Synthesis and structure activity relationship investigation of triazolo[1,5-a]pyrimidines as CB2 cannabinoid receptor inverse agonists

A systematic review of novel cannabinoids and their targets: Insights into the significance of structure in activity

To provide a comprehensive framework of the current information on the potency and efficacy of interaction between phyto- and synthetic cannabinoids and their respective receptors, an electronic search of the PubMed, Scopus, and EMBASE literature was performed. Experimental studies included reports of mechanistic data providing affinity, efficacy, and half-maximal effective concentration (EC50). Among the 108 included studies, 174 structures, and 16 targets were extracted. The most frequent ligands belonged to the miscellaneous category with 40.2% followed by phytocannabinoid-similar, indole-similar, and pyrrole-similar structures with an abundance of 17.8%, 16.6%, and 12% respectively. 64.8% of structures acted as agonists, 17.1 % appeared as inverse agonists, 10.8% as antagonists, and 7.2% of structures were reported with antagonist/inverse agonist properties. Our outcomes identify the affinity, EC50, and efficacy of the interactions between cannabinoids and their corresponding receptors and the subsequent response, evaluated in the available evidence. Considering structures' significance and very important effects of on the activities, the obtained results also provide clues to drug repurposing.

1,2,4-Triazolo-quinazolinones as Effective Antifoulants: Molecular Design, Synthesis, and Biological Evaluation

A series of 1,2,4-triazolo-quinazolinones and 1,2-benzisothiazolone derivatives (S1-S12) were successfully synthesized as environmentally friendly alternatives to copper-based antifouling paints using N-alkylation, cyclocondensation, and one-pot three-component and amide coupling reactions. The monoclinic structure of single-crystal 1,2,4-triazolo-quinazolin-acetic acid (S8) was confirmed by single-crystal X-ray diffraction analysis. All the synthesized molecules were studied for their in silico molecular docking interactions with three target proteins, namely, RbmA, ToxR, and Bap. Following that, the antialgal activity was assessed against two types of marine algae: Chlorella sp. and Chaetoceros curvisetus. The minimal inhibitory concentration and zone of inhibition have been used to evaluate the antibacterial activities of S1-S12 against both marine Gram-positive (Staphylococcus aureus) and Gram-negative (Vibrio parahemolyticus and Vibrio vulnificus) bacteria. Additionally, antifouling studies have been done on all the compounds, and among them, 1,2,4-triazolo-quinazolinyl-acetate (S7), 1,2,4-triazolo-quinazolinyl-acetic acid (S8), 1,2,4-triazolo-quinazolinyl-oxobutanoate (S9), benzo[d]isothiazolyl butanoate (S10), benzo[d]isothiazolyl-acetic acid (S11), and 1,2,4-triazolo-quinazolinyl-acetyl-benzo[d]isothiazolone (S12) exhibited good antialgal, antibacterial, and antifouling activities.

Integrating computational methods guided the discovery of phytochemicals as potential Pin1 inhibitors for cancer: pharmacophore modeling, molecular docking, MM-GBSA calculations and molecular dynamics studies

Pin1 is a pivotal player in interactions with a diverse array of phosphorylated proteins closely linked to critical processes such as carcinogenesis and tumor suppression. Its axial role in cancer initiation and progression, coupled with its overexpression and activation in various cancers render it a potential candidate for the development of targeted therapeutics. While several known Pin1 inhibitors possess favorable enzymatic profiles, their cellular efficacy often falls short. Consequently, the pursuit of novel Pin1 inhibitors has gained considerable attention in the field of medicinal chemistry. In this study, we employed the Phase tool from Schrödinger to construct a structure-based pharmacophore model. Subsequently, 449,008 natural products (NPs) from the SN3 database underwent screening to identify compounds sharing pharmacophoric features with the native ligand. This resulted in 650 compounds, which then underwent molecular docking and binding free energy calculations. Among them, SN0021307, SN0449787 and SN0079231 showed better docking scores with values of -9.891, -7.579 and -7.097 kcal/mol, respectively than the reference compound (-6.064 kcal/mol). Also, SN0021307, SN0449787 and SN0079231 exhibited lower free binding energies (-57.12, -49.81 and -46.05 kcal/mol, respectively) than the reference ligand (-37.75 kcal/mol). Based on these studies, SN0021307, SN0449787, and SN0079231 showed better binding affinity that the reference compound. Further the validation of these findings, molecular dynamics simulations confirmed the stability of the ligand-receptor complex for 100 ns with RMSD ranging from 0.6 to 1.8 Å. Based on these promising results, these three phytochemicals emerge as promising lead compounds warranting comprehensive biological screening in future investigations. These compounds hold great potential for further exploration regarding their efficacy and safety as Pin1 inhibitors, which could usher in new avenues for combating cancer.

Triazolopyrimidine Derivatives: An Updated Review on Recent Advances in Synthesis, Biological Activities and Drug Delivery Aspects

Molecules containing triazolopyrimidine core showed diverse biological activities, including anti-Alzheimer's, anti-diabetes, anti-cancer, anti-microbial, anti-tuberculosis, anti-viral, anti-malarial, anti-inflammatory, anti-parkinsonism, and anti-glaucoma activities. Triazolopyrimidines have 8 isomeric structures, including the most stable 1,2,4-triazolo[1,5- a] pyrimidine ones. Triazolopyrimidines were obtained by using various chemical reactions, including a) 1,2,4-triazole nucleus annulation to pyrimidine, b) pyrimidines annulation to 1,2,4-triazole structure, c) 1,2,4-triazolo[l,5-a] pyrimidines rearrangement, and d) pyrimidotetrazine rearrangement. This review discusses synthetic methods, recent pharmacological actions and drug delivery perspectives of triazolopyrimidines.

Mesomeric Betaines Based on Adamantylated 1,2,4-Triazolo[4,3-a]pyrimidin-5-ones: Synthesis, Structure and Conversion into Anionic N-Heterocyclic Carbenes

The C-N coupling of 1,2,4-triazolo[1,5-a]pyrimidin-7-ones with 1-adamantanol/1-bromoadamantane leads to 1,2,4-triazolo[4,3-a]pyrimidinium-5-olates, which are represented as mesomeric betaines (MBs). The formation of MBs involves not only N-alkylation of heterocyclic framework but also the rearrangement leading to a change in the type of fusion between pyrimidine and 1,2,4-triazole fragments. The structures of the obtained products were confirmed by the X-ray analysis and measurements of ¹³ C-¹³ C (J_CC ) coupling constants in the 1D ¹³ C NMR spectra of selectively ¹³ C-labeled samples. Treatment of the betaines with lithium bis(trimethylsilyl)amide (LiHMDS) gave anionic carbenes, which were detected by ¹³ C NMR spectroscopy and were trapped by reactions with phenyl isothiocyanate and sulfur. Density functional theory (DFT) and the quantum theory of atoms in molecules (QTAIM) analyses allowed for an insight into the electronic structure of the obtained betaines and N-heterocyclic carbene derivatives.

2-Furyl-6-Nitro-1,2,4-Triazolo [1,5-a]Pyrimidin-7-One

A sodium salt of 2-(fur-2-yl)-6-nitro-1,2,4-triazolo[1,5-a]pyrimidin-7-one as a close structural analogue of ZM-241385 was obtained. This heterocycle can serve as an effector for A2a adenosine receptors and possesses antiseptic activity. The structures of compounds were confirmed based on the data of 1H, 13C NMR spectroscopy, IR spectroscopy, and an elemental analysis. The structure of sodium salt 2-furyl-6-nitro-1,2,4-triazolo[1,5-a]pyrimidin-7-one was confirmed by an X-ray diffraction analysis.

Recent Advances in the Development of Pyrimidine-based CNS Agents

BACKGROUND

In the past few decades, considerable progress has been made in CNS drug discovery, and various new CNS agents have been developed. Pyrimidine is an important scaffold in the area of medicinal chemistry. Recently, pyrimidine-containing compounds have been successfully designed as potent CNS agents. Substantial research has been carried out on pyrimidine-bearing compounds to treat different disorders of CNS in various animal models.

METHODS

Utilizing various databases, including Google Scholar, PubMed, Science Direct, and Web of Science, the literature review was conducted. The specifics of significant articles were discussed with an emphasis on the potency of pyrimidines derivatives possessing CNS activity.

RESULTS

Recent papers indicating pyrimidine derivatives with CNS activity were incorporated into the manuscript. (46) to (50) papers included different pyrimidine derivatives as 5-HT agonist/antagonists, (62) to (67) as adenosine agonist/antagonist, (70) to (75) as anticonvulsant agents, (80) to (83) as cannabinoid receptor agonists, (102) to (103) as nicotinic and (110) as muscarinic receptor agonists. The remaining papers (113) to (114) represented pyrimidine-based molecular imaging agents.

CONCLUSION

Pyrimidine and its derivatives have been studied in detail to evaluate their efficacy in overcoming multiple central nervous system disorders. The article covers the current updates on pyrimidine-based compounds as potent CNS and molecular imaging agents and will definitely provide a better platform for the development of potent pyrimidine-based CNS drugs in the near future.

Understanding the Dynamics of the Structural States of Cannabinoid Receptors and the Role of Different Modulators

The cannabinoid receptors CB1R and CB2R are members of the G protein-coupled receptor (GPCR) family. These receptors have recently come to light as possible therapeutic targets for conditions affecting the central nervous system. However, because CB1R is known to have psychoactive side effects, its potential as a drug target is constrained. Therefore, targeting CB2R has become the primary focus of recent research. Using various molecular modeling studies, we analyzed the active, inactive, and intermediate states of both CBRs in this study. We conducted in-depth research on the binding properties of various groups of cannabinoid modulators, including agonists, antagonists, and inverse agonists, with all of the different conformational states of the CBRs. The binding effects of these modulators were studied on various CB structural features, including the movement of the transmembrane helices, the volume of the binding cavity, the internal fluids, and the important GPCR properties. Then, using in vitro experiments and computational modeling, we investigated how vitamin E functions as a lipid modulator to influence THC binding. This comparative examination of modulator binding to CBRs provides significant insight into the mechanisms of structural alterations and ligand affinity, which can directly help in the rational design of selective modulators that target either CB1R or CB2R.

Rational drug design of CB2 receptor ligands: from 2012 to 2021

Cannabinoid receptors belong to the large family of G-protein-coupled receptors, which can be divided into two receptor types, cannabinoid receptor type-1 (CB1) and cannabinoid receptor type-2 (CB2). Marinol, Cesamet and Sativex are marketed CB1 drugs which are still in use and work well, but the central nervous system side effects caused by activation CB1, which limited the development of CB1 ligands. So far, no selective CB2 ligand has been approved for marketing, but lots of its ligands in the clinical stage and pre-clinical stage have positive effects on the treatment of some disease models and have great potential for development. Most selective CB2 agonists are designed and synthesized based on non-selective CB2 agonists through the classical med-chem strategies, e.g. molecular hybridization, scaffold hopping, bioisosterism, etc. During these processes, the balance between selectivity, activity, and pharmacokinetic properties needs to be achieved. Hence, we summarized some reported ligands on the basis of the optimization strategies in recent 10 years, and the limitations and future directions.

An Overview on Synthetic and Medicinal Perspectives of [1,2,4]Triazolo[1,5-a]pyrimidine Scaffold

[1,2,4]Triazolo[1,5-a]pyrimidine is an important heterocyclic scaffold known to have a wide range of pharmacological activities such as anticancer, antimicrobial, anti-tubercular, CB₂ cannabinoid agonists, feticide, and adenosine antagonists. Several clinical trials and marketed drugs such as Trapidil, Essramycin, Pyroxsulam, DSM-265, Flumetsulam, GNF-6702, and Cevipabulin indicate the potential of [1,2,4]triazolo[1,5-a]pyrimidine moiety with various functional groups in medicinal chemistry. Herein, we represent a concise report focusing on the synthetic strategies used for diversely substituted [1,2,4]triazolo[1,5-a]pyrimidine analogs and their pharmacological applications. To the best of our knowledge, since 1980, we are the first to write a review on this emerging scaffold, which reveals the synthetic strategies, and pharmacological activities of differently substituted [1,2,4]triazolo[1,5-a]pyrimidine with special emphasis on structure-activity relationship studies.

Azolo[1,5-a]pyrimidines and Their Condensed Analogs with Anticoagulant Activity

Hypercytokinemia, or cytokine storm, is one of the severe complications of viral and bacterial infections, involving the release of abnormal amounts of cytokines, resulting in a massive inflammatory response. Cytokine storm is associated with COVID-19 and sepsis high mortality rate by developing epithelial dysfunction and coagulopathy, leading to thromboembolism and multiple organ dysfunction syndrome. Anticoagulant therapy is an important tactic to prevent thrombosis in sepsis and COVID-19, but recent data show the incompatibility of modern direct oral anticoagulants and antiviral agents. It seems relevant to develop dual-action drugs with antiviral and anticoagulant properties. At the same time, it was shown that azolo[1,5-a]pyrimidines are heterocycles with a broad spectrum of antiviral activity. We have synthesized a new family of azolo[1,5-a]pyrimidines and their condensed polycyclic analogs by cyclocondensation reactions and direct CH-functionalization and studied their anticoagulant properties. Five compounds among 1,2,4-triazolo[1,5-a]pyrimidin-7-ones and 5-alkyl-1,3,4-thiadiazolo[3,2-a]purin-8-ones demonstrated higher anticoagulant activity than the reference drug, dabigatran etexilate. Antithrombin activity of most active compounds was confirmed using lipopolysaccharide (LPS)-treated blood to mimic the conditions of cytokine release syndrome. The studied compounds affected only the thrombin time value, reliably increasing it 6.5–15.2 times as compared to LPS-treated blood.

Triazolopyrimidine Nuclei: Privileged Scaffolds for Developing Antiviral Agents with a Proper Pharmacokinetic Profile

Viruses are a continuing threat to global health. The lack or limited therapeutic armamentarium against some viral infections and increasing drug resistance issues make the search for new antiviral agents urgent. In recent years, a growing literature highlighted the use of triazolopyrimidine (TZP) heterocycles in the development of antiviral agents, with numerous compounds that showed potent antiviral activities against different RNA and DNA viruses. TZP core represents a privileged scaffold for achieving biologically active molecules, thanks to: i) the synthetic feasibility that allows to variously functionalize TZPs in the different positions of the nucleus, ii) the ability of TZP core to establish multiple interactions with the molecular target, and iii) its favorable pharmacokinetic properties. In the present review, after mentioning selected examples of TZP-based compounds with varied biological activities, we will focus on those antivirals that appeared in the literature in the last 10 years. Approaches used for their identification, the hit-to-lead studies, and the emerged structure-activity relationship will be described. A mention of the synthetic methodologies to prepare TZP nuclei will also be given. In addition, their mechanism of action, the binding mode within the biological target, and pharmacokinetic properties will be analyzed, highlighting the strengths and weaknesses of compounds based on the TZP scaffold, which is increasingly used in medicinal chemistry.

Cannabidiol induces antidepressant and anxiolytic-like effects in experimental type-1 diabetic animals by multiple sites of action

Cannabidiol (CBD), a phytocannabinoid compound, presents antidepressant and anxiolytic-like effects in the type-1 diabetes mellitus(DM1) animal model. Although the underlying mechanism remains unknown, the type-1A serotonin receptor (5-HT1A) and cannabinoids type-1 (CB1) and type-2 (CB2) receptors seem to play a central role in mediating the beneficial effects on emotional responses. We aimed to study the involvement of these receptors on an antidepressant- and anxiolytic-like effects of CBD and on some parameters of the diabetic condition itself. After 2 weeks of the DM1 induction in male Wistar rats by streptozotocin (60 mg/kg; i.p.), animals were treated continuously for 2-weeks with the 5-HT1A receptor antagonist WAY100635 (0.1 mg/kg, i.p.), CB1 antagonist AM251 (1 mg/kg i.p.) or CB2 antagonist AM630 (1 mg/kg i.p.) before the injection of CBD (30 mg/kg, i.p.) or vehicle (VEH, i.p.) and then, they were submitted to the elevated plus-maze and forced swimming tests. Our findings show the continuous treatment with CBD improved all parameters evaluated in these diabetic animals. The previous treatment with the antagonists - 5-HT1A, CB1, or CB2 - blocked the CBD-induced antidepressant-like effect whereas only the blockade of 5-HT1A or CB1 receptors was able to inhibit the CBD-induced anxiolytic-like effect. Regarding glycemic control, only the blockade of CB2 was able to inhibit the beneficial effect of CBD in reducing the glycemia of diabetic animals. These findings indicated a therapeutic potential for CBD in the treatment of depression/anxiety associated with diabetes pointing out a complex intrinsic mechanism in which 5-HT1A, CB1, and/or CB2 receptors are differently recruited.

Consensus Docking in Drug Discovery

Background:

Molecular docking is probably the most popular and profitable approach in computer-aided drug design, being the staple technique for predicting the binding mode of bioactive compounds and for performing receptor-based virtual screening studies. The growing attention received by docking, as well as the need for improving its reliability in pose prediction and virtual screening performance, has led to the development of a wide plethora of new docking algorithms and scoring functions. Nevertheless, it is unlikely to identify a single procedure outperforming the other ones in terms of reliability and accuracy or demonstrating to be generally suitable for all kinds of protein targets.

Methods:

In this context, consensus docking approaches are taking hold in computer-aided drug design. These computational protocols consist in docking ligands using multiple docking methods and then comparing the binding poses predicted for the same ligand by the different methods. This analysis is usually carried out calculating the root-mean-square deviation among the different docking results obtained for each ligand, in order to identify the number of docking methods producing the same binding pose.

Results:

The consensus docking approaches demonstrated to improve the quality of docking and virtual screening results compared to the single docking methods. From a qualitative point of view, the improvement in pose prediction accuracy was obtained by prioritizing ligand binding poses produced by a high number of docking methods, whereas with regards to virtual screening studies, high hit rates were obtained by prioritizing the compounds showing a high level of pose consensus.

Conclusion:

In this review, we provide an overview of the results obtained from the performance assessment of various consensus docking protocols and we illustrate successful case studies where consensus docking has been applied in virtual screening studies.

Triazolopyrimidinium salts: discovery of a new class of agents for cancer therapy

Aim: The [1,2,4]triazolo[1,5-a]pyrimidine core is highly privileged in medicinal chemistry due to its versatile pharmacological activity profile. Recently, the search for novel anticancer agents has focused on [1,2,4]triazolo[1,5-a]pyrimidine derivatives. Results: Our hit functionalization has led to the discovery of new [1,2,4]triazolo[1,5-a]pyrimidinium salts with potential anticancer activity. Among a small library of molecules, compound 9 significantly inhibits cancer cell growth in a panel of in vitro models. Molecular docking studies and preliminary binding assay have displayed that 9 could directly bind the Src homology 2 (SH2) domain of STAT3 protein. Conclusion: Compound 9 is a novel promising lead compound that motivates additional evaluation of [1,2,4]triazolo[1,5-a]pyrimidinium salts as novel potential chemotherapeutics.

Virtual screening identifies a PIN1 inhibitor with possible antiovarian cancer effects

Peptidyl-prolyl cis-trans isomerase, NIMA-interacting 1 (PIN1) is a peptidyl-prolyl isomerase that binds phospho-Ser/Thr-Pro motifs in proteins and catalyzes the cis-trans isomerization of proline peptide bonds. PIN1 is overexpressed in several cancers including high-grade serous ovarian cancer. Since few therapies are effective against this cancer, PIN1 could be a therapeutic target but effective PIN1 inhibitors are lacking. To identify molecules with in vivo inhibitory effects on PIN1, we used consensus docking to model existing PIN1-ligand X-ray structures and to screen a chemical database for candidate inhibitors. Ten molecules were selected and tested in cellular assays, leading to the identification of VS10 that bound and inhibited PIN1. VS10 treatment reduced the viability of ovarian cancer cell lines by inducing proteasomal PIN1 degradation, without effects on PIN1 transcription, and also reduced the levels of downstream targets β-catenin, cyclin D1, and pSer473-Akt. VS10 is a selective PIN1 inhibitor that may offer new opportunities for treating PIN1-overexpressing tumors.

Pyridazinone-substituted benzenesulfonamides display potent inhibition of membrane-bound human carbonic anhydrase IX and promising antiproliferative activity against cancer cell lines

An expanded set of pyridazine-containing benzene sulfonamides was investigated for inhibition of four human carbonic anhydrase isoforms, which revealed a pronounced inhibition trend toward hCA IX, a cancer-related, membrane-bound isoform of the enzyme. Comparison of antiproliferative effects of these compounds against cancer (PANC-1) and normal (ARPE-19) cells at 50 μM concentration narrowed the selection of compounds to the eight which displayed selective growth inhibition toward the cancer cells. More detailed investigation in concentration-dependent mode against normal (ARPE-19) and two cancer cell lines (PANC-1 and SK-MEL-2) identified two lead compounds one of which displayed a notable cytotoxicity toward pancreatic cancer cells while the other targeted the melanoma cells. These findings significantly expand the knowledge base concerning the hCA IX inhibitors whose inhibitory potency against a recombinant enzyme translates into selective anticancer activity under hypoxic conditions which are aimed to model the environment of a growing tumor.

Novel 8-Substituted Coumarins That Selectively Inhibit Human Carbonic Anhydrase IX and XII

A novel series of 8-substituted coumarin-based compounds, characterized by the presence of alkylpiperazine and arylpiperazine chains, were synthesized and tested for their inhibitory activity against four human carbonic anhydrase (hCA) isoforms. All compounds displayed nanomolar potency against the cancer-related hCA IX and hCA XII; moreover, they were shown to be devoid of any inhibitory activity toward the cytosolic hCA I and hCA II up to 10 µM concentration in the assay system. Therefore, the synthesized coumarin ligands demonstrated to be potent and selective hCA IX/XII inhibitors, and were shown to be as potent as the reference inhibitor acetazolamide against hCA XII, with single-digit nanomolar K_i values. Molecular modeling studies provided a rationale for explaining the selectivity profile of these non-classic hCA inhibitors and their interactions with the enzymes, according to their specific mechanism of action, thus paving the way for future structure-based lead optimization studies.

Computationally driven discovery of phenyl(piperazin-1-yl)methanone derivatives as reversible monoacylglycerol lipase (MAGL) inhibitors

Monoacylglycerol lipase (MAGL) is an attractive therapeutic target for many pathologies, including neurodegenerative diseases, cancer as well as chronic pain and inflammatory pathologies. The identification of reversible MAGL inhibitors, devoid of the side effects associated to prolonged MAGL inactivation, is a hot topic in medicinal chemistry. In this study, a novel phenyl(piperazin-1-yl)methanone inhibitor of MAGL was identified through a virtual screening protocol based on a fingerprint-driven consensus docking (CD) approach. Molecular modeling and preliminary structure-based hit optimization studies allowed the discovery of derivative 4, which showed an efficient reversible MAGL inhibition (IC₅₀ = 6.1 µM) and a promising antiproliferative activity on breast and ovarian cancer cell lines (IC₅₀ of 31-72 µM), thus representing a lead for the development of new and more potent reversible MAGL inhibitors. Moreover, the obtained results confirmed the reliability of the fingerprint-driven CD approach herein developed.

Design, Synthesis, Docking Studies and Monoamine Oxidase Inhibition of a Small Library of 1-acetyl- and 1-thiocarbamoyl-3,5-diphenyl-4,5-dihydro-(1H)-pyrazoles

New N-acetyl/N-thiocarbamoylpyrazoline derivatives were designed and synthesized in high yields to assess their inhibitory activity and selectivity against human monoamine oxidase A and B. The most important chiral compounds were separated into their single enantiomers and tested. The impact of the substituents at N1, C3 and C5 positions as well the influence of the configuration of the C5 on the biological activity were analyzed. Bulky aromatic groups at C5 were not tolerated. p-Prenyloxyaryl moiety at C3 oriented the selectivity toward the B isoform. The results were also corroborated by molecular modelling studies providing new suggestions for the synthesis of privileged structures to serve as lead compounds for the treatment of mood disorders and neurodegenerative diseases.

1,2,4-Triazolo[1,5-a]pyrimidines in drug design

The 1,2,4-triazolo[1,5-a]pyrimidine (TP) heterocycle, in spite of its relatively simple structure, has proved to be remarkably versatile as evidenced by its use in many different applications reported over the years in different areas of drug design. For example, as the ring system of TPs is isoelectronic with that of purines, this heterocycle has been proposed as a possible surrogate of the purine ring. However, depending on the choice of substituents, the TP ring has also been described as a potentially viable bio-isostere of the carboxylic acid functional group and of the N-acetyl fragment of ε-N-acetylated lysine. In addition, the metal-chelating properties of the TP ring have also been exploited to generate candidate treatments for cancer and parasitic diseases. In the present review article, we discuss recent applications of the TP scaffold in medicinal chemistry, and provide an overview of its properties and methods of synthesis.

Continued exploration of 1,2,4-oxadiazole periphery for carbonic anhydrase-targeting primary arene sulfonamides: Discovery of subnanomolar inhibitors of membrane-bound hCA IX isoform that selectively kill cancer cells in hypoxic environment

An expanded set of diversely substituted 1,2,4-oxadiazole-containing primary aromatic sulfonamides was synthesized and tested for inhibition of human carbonic anhydrase I, II, IX and XII isoforms. The initial biochemical profiling revealed a significantly more potent inhibition of cancer-related, membrane-bound isoform hCA IX (reaching into submicromolar range), on top of potent inhibition of hCA XII that is another cancer target. The observed structure-activity relationships have been rationalized by molecular modeling. Comparative single-concentration profiling of the carbonic anhydrase inhibitors synthesized for antiproliferative effects against normal (ARPE-19) and cancer (PANC-1) cell lines under chemically induced hypoxia conditions revealed several candidate compounds selectively targeting cancer cells. More in-depth characterization of these leads revealed two structurally related compounds that showed promising selective cytotoxicity against pancreatic cancer (PANC-1) and melanoma (SK-MEL-2) cell lines.

Triazolopyrimidine and triazolopyridine scaffolds as TDP2 inhibitors

Tyrosyl-DNA phosphodiesterase 2 (TDP2) repairs topoisomerase II (TOP2) mediated DNA damages and causes cellular resistance to clinically used TOP2 poisons. Inhibiting TDP2 can potentially sensitize cancer cells toward TOP2 poisons. Commercial compound P10A10, to which the structure was assigned as 7-phenyl triazolopyrimidine analogue 6a, was previously identified as a TDP2 inhibitor hit in our virtual and fluorescence-based biochemical screening campaign. We report herein that the hit validation through resynthesis and structure elucidation revealed the correct structure of P10A10 (Chembridge ID 7236827) to be the 5-phenyl triazolopyrimidine regioisomer 7a. Subsequent structure-activity relationship (SAR) via the synthesis of a total of 47 analogues of both the 5-phenyl triazolopyrimidine scaffold (7) and its bioisosteric triazolopyridine scaffold (17) identified four derivatives (7a, 17a, 17e, and 17z) with significant TDP2 inhibition (IC₅₀ < 50 µM), with 17z showing excellent cell permeability and no cytotoxicity.

New pyridazinone-4-carboxamides as new cannabinoid receptor type-2 inverse agonists: Synthesis, pharmacological data and molecular docking

In the last few years, cannabinoid type-2 receptor (CB₂R) selective ligands have shown a great potential as novel therapeutic drugs in several diseases. With the aim of discovering new selective cannabinoid ligands, a series of pyridazinone-4-carboxamides was designed and synthesized, and the new derivatives tested for their affinity toward the hCB₁R and hCB₂R. The 6-(4-chloro-3-methylphenyl)-2-(4-fluorobenzyl)-N-(cis-4-methylcyclohexyl)-3-oxo-2,3-dihydropyridazine-4-carboxamide (9) displayed high CB₂-affinity (K_iCB₂ = 2.0 ± 0.81 nM) and a notable selectivity (K_iCB₁/K_iCB₂ > 2000). In addition, 9 and other active new synthesized entities have demonstrated to behave as CB₂R inverse agonists in [³⁵S]-GTPγS binding assay. ADME predictions of the newly synthesized CB₂R ligands suggest a favourable pharmacokinetic profile. Docking studies disclosed the specific pattern of interactions of these derivatives. Our results support that pyridazinone-4-carboxamides represent a new promising scaffold for the development of potent and selective CB₂R ligands.

Efficient and regioselective one-step synthesis of 7-aryl-5-methyl- and 5-aryl-7-methyl-2-amino-[1,2,4]triazolo[1,5-a]pyrimidine derivatives

Two facile and efficient one-step procedures for the regioselective synthesis of 7-aryl-5-methyl- and 5-aryl-7-methyl-2-amino-[1,2,4]triazolo[1,5-a]pyrimidines.

Synthesis, molecular modeling and SAR study of novel pyrazolo[5,1-f][1,6]naphthyridines as CB2 receptor antagonists/inverse agonists

Pyrazolo[5,1-f][1,6]naphthyridine-carboxamide derivatives were synthesized and evaluated for the affinity at CB₁ and CB₂ receptors. Based on the AgOTf and proline-cocatalyzed multicomponent methodology, the ethyl 5-(p-tolyl)pyrazolo[5,1-f][1,6]naphthyridine-2-carboxylate (12) and ethyl 5-(2,4-dichlorophenyl)pyrazolo[5,1-f][1,6]naphthyridine-2-carboxylate (13) intermediates were synthesized from the appropriate o-alkynylaldehydes, p-toluenesulfonyl hydrazide and ethyl pyruvate. Most of the novel compounds feature a p-tolyl (8a-i) or a 2,4-dichlorophenyl (8j) motif at the C₅-position of the tricyclic pyrazolo[5,1-f][1,6]naphthyridine scaffold. Structural variation on the carboxamide moiety at the C₂-position includes basic monocyclic, terpenoid and adamantine-based amines. Among these derivatives, compound 8h (N-adamant-1-yl-5-(p-tolyl)pyrazolo[5,1-f][1,6]naphthyridine-2-carboxamide) exhibited the highest CB₂ receptor affinity (K_i=33nM) and a high degree of selectivity (K_iCB₁/K_iCB₂=173:1), whereas a similar trend in the near nM range was seen for the bornyl analogue (compound 8f, K_i=53nM) and the myrtanyl derivative 8j (K_i=67nM). Effects of 8h, 8f and 8j on forskolin-stimulated cAMP levels were determined, showing antagonist/inverse agonist properties for such compounds. Docking studies conducted for these derivatives and the reference antagonist/inverse agonist compound 4 (SR144528) disclosed the specific pattern of interactions probably related to the pyrazolo[5,1-f][1,6]naphthyridine scaffold as CB₂ inverse agonists.