Discovery of novel anti-influenza agents via contemporary medicinal chemistry strategies (2014–2018 update)

Target-based drug design strategies to overcome resistance to antiviral agents: opportunities and challenges

Viral infections have a major impact in human health. Ongoing viral transmission and escalating selective pressure have the potential to favor the emergence of vaccine- and antiviral drug-resistant viruses. Target-based approaches for the design of antiviral drugs can play a pivotal role in combating drug-resistant challenges. Drug design computational tools facilitate the discovery of novel drugs. This review provides a comprehensive overview of current drug design strategies employed in the field of antiviral drug resistance, illustrated through the description of a series of successful applications. These strategies include technologies that enhance compound-target affinity while minimizing interactions with mutated binding pockets. Furthermore, emerging approaches such as virtual screening, targeted protein/RNA degradation, and resistance analysis during drug design have been harnessed to curtail the emergence of drug resistance. Additionally, host targeting antiviral drugs offer a promising avenue for circumventing viral mutation. The widespread adoption of these refined drug design strategies will effectively address the prevailing challenge posed by antiviral drug resistance.

A novel N-heterocycles substituted oseltamivir derivatives as potent inhibitors of influenza virus neuraminidase: discovery, synthesis and biological evaluation

Our previous studies have shown that the introduction of structurally diverse benzyl side chains at the C5-NH2 position of oseltamivir to occupy 150-cavity contributes to the binding affinity with neuraminidase and anti-influenza activity. To obtain broad-spectrum neuraminidase inhibitors, we designed and synthesised a series of novel oseltamivir derivatives bearing different N-heterocycles substituents that have been proved to induce opening of the 150-loop of group-2 neuraminidases. Among them, compound 6k bearing 4-((r)-2-methylpyrrolidin-1-yl) benzyl group exhibited antiviral activities similar to or weaker than those of oseltamivir carboxylate against H1N1, H3N2, H5N1, H5N6 and H5N1-H274Y mutant neuraminidases. More encouragingly, 6k displayed nearly 3-fold activity enhancement against H3N2 virus over oseltamivir carboxylate and 2-fold activity enhancement over zanamivir. Molecular docking studies provided insights into the explanation of its broad-spectrum potency against wild-type neuraminidases. Overall, as a promising lead compound, 6k deserves further optimisation by fully considering the ligand induced flexibility of the 150-loop.

Discovery of N-substituted oseltamivir derivatives as novel neuraminidase inhibitors with improved drug resistance profiles and favorable drug-like properties

To yield potent neuraminidase inhibitors with improved drug resistance and favorable drug-like properties, two series of novel oseltamivir derivatives targeting the 150-cavity of neuraminidase were designed, synthesized, and biologically evaluated. Among the synthesized compounds, the most potent compound 43b bearing 3-floro-4-cyclopentenylphenzyl moiety exhibited weaker or slightly improved inhibitory activity against wild-type neuraminidases (NAs) of H1N1, H5N1, and H5N8 compared to oseltamivir carboxylate (OSC). Encouragingly, 43b displayed 62.70- and 5.03-fold more potent activity than OSC against mutant NAs of H5N1-H274Y and H1N1-H274Y, respectively. In cellular antiviral assays, 43b exerted equivalent or more potent activities against H1N1, H5N1, and H5N8 compared to OSC with no significant cytotoxicity up to 200 μM. Notably, 43b displayed potent antiviral efficacy in the embryonated egg model, in which achieved a protective effect against H5N1 and H5N8 similar to OSC. Molecular docking studies were implemented to reveal the binding mode of 43b in the binding pocket. Moreover, 43b possessed improved physicochemical properties and ADMET properties compared to OSC by in silico prediction. Taken together, 43b appeared to be a promising lead compound for further investigation.

Discovery of Novel Boron-Containing N-Substituted Oseltamivir Derivatives as Anti-Influenza A Virus Agents for Overcoming N1-H274Y Oseltamivir-Resistant

To address drug resistance to influenza virus neuraminidase inhibitors (NAIs), a series of novel boron-containing N-substituted oseltamivir derivatives were designed and synthesized to target the 150-cavity of neuraminidase (NA). In NA inhibitory assays, it was found that most of the new compounds exhibited moderate inhibitory potency against the wild-type NAs. Among them, compound 2c bearing 4-(3-boronic acid benzyloxy)benzyl group displayed weaker or slightly improved activities against group-1 NAs (H1N1, H5N1, H5N8 and H5N1-H274Y) compared to that of oseltamivir carboxylate (OSC). Encouragingly, 2c showed 4.6 times greater activity than OSC toward H5N1-H274Y NA. Moreover, 2c exerted equivalent or more potent antiviral activities than OSC against H1N1, H5N1 and H5N8. Additionally, 2c demonstrated low cytotoxicity in vitro and no acute toxicity at the dose of 1000 mg/kg in mice. Molecular docking of 2c was employed to provide a possible explanation for the improved anti-H274Y NA activity, which may be due to the formation of key additional hydrogen bonds with surrounding amino acid residues, such as Arg152, Gln136 and Val149. Taken together, 2c appeared to be a promising lead compound for further optimization.

New drug approvals for 2020: Synthesis and clinical applications

53 New drugs including 38 chemical entities and 15 biologics were approved by the U.S. Food and Drug Administration during 2020. Among the marketed drugs, 34 new small molecule drugs and 4 new diagnostic agents with privileged structures and novel clinical applications represent as promising leads for the development of new drugs with the similar indications and improved therapeutic efficacy. This review is mainly focused on the clinical applications and synthetic methods of 34 small-molecule drugs newly approved by the FDA in 2020.

Dual-targeting Approach on Histamine H3 and Sigma-1 Receptor Ligands as Promising Pharmacological Tools in the Treatment of CNS-linked Disorders

With the recent market approval of Pitolisant (Wakix®), the interest in clinical application for novel multifunctional histamine H3 receptor antagonists has clearly increased. Several combinations of different H3R pharmacophores with pharmacophoric elements of other G-protein coupled receptors, transporters, or enzymes have been synthesized by numerous pharmaceutical companies and academic institutions. Since central nervous system disorders are characterized by diverse physiological dysfunctions and deregulations of a complex network of signaling pathways, optimal multipotent drugs should simultaneously and peculiarly modulate selected groups of biological targets. Interestingly, very recent studies have shown that some clinically evaluated histamine H3 receptor antagonists possess a nanomolar affinity for sigma-1 receptor binding sites, suggesting that this property might play a role in their overall efficacy. The sigma-1 receptor, unusual and yet obscure protein, is supposed to be involved in numerous CNS pathologies through neuroprotection and neuroplasticity. These two different biological structures, histamine H3 and sigma-1 receptors, combined, can represent a potential fruitful target for therapeutic developments in tackling numerous human diseases.

Discovery of highly potent and selective influenza virus neuraminidase inhibitors targeting 150-cavity

Encouraged by our earlier discovery of N1-selective inhibitors, the 150-cavity of influenza virus neuraminidases (NAs) could be further exploited to yield more potent oseltamivir derivatives. Herein, we report the design, synthesis and biological evaluation of a series of novel oseltamivir derivatives via the structural modifications at C₅-NH₂ of oseltamivir targeting 150-cavity. Among them, compound 5c bearing 4-(3-methoxybenzyloxy)benzyl group exhibited the most potent activity, which was lower or modestly improved activities than oseltamivir carboxylate (OSC) against N1 (H1N1), N1 (H5N1) and N1 (H5N1-H274Y). Specifically, there was 30-fold loss of activity against the wild-type strain H1N1. However, 5c displayed 4.85-fold more potent activity than OSC against H5N1-H274Y NA. Also, 5c demonstrated low cytotoxicity in vitro and no acute toxicity in mice. Molecular docking studies provided insights into the high potency of 5c against N1 and N1-H274Y mutant NAs. Besides, the in silico prediction of physicochemical properties and CYP enzymatic inhibitory ability of representative compounds were conducted to evaluate their drug-like properties.

Discovery and optimization of benzenesulfonamides-based hepatitis B virus capsid modulators via contemporary medicinal chemistry strategies

Hepatitis B is a vaccine-preventable, but potentially life-threatening liver infection caused by the Hepatitis B virus (HBV). It represents an important health burden, with 257 million active cases globally. Current HBV treatments using nucleos(t)ide analogs and pegylated interferons cannot alleviate the situation completely since they are unable to cure the infection or reduce the amount of viral covalently closed circular DNA (cccDNA). The HBV core protein is a small protein of 183 amino acids that participates in multiple essential functions in the HBV replicative cycle. Capsid assembly modulators that target the core protein are being developed. Sulfonamides are synthetic functional groups, found in several drugs. Herein, we provide a concise report focusing on the sulfamoylbenzamides as HBV capsid modulators, and medicinal chemistry strategies used in their design and development.