Computationally Driven Structure Optimization, Synthesis, and Biological Evaluation of Imidazole-Based Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) Inhibitors

PCSK9 inhibitors: a patent review 2018-2023

INTRODUCTION

Proprotein convertase subtilisin/kexin 9 (PCSK9) plays a crucial role in breaking down the hepatic low-density lipoprotein receptor (LDLR), thereby influencing the levels of circulating low-density lipoprotein cholesterol (LDL-C). Consequently, inhibiting PCSK9 through suitable ligands has been established as a validated therapeutic strategy for combating hypercholesterolemia and cardiovascular diseases.

AREA COVERED

Patent literature claiming novel compounds inhibiting PCSK9 disclosed from 2018 to June 2023 available in the espacenet database, which contains more than 150 million patent documents from over 100 patent-granting authorities worldwide.

EXPERT OPINION

The undisputable beneficial influence of PCSK9 as a pharmacological target has prompted numerous private and public institutions to patent chemical frameworks as inhibitors of PCSK9. While several compounds have advanced to clinical trials for treating hypercholesterolemia, they have not completed these trials yet. These compounds must contend in a complex market where new, costly, and advanced drugs, such as monoclonal antibodies and siRNA, are prescribed instead of inexpensive and less potent statins.

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.

Discovery of (2-(4-Substituted phenyl)quinolin-4-yl)(4-isopropylpiperazin-1-yl)methanone Derivatives as Potent Proprotein Convertase Subtilisin/Kexin Type 9 Inhibitors

Inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9) plays an increasingly important role in the treatment of hyperlipidemia. In pursuit of potent small molecules that block the PCSK9/low-density lipoprotein receptor (LDLR) protein-protein interaction (PPI), a series of 2-phenylquinoline-4-carboxylic acid derivatives were designed and synthesized based on previously derived molecules. In the in vitro PPI inhibition test, compounds M1, M12, M14, M18 and M27 exhibited potent activities with IC50 values of 6.25 μM, 0.91 μM, 2.81 μM, 4.26 μM and 0.76 μM, respectively, compared with SBC-115337 (IC50 value of 9.24 μM). Molecular docking and molecular dynamics simulations revealed the importance of hydrophobic interactions in the binding of inhibitors to the PPI interface of PCSK9. In LDLR expression and LDL uptake assays, the tested compounds M1, M12 and M14 were found to restore LDLR expression levels and to increase the extracellular LDL uptake capacity of HepG2 cells in the presence of exogenous PCSK9. Collectively, novel small-molecule PCSK9/LDLR PPI inhibitors (especially M12) with in vitro lipid lowering ability, were discovered as lead compounds for further development of hypolipidemic drugs.

Identification of benzothiazoles as novel PCSK9 inhibitors

Proprotein convertase subtilisin kexin type 9 (PCSK9) is a clinically validated target on the treatment of cardiovascular disease (CVD). PCSK9 can regulate the hepatocyte surface low density lipoprotein receptor (LDLR) level by binding to LDLR and leading to their degradation in the lysosome. The clinical use of two monoclonal antibodies (alirocumab and evolocumab, approved in 2015) and one small interfering RNA (inclisiran, approved in 2020) which can inhibit PCSK9 function proved that they are very effective in lowering low density lipoprotein cholesterol (LDL-C). However, the high treatment costs and parenteral administration of these drugs prohibited widespread use and reduced their long-term advantage. Comparatively, small molecule drugs have many incomparable advantages of macromolecules, such as lower treatment cost, more drug administration options, superior pharmacokinetic properties, less adverse immunogenic responses and better affordable production. In this paper, we identified a series of benzothiazoles small molecule PCSK9 inhibitors through extensive screening. The structure and activity relationship (SAR) was summarized to facilitate further optimization. Moreover, the primary mechanism of action of the most potent compound was also investigated.

Palladium-Catalyzed Synthesis of Linked Bis-Heterocycles─Synthesis and Investigation of Photophysical Properties

A palladium-catalyzed domino C-N coupling/Cacchi reaction is reported. Design of photoluminescent bis-heterocycles, aided by density functional theory calculations, was performed with synthetic yields up to 98%. The photophysical properties of the products accessed via this strategy were part of a comprehensive study that led to broad emission spectra and quantum yields of up to 0.59. Mechanistic experiments confirmed bromoalkynes as competent intermediates, and a density functional theory investigation suggests a pathway involving initial oxidative addition into the cis C-Br bond of the gem-dihaloolefin.

Unlocking the Antibiofilm Potential of Natural Compounds by Targeting the NADH:quinone Oxidoreductase WrbA

Biofilm-dwelling cells endure adverse conditions, including oxidative imbalances. The NADH:quinone oxidoreductase enzyme WrbA has a crucial role in the mechanism of action of antibiofilm molecules such as ellagic and salicylic acids. This study aimed to exploit the potential of the WrbA scaffold as a valuable target for identifying antibiofilm compounds at non-lethal concentrations. A three-dimensional computational model, based on the published WrbA structure, was used to screen natural compounds from a virtual library of 800,000 compounds. Fisetin, morin, purpurogallin, NZ028, and NZ034, along with the reference compound ellagic acid, were selected. The antibiofilm effect of the molecules was tested at non-lethal concentrations evaluating the cell-adhesion of wild-type and WrbA-deprived Escherichia coli strains through fluorochrome-based microplate assays. It was shown that, except for NZ028, all of the selected molecules exhibited notable antibiofilm effects. Purpurogallin and NZ034 showed excellent antibiofilm performances at the lowest concentration of 0.5 μM, in line with ellagic acid. The observed loss of activity and the level of reactive oxygen species in the mutant strain, along with the correlation with terms contributing to the ligand-binding free energy on WrbA, strongly indicates the WrbA-dependency of purpurogallin and NZ034. Overall, the molecular target WrbA was successfully employed to identify active compounds at non-lethal concentrations, thus revealing, for the first time, the antibiofilm efficacy of purpurogallin and NZ034.

Discovery of [5,5'-bibenzo[d][1,3]dioxol]-6-substituted amine derivatives as potent proprotein convertase subtilisin/kexin type 9 inhibitors

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a promising therapeutic target for the treatment of hyperlipidemia. In discovery of novel small molecules that interfere PCSK9/LDLR protein-protein interaction (PPI), structural modification was performed based on our previously derived compounds. A series of [5,5'-bibenzo[d][1,3]dioxol]-6-amine analogs were designed and synthesized for the activity evaluation. In the PCSK9/LDLR PPI impairing test, molecules D28 and D29, exhibited remarkable inhibitory potency with IC50 values of 8.30 and 6.70 μM compared with SBC-115337 (17.89 μM), respectively. Molecular docking predicted the binding pattern of compounds D28 and D29 in the LDLR binding site of PCSK9. Hydrophobic interactions play an important role in the binding of aromatic molecular fragments to the pockets in the PCSK9/LDLR binding interface. Further LDLR expression and LDL uptake studies revealed that both D28 and D29 restored LDLR expression on the surface of hepatic HepG2 cells and improved extracellular LDL uptake in the presence of PCSK9. It is significant that molecules D28 and D29 exhibited potential for the treatment of hyperlipidemia in current in vitro investigations. Generally, lead compounds with novel structures were developed in the present study for further design of lipid-lowering molecules by targeting PCSK9/LDLR PPI.

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.

N-Iodosuccinimide-Mediated Synthesis of Benzo-Fused Bisimidazoles Enabled by a One-Pot Tandem Reaction of Fluorinated Propargyl Amidines

A N-iodosuccinimide (NIS)-mediated divergent and efficient tandem reaction between fluorinated propargyl amidines and aromatic o-diamines without any metal catalyst and additive under mild reaction conditions was developed for the synthesis of benzo-fused bisimidazoles in moderate to excellent yields. Preliminary mechanistic studies suggested that this reaction proceeded by an intermediate of secondary amine derived from 5-iodomethyl imidazole, and NIS played another role of oxidation reagent to promote the formation of a benzimidazole motif.

Computational Design, Synthesis, and Biophysical Evaluation of β-Amido Boronic Acids as SARS-CoV-2 Mpro Inhibitors

The COVID-19 pandemic has given a strong impetus to the search for antivirals active on SARS-associated coronaviruses. Over these years, numerous vaccines have been developed and many of these are effective and clinically available. Similarly, small molecules and monoclonal antibodies have also been approved by the FDA and EMA for the treatment of SARS-CoV-2 infection in patients who could develop the severe form of COVID-19. Among the available therapeutic tools, the small molecule nirmatrelvir was approved in 2021. It is a drug capable of binding to the M^pro protease, an enzyme encoded by the viral genome and essential for viral intracellular replication. In this work, by virtual screening of a focused library of β-amido boronic acids, we have designed and synthesized a focused library of compounds. All of them were biophysically tested by microscale thermophoresis, attaining encouraging results. Moreover, they also displayed M^pro protease inhibitory activity, as demonstrated by performing enzymatic assays. We are confident that this study will pave the way for the design of new drugs potentially useful for the treatment of SARS-CoV-2 viral infection.

Recent Update on the Development of PCSK9 Inhibitors for Hypercholesterolemia Treatment

The proprotein convertase subtilisin/kexin-type 9 (PCSK9) binds to low-density lipoprotein receptors (LDLR), thereby trafficking them to lysosomes upon endocytosis and enhancing intracellular degradation to prevent their recycling. As a result, the levels of circulating LDL cholesterol (LDL-C) increase, which is a prominent risk factor for developing atherosclerotic cardiovascular diseases (ASCVD). Thus, PCSK9 has become a promising therapeutic target that offers a fertile testing ground for new drug modalities to regulate plasma LDL-C levels to prevent ASCVD. In this review, we have discussed the role of PCSK9 in lipid metabolism and briefly summarized the current clinical status of modalities targeting PCSK9. In particular, a detailed overview of peptide-based PCSK9 inhibitors is presented, which emphasizes their structural features and design, therapeutic effects on patients, and preclinical cardiovascular disease (CVD) models, along with PCSK9 modulation mechanisms. As a promising alternative to monoclonal antibodies (mAbs) for managing LDL-C, anti-PCSK9 peptides are emerging as a prospective next generation therapy.

Discovery and SAR analysis of phenylbenzo[d][1,3]dioxole-based proprotein convertase subtilisin/kexin type 9 inhibitors

Proprotein convertase subtilisin/kexin type 9 (PCSK9) has emerged as a novel therapeutic target for the development of cholesterol-lowering drugs. In the discovery of PCSK9/LDLR (low-density lipoprotein receptor) protein-protein interaction (PPI) impairing small molecules, a total of 47 phenylbenzo[d][1,3] dioxole-based compounds were designed and synthesised. The result revealed that the 4-chlorobenzyl substitution in the amino group is important for the PPI disrupting activity. In the hepatocyte-based functional tests, active compounds such as A12, B1, B3, B4 and B14, restored the LDLR levels on the surface of hepatic HepG2 cells and increased extracellular LDL uptake in the presence of PCSK9. It is notable that molecule B14 exhibited good performance in all the evaluations. Collectively, novel structures targeting PCSK9/LDLR PPI have been developed with hypolipidemic potential. Further structural modification of derived active compounds is promising in the discovery of lead compounds with improved activity for the treatment of hyperlipidaemia-related disorders.

Computational Design and Biological Evaluation of Analogs of Lupin Peptide P5 Endowed with Dual PCSK9/HMG-CoAR Inhibiting Activity

(1) Background: Proprotein convertase subtilisin/kexin 9 (PCSK9) is responsible for the degradation of the hepatic low-density lipoprotein receptor (LDLR), which regulates the circulating cholesterol level. In this field, we discovered natural peptides derived from lupin that showed PCSK9 inhibitory activity. Among these, the most active peptide, known as P5 (LILPHKSDAD), reduced the protein-protein interaction between PCSK9 and LDLR with an IC₅₀ equals to 1.6 µM and showed a dual hypocholesterolemic activity, since it shows complementary inhibition of the 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoAR). (2) Methods: In this study, by a computational approach, the P5 primary structure was optimized to obtain new analogs with improved affinity to PCSK9. Then, biological assays were carried out for fully characterizing the dual cholesterol-lowering activity of the P5 analogs by using both biochemical and cellular techniques. (3) Results: A new peptide, P5-Best (LYLPKHSDRD) displayed improved PCSK9 (IC₅₀ 0.7 µM) and HMG-CoAR (IC₅₀ 88.9 µM) inhibitory activities. Moreover, in vitro biological assays on cells demonstrated that, not only P5-Best, but all tested peptides maintained the dual PCSK9/HMG-CoAR inhibitory activity and remarkably P5-Best exerted the strongest hypocholesterolemic effect. In fact, in the presence of this peptide, the ability of HepG2 cells to absorb extracellular LDL was improved by up to 254%. (4) Conclusions: the atomistic details of the P5-Best/PCSK9 and P5-Best/HMG-CoAR interactions represent a reliable starting point for the design of new promising molecular entities endowed with hypocholesterolemic activity.

Caffeine blocks SREBP2-induced hepatic PCSK9 expression to enhance LDLR-mediated cholesterol clearance

Evidence suggests that caffeine (CF) reduces cardiovascular disease (CVD) risk. However, the mechanism by which this occurs has not yet been uncovered. Here, we investigated the effect of CF on the expression of two bona fide regulators of circulating low-density lipoprotein cholesterol (LDLc) levels; the proprotein convertase subtilisin/kexin type 9 (PCSK9) and the low-density lipoprotein receptor (LDLR). Following the observation that CF reduced circulating PCSK9 levels and increased hepatic LDLR expression, additional CF-derived analogs with increased potency for PCSK9 inhibition compared to CF itself were developed. The PCSK9-lowering effect of CF was subsequently confirmed in a cohort of healthy volunteers. Mechanistically, we demonstrate that CF increases hepatic endoplasmic reticulum (ER) Ca²⁺ levels to block transcriptional activation of the sterol regulatory element-binding protein 2 (SREBP2) responsible for the regulation of PCSK9, thereby increasing the expression of the LDLR and clearance of LDLc. Our findings highlight ER Ca²⁺ as a master regulator of cholesterol metabolism and identify a mechanism by which CF may protect against CVD.

Development of small-molecule PCSK9 inhibitors for the treatment of hypercholesterolemia

When secreted into the circulation, proprotein convertase subtilisin kexin type 9 (PCSK9) blocks the low-density lipoprotein receptors (LDL-R) and, as a consequence, low-density lipoprotein cholesterol (LDL-C) levels increase. Therefore, PCSK9 has emerged as a potential therapeutic target for lowering LDL-C levels and preventing atherosclerosis. The US Food and Drug Administration (FDA) has approved two monoclonal antibodies (mAbs) against PCSK9, but the expensive manufacturing process limits their use. Subsequently, there have been tremendous efforts to develop cost-effective small molecules specific to PCSK9 over the past few years. These small molecules are promising therapeutics that act by preventing the synthesis of PCSK9, its secretion from cells, or the PCSK9-LDRL interaction. In this review, we summarize recent developments in the discovery of small-molecule PCSK9 inhibitors, focusing on their design, therapeutic effects, specific targets, and mechanisms of action.

Discovery of Novel Small Molecule Inhibitors Disrupting the PCSK9-LDLR Interaction

Proprotein convertase subtilisin kexin 9 (PCSK9) has been identified as a reliable therapeutic target for hypercholesterolemia and coronary artery heart diseases since the monoclonal antibodies of PCSK9 have launched. Disrupting the protein-protein interaction (PPI) between PCSK9 and the low-density lipoprotein receptor (LDLR) has been considered as a promising approach for developing PCSK9 inhibitors. However, PPIs have been traditionally considered difficult to target by small molecules since the PPI surface is usually large, flat, featureless, and without a "pocket" or "groove" for ligand binding. The PCSK9-LDLR PPI interface is such a typical case. In this study, a potential binding pocket was generated on the PCSK9-LDLR PPI surface of PCSK9 through induced-fit docking. On the basis of this induced binding pocket, virtual screening, molecular dynamics (MD) simulation, and biological evaluations have been applied for the identification of novel small molecule inhibitors of PCSK9-LDLR PPI. Among the selected compounds, compound 13 exhibited certain PCSK9-LDLR PPI inhibitory activity (IC₅₀: 7.57 ± 1.40 μM). The direct binding affinity between 13 and PCSK9 was determined with a K_D value of 2.50 ± 0.73 μM. The LDLR uptake function could be also restored to a certain extent by 13 in HepG2 cells. This well-characterized hit compound will facilitate the further development of novel small molecule inhibitors of PCSK9-LDLR PPI.

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).

The emerging landscape of peptide-based inhibitors of PCSK9

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a clinically validated target for treating cardiovascular disease (CVD) due to its involvement in cholesterol metabolism. Although approved monoclonal antibodies (alirocumab and evolocumab) that inhibit PCSK9 function are very effective in lowering cholesterol, their limitations, including high treatment costs, have so far prohibited widespread use. Accordingly, there is great interest in alternative drug modalities to antibodies. Like antibodies, peptides are valuable therapeutics due to their high target potency and specificity. Furthermore, being smaller than antibodies means they have access to more drug administration options, are less likely to induce adverse immunogenic responses, and are better suited to affordable production. This review surveys the current peptide-based landscape aimed towards PCSK9 inhibition, covering pre-clinical to patented drug candidates and comparing them to current cholesterol lowering therapeutics. Classes of peptides reported to be inhibitors include nature-inspired disulfide-rich peptides, combinatorially derived cyclic peptides, and peptidomimetics. Their functional activities have been validated in biophysical and cellular assays, and in some cases pre-clinical mouse models. Recent efforts report peptides with potent sub-nanomolar binding affinities to PCSK9, which highlights their potential to achieve antibody-like potency. Studies are beginning to address pharmacokinetic properties of PCSK9-targeting peptides in more detail. We conclude by highlighting opportunities to investigate their biological effects in pre-clinical models of cardiovascular disease. The anticipation concerning the PCSK9-targeting peptide landscape is accelerating and it seems likely that a peptide-based therapeutic for treating PCSK9-mediated hypercholesterolemia may be clinically available in the near future.

Trans-Epithelial Transport, Metabolism, and Biological Activity Assessment of the Multi-Target Lupin Peptide LILPKHSDAD (P5) and Its Metabolite LPKHSDAD (P5-Met)

P5 (LILPKHSDAD) is a hypocholesterolemic peptide from lupin protein with a multi-target activity, since it inhibits both 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGCoAR) and proprotein convertase subtilisin/kexin type-9 (PCSK9). This work shows that, during epithelial transport experiments, the metabolic transformation mediated by intestinal peptidases produces two main detected peptides, ILPKHSDAD (P5-frag) and LPKHSDAD (P5-met), and that both P5 and P5-met are linearly absorbed by differentiated human intestinal Caco-2 cells. Extensive comparative structural, biochemical, and cellular characterizations of P5-met and the parent peptide P5 demonstrate that both peptides have unique characteristics and share the same mechanisms of action. In fact, they exert an intrinsically multi-target behavior being able to regulate cholesterol metabolism by modulating different pathways. The results of this study also highlight the dynamic nature of bioactive peptides that may be modulated by the biological systems they get in contact with.

Engineered EGF-A Peptides with Improved Affinity for Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9)

The epidermal growth-factor-like domain A (EGF-A) of the low-density lipoprotein (LDL) receptor is a promising lead for therapeutic inhibition of proprotein convertase subtilisin/kexin type 9 (PCSK9). However, the clinical potential of EGF-A is limited by its suboptimal affinity for PCSK9. Here, we use phage display to identify EGF-A analogues with extended bioactive segments that have improved affinity for PCSK9. The most potent analogue, TEX-S2_03, demonstrated ∼130-fold improved affinity over the parent domain and had a reduced calcium dependency for efficient PCSK9 binding. Thermodynamic binding analysis suggests the improved affinity of TEX-S2_03 is enthalpically driven, indicating favorable interactions are formed between the extended segment of TEX-S2_03 and the PCSK9 surface. The improved affinity of TEX-S2_03 resulted in increased activity in competition binding assays and more efficient restoration of LDL receptor levels with clearance of extracellular LDL cholesterol in functional cell assays. These results confirm that TEX-S2_03 is a promising therapeutic lead for treating hypercholesterolemia. Many EGF-like domains are involved in disease-related protein-protein interactions; therefore, our strategy for engineering EGF-like domains has the potential to be broadly implemented in EGF-based drug design.

Bioactive Cyclization Optimizes the Affinity of a Proprotein Convertase Subtilisin/Kexin Type 9 (PCSK9) Peptide Inhibitor

Peptides are regarded as promising next-generation therapeutics. However, an analysis of over 1000 bioactive peptide candidates suggests that many have underdeveloped affinities and could benefit from cyclization using a bridging linker sequence. Until now, the primary focus has been on the use of inert peptide linkers. Here, we show that affinity can be significantly improved by enriching the linker with functional amino acids. We engineered a peptide inhibitor of PCSK9, a target for clinical management of hypercholesterolemia, to demonstrate this concept. Cyclization linker optimization from library screening produced a cyclic peptide with ∼100-fold improved activity over the parent peptide and efficiently restored low-density lipoprotein (LDL) receptor levels and cleared extracellular LDL. The linker forms favorable interactions with PCSK9 as evidenced by thermodynamics, structure-activity relationship (SAR), NMR, and molecular dynamics (MD) studies. This PCSK9 inhibitor is one of many peptides that could benefit from bioactive cyclization, a strategy that is amenable to broad application in pharmaceutical design.

Synthesis, biological activities, and SAR studies of novel 1-(2-chloro-4,5-difluorophenyl)-1H-pyrazole derivatives

In order to search for the new ryanodine receptor (RyR) regulator, a series of 35 novel fluoro-substituted compounds introduced 1-(2-chloro-4,5-difluorophenyl)-1H-pyrazole moiety containing modified pyrazole heterocycle were designed and synthesized. Then, they were tested for the insecticidal activities against Mythimna separata and Plutella xylostella in our greenhouse. After a systematic biological screening, it was found out that IVc showed 50% larvicidal activities against Mythimna separata at 0.1 mg L^-1, equivalent to that of chlorantraniliprole (36%, 0.1 mg L^-1). The activity of IVc against Plutella xylostella was 90% at 10^-5 mg L^-1, whereas the chlorantraniliprole was 70% at the same concentration. Then, insect electrophysiology experiments were conducted to study the pattern of action of IVc and IVe. It was confirmed by the experimental results that both compounds could lead to the release of calcium from the endoplasmic reticulum of neurons as classical anthranilic diamide insecticides.

Exploring Proprotein Convertase Subtilisin/Kexin 9 (PCSK9) Autoproteolysis Process by Molecular Simulations: Hints for Drug Design

Proprotein convertase subtilisin/kexin 9 (PCSK9) is a notable target for the treatment of hypercholesterolemia because it regulates the population of the low-density lipoprotein receptor (LDLR) on liver cells. The PCSK9 zymogen is a serine protease that spontaneously undergoes a double self-cleavage step. Available X-ray structures depict the PCSK9 mature state, but the atomic details of the zymogen state of the enzyme are still unknown. Additionally, why the protease activity of PCSK9 is blocked after the second autoprocessing step remains unclear, as this deviates from other members of the PCSK family. By performing constant-pH molecular dynamics (MD) simulations, we investigated the protonation state of the catalytic triad of PCSK9 and found that it strongly influences the catalytic properties of the enzyme. Moreover, we determined the final step of the maturation process by classical and steered MD simulations. This study could facilitate the identification of ligands capable of interfering with the PCSK9 maturation process.

Synthesis of Imidazole-Based Medicinal Molecules Utilizing the van Leusen Imidazole Synthesis

Imidazole and its derivatives are one of the most vital and universal heterocycles in medicinal chemistry. Owing to their special structural features, these compounds exhibit a widespread spectrum of significant pharmacological or biological activities, and are widely researched and applied by pharmaceutical companies for drug discovery. The van Leusen reaction based on tosylmethylisocyanides (TosMICs) is one of the most appropriate strategies to synthetize imidazole-based medicinal molecules, which has been increasingly developed on account of its advantages. In this review, we summarize the recent developments of the chemical synthesis and bioactivity of imidazole-containing medicinal small molecules, utilizing the van Leusen imidazole synthesis from 1977.

Design of Organo-Peptides As Bipartite PCSK9 Antagonists

Proprotein convertase subtilisin/kexin 9 (PCSK9) has become an important therapeutic target for lipid lowering, since it regulates low-density lipoprotein cholesterol (LDL-c) levels by binding to liver LDL receptors (LDLR) and effecting their intracellular degradation. However, the development of small molecule inhibitors is hampered by the lack of attractive PCSK9 target sites. We recently discovered helical peptides that are able to bind to a cryptic groove site on PCSK9, which is situated in proximity to the main LDLR binding site. Here, we designed potent bipartite PCSK9 inhibitors by appending organic moieties to a helical groove-binding peptide to reach a hydrophobic pocket in the proximal LDLR binding region. The ultimately designed 1-amino-4-phenylcyclohexane-1-carbonyl extension improved the peptide affinity by >100-fold, yielding organo-peptide antagonists that potently inhibited PCSK9 binding to LDLR and preserved cellular LDLR. These new bipartite antagonists have reduced mass and improved potency compared to the first-generation peptide antagonists, further validating the PCSK9 groove as a viable therapeutic target site.