Discovery of [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives as novel, potent and selective c-Met kinase inhibitors: Synthesis, SAR study, and biological activity

Targeting c-Met in Cancer Therapy: Unravelling Structure-activity Relationships and Docking Insights for Enhanced Anticancer Drug Design

The c-Met receptor, a pivotal player in oncogenesis and tumor progression, has become a compelling target for anticancer drug development. This review explores the intricate landscape of Structure-Activity Relationship (SAR) studies and molecular binding analyses performed on c-Met inhibitors. Through a comprehensive examination of various chemical scaffolds and modifications, SAR investigations have elucidated critical molecular features essential for the potent inhibition of c-Met activity. Additionally, molecular docking studies have provided invaluable insights into how c-Met inhibitors interact with their target receptor, facilitating the rational design of novel compounds with enhanced efficacy and selectivity. This review highlights key findings from recent SAR and docking studies, particularly focusing on the structural determinants that govern inhibition potency and selectivity. Furthermore, the integration of computational methodologies with experimental approaches has accelerated the discovery and optimization of c-Met inhibitors, fostering the advancement of promising candidates for clinical applications. Overall, this review underscores the pivotal role of SAR and molecular docking studies in advancing our understanding of c-Met inhibition and guiding the rational design of next-generation anticancer agents targeting this pathway.

Current development of pyrazole-azole hybrids with anticancer potential

Chemotherapy is a critical treatment modality for cancer patients, but multidrug resistance remains one of the major challenges in cancer therapy, creating an urgent need for the development of novel potent chemical entities. Azoles, particularly pyrazole, could interact with different biological targets and exhibit diverse biological properties including anticancer activity. Many clinically used anticancer agents own an azole moiety, demonstrating that azoles are privileged and pivotal templates in the discovery of novel anticancer chemotherapeutics. The present article is an attempt to highlight the recent advances in pyrazole-azole hybrids with anticancer potential and discuss the structure-activity relationships, covering articles published from 2018 to present, to facilitate the rational design of more effective anticancer candidates.

Structural and Energetic Properties of Weak Noncovalent Interactions in Two Closely Related 3,6-Disubstituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole Derivatives: In Vitro Cyclooxygenase Activity, Crystallography, and Computational Investigations

Two 3,6-disubstituted-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives, namely, 3-(adamantan-1-yl)-6-(2-chloro-6-fluorophenyl)-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 1 and 6-(2-chloro-6-fluorophenyl)-3-phenyl-[1,2,4]triazolo[3,4-b][1,3,4]thiadiazole 2, were prepared, and the detailed analysis of the weak intermolecular interactions responsible for the supramolecular self-assembly was performed using X-ray diffraction and theoretical tools. Analyses of Hirshfeld surface and 2D fingerprint plot demonstrated the effect of adamant-1-yl/phenyl moieties on intermolecular interactions in solid-state structures. The effect of these substituents on H···H/Cl/N contacts was more specific. The CLP-PIXEL and density functional theory methods provide information on the energetics of molecular dimers observed in these compounds. The crystal structure of compound 1 stabilizes with a variety of weak intermolecular interactions, including C-H···N, C-H···π, and C-H···Cl hydrogen bonds, a directional C-S···π chalcogen bond, and unconventional short F···C/N contacts. The crystal structure of compound 2 is stabilized by π-stacking interactions, C-H···N, C-H···π, and C-H···Cl hydrogen bonds, and highly directional attractive σ-hole interactions such as the C-Cl···N halogen bond and the C-S···N chalcogen bond. In addition, S(lp)···C(π) and short N···N contacts play a supportive role in the stabilization of certain molecular dimers. The final supramolecular architectures resulting from the combination of different intermolecular interactions are observed in both the crystal packing. The molecular electrostatic potential map reveals complementary electrostatic potentials of the interacting atoms. The quantum theory of atoms in molecules approach was used to delineate the nature and strength of different intermolecular interactions present in different dimers of compounds 1 and 2. The in vitro experiments suggest that both compounds showed selectivity against COX-2 targets rather than COX-1. Molecular docking analysis showed the binding pose of the compounds at the active sites of COX-1/2 enzymes.

Comparing the Performance of Different AMBER Protein Forcefields, Partial Charge Assignments, and Water Models for Absolute Binding Free Energy Calculations

Identifying chemical starting points is a vital first step in small molecule drug discovery and can take significant time and money. For this reason, computational approaches to virtual screening are of great interest as they can lower the cost and shorten timeframes. However, simple approaches such as molecular docking and pharmacophore screening are of limited accuracy and provide a low probability of success. Alchemical binding free energies represent a promising approach for virtual screening as they naturally incorporate the key effects of water molecules, protein flexibility, and binding entropy. However, the calculations are technically very challenging, with performance depending on the specific forcefield used. For this reason, it is important that the community has access to benchmark test sets to assess prediction accuracy. In this paper, we present an approach to alchemical binding free energies using OpenMM. We identify effective simulation parameters using an existing BRD4(1) test set and present two new benchmark sets (cMET and PDE2A) that can be used in the community for validation purposes. Our findings also highlight the effectiveness of some AMBER forcefields, in particular, AMBER ff15ipq.

New N-(3′-acetyl-8-nitro-2,3-dihydro-1H,3′H-spiro[quinoline-4,2′-[1,3,4]thiadiazol]-5′-yl) acetamides induced cell death in MCF-7 cells via G2/M phase cell cycle arrest

A series of new N-(3′-acetyl-8-nitro-2,3-dihydro-1H,3′H-spiro[quinoline-4,2′-[1,3,4]thiadiazol]-5′-yl) acetamide derivatives were synthesized from potent 8-nitroquinoline-thiosemicarbazones.

Recent contributions of quinolines to antimalarial and anticancer drug discovery research

Quinoline, a privileged scaffold in medicinal chemistry, has always been associated with a multitude of biological activities. Especially in antimalarial and anticancer research, quinoline played (and still plays) a central role, giving rise to the development of an array of quinoline-containing pharmaceuticals in these therapeutic areas. However, both diseases still affect millions of people every year, pointing to the necessity of new therapies. Quinolines have a long-standing history as antimalarial agents, but established quinoline-containing antimalarial drugs are now facing widespread resistance of the Plasmodium parasite. Nevertheless, as evidenced by a massive number of recent literature contributions, they are still of great value for future developments in this field. On the other hand, the number of currently approved anticancer drugs containing a quinoline scaffold are limited, but a strong increase and interest in quinoline compounds as potential anticancer agents can be seen in the last few years. In this review, a literature overview of recent contributions made by quinoline-containing compounds as potent antimalarial or anticancer agents is provided, covering publications between 2018 and 2020.

Monoamine oxidase A and B inhibitory activities of 3,5-diphenyl-1,2,4-triazole substituted [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives

Monoamine oxidase (EC 1.4.3.4, MAO) is a flavin adenine dinucleotide-containing flavoenzyme located on the outer mitochondrial membrane and catalyzes the oxidative deamination of monoaminergic neurotransmitters and dietary amines. MAO exists in humans as two isoenzymes, hMAO-A and hMAO-B, which are distinguished by their tertiary structures, preferred substrates and inhibitors, and selective inhibition of these isoenzymes are used in the treatment of different diseases such as Alzheimer's, Parkinson's and depression. In the present study, we report the design, synthesis and characterization of 3,5-diphenyl-1,2,4-triazole substituted [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole derivatives as novel and selective inhibitors of hMAO-B. Twenty one compounds (38, 39a-h, 41a-d, 42a-h) were screened for their inhibitory activity against hMAO-A and hMAO-B by using in vitro Amplex Red® reagent based fluorometric method and all compounds were found to be as selective h-MAO-B inhibitors to a different degree. The compound 42e and 42h displayed the highest inhibitory activity against hMAO-B with IC₅₀ values of 2.51 and 2.81 µM, respectively, and more than 25-fold selectivity towards inhibition of hMAO-B. A further kinetic evaluation of the most potent derivative (42e) was also performed and a mixed mode of inhibition of hMAO-B by the compound 42e was determined (K_i = 0,26 µM). According to our findings the [1,2,4]triazolo[3,4-b][1,3,4]thiadiazole emerged as a promising scaffold for the development of novel and selective hMAO-B inhibitors.

Transforming Type II to Type I c-Met kinase inhibitors via combined scaffold hopping and structure-guided synthesis of new series of 1,3,4-thiadiazolo[2,3-c]-1,2,4-triazin-4-one derivatives

Novel 1,3,4-thiadiazolo[2,3-c]-1,2,4-triazin-4-one derivatives 3a-e, 4a-f and 5a-f were designed as Type I c-Met kinase inhibitors based on scaffold hopping of our previous Type II c-Met kinase lead. Target compounds were then synthesized under the guidance of molecular docking analysis to identify the potential inhibitors that fit the binding pocket of c-Met kinase in the characteristic manner as the reported Type I c-Met kinase inhibitors. All synthesized derivatives were evaluated for their c-Met kinase inhibitory activity at 10 µM concentration, where 3d, 5d and 5f displayed >80% inhibition. Further IC₅₀ investigation of these compounds identified 5d as the most potent c-Met kinase inhibitor with IC₅₀ value of 1.95 µM. Moreover, 5d showed selective antitumor activity against c-Met over-expressing colon HCT-116 and lung A549 adenocarcinoma cells with IC₅₀ values of 6.18 and 10.6 µg/ml, respectively. More significantly, 5d effectively inhibited c-Met phosphorylation in the Western blot experiment. Also, 5d induced cellular apoptosis in HCT-116 cancer cells as well as cell cycle arrest with accumulation of cells in G2/M phase. Finally, kinase selectivity profiling of 5d against nine oncogenic kinases revealed its selectivity to only Tyro3 kinase (% inhibition = 80%, IC₅₀ = 3 µM). All these experimental findings clearly demonstrate that 5d is a potential dual acting inhibitor against c-Met and Tyro3 kinases, standing out as a viable lead that deserves further investigation and development to new generation of antitumor agents.

Structure-activity relationship study of novel quinazoline-based 1,6-naphthyridinones as MET inhibitors with potent antitumor efficacy

As a privileged scaffold, the quinazoline ring is widely used in the development of EGFR inhibitors, while few quinazoline-based MET inhibitors are reported. In our ongoing efforts to develop new MET-targeted anticancer drug candidates, a series of quinazoline-based 1,6-naphthyridinone derivatives were designed, synthesized, and evaluated for their biological activities. The preliminary SARs studies indicate that the quinazoline scaffold was also acceptable for the block A of class II MET inhibitors. The further pharmacokinetic studies led to the identification of the most promising compound 22a with favorable in vitro potency (MET, IC₅₀ = 9.0 nM), human microsomal metabolic stability (t_1/2 = 621.2 min) and oral bioavailability (F = 42%). Moreover, 22a displayed good in vivo antitumor efficacy (IR of 81% in 75 mg/kg) in MET-positive human glioblastoma U-87 MG xenograft model. These positive results indicated that 22a is a potential new MET-targeted antitumor drug lead, which is worthy of further development.

Anti-biofilm Fe3O4@C18-[1,3,4]thiadiazolo[3,2-a]pyrimidin-4-ium-2-thiolate Derivative Core-shell Nanocoatings

The derivatives 5,7-dimethyl[1,3,4]thiadiazolo[3,2-a]pyrimidin-4-ium-2-thiolate (1) and 7-methyl-5-phenyl[1,3,4]thiadiazolo[3,2-a]pyrimidin-4-ium-2-thiolate (2) were fully characterized by single-crystal X-ray diffraction. Their supramolecular structure is built through both π–π stacking and C=S–π interactions for both compounds. The embedment of the tested compounds into Fe₃O₄@C₁₈ core-shell nanocoatings increased the protection degree against Candida albicans biofilms on the catheter surface, suggesting that these bioactive nanocoatings could be further developed as non-cytotoxic strategies for fighting biofilm-associated fungal infections.

Design, synthesis and biological evaluation of novel 1,3,4-thiadiazole derivatives as anti-glioblastoma agents targeting the AKT pathway

In spite of progress in understanding biology of glioblastoma (GBM), this tumor remains incurable with a median survival rate of 15 months. Previous studies have shown that 2-(4-fluorophenyloamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (FPDT) and 2-(3-chlorophenyloamino)-5-(2,4-dihydroxyphenyl)-1,3,4-thiadiazole (CPDT) diminished viability of cancer cell lines of different origin. In the current study, we have examined activity of these compounds in several GBM cell lines and patient-derived GBM cells. We have also designed, synthesized and evaluated anti-GBM activity of novel 1,3,4-thiadiazole derivatives containing additional Cl or CH₂CH₃ substitute at C5-position of 2,4-dihydroxyphenyl. The tested compounds presented a considerable cytotoxicity against all GBM cell lines examined as well as patient-derived GBM cells. They were 15-110 times more potent than temozolomide, the first-line chemotherapeutic agent for GBM. Notably, in anticancer concentrations three of the derivatives were not toxic to human astrocytes. FPDT appeared to be the most promising compound with IC₅₀ values between 45 μM and 68 μM for GBM cells and >100 μM for astrocytes. It augmented activity of temozolomide and inhibited proliferation migration and invasion of GBM cells. Treatment with FPDT diminished phosphorylation level of GSK3β and AKT. Pretreatment with PDGF-BB, an AKT activator, partially protected cells from death caused by FPDT, indicating that FPDT-mediated decrease in cell viability is causatively related to the inhibition of the AKT pathway.

Cytotoxic Properties of 1,3,4-Thiadiazole Derivatives-A Review

During recent years, small molecules containing five-member heterocyclic moieties have become the subject of considerable growing interest for designing new antitumor agents. One of them is 1,3,4-thiadiazole. This study is an attempt to collect the 1,3,4-thiadiazole and its derivatives, which can be considered as potential anticancer agents, reported in the literature in the last ten years.

Design, Synthesis, and Biological Evaluation of Pyridineamide Derivatives Containing a 1,2,3-Triazole Fragment as Type II c-Met Inhibitors

A series of 4-(pyridin-4-yloxy)benzamide derivatives containing a 1,2,3-triazole fragment were designed, synthesized, and their inhibitory activity against A549, HeLa, and MCF-7 cancer cell lines was evaluated. Most compounds exhibited moderate to potent antitumor activity against the three cell lines. Among them, the promising compound B26 showed stronger inhibitory activity than Golvatinib, with IC₅₀ values of 3.22, 4.33, and 5.82 μM against A549, HeLa, and MCF-7 cell lines, respectively. The structure–activity relationships (SARs) demonstrated that the modification of the terminal benzene ring with a single electron-withdrawing substituent (fluorine atom) and the introduction of a pyridine amide chain with a strong hydrophilic group (morpholine) to the hinge region greatly improved the antitumor activity. Meanwhile, the optimal compound B26 showed potent biological activity in some pharmacological experiments in vitro, such as cell morphology study, dose-dependent test, kinase activity assay, and cell cycle experiment. Finally, the molecular docking simulation was performed to further explore the binding mode of compound B26 with c-Met.

Synthesis of novel 6,7-dimethoxy-4-anilinoquinolines as potent c-Met inhibitors

HGF/c-Met signalling pathway plays an important role in the development of cancers. A series of 6,7-dimethoxy-4-anilinoquinolines possessing benzimidazole moiety were synthesised and identified as potent inhibitors of the tyrosine kinase c-Met. Their in vitro biological activities against three cancer cell lines (A549, MCF-7, and MKN-45) were also evaluated. Most of these compounds exhibited moderate to remarkable potency. Among them, compound 12n showed the most potent inhibitory activity against c-Met with IC₅₀ value of 0.030 ± 0.008 µM and it also showed excellent anticancer activity against the tested cancer cell lines at low micromolar concentration. Molecular docking verified the results and revealed the possible binding mode of the most promising compound 12n into the ATP-binding site of c-Met kinase.