy in regulating atherosclerosis?

Proprotein convertase subtilisin kexin 9 (PCSK9) regulates lipid metabolism by degrading low-density lipoprotein receptor on the surface of hepatocytes. PCSK9-mediated lipid degradation is associated with lipophagy. Lipophagy is a process by which autophagosomes selectively sequester lipid-droplet-stored lipids and are delivered to lysosomes for degradation. Lipophagy was first discovered in hepatocytes, and its occurrence provides important fundamental insights into how lipid metabolism regulates cellular physiology and pathophysiology. Furthermore, PCSK9 may regulate lipid levels by affecting lipophagy. This review will discuss recent advances by which PCSK9 mediates lipid degradation via the lipophagy pathway and present lipophagy as a potential therapeutic target for atherosclerosis.

Hydrogen sulfide inhibits PCSK9 expression through the PI3K/Akt‑SREBP‑2 signaling pathway to influence lipid metabolism in HepG2 cells

Hydrogen sulfide (H₂S) is an endogenous gaseous signaling molecule that plays important roles in the cardiovascular system. In our previous studies, we demonstrated that H₂S regulates lipid metabolism. In the present study, we aimed to explore the mechanisms through which H₂ regulates lipid metabolism in HepG2 cells in vitro. Treatment of the HepG2 cells with H₂S inhibited the expression of proprotein convertase subtilisin/kexin type 9 (PCSK9) and increased the level of low-density lipoprotein receptor (LDLR) in a time- and dose-dependent manner. The knockdown of PCSK9 by siRNA effectively increased the levels of LDLR and 1,1′-dioctadecyl-3,3,3′,3′-tetramethyl-indocarbocyanine perchlorate-labeled LDL (DiI-LDL) uptake in the H₂S-treated HepG2 cells. Furthermore, the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)-sterol regulatory element binding proteins 2 (SREBP-2) signaling pathway was confirmed to be involved in H₂S-regulated PCSK9 expression. Notably, the HepG2 cells were incubated with 30% serum and DiI-LDL for 24 h, and the results revealed that H₂S increased lipid uptake, but caused no increase in lipid accumulation. On the whole, the findings of this study demonstrate that H₂S is involved in the regulation of lipid metabolism in HepG2 cells through the regulation of the expression of PCSK9 via the PI3K/Akt-SREBP-2 signaling pathway. To the very best of our knowledge, this study is the first to report that H₂S can regulate the expression of PCSK9.

Non-antibody Approaches to Proprotein Convertase Subtilisin Kexin 9 Inhibition: siRNA, Antisense Oligonucleotides, Adnectins, Vaccination, and New Attempts at Small-Molecule Inhibitors Based on New Discoveries

Low-density lipoprotein (LDL) is one of the principal risk factors for atherosclerosis. Circulating LDL particles can penetrate into the sub-endothelial space of arterial walls. These particles undergo oxidation and promote an inflammatory response, resulting in injury to the vascular endothelial wall. Persistent elevation of LDL-cholesterol (LDL-C) is linked to the progression of fatty streaks to lipid-rich plaque and thus atherosclerosis. LDL-C is a causal factor for atherosclerotic cardiovascular disease and lowering it is beneficial across a range of conditions associated with high risk of cardiovascular events. Therefore, all guidelines-recommended initiations of statin therapy for patients at high cardiovascular risk is irrespective of LDL-C. In addition, intensive LDL-C lowering therapy with statins has been demonstrated to result in a greater reduction of cardiovascular event risk in large clinical trials. However, many high-risk patients receiving statins fail to achieve the guideline-recommended reduction in LDL-C levels in routine clinical practice. Moreover, low levels of adherence and often high rates of discontinuation demand the need for further therapies. Ezetimibe has typically been used as a complement to statins when further LDL-C reduction is required. More recently, proprotein convertase subtilisin kexin 9 (PCSK9) has emerged as a novel therapeutic target for lowering LDL-C levels, with PCSK9 inhibitors offering greater reductions than feasible through the addition of ezetimibe. PCSK9 monoclonal antibodies have been shown to not only considerably lower LDL-C levels but also cardiovascular events. However, PCSK9 monoclonal antibodies require once- or twice-monthly subcutaneous injections. Further, their manufacturing process is expensive, increasing the cost of therapy. Therefore, several non-antibody treatments to inhibit PCSK9 function are being developed as alternative approaches to monoclonal antibodies. These include gene-silencing or editing technologies, such as antisense oligonucleotides, small interfering RNA, and the clustered regularly interspaced short palindromic repeats/Cas9 platform; small-molecule inhibitors; mimetic peptides; adnectins; and vaccination. In this review, we summarize the current knowledge base on the role of PCSK9 in lipid metabolism and an overview of non-antibody approaches for PCSK9 inhibition and their limitations. The subsequent development of alternative approaches to PCSK9 inhibition may give us more affordable and convenient therapeutic options for the management of high-risk patients.

RNA-guided transcriptional silencing in vivo with S. aureus CRISPR-Cas9 repressors

CRISPR-Cas9 transcriptional repressors have emerged as robust tools for disrupting gene regulation in vitro but have not yet been adapted for systemic delivery in adult animal models. Here we describe a Staphylococcus aureus Cas9-based repressor (dSaCas9KRAB) compatible with adeno-associated viral (AAV) delivery. To evaluate dSaCas9KRAB efficacy for gene silencing in vivo, we silenced transcription of Pcsk9, a regulator of cholesterol levels, in the liver of adult mice. Systemic administration of a dual-vector AAV8 system expressing dSaCas9KRAB and a Pcsk9-targeting guide RNA (gRNA) results in significant reductions of serum Pcsk9 and cholesterol levels. Despite a moderate host response to dSaCas9KRAB expression, Pcsk9 repression is maintained for 24 weeks after a single treatment, demonstrating the potential for long-term gene silencing in post-mitotic tissues with dSaCas9KRAB. In vivo programmable gene silencing enables studies that link gene regulation to complex phenotypes and expands the CRISPR-Cas9 perturbation toolbox for basic research and gene therapy applications.

Usefulness of alirocumab and evolocumab for the treatment of patients with diabetic dyslipidemia

In 2015, the US Food and Drug Administration (FDA) approved the anti-proprotein convertase subtilsin/kexin type 9 (PCSK9) monoclonal antibodies, alirocumab and evolocumab, to treat patients with hypercholesterolemia and mixed dyslipidemia. Since then, considerable attention has been paid to the use of these monoclonal antibodies for the treatment of diabetic dyslipidemia with a goal of reducing the risk for cardiovascular disease. Recently, consensus statements on the clinical use of PCSK9 inhibitors in patients with type 2 diabetes mellitus, who are unable to achieve the goal of low-density lipoprotein cholesterol (<70 mg/dL or <1.8 mmol/L), have been published by panels of experts in Greece, Europe (European Society of Cardiology and European Atherosclerosis Society Task Force), and the United States (American College of Cardiology Consensus Committee). On December 1, 2017, the FDA approved evolocumab to prevent heart attack, stroke, and coronary revascularization. In this article, we review recent advances concerning the pathophysiology of diabetic dyslipidemia, the physiology of PCSK9, the mechanisms of action of PCSK9 inhibitors, clinical trials examining PCSK9 inhibitors in type 2 diabetes, and perspectives of nonstatin therapy in the treatment of diabetic dyslipidemia.