Pyrimidine-based fluorescent COX-2 inhibitors: synthesis and biological evaluation

Design and Development of COX-II Inhibitors: Current Scenario and Future Perspective

Innate inflammation beyond a threshold is a significant problem involved in cardiovascular diseases, cancer, and many other chronic conditions. Cyclooxygenase (COX) enzymes are key inflammatory markers as they catalyze prostaglandins production and are crucial for inflammation processes. While COX-I is constitutively expressed and is generally involved in "housekeeping" roles, the expression of the COX-II isoform is induced by the stimulation of different inflammatory cytokines and also promotes the further generation of pro-inflammatory cytokines and chemokines, which affect the prognosis of various diseases. Hence, COX-II is considered an important therapeutic target for drug development against inflammation-related illnesses. Several selective COX-II inhibitors with safe gastric safety profiles features that do not cause gastrointestinal complications associated with classic anti-inflammatory drugs have been developed. Nevertheless, there is mounting evidence of cardiovascular side effects from COX-II inhibitors that resulted in the withdrawal of market-approved anti-COX-II drugs. This necessitates the development of COX-II inhibitors that not only exhibit inhibit potency but also are free of side effects. Probing the scaffold diversity of known inhibitors is vital to achieving this goal. A systematic review and discussion on the scaffold diversity of COX inhibitors are still limited. To address this gap, herein we present an overview of chemical structures and inhibitory activity of different scaffolds of known COX-II inhibitors. The insights from this article could be helpful in seeding the development of next-generation COX-II inhibitors.

Novel Benzo[4,5]imidazo[1,2-a]pyrimidine derivatives as selective Cyclooxygenase-2 Inhibitors: Design, synthesis, docking studies, and biological evaluation

The present study was aimed at the synthesis and evaluation of a new series of benzo[4,5]imidazo[1,2-a]pyrimidine having a methylsulfonyl group as COX-2 (cyclooxygenase-2) inhibitor pharmacophore. Molecular modeling studies were performed using the Autodock program, and the results demonstrated that methylsulfonyl pharmacophore was adequately placed into the COX-2 active site. The in vitro and in vivo COX-2 inhibitory effects were also evaluated. In the in vitro assay, all newly synthesized compounds showed moderate to good selectivity for the inhibition of the COX-2 enzyme. However, compound 2-(4-(methylsulfonyl) phenyl)-4-phenylbenzo[4,5]imidazo[1,2-a]pyrimidine (5a) showed the highest COX-2 inhibitory effect (IC₅₀: 0.05 μM) even more than celecoxib as the reference drug (IC₅₀: 0.06 μM). For the in vivo study, the writing reflex test was used, and the results indicated that all synthesized compounds had well dose-dependent anti-nociceptive activity. The in vivo evaluation also showed that compound 2-(4-(methylsulfonyl)phenyl)-4-(p-tolyl)benzo[4,5]imidazo[1,2-a]pyrimidine (5d) had the highest activity in the writing reflex test (ED₅₀: 5.75 mg/kg). In addition, the cytotoxicity effects of the synthesized compounds were tested on MCF-7 breast cancer cells, and all compounds showed considerable inhibitory results.

Conjugates of Lupane Triterpenoids with Arylpyrimidines: Synthesis and Anti-inflammatory Activity

Semisynthetic triterpenoid betulonic acid is of significant interest due to its biological activity and synthetic application. In this study, we report the synthesis of hybrid compounds, containing betulonic acid carboxamide and arylpyrimidine fragments. A total of 15 conjugates were prepared using the cyclocondensation reaction of new terpenoid alkynyl ketones with amidinium salts. The main synthetic approach to betulonic acid amide-derived alkynylketones was based on the cross-coupling reaction of N-(4-ethynylphenyl)- or N-(2-(4-ethynylphenyl)-1-(methoxycarbonyl)ethyl)- substituted betulonic acid carboxamide with aroylchlorides. Cyclocondensation of alkynones with amidine or guanidine hydrochlorides by reflux in MeCN in the presence of K₂CO₃ led to the formation of terpenoid pyrimidine hybrids in 52-89% isolated yield. Anti-inflammatory properties of new type of triterpenoid-pyrimidine conjugates were studied using the histamine- and concanavalin A- induced mouse paw edema models. In a model of acute inflammation betulonic acid amide-arylpyrimidines containing a 4-fluorophenyl substituent at the C-6 position of pyrimidine ring exhibited significant and selective anti-inflammatory activity. Compounds containing the 4-bromophenyl- substituent in the pyrimidine ring revealed selective anti-inflammatory activity in the model of immunogenic inflammation (concanavalin-A model). It should be noted that the methoxycarbonyl substituted ethane link between pharmacophore ligands (betulonic acid carboxamide and arylpyrimidine) has a significant effect on anti-inflammatory activity in both in vivo models of inflammation. It was shown by molecular docking that the new derivatives are incorporated into the binding site of the protein Keap1 Kelch-domain by their pyrimidine substituent with the formation of more non-covalent bonds.

Positron Emission Tomography Imaging of Autotaxin in Thyroid and Breast Cancer Models Using [18F]PRIMATX

Autotaxin (ATX) is a secreted enzyme responsible for producing lysophosphatidic acid (LPA). The ATX/LPA signaling axis is typically activated in wound healing and tissue repair processes. The ATX/LPA axis is highjacked and upregulated in the progression and persistence of several chronic inflammatory diseases, including cancer. As ATX inhibitors are now progressing to clinical testing, innovative diagnostic tools such as positron emission tomography (PET) are needed to measure ATX expression in vivo accurately. The radiotracer, [¹⁸F]PRIMATX, was recently developed and tested for PET imaging of ATX in vivo in a murine melanoma model. The goal of the present work was to further validate [¹⁸F]PRIMATX as a PET imaging agent by analyzing its in vivo metabolic stability and suitability for PET imaging of ATX in models of human 8305C thyroid tumor and murine 4T1 breast cancer. [¹⁸F]PRIMATX displayed favorable metabolic stability in vivo (65% of intact radiotracer after 60 min p.i.) and provided sufficient tumor uptake profiles in both tumor models. Radiotracer uptake could be blocked by 8-12% in 8305C thyroid tumors in the presence of ATX inhibitor AE-32-NZ70 as determined by PET and ex vivo biodistribution analyses. [¹⁸F]PRIMATX also showed high brain uptake, which was reduced by 50% through the administration of ATX inhibitor AE-32-NZ70. [¹⁸F]PRIMATX is a suitable radiotracer for PET imaging of ATX in the brain and peripheral tumor tissues.

Development of Fluorescence Imaging Probes for Labeling COX-1 in Live Ovarian Cancer Cells

Recent experimental evidence demonstrated an aberrant overexpression of cyclooxygenase-1 (COX-1) in various cancers, which has stimulated the development of COX-1-selective inhibitors as promising anticancer drugs and cancer imaging agents. Herein we describe the synthesis and validation of 3-(furan-2-yl)-N-aryl 5-amino-pyrazoles as a novel class of COX-1 inhibitors, including molecular docking studies. Among all tested compounds, 4-(5-azido-3-(furan-2-yl)-1H-pyrazol-1-yl)benzoic 17 displayed a favorable COX-1 inhibition and selectivity profile (COX-1 IC₅₀ = 0.1 μM, SI >1000 over COX-2). Compound 17 was selected as a lead structure for developing the novel COX-1-selective fluorescent probe 22. Fluorescent probe 22 was prepared via click chemistry by installing a nitro-benzoxadiazole motif as a fluorophore into the 3-(furan-2-yl)-N-aryl 5-amino-pyrazole scaffold. Fluorescence probe 22 was tested in ovarian cancer cell line OVCAR-3, confirming its usefulness for targeting and visualizing COX-1 in living cells with confocal microscopy.

Research developments in the syntheses, anti-inflammatory activities and structure-activity relationships of pyrimidines

Pyrimidines are aromatic heterocyclic compounds that contain two nitrogen atoms at positions 1 and 3 of the six-membered ring. Numerous natural and synthetic pyrimidines are known to exist. They display a range of pharmacological effects including antioxidants, antibacterial, antiviral, antifungal, antituberculosis, and anti-inflammatory. This review sums up recent developments in the synthesis, anti-inflammatory effects, and structure-activity relationships (SARs) of pyrimidine derivatives. Numerous methods for the synthesis of pyrimidines are described. Anti-inflammatory effects of pyrimidines are attributed to their inhibitory response versus the expression and activities of certain vital inflammatory mediators namely prostaglandin E2, inducible nitric oxide synthase, tumor necrosis factor-α, nuclear factor κB, leukotrienes, and some interleukins. Literature studies reveal that a large number of pyrimidines exhibit potent anti-inflammatory effects. SARs of numerous pyrimidines have been discussed in detail. Several possible research guidelines and suggestions for the development of new pyrimidines as anti-inflammatory agents are also given. Detailed SAR analysis and prospects together provide clues for the synthesis of novel pyrimidine analogs possessing enhanced anti-inflammatory activities with minimum toxicity.

Synthesis, Anti-Inflammatory Activity and Molecular Docking Studies of 1,4,5,6-Tetrahydropyrimidine-2-Carboxamides

Background: Nonsteroidal anti-inflammatory drugs (NSAIDs) are among the most commonly used drugs in the world. The widespread use of NSAIDs is associated with a number of serious side effects and complications observed for both selective and non-selective COX inhibitors. Therefore, the search for new COX inhibitors, which along with their effectiveness will have minimal side effects, is a very important and urgent task. Methods: This work studied the synthesis of new 1,4,5,6-tetrahydropyrimidine-2-carboxamides based on the reaction of 2-morpholin-4-yl-N-(het)aryl-2-thioxoacetamides with 1,3-diaminopropane. All obtained compounds were tested for anti-inflammatory activity in vitro and in silico conditions. All synthesized 1,4,5,6-tetrahydropyrimidine-2-carboxamides were tested for influence on the course of the exudative phase of the inflammatory process based on the carrageenan model of paw edema of laboratory nonlinear heterosexual white rats weighing 220-250 g, using Diclofenac as a reference. Optimization of the geometry of the studied structures and molecular docking was carried out using the ArgusLab 4.0.1 software package. Results: The target products were obtained with yields of 71-98% and easily isolated from the reaction mixture. The best anti-inflammatory activity was found in N-(4-chlorophenyl)-1,4,5,6-tetrahydropyrimidine-2-carboxamide and in N-[4-chloro-3-(trifluoromethyl)phenyl]-1,4,5,6-tetrahydropyrimidine-2-carboxamide, suppression of the inflammatory response was 46.7 and 46.4%, respectively. The results of molecular docking with COX-1 and COX-2 enzymes were in good agreement with the experimental data, R2 ˃ 0.92 and R2 ˃ 0.83, respectively. Conclusion: The compounds under study were shown to be promising as potential anti-inflammatory agents.

Multiscale time-resolved fluorescence study of a glycogen phosphorylase inhibitor combined with quantum chemistry calculations

A fluorescence study of N1-(β-d-glucopyranosyl)-N4-[2-acridin-9(10H)-onyl]-cytosine (GLAC), the first fluorescent potent inhibitor of glycogen phosphorylase (GP), in neutral aqueous solution, is presented herein. Quantum chemistry (TD-DFT) calculations show the existence of several conformers both in the ground and first excited states. They result from rotations of the acridone and cytosine moieties around an NH bridge which may lead to the formation of non-emitting charge-transfer states. The fingerprints of various conformers have been detected by time-resolved fluorescence spectroscopy (fluorescence upconversion and time-correlated single photon counting) and identified using as criteria their energy, polarization and relative population resulting from computations. Such an analysis should contribute to the design of new GP inhibitors with better fluorescence properties, suitable for imaging applications.

In situ imaging of quantum dot-AZD4547 conjugates for tracking the dynamic behavior of fibroblast growth factor receptor 3

Fibroblast growth factor receptors (FGFRs) play an important role in determining cell proliferation, differentiation, migration, and survival. Although a variety of small-molecule FGFR inhibitors have been developed for cancer therapeutics, the interaction between FGFRs and FGFR inhibitors has not been well characterized. The FGFR–inhibitor interaction can be characterized using a new imaging probe that has strong, stable signal properties for in situ cellular imaging of the interaction without quenching. We developed a kinase–inhibitor-modified quantum dot (QD) probe to investigate the interaction between FGFR and potential inhibitors. Especially, turbo-green fluorescent protein-FGFR3s were overexpressed in HeLa cells to investigate the colocalization of FGFR3 and AZD4547 using the QD-AZD4547 probe. The result indicates that this probe is useful for investigating the binding behaviors of FGFR3 with the FGFR inhibitor. Thus, this new inhibitor-modified QD probe is a promising tool for understanding the interaction between FGFR and inhibitors and for creating future high-content, cell-based drug screening strategies.