Design, synthesis and biological evaluation of novel, orally bioavailable pyrimidine-fused heterocycles as influenza PB2 inhibitors

Synthesis and structure-activity optimization of 7-azaindoles containing aza-β-amino acids targeting the influenza PB2 subunit

The PB2 subunit of influenza virus polymerase has been demonstrated as a promising drug target for anti-influenza therapy. In this work, 7-azaindoles containing aza-β³- or β^2,3 -amino acids were synthesized possessing a good binding affinity of PB2. The aza-β-amino acid moieties with diverse size, shape, steric hindrance and configuration were investigated. Then a lead HAA-09 was validated, and the attached aza-β³-amino acid moiety with acyclic tertiary carbon side chain well occupied in the key hydrophobic cavity of PB2_cap binding domain. Importantly, HAA-09 displays potent polymerase inhibition capacity, low cytotoxicity (selectivity index up to 2915) as well as robust anti-viral activity against A/WSN/33 (H1N1) virus and oseltamivir-resistant H275Y variant. Moreover, HAA-09 exhibited druggability with high plasma stability (t_1/2 ≥ 12 h) and no obvious hERG inhibition (IC₅₀ > 10 μM). Also, HAA-09 demonstrated a favorable safety profile when orally administrated in healthy mice at a high dose of 40 mg/kg QD for consecutive 3 days. Besides, in vivo therapeutic efficacy (85.7% survival observed at the day 15 post infection) was demonstrated when HAA-09 was administrated orally at 12.5 mg/kg BID starting 48 h post infection for 9 days. These data support that exploring the interactions between side chains on aza-β³- or β^2,3 -amino acid moieties and hydrophobic pocket of PB2_cap binding domain is a potential medicinal chemistry strategy for developing potent PB2 inhibitors.

Identification of N- and C-3-Modified Laudanosoline Derivatives as Novel Influenza PAN Endonuclease Inhibitors

Influenza PA_N inhibitors are of particular importance in current efforts to develop a new generation of antiviral drugs due to the growing emergence of highly pathogenic influenza viruses and the resistance to existing antiviral inhibitors. Herein, we design and synthesize a set of 1,3-cis-N-substituted-1,2,3,4-tetrahydroisoquinoline derivatives to enhance their potency by further exploiting the pockets 3 and 4 in the PA_N endonuclease based on the hit d,l-laudanosoline. Particularly, the lead compound 35 exhibited potent and broad anti-influenza virus effects with EC₅₀ values ranging from 0.43 to 1.12 μM in vitro and good inhibitory activity in a mouse model. Mechanistic studies demonstrated that 35 could bind tightly to the PA_N endonuclease of RNA-dependent RNA polymerase, thus blocking the viral replication to exert antiviral activity. Overall, our study might establish the importance of 1,2,3,4-tetrahydroisoquinoline-6,7-diol-based derivatives for the development of novel PA_N inhibitors of influenza viruses.

An approach to pharmacological targets of pyrrole family from a medicinal chemistry viewpoint

Pyrrole is one of the most widely used heterocycles in the pharmaceutical industry. Due to the importance of pyrrole structure in drug design and development, herein, we tried to conduct an extensive review of the bioactive pyrrole based compounds reported recently. The bioactivity of pyrrole derivatives varies, so in the review, we categorized them based on their direct pharmacologic targets. Therefore, readers are able to find the variety of biologic targets for pyrrole containing compounds easily. This review explains around seventy different biologic targets for pyrrole based derivatives, so, it is helpful for medicinal chemists in design and development novel bioactive compounds for different diseases. This review presents an extensive meaningful structure activity relationship for each reported structure as much as possible. The review focuses on papers published between 2018 and 2020.

Approaches for discovery of small-molecular antivirals targeting to influenza A virus PB2 subunit

Influenza is an acute respiratory infectious disease caused by influenza virus, leading to huge morbidity and mortality in humans worldwide. Despite the availability of antivirals in the clinic, the emergence of resistant strains calls for antivirals with novel mechanisms of action. The PB2 subunit of the influenza A virus polymerase is a promising target because of its vital role in the 'cap-snatching' mechanism. In this review, we summarize the technologies and medicinal chemistry strategies for hit identification, hit-to-lead and lead-to-candidate optimization, and current challenges in PB2 inhibitor development, as well as offering insights for the fight against drug resistance.

Discovery of Aryl Benzoyl Hydrazide Derivatives as Novel Potent Broad-Spectrum Inhibitors of Influenza A Virus RNA-Dependent RNA Polymerase (RdRp)

Influenza A viruses possess a high antigenic shift, and the approved anti-influenza drugs are extremely limited, which makes the development of novel anti-influenza drugs for the clinical treatment and prevention of influenza outbreaks imperative. Herein, we report a series of novel aryl benzoyl hydrazide analogs as potent anti-influenza agents. Particularly, analogs 10b, 10c, 10g, 11p, and 11q exhibited potent inhibitory activity against the avian H5N1 flu strain with EC₅₀ values ranging from 0.009 to 0.034 μM. Moreover, compound 11q exhibited nanomolar antiviral effects against both the H1N1 virus and Flu B virus and possessed good oral bioavailability and inhibitory activity against influenza A virus in a mouse model. Preliminary mechanistic studies suggested that these compounds exert anti-influenza virus effects mainly by interacting with the PB1 subunit of RNA-dependent RNA polymerase (RdRp). These results revealed that 11q has the potential to become a potent clinical candidate to combat seasonal influenza and influenza pandemics.

Synthesis and fungicidal activity of novel benzimidazole derivatives bearing pyrimidine-thioether moiety against Botrytis cinerea

BACKGROUND

Botrytis cinerea is a serious plant fungus and strongly affects the yield and quality of crops. The main control strategy is the employment of fungicides. To research for efficient fungicide with novel structure, a series of novel benzimidazole derivatives bearing pyrimidine and thioether moieties were designed and synthesized.

RESULTS

Some target compounds such as 4h, 4i, 4k, 4l, 4m, 4s, 4t and 4u exhibited notable fungicidal activities, with half maximal effective concentration (EC₅₀ ) values in the range 0.13-0.24 μg mL^-1 , which means that their activities were comparable or higher than that of carbendazim (EC₅₀ = 0.21 μg mL^-1 ). Among them, N-(4-fluorophenyl)-2-((4-(1H-benzimidazol-2-yl)-6-(4-methoxyphenyl) pyrimidin-2-yl)thio)acetamide (4m) displayed the best activity (EC₅₀ = 0.13 μg mL^-1 ). Molecular electrostatic potential analysis of 4m elucidated that the NH moiety of benzimidazole ring was located in the positive potential region and may generate hydrogen bond with target amino acid residue. Molecular docking analysis revealed that there was one hydrogen bond and one 𝜋-𝜋 interaction between 4m and target protein.

CONCLUSIONS

This study demonstrated that the benzimidazole derivatives bearing pyrimidine and thioether moieties can be further optimized as a lead compound for the control of B. cinerea. The combination of molecular electrostatic potential and molecular docking analyses may provide a valuable reference for studying the interaction between the ligand and target protein. © 2021 Society of Chemical Industry.

Synthesis and evaluation of FAK inhibitors with a 5-fluoro-7H-pyrrolo[2,3-d]pyrimidine scaffold as anti-hepatocellular carcinoma agents

Focal adhesion kinase (FAK) is a ubiquitous intracellular non-receptor tyrosine kinase, which is involved in multiple cellular functions, including cell adhesion, migration, invasion, survival, and angiogenesis. In this study, a series of 7H-pyrrolo[2,3-d]pyrimidines were designed and synthesized according to the E-pharmacophores generated by docking a library of 667 fragments into the ATP pocket of the co-crystal complex of FAK and PF-562271 (PDB ID: 3BZ3). The 5-fluoro-7H-pyrrolo[2,3-d]pyrimidine derivatives demonstrated excellent activity against FAK and the cell lines SMMC7721 and YY8103. 2-((2-((3-(Acetamidomethyl)phenyl)amino)-5-fluoro-7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino)-N-methylbenzamide (16c) was selected for further bioactivity evaluations in vivo, including preliminary pharmacokinetic profiling in rats and toxicity assays in mice, and tumor growth inhibition studies in a xenograft tumor model. The results showed that 16c did not affect the body weight gain of the animals up to a dose of 200 mg/kg, and significantly inhibited tumor growth with a tumor growth inhibition rate of 78.6% compared with the negative control group. Furthermore, phosphoantibody array analyses of a sample of the tumor suggested that 16c inhibited the malignant proliferation of hepatocellular carcinoma (HCC) cells through decreasing the phosphorylation in the FAK cascade.

A comprehensive review of in silico approaches for the prediction and modulation of aldehyde oxidase-mediated drug metabolism: The current features, challenges and future perspectives

The importance of aldehyde oxidase (AOX) in drug metabolism necessitates the development and application of the in silico rational drug design methods as an integral part of drug discovery projects for the early prediction and modulation of AOX-mediated metabolism. The current study represents an up-to-date and thorough review of in silico studies of AOX-mediated metabolism and modulation methods. In addition, the challenges and the knowledge gap that should be covered have been discussed. The importance of aldehyde oxidase (AOX) in drug metabolism is a hot topic in drug discovery. Different strategies are available for the modulation of the AOX-mediated metabolism of drugs. Application of the rational drug design methods as an integral part of drug discovery projects is necessary for the early prediction of AOX-mediated metabolism. The current study represents a comprehensive review of AOX molecular structure, AOX-mediated reactions, AOX substrates, AOX inhibition, approaches to modify AOX-mediated metabolism, prediction of AOX metabolism/substrates/inhibitors, and the AOX related structure-activity relationship (SAR) studies. Furthermore, an up-to-date and thorough review of in silico studies of AOX metabolism has been carried out. In addition, the challenges and the knowledge gap that should be covered in the scientific literature have been discussed in the current review.

Synthesis and antiviral activity of a series of novel quinoline derivatives as anti-RSV or anti-IAV agents

We report herein the synthesis of a series of novel quinoline derivatives, based on the lead compound 1a, identified from a rRSV-mGFP high-throughput screening assay. Our results revealed that target compounds 1b, 1g-h, 1af and 1ah (IC₅₀ = 3.10-6.93 μM) had good in vitro activity against RSV, which were better than 1a and ribavirin. In addition, we found that compound 1g displayed the lower cytotoxicity (CC₅₀: 2490.33 μM) and the highest selective index (SI = 673.06), suggesting its promising potential as a candidate for further development. On the other hand, compounds 1a, 1m, 1v, 1ad-1af and 1ah-1ai (IC₅₀s: 1.87-14.28 μM) were more active against IAV than or comparable to ribavirin (IC₅₀: 15.36 ± 0.93 μM). Particularly, the most active compound 1ae (IC₅₀: 1.87 ± 0.58 μM) was found to be 8.2-fold more potent than the reference drug, which could inhibit the virus transcription and replication cycle at an early stage.

Preparation of some chromeno[4,3-d]pyrido[1,2-a]pyrimidine derivatives by ultrasonic irradiation using NiFe2O4@SiO2 grafted di(3-propylsulfonic acid) nanoparticles

NiFe₂O₄@SiO₂ grafted di(3-propylsulfonic acid) was prepared by a facile method and characterized by XRD, FT-IR, SEM-EDX, TGA, and BET techniques.

Design, Synthesis, and Biological Evaluation of Novel Indoles Targeting the Influenza PB2 Cap Binding Region

In the search for novel influenza inhibitors we evaluated 7-fluoro-substituted indoles as bioisosteric replacements for the 7-azaindole scaffold of Pimodivir, a PB2 (polymerase basic protein 2) inhibitor currently in clinical development. Specifically, a 5,7-difluoroindole derivative 11a was identified as a potent and metabolically stable influenza inhibitor. 11a demonstrated a favorable oral pharmacokinetic profile and in vivo efficacy in mice. In addition, it was found that 11a was not at risk of metabolism via aldehyde oxidase, an advantage over previously described inhibitors of this class. The crystal structure of 11a bound to influenza A PB2 cap region is disclosed here and deposited to the PDB.

Investigational antiviral therapies for the treatment of influenza

INTRODUCTION

Influenza viral ribonucleoprotein complexes (vRNPs) play a key role in viral transcription and replication; hence, the recent development of novel anti-influenza drugs targeting vRNPs has garnered widespread interest.

AREAS COVERED

We discuss the function of the constituents of vRNPs and summarize those vRNPs-targeted synthetic drugs that are in preclinical and early clinical development.

EXPERT OPINION

vRNPs contain high-value drug targets; such targets include the subunits PA, PB1, PB2, and NP. Developing a new generation of antiviral therapies with strategies that utilize existing drugs, natural compounds originated from new resources and novel drug combinations may open up new therapeutic approaches to influenza.