Design and synthesis of 1,2,3-triazole-containing N-acyl zanamivir analogs as potent neuraminidase inhibitors

Antiviral Activity of (1S,9aR)-1-[(1,2,3-Triazol-1-yl)methyl]octahydro-1H-quinolizines from the Alkaloid Lupinine

Influenza is a disease of significant morbidity and mortality. The number of anti-influenza drugs is small; many of them stimulate the appearance of resistant strains. This article presents the results of assessing the antiviral activity of 1,2,3-triazole-containing derivatives of alkaloid lupinine for their ability to suppress the reproduction of orthomyxoviruses (influenza viruses: A/Vladivostok/2/09 (H1N1) and A/Almaty/8/98 (H3N2)). The ability of (1S,9aR)-1-[(1,2,3-triazol-1-yl)-methyl]octahydro-1H-quinolizines with aryl-, 4-((4-formylphenoxy)methyl)- or 4-((3-tert-butyl-5-ethyl-2-hydroxy-benzoyloxy)methyl)- substituents at the C-4 position of the triazole ring to reduce the infectivity of the virus when processing virus-containing material was established, indicating good prospects for the studied compounds as virucidal agents affecting extracellular virions. The experimental results demonstrated that the triazolyl lupinine derivatives exhibited varying degrees of affinity for both hemagglutinin and neuraminidase proteins. Furthermore, these compounds demonstrated inhibitory effects on the replication of influenza viruses with different antigenic subtypes. The obtained biological data are in agreement with the results of molecular docking, which showed strong binding energies of the investigated compounds under study with biological targets-hemagglutinin and neuraminidase proteins. Following the evaluation of antiviral efficacy among the studied triazolyl derivatives of lupinine, four compounds have been identified for subsequent comprehensive in vitro and in vivo investigations to further elucidate their antiviral properties.

Discovery of new quinoline derivatives bearing 1-aryl-1,2,3-triazole motif as influenza H1N1 virus neuraminidase inhibitors

Sporadically and periodically, influenza outbreaks threaten global health and the economy. Antigen drift-induced influenza virus mutations hamper antiviral drug development. Thus, a novel antiviral agent is urgently needed to address medication inefficacy issues. Herein, sixteen new quinoline-triazole hybrids 6a-h and 9a-h were prepared and evaluated in vitro against the H1N1 virus. In particular, 6d, 6e, and 9b showed promising H1N1 antiviral activity with selective index (SI) CC50/IC50 values of 15.8, 37, and 29.15. After that, the inhibition rates for various mechanisms of action (virus replication, adsorption, and virucidal activity) were investigated for the most efficient candidates 6d, 6e, and 9b. Additionally, their ability to inhibit neuraminidase was evaluated. With an IC50 value of 0.30 µM, hybrid 6d demonstrated effective and comparable inhibitory activity to Oseltamivir. Ultimately, molecular modeling investigations, encompassing molecular docking and molecular dynamic simulations, were conducted to provide a scientific basis for the observed antiviral results.

Antiviral Compounds to Address Influenza Pandemics: An Update from 2016-2022

In recent decades, the world has gained experience of the dangerous effects of pandemic events caused by emerging respiratory viruses. In particular, annual epidemics of influenza are responsible for severe illness and deaths. Even if conventional influenza vaccines represent the most effective tool for preventing virus infections, they are not completely effective in patients with severe chronic disease and immunocompromised and new small molecules have emerged to prevent and control the influenza viruses. Thus, the attention of chemists is continuously focused on the synthesis of new antiviral drugs able to interact with the different molecular targets involved in the virus replication cycle. To date, different classes of influenza viruses inhibitors able to target neuraminidase enzyme, hemagglutinin protein, Matrix-2 (M2) protein ion channel, nucleoprotein or RNAdependent RNA polymerase have been synthesized using several synthetic strategies comprising the chemical modification of currently used drugs. The best results, in terms of inhibitory activity, are in the nanomolar range and have been obtained from the chemical modification of clinically used drugs such as Peramivir, Zanamivir, Oseltamir, Rimantadine, as well as sialylated molecules, and hydroxypyridinone derivatives. The aim of this review is to report, covering the period 2016-2022, the most recent routes related to the synthesis of effective influenza virus inhibitors.

Structurally various p-terphenyls with neuraminidase inhibitory from a sponge derived fungus Aspergillus sp. SCSIO41315

Guided by Global Natural Products Social molecular networking, 14 new p-terphenyl derivatives, asperterphenyls A-N (1-14), together with 20 known p-terphenyl derivatives (15-34), were obtained from a sponge derived fungus Aspergillus sp. SCSIO41315. Among them, new compounds 2-8 and 15-17 were ten pairs of enantiomers. Comprehensive methods such as chiral-phase HPLC analysis, ECD calculations and X-ray diffraction analysis were applied to determine the absolute configurations. Asperterphenyls B (2) and C (3) represented the first reported natural p-terphenyl derivatives possessing a dicarboxylic acid system. Asperterphenyl A (1) displayed neuraminidase inhibitory activity with an IC₅₀ value of 1.77 ± 0.53 µM and could efficiently inhibit infection of multiple strains of H1N1 with IC₅₀ values from 0.67 ± 0.28 to 1.48 ± 0.60 µM through decreasing viral plaque formation in a dose-dependent manner, which suggested that asperterphenyl A (1) might be exploited as a potential antiviral compound in the pharmaceutical fields.

Discovery of novel thiophene derivatives as potent neuraminidase inhibitors

Neuraminidase (NA) is an important target for the treatment of influenza. In this study, a new lead NA inhibitor, 4 (ZINC01121127), was discovered by pharmacophore-based virtual screening and molecular dynamic (MD) simulation. Some novel NA inhibitors containing thiophene ring were synthesized by optimizing the skeleton of the lead compound 4. Compound 4b had the most potent inhibitory activity against NA (IC₅₀ = 0.03 μM), which was better than the positive control oseltamivir carboxylate (IC₅₀ = 0.06 μM). 4b (EC₅₀ = 1.59 μM) also exhibits excellent antiviral activity against A/chicken/Hubei/327/2004 (H5N1-DW), which is superior to the reference drug OSC (EC₅₀ = 5.97 μM). Molecular docking study shows that the thiophene moiety plays an essential role in compound 4b, which can bind well to the active site of NA. The good activity of 4b may be also ascribed to the extending of quinoline ring into the 150-cavity. The results of this study may provide an insightful help for the development of new NA inhibitors.

Direct access to various C3-substituted sialyl glycal derivatives from 3-iodo-sialyl glycals

A new and efficient method was developed for the synthesis of C3-substituted sialyl glycals that are useful for novel sialidase inhibitor discovery. This method was based on the cross-coupling reactions of 3-iodo-sialyl glycal methyl ester with boronic acids, alkenes and alkynes to directly introduce various functional groups to the sialyl glycal C3-position. A series of C3-aryl, alkyl, alkenyl, and alkynyl derivatives of sialyl glycal were efficiently and conveniently synthesized for the first time by this method, which has demonstrated its wide application scope.

Discovery of hydrazide-containing oseltamivir analogues as potent inhibitors of influenza A neuraminidase

Neuraminidase (NA) inhibitors play a prime role in treating influenza. However, a variety of viruses containing mutant NAs have developed severe drug resistance towards NA inhibitors, so it is of crucial significance to solve this problem. Encouraged by urea-containing compound 12 disclosed by our lab, we designed a series of oseltamivir derivatives bearing hydrazide fragment for targeting the 150 cavity. Among the synthesized compounds, compound 17a showed 8.77-fold, 4.12-fold, 203-fold and 6.23-fold more potent activity than oseltamivir carboxylate against NAs from H5N1, H1N1, H5N1-H274Y, H1N1-H274Y, respectively. Meanwhile, the best compound 17a exhibited satisfactory metabolic stability in vitro. This study offers an important reference for the structural optimization of oseltamivir aiming at potent inhibition against H274Y mutant of NAs.

Five Novel Non-Sialic Acid-Like Scaffolds Inhibit In Vitro H1N1 and H5N2 Neuraminidase Activity of Influenza a Virus

Neuraminidase (NA) of influenza viruses enables the virus to access the cell membrane. It degrades the sialic acid contained in extracellular mucin. Later, it is responsible for releasing newly formed virions from the membrane of infected cells. Both processes become key functions within the viral cycle. Therefore, it is a therapeutic target for research of the new antiviral agents. Structure–activity relationships studies have revealed which are the important functional groups for the receptor–ligand interaction. Influenza virus type A NA activity was inhibited by five scaffolds without structural resemblance to sialic acid. Intending small organic compound repositioning along with drug repurposing, this study combined in silico simulations of ligand docking into the known binding site of NA, along with in vitro bioassays. The five proposed scaffolds are N-acetylphenylalanylmethionine, propanoic 3-[(2,5-dimethylphenyl) carbamoyl]-2-(piperazin-1-yl) acid, 3-(propylaminosulfonyl)-4-chlorobenzoic acid, ascorbic acid (vitamin C), and 4-(dipropylsulfamoyl) benzoic acid (probenecid). Their half maximal inhibitory concentration (IC₅₀) was determined through fluorometry. An acidic reagent 2′-O-(4-methylumbelliferyl)-α-dN-acetylneuraminic acid (MUNANA) was used as substrate for viruses of human influenza H1N1 or avian influenza H5N2. Inhibition was observed in millimolar ranges in a concentration-dependent manner. The IC₅₀ values of the five proposed scaffolds ranged from 6.4 to 73 mM. The values reflect a significant affinity difference with respect to the reference drug zanamivir (p < 0.001). Two compounds (N-acetyl dipeptide and 4-substituted benzoic acid) clearly showed competitive mechanisms, whereas ascorbic acid reflected non-competitive kinetics. The five small organic molecules constitute five different scaffolds with moderate NA affinities. They are proposed as lead compounds for developing new NA inhibitors which are not analogous to sialic acid.

Design, synthesis and biological evaluation of oseltamivir derivatives containing pyridyl group as potent inhibitors of neuraminidase for influenza A

Influenza A neuraminidase plays an indispensable role in the process of replication and transmission of influenza, so the neuraminidase inhibition can prevent the reproduction of the viruses therefore achieve the effect of treatment of influenza. However, drug resistance of neuraminidase inhibitors such as oseltamivir highlights the need to develop novel structural neuraminidase inhibitors. Here we explored a series of oseltamivir derivatives bearing pyridyl group. Among them, compound 23b exhibiting potent inhibitory activity against neuraminidase from H5N1 subtype was comparable to oseltamivir carboxylate. Cytopathic effect inhibition assay in MDCK cells indicated that compound 23b exerted powerful inhibitions on influenza viruses. And compound 23b were nontoxic to MDCK cells. Meanwhile, compound 23b showed high stability towards rat liver microsomes, human liver microsomes and human plasma. This research enriched the structural type of neuraminidase inhibitors.

Development of effective anti-influenza drugs: congeners and conjugates - a review

Influenza is a long-standing health problem. For treatment of seasonal flu and possible pandemic infections, there is a need to develop new anti-influenza drugs that have good bioavailability against a broad spectrum of influenza viruses, including the resistant strains. Relenza™ (zanamivir), Tamiflu™ (the phosphate salt of oseltamivir), Inavir™ (laninamivir octanoate) and Rapivab™ (peramivir) are four anti-influenza drugs targeting the viral neuraminidases (NAs). However, some problems of these drugs should be resolved, such as oral availability, drug resistance and the induced cytokine storm. Two possible strategies have been applied to tackle these problems by devising congeners and conjugates. In this review, congeners are the related compounds having comparable chemical structures and biological functions, whereas conjugate refers to a compound having two bioactive entities joined by a covalent bond. The rational design of NA inhibitors is based on the mechanism of the enzymatic hydrolysis of the sialic acid (Neu5Ac)-terminated glycoprotein. To improve binding affinity and lipophilicity of the existing NA inhibitors, several methods are utilized, including conversion of carboxylic acid to ester prodrug, conversion of guanidine to acylguanidine, substitution of carboxylic acid with bioisostere, and modification of glycerol side chain. Alternatively, conjugating NA inhibitors with other therapeutic entity provides a synergistic anti-influenza activity; for example, to kill the existing viruses and suppress the cytokines caused by cross-species infection.

Exploring the Chemistry and Therapeutic Potential of Triazoles: A Comprehensive Literature Review

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Triazole is a valuable platform in medicinal chemistry, possessing assorted pharmacological properties, which could play a major role in the common mechanisms associated with various disorders like cancer, infections, inflammation, convulsions, oxidative stress and neurodegeneration. Structural modification of this scaffold could be helpful in the generation of new therapeutically useful agents. Although research endeavors are moving towards the growth of synthetic analogs of triazole, there is still a lot of scope to achieve drug discovery break-through in this area. Upcoming therapeutic prospective of this moiety has captured the attention of medicinal chemists to synthesize novel triazole derivatives. The authors amalgamated the chemistry, synthetic strategies and detailed pharmacological activities of the triazole nucleus in the present review. Information regarding the marketed triazole derivatives has also been incorporated. The objective of the review is to provide insights to designing and synthesizing novel triazole derivatives with advanced and unexplored pharmacological implications.

Design, synthesis and biological evaluation of novel zanamivir derivatives as potent neuraminidase inhibitors

Neuraminidase (NA) is an important antiviral drug target. Zanamivir is one of the most potent NA inhibitors. In this paper, a series of zanamivir derivatives as potential NA inhibitors were studied by combination of molecular modeling techniques including 3D-QSAR, molecular docking, and molecular dynamics (MD) simulation. The results show that the best CoMFA (comparative molecular field analysis) model has q² = 0.728 and r² = 0.988, and the best CoMSIA (comparative molecular similarity indices analysis) model has q² = 0.750 and r² = 0.981, respectively. The built 3D-QSAR models show significant statistical quality and excellent predictive ability. Seven new NA inhibitors were designed and predicted. 20 ns of MD simulations were carried out and their binding free energies were calculated. Two designed compounds were selected to be synthesized and biologically evaluated by NA inhibition and virus inhibition assays. One compound (IC₅₀ = 0.670 µM, SI > 149) exhibits excellent antiviral activity against A/WSN/33 H1N1, which is superior to the reference drug zanamivir (IC₅₀ = 0.873 µM, SI > 115). The theoretical and experimental results may provide reference for development of new anti-influenza drugs.

Discovery of (E)-1-amino-4-phenylbut-3-en-2-ol derivatives as novel neuraminidase inhibitors

Neuraminidase has been considered as an important target for designing agents against influenza viruses. In a discovery of anti-influenza agents with epigoitrin as the initial lead compound, a series of 1-amino-2-alkanols were synthesized and biologically evaluated. The in vitro evaluation indicated that (E)-1-amino-4-phenylbut-3-en-2-ol (C1) had better inhibitory activities than 2-amino-1-arylethan-1-ol derivatives. To our surprise, sulfonation of C1 with 4-methoxybenzenesulfonyl chloride afforded more active inhibitor II with up to 6.4 μM IC₅₀ value against neuraminidase. Furthermore, docking of inhibitor II into the active site of NA found that the H atoms in both NH₂ and OH groups of inhibitor II were the key factors for potency. Molecular docking research did not explained very well the observed structure-activity relationship (SAR) from amino acid residue level, but also aided the discovery of (E)-1-amino-4-phenylbut-3-en-2-ol derivatives as novel and potent NA inhibitors.

Exploration of the 150 cavity and the role of serendipity in the discovery of inhibitors of influenza virus A neuraminidase

Influenza pandemics are an ongoing threat for the human population, as the avian influenza viruses H5N1 and H7N9 continue to circulate in the bird population and the chance of avian to human transmission increases. Neuraminidase, a glycoprotein located on the surface of the influenza virus, plays a crucial role in the viral replication process and, hence, has proven to be a useful target enzyme for the treatment of influenza infections. The discovery that certain subtypes of influenza neuraminidase have an additional cavity, the 150 cavity, near the substrate binding site has triggered considerable interest in the design of influenza inhibitors that exploit this feature. Currently available antiviral drugs, neuraminidase inhibitors oseltamivir and zanamivir, were designed using crystal structures predating this discovery by some years. This mini review is aimed at summarizing our group’s efforts, together with related work from other groups, on neuraminidase inhibitors that are designed to exploit both the catalytic site and the 150 cavity. The design of a parent scaffold that yields a potent inhibitor that is active in cell culture assays and retains activity against several neuraminidases from mutant strains is also described. Finally, the role of serendipity in the discovery of a new class of potent neuraminidase inhibitors with a novel spirolactam scaffold is also highlighted.

Synthesis and biological evaluation of NH2-acyl oseltamivir analogues as potent neuraminidase inhibitors

Neuraminidase inhibitors can deter nascent viruses from infecting intact cells by preventing their release from host cells. Herein, a neuraminidase inhibitor 11b absent of basic moieties was discovered in the process of searching for inhibitors targeting 150 cavity. It exhibited potent inhibitions against wild-type neuraminidases from group 1 (H5N1 and H1N1) and group 2 (H7N9) subtypes with IC₅₀ values similar to those of oseltamivir carboxylate. Moreover, 11b showed moderate inhibitions against mutant neuraminidases from H5N1-H274Y and H1N1-H274Y with IC₅₀ values of 2075 nM and 1382 nM, which were inferior to those of oseltamivir carboxylate (6095 nM and 4071 nM). The results were not consistent with the recognized SARs that a basic moiety was an indispensable part of a potent inhibitor.