Potent Analogue Research Articles

Divergent Nine-Step Syntheses of Perhydrohistrionicotoxin Analogs and Their Inhibition Activity Toward Chicken α4β2-Neuronal Nicotinic Acetylcholine Receptors.

Histrionicotoxin (HTX) alkaloids, which are isolated from Colombian poison dart frogs, are analgesic neurotoxins that modulate nicotinic acetylcholine receptors (nAChRs) as antagonists. Perhydrohistrionicotoxin (pHTX) is the potent synthetic analogue of HTX and possesses a 1-azaspiro[5.5]undecane skeleton common to the HTX family. Here, we show for the first time the divergent nine-step synthesis of pHTX and its three stereoisomers from the known aldehyde through a one-step construction of the 1-azaspiro[5.5]undecane framework from a linear amino ynone substrate. Surprisingly, some pHTX diastereomers exhibited antagonistic activities on the chicken α4β2-neuronal nAChRs that were more potent than pHTX.

Toward a Template for Synthetic Actin-Targeting Macrolide Analogues That Inhibit Cancer Cell Invasiveness.

Actin barbed end-binding macrolides have been shown to inhibit cancer cell motility and invasion of extracellular matrix (ECM), evoking their potential utility as therapies for metastatic cancers. Unfortunately, the direct use of these compounds in clinical settings is impeded by their limited natural abundance, challenging total synthesis, and detrimental effects on normal tissues. To develop potent analogues of these compounds that are simpler to synthesize and compatible with cell-specific targeting systems, such as antibodies, we designed over 20 analogues of the acyclic side chain (tail) of the macrolide Mycalolide B. These analogues probed the contributions of four distinct regions of the tail towards the inhibition of actin polymerization and ECM invasion by human lung cancer A549 cells. We observed that two of these regions tolerate considerable substituent variability, and we identified a specific combination of substituents that leads to the optimal inhibition of the ECM invasion activity of A549 cells.

Chelation of the Optimal Antifungal Pogostone Analogue with Copper(II) to Explore the Dual Antifungal and Antibacterial Agent.

In an ongoing effort to explore more potent antifungal pogostone (Po) analogues, we maintained the previously identified 3-acetyl-4-hydroxy-2-pyrone core motif while synthesizing a series of Po analogues with variations in the alkyl side chain. The in vitro bioassay results revealed that compound 21 was the most potent antifungal analogue with an EC50 value of 1.1 μg/mL against Sclerotinia sclerotiorum (Lib.) de Bary. Meanwhile, its Cu(II) complex 34 manifested significantly enhanced antibacterial activity against Xanthomonas campestris pv campestris (Xcc) with a minimum inhibitory concentration (MIC) value of 300 μg/mL compared with 21 (MIC = 700 μg/mL). Complex 34 exhibited a striking preventive effect against S. sclerotiorum and Xcc in rape leaves, with control efficacies of 98.8% (50 μg/mL) and 80.7% (1000 μg/mL), respectively. The 3D-QSAR models generated using Topomer comparative molecular field analysis indicated that a shorter alkyl chain (carbon atom number <8), terminal rings, or electron-deficient groups on the alkyl side chain are beneficial for antifungal potency. Further, bioassay results revealed that the component of 21 in complex 34 dominated the antifungal activity, but the introduction of Cu(II) significantly enhanced its antibacterial activity. The toxicological observations demonstrated that 21 could induce abnormal mitochondrial morphology, loss of mitochondrial membrane potential, and reactive oxygen species (ROS) accumulation in S. sclerotiorum. The enzyme assay results showed that 21 is a moderate promiscuous inhibitor of mitochondrial complexes II and III. Besides, the introduction of Cu(II) to 34 could promote the disruption of the cell membrane and intracellular proteins and the ROS level in Xcc compared with 21. In summary, these results highlight the potential of 34 as a dual antifungal and antibacterial biocide for controlling rape diseases or as a promising candidate for further optimization.

Symmetrical Bispyridinium Compounds Act as Open Channel Blockers of Cation-Selective Ion Channels.

Current treatments against organophosphate poisoning (OPP) do not directly address effects mediated by the overstimulation of nicotinic acetylcholine receptors (nAChR). Non-oxime bispyridinium compounds (BPC) promote acetylcholine esterase-independent recovery of organophosphate-induced paralysis. Here, we test the hypothesis that they act by positive modulatory action on nAChRs. Using two-electrode voltage clamp analysis in combination with mutagenesis and molecular docking analysis, the potency and molecular mode of action of a series of nine BPCs was investigated on human α7 and muscle-type nAChRs expressed in Xenopus laevis oocytes. The investigated BPCs inhibited α7 and/or muscle-type nAChRs with IC50 values in the high nanomolar to high micromolar range. Further analysis of the most potent analogues revealed a noncompetitive, voltage-dependent inhibition. Co-application with the α7-selective positive allosteric modulator PNU120596 and generation of α7/5HT3 receptor chimeras excluded direct interaction with the PNU120596 binding site and binding to the extracellular domain of the α7 nAChR, suggesting that they act as open channel blockers (OCBs). Molecular docking supported by mutagenesis localized the BPC binding area in the outer channel vestibule between the extracellular and transmembrane domains. Analysis of BPC action on other cation-selective channels suggests a rather nonspecific inhibition of pentameric cation channels. BPCs have been shown to ameliorate organophosphate-induced paralysis in vitro and in vivo. Our data support molecular action as OCBs at α7 and muscle-type nAChRs and suggest that their positive physiological effects are more complex than anticipated and require further investigation.

An Improved and Scalable Synthesis of the Potent SREBP Inhibitor KK-052 via [3+2] Cycloaddition

AbstractKK-052 is a novel vitamin-D-based selective sterol regulatory element-binding protein (SREBP) suppressor that lacks vitamin D genomic activity mediated through the vitamin D receptor in both in vitro and in vivo settings. In our initial synthetic effort, KK-052 was produced as one of the structural isomers obtained via the Mitsunobu reaction involving a CD-ring allyl alcohol and 5-phenyl-1H-tetrazole. In this work, we present a refined methodology for enhancing the selective synthesis of KK-052 through a [3+2] cycloaddition between a CD-ring benzimidoyl chloride and sodium azide, a technique that proved amenable to gram-scale production. Additionally, this synthetic method permitted the production of a more potent m-methyl analogue of KK-052.

Hibernation-Like Behavior Induced by 2-Methyl-2-Thiazoline and Its Organ-Protective Effects and Mechanisms.

Hibernation is a prolonged state of low metabolism that animals enter in response to extreme environmental conditions to enhance their survival in harsh environments. Recent studies have shown that non-hibernating species can also be induced to enter a hibernation-like state. 2-methyl-2-thiazoline (2MT), a potent analog of fox odor, can induce fear-related behavior in mice with low body temperature and low metabolism, and has specific organ-protective effects. A systematic understanding of 2MT-induced hibernation and its underlying mechanisms may aid in expanding its applications in medicine and other fields.

New Ref-1/APE1 targeted inhibitors demonstrating improved potency for clinical applications in multiple cancer types

AP endonuclease-1/Redox factor-1 (APE1/Ref-1 or Ref-1) is a multifunctional protein that is overexpressed in most aggressive cancers and impacts various cancer cell signaling pathways. Ref-1′s redox activity plays a significant role in activating transcription factors (TFs) such as NFκB, HIF1α, STAT3 and AP-1, which are crucial contributors to the development of tumors and metastatic growth. Therefore, development of potent, selective inhibitors to target Ref-1 redox function is an appealing approach for therapeutic intervention. A first-generation compound, APX3330 successfully completed phase I clinical trial in adults with progressing solid tumors with favorable response rate, pharmacokinetics (PK), and minimal toxicity. These positive results prompted us to develop more potent analogs of APX3330 to effectively target Ref-1 in solid tumors. In this study, we present structure-activity relationship (SAR) identification and validation of lead compounds that exhibit a greater potency and a similar or better safety profile to APX3330. In order to triage and characterize the most potent and on-target second-generation Ref-1 redox inhibitors, we assayed for PK, mouse and human S9 fraction metabolic stability, in silico ADMET properties, ligand-based WaterLOGSY NMR measurements, pharmacodynamic markers, cell viability in multiple cancer cell types, and two distinct 3-dimensional (3D) cell killing assays (Tumor-Microenvironment on a Chip and 3D spheroid). To characterize the effects of Ref-1 inhibition in vivo, global proteomics was used following treatment with the top four analogs. This study identified and characterized more potent inhibitors of Ref-1 redox function (that outperformed APX3330 by 5–10-fold) with PK studies demonstrating efficacious doses for translation to clinic.

Cancer sensitizing effect of deazaflavin analogs is associated with increased intracellular drug accumulation

As part of our efforts geared towards developing mechanism-based cancer sensitizing agents, we have previously synthesized and characterized novel deazaflavin analogs as potent tyrosyl DNA phosphodiesterase 2 (TDP2) inhibitors for combination treatments with topoisomerase II (TOP2) poisons. Interestingly, the sensitizing effect of a few analogs toward TOP2 poison etoposide (ETP) was associated with a significant increase in intracellular drug accumulation, which could be an alternative mechanism to boost the clinical efficacy of ETP in cancer chemotherapies. Hence, we evaluated more deazaflavin TDP2 inhibitors for their impact on drug retention in cancer cells. We found that all but one tested TDP2 inhibitors substantially increased the ETP retention in DT40 cells. Particularly, we identified an exceptionally potent analog, ZW-1226, which at 3 nM increased the intracellular ETP by 13-fold. Significantly, ZW-1226 also stimulated cellular accumulation of two other anticancer drugs, TOP2 poison teniposide and antifolate pemetrexed, and produced an effect more pronounced than those of ABC transporter inhibitors verapamil and elacridar in human leukemic CCRF-CEM cells toward ETP. Lastly, ZW-1226 potentiated the action of ETP in the sensitive human CCRF-CEM cells and a few resistant non-small-cell lung cancer cells, including H460 and H838 cells. Collectively, the results of this study strongly suggest that deazaflavin analog ZW-1226 could be an effective cancer sensitizing agent which warrants further investigation.

Total synthesis of antifungal lipopeptide iturin A analogues and evaluation of their bioactivity against F. graminearum.

The pursuit of novel antifungal agents is imperative to tackle the threat of antifungal resistance, which poses major risks to both human health and to food security. Iturin A is a cyclic lipopeptide, produced by Bacillus sp., with pronounced antifungal properties against several pathogens. Its challenging synthesis, mainly due to the laborious synthesis of the β-amino fatty acid present in its structure, has hindered the study of its mode of action and the development of more potent analogues. In this work, a facile synthesis of bioactive iturin A analogues containing an alkylated cysteine residue is presented. Two analogues with opposite configurations of the alkylated cysteine residue were synthesized, to evaluate the role of the stereochemistry of the newly introduced amino acid on the bioactivity. Antifungal assays, conducted against F. graminearum, showed that the novel analogues are bioactive and can be used as a synthetic model for the design of new analogues and in structure-activity relationship studies. The assays also highlight the importance of the β-amino acid in the natural structure and the role of the stereochemistry of the amino fatty acid, as the analogue with the D configuration showed stronger antifungal properties than the one with the L configuration.

Biaryl carboxamide-based peptidomimetics analogs as potential pancreatic lipase inhibitors for treating obesity.

A series of 1,1'-biphenyl-3-carboxamide and furan-phenyl-carboxamide analogs were synthesized using an optimized scheme and confirmed by 1H and 13C nuclear magnetic resonance and high-resolution mass spectrometry techniques. The synthesized peptidomimetics analogs were screened in vitro to understand the inhibitory potential of pancreatic lipase (PL). Analogs were assessed for the PL inhibitory activity based on interactions, geometric complementarity, and docking score. Among the synthesized analogs, 9, 29, and 24 were found to have the most potent PL inhibitory activity with IC50 values of 3.87, 4.95, and 5.34 µM, respectively, compared to that of the standard drug, that is, orlistat, which inhibits PL with an IC50 value of 0.99 µM. The most potent analog, 9, exhibited a competitive-type inhibition with an inhibition constant (Ki) of 2.72 µM. In silico molecular docking of analog 9 with the PL (PDB ID:1LPB) showed a docking score of -11.00 kcal/mol. Analog 9 formed crucial hydrogen bond interaction with Ser152, His263, π-cation interaction with Asp79, Arg256, and π-π stacking with Phe77, Tyr114 at the protein's active site. The molecular dynamic simulation confirmed that analog 9 forms stable interactions with PL at the end of 200 ns with root mean square deviation values of 2.5 and 6 Å. No toxicity was observed for analog 9 (concentration range of 1-20 µM) when tested by MTT assay in RAW 264.7 cells.

Syntheses of Cannabinoid Metabolites: Ajulemic Acid and HU-210.

Cannabinoid metabolites have been reported to be more potent than their parent compounds. Among them, ajulemic acid (AJA) is a side-chain analog of Δ9-THC-11-oic acid, which would be a good template structure for the discovery of more potent analogues. Herein, we optimized the key allylic oxidation step to introduce the C-11 hydroxy group with a high yield. A series of compounds was prepared with this condition applied including HU-210, 11-nor-Δ8-tetrahydrocannabinol (THC)-carboxylic acid and Δ9-THC-carboxylic acid.

Structure-based development of 3,5-dihydroxybenzoyl-hydrazineylidene as tyrosinase inhibitor; in vitro and in silico study

A series of new analogs of 3,5-dihydroxybenzoyl-hydrazineylidene conjugated to different methoxyphenyl triazole (11a-n) synthesized using click reaction. The structures of all synthesized compounds were characterized by FTIR, 1H, 13C-NMR spectroscopy, and CHO analysis. The tyrosinase inhibitory potential of the synthesized compounds was studied. The newly synthesized scaffolds were found to illustrate the variable degree of the inhibitory profile, and the most potent analog of this series was that one bearing 4-methoxyphenyl moiety, and exhibited an IC50 value of 55.39 ± 4.93 µM. The kinetic study of the most potent derivative reveals a competitive mode of inhibition. Next, molecular docking studies were performed to understand the potent inhibitor's binding mode within the enzyme's binding site. Molecular dynamics simulations were accomplished to further investigate the orientation and binding interaction over time and the stability of the 11m-tyrosinase complex.

In vitro and in silico correlation of bis-thiazole based Schiff base hybrids analogues: A computational approach develop to promising acetylcholinesterase and butyrylcholinesterase inhibitors

We have synthesized sixteen bis-thiazole based Schiff bases hybrid derivatives (1–16) and evaluated against acetylcholinesterase and butyrylcholinesterase enzymes. All analogues showed outstanding activities having IC50 values ranged from 3.57 ± 0.33 to 32.64 ± 0.70 µM (AChE) and 2.84 ± 0.11 to 34.11 ± 0.59 µM (BuChE) as compared to standard drug Donepezil (IC50 = 7.47 ± 0.35 and 7.42 ± 0.58 µM, respectively). In both cases, analogues 15 (IC50 = 3.57 ± 0.33), 10 (3.55 ± 0.51 µM) and 3 (IC50 = 3.87 ± 0.34) against AChE while analogue 4 (IC50 = 2.84 ± 0.11), 8 (IC50 = 3.48 ± 0.96) and 2 (4.02 ± 0.39 µM) against BuChE withstand most potent among the whole series. There is a relationship between structure and activity for all analogues, and the degree of this relationship varies depending on the number, nature, and position of the substituent. Docking studies were performed in order to determine how the most potent analogue interacts with the enzyme's active site.

Design, Synthesis, and Evaluation of Inhibitors of Hedgehog Acyltransferase.

Hedgehog signaling is involved in embryonic development and cancer growth. Functional activity of secreted Hedgehog signaling proteins is dependent on N-terminal palmitoylation, making the palmitoyl transferase Hedgehog acyltransferase (HHAT), a potential drug target and a series of 4,5,6,7-tetrahydrothieno[3,2-c]pyridines have been identified as HHAT inhibitors. Based on structural data, we designed and synthesized 37 new analogues which we profiled alongside 13 previously reported analogues in enzymatic and cellular assays. Our results show that a central amide linkage, a secondary amine, and (R)-configuration at the 4-position of the core are three key factors for inhibitory potency. Several potent analogues with low- or sub-μM IC50 against purified HHAT also inhibit Sonic Hedgehog (SHH) palmitoylation in cells and suppress the SHH signaling pathway. This work identifies IMP-1575 as the most potent cell-active chemical probe for HHAT function, alongside an inactive control enantiomer, providing tool compounds for validation of HHAT as a target in cellular assays.

Synthesis and antiviral activity of novel imidazo[2,1‐b]thiazoles coupled with morpholine and thiomorpholines

AbstractHerein described the synthesis and antiviral evaluation of a novel series of morpholine and thio‐morpholine coupled imidazo[2,1‐b]thiazoles. The three‐step reaction sequence involving the condensation of 1,3‐dichloroacetone with thiourea followed by coupling with morpholine and thiomorpholine and finally cyclization with substituted α‐bromoacetophenones yielded the desired imidazothiazoles 7(a–l). Screening of all the new compounds for their in vitro antiviral activity against influenza virus A/Puerto Rico/8/34 (H1N1) in MDCK cells, resulted in two potent analogs, 7d (IC50: 1.1 μM, C50: &gt;300 μM, SI = 273) and 7e (IC50: 2.0 μM, C50: &gt;300 μM, SI = 150), with a favorable toxicity profile and are the best anti‐influenza hit analogs for further structural optimization.

Alpha-glucosidase inhibitory and hypoglycemic effects of imidazole-bearing thioquinoline derivatives with different substituents: In silico, in vitro, and in vivo evaluations

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by high blood sugar levels. It was shown that modulating the activity of α-glucosidase, an enzyme involved in carbohydrate digestion and absorption, can improve blood sugar control and overall metabolic health in individuals with T2DM. As a result, in the current study, a series of imidazole bearing different substituted thioquinolines were designed and synthesized as α-glucosidase inhibitors. All derivatives exhibited significantly better potency (IC50 = 12.1 ± 0.2 to 102.1 ± 4.9 µM) compared to the standard drug acarbose (IC50 = 750.0 ± 5.0 µM). 8g as the most potent analog, indicating a competitive inhibition with Ki = 9.66 µM. Also, the most potent derivative was subjected to molecular docking and molecular dynamic simulation against α-glucosidase to determine its mode of action in the enzyme and study the complex's behavior over time. In vivo studies showed that 8g did not cause acute toxicity at 2000 mg/kg doses. Additionally, in a diabetic rat model, treatment with 8g significantly reduced fasting blood glucose levels and decreased blood glucose levels following sucrose loading compared to acarbose, a standard drug used for blood sugar control. The findings suggest that the synthesized compound 8g holds promise as an α-glucosidase inhibitor for improving blood sugar control and metabolic health.

1,2,4-Triazole-Tethered Indolinones as New Cancer-Fighting Small Molecules Targeting VEGFR-2: Synthesis, Biological Evaluations and Molecular Docking.

Targeting the VEGFR-2 signaling pathway is an inveterate approach toward combating pancreatic and hepatocellular cancers. Based on Sunitinib, the FDA-approved VEGFR-2 inhibitor, novel indolin-2-one-triazole hybrids were designed and synthesized as anti-hepatocellular and anti-pancreatic cancer agents with VEGFR-2 inhibitory activity. All the targeted compounds were assessed for their anti-cancer activity, revealing IC50 values extending from 0.17 to 4.29 µM for PANC1 and 0.58 to 4.49 µM for HepG2 cell lines. An extensive SAR study was conducted to explore the effect of different substituents along with N-alkylation. The potent anti-cancer analogs 11d, 11e, 11g, 11k and 14c were evaluated for their VEGFR-2 inhibitory actions, where their IC50 values ranged from 16.3 to 119.6 nM compared to Sorafenib, which revealed an IC50 of 29.7 nM, having compound 11d as the most active analog. An in silico ADME study was performed to confirm the drug-likeness of the synthesized compounds. Finally, molecular docking simulation was conducted for the most potent VEGFR-2 inhibitor (11d), demonstrating the strong binding with the vital amino acid residues of the VEGFR-2 ATP binding site.

Machine learning-guided design of potent darunavir analogs targeting HIV-1 proteases: A computational approach for antiretroviral drug discovery.

In the pursuit of novel antiretroviral therapies for human immunodeficiency virus type-1 (HIV-1) proteases (PRs), recent improvements in drug discovery have embraced machine learning (ML) techniques to guide the design process. This study employs ensemble learning models to identify crucial substructures as significant features for drug development. Using molecular docking techniques, a collection of 160 darunavir (DRV) analogs was designed based on these key substructures and subsequently screened using molecular docking techniques. Chemical structures with high fitness scores were selected, combined, and one-dimensional (1D) screening based on beyond Lipinski's rule of five (bRo5) and ADME (absorption, distribution, metabolism, and excretion) prediction implemented in the Combined Analog generator Tool (CAT) program. A total of 473 screened analogs were subjected to docking analysis through convolutional neural networks scoring function against both the wild-type (WT) and 12 major mutated PRs. DRV analogs with negative changes in binding free energy ( ) compared to DRV could be categorized into four attractive groups based on their interactions with the majority of vital PRs. The analysis of interaction profiles revealed that potent designed analogs, targeting both WT and mutant PRs, exhibited interactions with common key amino acid residues. This observation further confirms that the ML model-guided approach effectively identified the substructures that play a crucial role in potent analogs. It is expected to function as a powerful computational tool, offering valuable guidance in the identification of chemical substructures for synthesis and subsequent experimental testing.

Pseudouridine and N1-methylpseudouridine as potent nucleotide analogues for RNA therapy and vaccine development.

Modified nucleosides are integral to modern drug development, serving as crucial building blocks for creating safer, more potent, and more precisely targeted therapeutic interventions. Nucleobase modifications often confer antiviral and anti-cancer activity as monomers. When incorporated into nucleic acid oligomers, they increase stability against degradation by enzymes, enhancing the drugs' lifespan within the body. Moreover, modification strategies can mitigate potential toxic effects and reduce immunogenicity, making drugs safer and better tolerated. Particularly, N1-methylpseudouridine modification improved the efficacy of the mRNA coding for spike protein of COVID-19. This became a crucial step for developing COVID-19 vaccine applied during the 2020 pandemic. This makes N1-methylpseudouridine, and its "parent" analogue pseudouridine, potent nucleotide analogues for future RNA therapy and vaccine development. This review focuses on the structure and properties of pseudouridine and N1-methylpseudouridine. RNA has a greater structural versatility, different conformation, and chemical reactivity than DNA. Watson-Crick pairing is not strictly followed by RNA that has more unusual base pairs and base-triplets. This requires detailed structural studies and structure-activity relationship analyses for RNA, also when modifications are incorporated. Recent successes in this direction are revised in this review. We describe recent successes with using pseudouridine and N1-methylpseudouridine in mRNA drug candidates. We also highlight remaining challenges that need to be solved to develop new mRNA vaccines and therapies.

S-Alkylated quinazolin-4(3H)-ones as dual EGFR/VEGFR-2 kinases inhibitors: design, synthesis, anticancer evaluation and docking study.

Dual targeting by a single molecule has emerged as a promising strategy for fighting cancer. In this study, a new set of 2-thioquinazolin-4(3H)-ones as potential anti-cancer surrogates endowed with dual EGFR/VEGFR-2 kinases inhibitory activities were synthesized. The anti-tumor potency of the newly synthesized candidates 4-27 was evaluated against a panel of four cancer cell lines. The prepared candidates 4-27 showed comparable activity to that of the standard drug sorafenib. For instance, compound 4 (IC50 = 1.50-5.86 μM) and compound 20 (IC50 = 4.42-6.39 μM) displayed superior potencies against all cell lines compared to sorafenib (IC50 = 5.47-7.26 μM). Dual EGFR/VEGFR-2 inhibitory activities of the most active analogues (4, 11, and 20) were investigated. Compound 4 showed comparable EGFR/VEGFR-2 inhibitory activity to the used control drugs. Flow cytometric analysis indicates that the most potent analogue 4 stopped the cell cycle at the G1 phase and induced 46.53% total apoptosis in HCT-116 cells that was much more powerful than the untreated cells with 2.15% apoptosis. Molecular docking and dynamic simulations of 4, 11, and 20 with EGFR and VEGFR-2 were performed to examine the binding mode and interaction within the enzyme binding pockets.