Discovery of dapivirine, a nonnucleoside HIV-1 reverse transcriptase inhibitor, as a broad-spectrum antiviral against both influenza A and B viruses

Antiviral effects and mechanism of Qi pi pill against influenza viruses

BACKGROUND

Qi pi pill (QPP), which contains Renshen, Baizhu, Fuling, Gancao, Chenpi, Shanyao, Lianzi, Shanzha, Liushenqu, Maiya, and Zexie, was recommended for preventing and treating COVID-19 in Shandong Province (China). However, the mechanism by which QPP treats infectious diseases remains unclear. This study aims to investigate the therapeutic effect of QPP in vitro and on acute influenza infection in mice, exploring its mechanism of action against influenza A virus (IAV).

METHODS

The in vitro activity of QPP was assessed using dose-response curve analysis and titer reduction assay, and its antiviral mechanism was identified in vitro by real-time polymerase chain reaction (PCR), time-of-addition, and enzymatic assays. The antiviral efficacy of QPP was further evaluated in vivo using BALB/c mice infected with IAV. At the same time, each single Chinese herbal medicine in QPP was evaluated to preliminarily identify those with antiviral effects.

RESULTS

In vitro results showed that QPP exhibited a higher potency antiviral effect against both influenza A and B viruses, inhibiting viral RNA replication and release by targeting RNA-dependent RNA polymerase and neuraminidase. Additionally, QPP significantly decreased the expression of inflammatory cytokines in A549 cells. In vivo study revealed that QPP significantly reduced the lung index and viral load in lung tissue of mice infected with IAV. Renshen, Gancao, Zexie, and Lianzi were the Chinese herbal medicines from QPP that showed anti-IAV activity.

CONCLUSION

The antiviral activity of QPP targets IAV replication and release, cytokine modulation in host cells, and provides protection in mice with acute influenza infection.

6-aryloxy-2-aminopyrimidine-benzonitrile hybrids as anti-infective agents: Synthesis, bioevaluation, and molecular docking

This report explores the potential of novel 6-aryloxy-2-aminopyrimidine-benzonitrile scaffolds as promising anti-infective agents in the face of the increasing threat of infectious diseases. Starting from 2-amino-4,6-dichloropyrimidine, a series of 24 compounds inspired from the antiviral drugs dapivirine, etravirine, and rilpivirine were designed and synthesized via a two-step reaction sequence in good yields. Biological testing of synthetic analogs revealed potent inhibition against both viral and tuberculosis targets. Notably, compounds 5p (2,4-dimethyl substitution; IC50 = 44 ± 4.9 µM; selectivity index [SI] = 20) and 5 s (3-thiophenphenyl; IC50 = 6 ± 1 µM; SI = 120) showed significant antiviral activity against pandemic influenza virus A/Puerto Rico/8/34 (H1N1) with positive toxicity profiles and also exhibited good IC50 values (5p, IC50 = 10 ± 2 µM; SI = 9 and 5 s, IC50 = 16 ± 2 µM; SI = 60) against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (Wuhan strain) compared with favipiravir. In addition, analogs 5a, 5r, 5t, and 5u showed good antitubercular activity against Mycobacterium tuberculosis H37Rv strain and compounds 3, 5f, 5n, and 5q showed moderate antibacterial activity against gram+ve and gram-ve bacterial strains, suggesting that this scaffold has a broad spectrum of therapeutic effects.

Platelet distribution width as an useful indicator of influenza severity in children

PURPOSE

The present study aims to investigate the potential of platelet distribution width as an useful parameter to assess the severity of influenza in children.

METHODS

Baseline characteristics and laboratory results were collected and analyzed. Receiver operating characteristic (ROC) curve analysis was used to joint detection of inflammatory markers for influenza positive children, and the scatter-dot plots were used to compare the differences between severe and non-severe group.

RESULTS

Influenza B positive children had more bronchitis and pneumonia (P < 0.05), influenza A infected children had more other serious symptoms (P = 0.007). Neutrophil count, lymphocyte count, neutrophil-to-lymphocyte ratio (NLR), and platelet parameters performed differently among < 4 years and ≥ 4 years children with influenza. Combined detection of platelet parameters and other indicators could better separate healthy children from influenza infected children than single indicator detection. The levels of platelet distribution width of children with severe influenza (A and B) infection was significantly dropped, compared with non-severe group (P < 0.05).

CONCLUSIONS

Platelet distribution width could be a very useful and economic indicator in distinction and severity assessment for children with influenza.

Identification of the Imidazo[1,2-a]pyrazine Derivative as a Potential Influenza Virus Nucleoprotein Inhibitor

Influenza A viruses (IAVs) have gradually developed resistance to FDA-approved drugs, which increases the need to discover novel antivirals with new mechanisms of action. Here, we used a phenotypic screening strategy and discovered that the imidazo[1,2-a]pyrazine derivative A4 demonstrates potent and broad-spectrum anti-influenza activity, especially for the oseltamivir-resistant H1N1/pdm09 strain. Indirect immunofluorescence assays revealed that A4 induces clustering of the viral nucleoprotein (NP) and prevents its nuclear accumulation. Furthermore, upon conducting binding analyses between A4 and the influenza NP using surface plasmon resonance assays and molecular docking simulations, we were able to confirm that A4 binds directly to the viral NP. Additionally, A4 exhibits high human plasma metabolic stability (remaining120 min > 90%, T1/2 = 990 min) and moderate inhibitory effects on CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 as well as low acute toxicity in Kunming mice. Overall, this study provides valuable insights and lays the groundwork for future efforts in medicinal chemistry to identify effective drugs against influenza.

Water-Soluble Fullerene C60 Derivatives Are Effective Inhibitors of Influenza Virus Replication

The influenza virus genome features a very high mutation rate leading to the rapid selection of drug-resistant strains. Due to the emergence of drug-resistant strains, there is a need for the further development of new potent antivirals against influenza with a broad activity spectrum. Thus, the search for a novel, effective broad-spectrum antiviral agent is a top priority of medical science and healthcare systems. In this paper, derivatives based on fullerenes with broad virus inhibiting activities in vitro against a panel of influenza viruses were described. The antiviral properties of water-soluble fullerene derivatives were studied. It was demonstrated that the library of compounds based on fullerenes has cytoprotective activity. Maximum virus-inhibiting activity and minimum toxicity were found with compound 2, containing residues of salts of 2-amino-3-cyclopropylpropanoic acid (CC₅₀ > 300 µg/mL, IC₅₀ = 4.73 µg/mL, SI = 64). This study represents the initial stage in a study of fullerenes as anti-influenza drugs. The results of the study lead us conclude that five leading compounds (1-5) have pharmacological prospects.

Cytopathic Effect Assay and Plaque Assay to Evaluate in vitro Activity of Antiviral Compounds Against Human Coronaviruses 229E, OC43, and NL63

Coronaviruses are important human pathogens, among which the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent for the COVID-19 pandemic. To combat the SARS-CoV-2 pandemic, there is a pressing need for antivirals, especially broad-spectrum antivirals that are active against all seven human coronaviruses (HCoVs). For this reason, we are interested in developing antiviral assays to expedite the drug discovery process. Here, we provide the detailed protocol for the cytopathic effect (CPE) assay and the plaque assay for human coronaviruses 229E (HCoV-229E), HCoV-OC43, and HCoV-NL63, to identify novel antivirals against HCoVs. Neutral red was used in the CPE assay, as it is relatively inexpensive and more sensitive than other reagents. Multiple parameters including multiplicity of infection, incubation time and temperature, and staining conditions have been optimized for CPE and plaque assays for HCoV-229E in MRC-5, Huh-7, and RD cell lines; HCoV-OC43 in RD, MRC-5, and BSC-1 cell lines, and HCoV-NL63 in Vero E6, Huh-7, MRC-5, and RD cell lines. Both CPE and plaque assays have been calibrated with the positive control compounds remdesivir and GC-376. Both CPE and plaque assays have high sensitivity, excellent reproducibility, and are cost-effective. The protocols described herein can be used as surrogate assays in the biosafety level 2 facility to identify entry inhibitors and protease inhibitors for SARS-CoV-2, as HCoV-NL63 also uses ACE2 as the receptor for cell entry, and the main proteases of HCoV-OC43 and SARS-CoV-2 are highly conserved. In addition, these assays can also be used as secondary assays to profile the broad-spectrum antiviral activity of existing SARS-CoV-2 drug candidates.

Brilacidin, a COVID‐19 Drug Candidate, demonstrates broad‐spectrum antiviral activity against human coronaviruses OC43, 229E and NL63 through targeting both the virus and the host cell

Brilacidin, a mimetic of host defense peptides (HDPs), is currently in Phase 2 clinical trial as an antibiotic drug candidate. A recent study reported that brilacidin has antiviral activity against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) by inactivating the virus. In this study, we discovered an additional mechanism of action of brilacidin by targeting heparan sulfate proteoglycans (HSPGs) on the host cell surface. Brilacidin, but not acetyl brilacidin, inhibits the entry of SARS‐CoV‐2 pseudovirus into multiple cell lines, and heparin, an HSPG mimetic, abolishes the inhibitory activity of brilacidin on SARS‐CoV‐2 pseudovirus cell entry. In addition, we found that brilacidin has broad‐spectrum antiviral activity against multiple human coronaviruses (HCoVs) including HCoV‐229E, HCoV‐OC43, and HCoV‐NL63. Mechanistic studies revealed that brilacidin has a dual antiviral mechanism of action including virucidal activity and binding to coronavirus attachment factor HSPGs on the host cell surface. Brilacidin partially loses its antiviral activity when heparin was included in the cell cultures, supporting the host‐targeting mechanism. Drug combination therapy showed that brilacidin has a strong synergistic effect with remdesivir against HCoV‐OC43 in cell culture. Taken together, this study provides appealing findings for the translational potential of brilacidin as a broad‐spectrum antiviral for coronaviruses including SARS‐CoV‐2.

Brilacidin has broad‐spectrum antiviral activity against multiple human coronaviruses (HCoVs) including HCoV‐229E, HCoV‐OC43, and HCoV‐NL63

Brilacidin, but not acetyl brilacidin, inhibits the entry of SARS‐CoV‐2 pseudovirus into multiple cell lines

Heparin, an heparan sulfate proteoglycans (HSPG) mimetic, abolishes the inhibitory activity of brilacidin on SARS‐CoV‐2 pseudovirus cell entry

Brilacidin has a dual antiviral mechanism of action including virucidal activity and binding to coronavirus attachment factor HSPGs on the host cell surface.

The in vitro antiviral activity of lactoferrin against common human coronaviruses and SARS-CoV-2 is mediated by targeting the heparan sulfate co-receptor

Coronavirus disease 2019 (COVID-19) is an ongoing pandemic that lacks effective therapeutic interventions. SARS-CoV-2 infects ACE2-expressing cells and gains cell entry through either direct plasma membrane fusion or endocytosis. Recent studies have shown that in addition to ACE2, heparan sulfate proteoglycans (HSPGs) also play an important role in SARS-CoV-2 cell attachment by serving as an attachment factor. Binding of viral spike protein to HSPGs leads to the enrichment of local concentration for the subsequent specific binding with ACE2. We therefore hypothesize that blocking the interactions between viral spike protein and the HSPGs will lead to inhibition of viral replication. In this study, we report our findings of the broad-spectrum antiviral activity and the mechanism of action of lactoferrin (LF) against multiple common human coronaviruses as well as SARS-CoV-2. Our study has shown that LF has broad-spectrum antiviral activity against SARS-CoV-2, HCoV-OC43, HCoV-NL63, and HCoV-229E in cell culture, and bovine lactoferrin (BLF) is more potent than human lactoferrin. Mechanistic studies revealed that BLF binds to HSPGs, thereby blocking viral attachment to the host cell. The antiviral activity of BLF can be antagonized by the HSPG mimetic heparin. Combination therapy experiment showed that the antiviral activity of LF is synergistic with remdesivir in cell culture. Molecular modelling suggests that the N-terminal positively charged region in BLF (residues 17-41) confers the binding to HSPGs. Overall, LF appears to be a promising drug candidate for COVID-19 that warrants further investigation.

Rational design of a deuterium-containing M2-S31N channel blocker UAWJ280 with in vivo antiviral efficacy against both oseltamivir sensitive and -resistant influenza A viruses

Seasonal influenza A virus (IAV) infections are among the most important global health problems. FDA-approved antiviral therapies against IAV include neuraminidase inhibitors, M2 inhibitors, and polymerase inhibitor baloxavir. Resistance against adamantanes (amantadine and rimantadine) is widespread as virtually all IAV strains currently circulating in the human population are resistant to adamantanes through the acquisition of the S31N mutation. The neuraminidase inhibitor-resistant strains also contain the M2-S31N mutant, suggesting M2-S31N is a high-profile antiviral drug target. Here we report the development of a novel deuterium-containing M2-S31N inhibitor UAWJ280. UAWJ280 had broad-spectrum antiviral activity against both oseltamivir sensitive and -resistant influenza A strains and had a synergistic antiviral effect in combination with oseltamivir in cell culture. In vivo pharmacokinetic (PK) studies demonstrated that UAWJ280 had favourable PK properties. The in vivo mouse model study showed that UAWJ280 was effective alone or in combination with oseltamivir in improving clinical signs and survival after lethal challenge with an oseltamivir sensitive IAV H1N1 strain. Furthermore, UAWJ280 was also able to ameliorate clinical signs and increase survival when mice were challenged with an oseltamivir-resistant IAV H1N1 strain. In conclusion, we show for the first time that the M2-S31N channel blocker UAWJ280 has in vivo antiviral efficacy in mice that are infected with either oseltamivir sensitive or -resistant IAVs, and it has a synergistic antiviral effect with oseltamivir.

Overview of Viral Pneumonia Associated With Influenza Virus, Respiratory Syncytial Virus, and Coronavirus, and Therapeutics Based on Natural Products of Medicinal Plants

Viral pneumonia has been a serious threat to global health, especially now we have dramatic challenges such as the COVID-19 pandemic. Approximately six million cases of community-acquired pneumonia occur every year, and over 20% of which need hospital admission. Influenza virus, respiratory virus, and coronavirus are the noteworthy causative agents to be investigated based on recent clinical research. Currently, anaphylactic reaction and inflammation induced by antiviral immunity can be incriminated as causative factors for clinicopathological symptoms of viral pneumonia. In this article, we illustrate the structure and related infection mechanisms of these viruses and the current status of antiviral therapies. Owing to a set of antiviral regiments with unsatisfactory clinical effects resulting from side effects, genetic mutation, and growing incidence of resistance, much attention has been paid on medicinal plants as a natural source of antiviral agents. Previous research mainly referred to herbal medicines and plant extracts with curative effects on viral infection models of influenza virus, respiratory virus, and coronavirus. This review summarizes the results of antiviral activities of various medicinal plants and their isolated substances, exclusively focusing on natural products for the treatment of the three types of pathogens that elicit pneumonia. Furthermore, we have introduced several useful screening tools to develop antiviral lead compounds.

Discovery of Potent and Broad-Spectrum Pyrazolopyridine-Containing Antivirals against Enteroviruses D68, A71, and Coxsackievirus B3 by Targeting the Viral 2C Protein

The enterovirus genus of the picornavirus family contains many important human pathogens. EV-D68 primarily infects children, and the disease manifestations range from respiratory illnesses to neurological complications such as acute flaccid myelitis (AFM). EV-A71 is a major pathogen for the hand, foot, and mouth disease (HFMD) in children and can also lead to AFM and death in severe cases. CVB3 infection can cause cardiac arrhythmias, acute heart failure, as well as type 1 diabetes. There is currently no FDA-approved antiviral for any of these enteroviruses. In this study, we report our discovery and development of pyrazolopyridine-containing small molecules with potent and broad-spectrum antiviral activity against multiple strains of EV-D68, EV-A71, and CVB3. Serial viral passage experiments, coupled with reverse genetics and thermal shift binding assays, suggested that these molecules target the viral protein 2C. Overall, the pyrazolopyridine inhibitors represent a promising class of candidates for the urgently needed nonpolio enterovirus antivirals.

Boceprevir, Calpain Inhibitors II and XII, and GC-376 Have Broad-Spectrum Antiviral Activity against Coronaviruses

As the COVID-19 pandemic continues to unfold, the morbidity and mortality are increasing daily. Effective treatment for SARS-CoV-2 is urgently needed. We recently discovered four SARS-CoV-2 main protease (Mpro) inhibitors including boceprevir, calpain inhibitors II and XII, and GC-376 with potent antiviral activity against infectious SARS-CoV-2 in cell culture. In this study, we further characterized the mechanism of action of these four compounds using the SARS-CoV-2 pseudovirus neutralization assay. It was found that GC-376 and calpain inhibitors II and XII have a dual mechanism of action by inhibiting both viral Mpro and host cathepsin L in Vero cells. To rule out the cell-type dependent effect, the antiviral activity of these four compounds against SARS-CoV-2 was also confirmed in type 2 transmembrane serine protease-expressing Caco-2 cells using the viral yield reduction assay. In addition, we found that these four compounds have broad-spectrum antiviral activity in inhibiting not only SARS-CoV-2 but also SARS-CoV, and MERS-CoV, as well as human coronaviruses (CoVs) 229E, OC43, and NL63. The mechanism of action is through targeting the viral Mpro, which was supported by the thermal shift-binding assay and enzymatic fluorescence resonance energy transfer assay. We further showed that these four compounds have additive antiviral effect when combined with remdesivir. Altogether, these results suggest that boceprevir, calpain inhibitors II and XII, and GC-376 might be promising starting points for further development against existing human coronaviruses as well as future emerging CoVs.

A SARS-CoV-2 cytopathicity dataset generated by high-content screening of a large drug repurposing collection

SARS-CoV-2 is a novel coronavirus responsible for the COVID-19 pandemic, in which acute respiratory infections are associated with high socio-economic burden. We applied high-content screening to a well-defined collection of 5632 compounds including 3488 that have undergone previous clinical investigations across 600 indications. The compounds were screened by microscopy for their ability to inhibit SARS-CoV-2 cytopathicity in the human epithelial colorectal adenocarcinoma cell line, Caco-2. The primary screen identified 258 hits that inhibited cytopathicity by more than 75%, most of which were not previously known to be active against SARS-CoV-2 in vitro. These compounds were tested in an eight-point dose response screen using the same image-based cytopathicity readout. For the 67 most active molecules, cytotoxicity data were generated to confirm activity against SARS-CoV-2. We verified the ability of known inhibitors camostat, nafamostat, lopinavir, mefloquine, papaverine and cetylpyridinium to reduce the cytopathic effects of SARS-CoV-2, providing confidence in the validity of the assay. The high-content screening data are suitable for reanalysis across numerous drug classes and indications and may yield additional insights into SARS-CoV-2 mechanisms and potential therapeutic strategies.

Anti-Influenza Drug Discovery and Development: Targeting the Virus and Its Host by All Possible Means

Infections by influenza virus constitute a major and recurrent threat for human health. Together with vaccines, antiviral drugs play a key role in the prevention and treatment of influenza virus infection and disease. Today, the number of antiviral molecules approved for the treatment of influenza is relatively limited, and their use is threatened by the emergence of viral strains with resistance mutations. There is therefore a real need to expand the prophylactic and therapeutic arsenal. This chapter summarizes the state of the art in drug discovery and development for the treatment of influenza virus infections, with a focus on both virus-targeting and host cell-targeting strategies. Novel antiviral strategies targeting other viral proteins or targeting the host cell, some of which are based on drug repurposing, may be used in combination to strengthen our therapeutic arsenal against this major pathogen.

Boceprevir, calpain inhibitors II and XII, and GC-376 have broad-spectrum antiviral activity against coronaviruses in cell culture

As the COVID-19 pandemic continues to fold out, the morbidity and mortality are increasing daily. Effective treatment for SARS-CoV-2 is urgently needed. We recently discovered four SARS-CoV-2 main protease (Mpro) inhibitors including boceprevir, calpain inhibitors II and XII and GC-376 with potent antiviral activity against infectious SARS-CoV-2 in cell culture. Despite the weaker enzymatic inhibition of calpain inhibitors II and XII against Mpro compared to GC-376, calpain inhibitors II and XII had more potent cellular antiviral activity. This observation promoted us to hypothesize that the cellular antiviral activity of calpain inhibitors II and XII might also involve the inhibition of cathepsin L in addition to Mpro. To test this hypothesis, we tested calpain inhibitors II and XII in the SARS-CoV-2 pseudovirus neutralization assay in Vero E6 cells and found that both compounds significantly decreased pseudoviral particle entry into cells, indicating their role in inhibiting cathepsin L. The involvement of cathepsin L was further confirmed in the drug time-of-addition experiment. In addition, we found that these four compounds not only inhibit SARS-CoV-2, but also SARS-CoV, MERS-CoV, as well as human coronaviruses (CoVs) 229E, OC43, and NL63. The mechanism of action is through targeting the viral Mpro, which was supported by the thermal shift binding assay and enzymatic FRET assay. We further showed that these four compounds have additive antiviral effect when combined with remdesivir. Altogether, these results suggest that boceprevir, calpain inhibitors II and XII, and GC-376 are not only promising antiviral drug candidates against existing human coronaviruses, but also might work against future emerging CoVs.

Searching for effective antiviral small molecules against influenza A virus: A patent review

Introduction: Despite the current interest caused by SARS-Cov-2, influenza continues to be one of the most serious health concerns, with an estimated 1 billion cases across the globe, including 3-5 million severe cases and 290,000-650,000 deaths worldwide. Areas covered: This manuscript reviews the efforts made in the development of small molecules for the treatment of influenza virus, primarily focused on patent applications in the last 5 years. Attention is paid to compounds targeting key functional viral proteins, such as the M2 channel, neuraminidase, and hemagglutinin, highlighting the evolution toward new ligands and scaffolds motivated by the emergence of resistant strains. Finally, the discovery of compounds against novel viral targets, such as the RNA-dependent RNA polymerase, is discussed. Expert opinion: The therapeutic potential of antiviral agents is limited by the increasing presence of resistant strains. This should encourage research on novel strategies for therapeutic intervention. In this context, the discovery of arbidol and JNJ7918 against hemagglutinin, and current efforts on RNA-dependent RNA polymerase have disclosed novel opportunities for therapeutic treatment. Studies should attempt to expand the therapeutic arsenal of anti-flu agents, often in combined therapies, to prevent future health challenges caused by influenza virus. Abbreviations: AlphaLISA: amplified luminescent proximity homogeneous assay; HA: hemagglutinin; NA: neuraminidase; RBD: receptor binding domain; RdRp: RNA-dependent RNA polymerase; SA: sialic Acid; TBHQ: tert-butyl hydroquinone; TEVC: two-electrode voltage clamp.

A Novel Capsid Binding Inhibitor Displays Potent Antiviral Activity against Enterovirus D68

Enterovirus D68 (EV-D68) is a respiratory viral pathogen that primarily infects children under the age of 8. Although EV-D68 infection typically leads to moderate to severe respiratory illnesses, recent years have seen increasing cases of EV-D68 triggered neurological complications such as acute flaccid myelitis (AFM). There is currently no vaccine or antiviral available for EV-D68; we therefore aimed to develop potent and specific small molecule antivirals against EV-D68. In this study, we report our discovery of a viral capsid inhibitor R856932 that inhibits multiple contemporary EV-D68 strains with single-digit to submicromolar efficacy. Mechanistic studies have shown that the tetrazole compound R856932 binds to the hydrophobic pocket of viral capsid protein VP1, thereby preventing viral uncoating and release of viral genome in the infected cells. The mechanism of action of R856932 was confirmed by time-of-addition, Western blot, RT-qPCR, viral heat inactivation, serial viral passage, and reverse genetics experiments. A single mutation located at VP1, A129V, confers resistance against R856932. However, a recombination virus encoding VP1-A129V appeared to have compromised fitness of replication compared to the wild-type EV-D68 virus as shown by the competition growth assay. Overall, the hit compound identified in this study, R856932, represents a promising starting point with a confirmed mechanism of action that can be further developed into EV-D68 antivirals.

Zeylanone epoxide isolated from Diospyros anisandra stem bark inhibits influenza virus in vitro

Influenza virus infection is a public health problem, causing significant morbidity and mortality. Currently, zanamivir and oseltamivir are in common use, and there are already reports of antiviral resistance. Several studies have shown the antiviral potential of a wide variety of plant-based natural compounds, among them those of the quinone type. In this study, we evaluated the antiviral activity of naphthoquinones isolated from the stem bark of Diospyros anisandra, and we selected zeylanone epoxide (ZEP) to study its effects on influenza A and B viruses. Our results indicated that ZEP inhibits the replication of influenza A and B viruses, at early and middle stages of the replication cycle. Confined nuclear localization of the viral NP indicated that ZEP affects its intracellular distribution and reduces viral yield. This is the first report on the antiviral properties and possible mechanism of action of ZEP in vitro, showing its broad-spectrum activity against influenza A and B viruses.

Identification of NMS-873, an allosteric and specific p97 inhibitor, as a broad antiviral against both influenza A and B viruses

Influenza virus infection causes substantial morbidity and mortality worldwide. The limited efficacy of oseltamivir in delayed treatment, coupled with the increasing incidences of oseltamivir-resistant strains, calls for next-generation of antiviral drugs. In this study, we discovered NMS-873, an allosteric and specific p97 inhibitor, as a broad-spectrum influenza antiviral through forward chemical genomics screening. NMS-873 shows potent antiviral activity with low-nanomolar EC₅₀s against multiple human influenza A and B viruses, including adamantine-, oseltamivir-, or double resistant strains. Our data further showed that silencing of p97 via siRNA or inhibiting p97 by NMS-873 both inhibited virus replication and retained viral ribonucleoproteins (vRNPs) in the nucleus, confirming p97 is the drug target. Mechanistic studies have shown that the nuclear retention of vRNP with NMS-873 treatment is a combined result of two effects: the reduced viral M1 protein level (indirect effect), and the disruption of p97-NP interactions (direct effect). Taken together, our results suggest that p97 could be a novel antiviral target and its inhibitor, NMS-873, is a promising antiviral drug candidate.

Drug Repurposing Approaches for the Treatment of Influenza Viral Infection: Reviving Old Drugs to Fight Against a Long-Lived Enemy

Influenza viruses still constitute a real public health problem today. To cope with the emergence of new circulating strains, but also the emergence of resistant strains to classic antivirals, it is necessary to develop new antiviral approaches. This review summarizes the state-of-the-art of current antiviral options against influenza infection, with a particular focus on the recent advances of anti-influenza drug repurposing strategies and their potential therapeutic, regulatory and economic benefits. The review will illustrate the multiple ways to reposition molecules for the treatment of influenza, from adventitious discovery to in silico-based screening. These novel antiviral molecules, many of which targeting the host cell, in combination with conventional antiviral agents targeting the virus, will ideally enter the clinics and reinforce the therapeutic arsenal to combat influenza virus infections.

Potent and broad-spectrum cycloheptathiophene-3-carboxamide compounds that target the PA-PB1 interaction of influenza virus RNA polymerase and possess a high barrier to drug resistance

Influenza viruses are major respiratory pathogens responsible for both seasonal epidemics and occasional pandemics worldwide. The current available treatment options have limited efficacy and thus the development of new antivirals is highly needed. We previously reported the identification of a series of cycloheptathiophene-3-carboxamide compounds as influenza A virus inhibitors that act by targeting the protein-protein interactions between the PA-PB1 subunits of the viral polymerase. In this study, we characterized the antiviral properties of the most promising compounds as well as investigated their propensity to induce drug resistance. Our results show that some of the selected compounds possess potent, broad-spectrum anti-influenza activity as they efficiently inhibited the replication of several strains of influenza A and B viruses, including an oseltamivir-resistant clinical isolate, with nanomolar or low-micromolar potency. The most promising compounds specifically inhibited the PA-PB1 binding in vitro and interfered with the influenza A virus polymerase activity in a cellular context, without showing cytotoxicity. The most active PA-PB1 inhibitors showed to possess a drug resistance barrier higher than that of oseltamivir. Indeed, no viral variants with reduced susceptibility to the selected compounds emerged after serial passages of influenza A virus under drug selective pressure. Overall, our studies identified potent PA-PB1 inhibitors as promising candidates for the development of new anti-influenza drugs.

Drug Repurposing for Viral Infectious Diseases: How Far Are We?

Despite the recent advances in controlling some viral pathogens, most viral infections still lack specific treatment. Indeed, the need for effective therapeutic strategies to combat 'old', emergent, and re-emergent viruses is not paralleled by the approval of new antivirals. In the past years, drug repurposing combined with innovative approaches for drug validation, and with appropriate animal models, significantly contributed to the identification of new antiviral molecules and targets for therapeutic intervention. In this review, we describe the main strategies of drug repurposing in antiviral discovery, discuss the most promising candidates that could be repurposed to treat viral infections, and analyze the possible caveats of this trendy strategy of drug discovery.

Viral pneumonia: etiologies and treatment

Viral pathogens are increasingly recognized as a cause of pneumonia, in immunocompetent patients and more commonly among immunocompromised. Viral pneumonia in adults could present as community-acquired pneumonia (CAP), ranging from mild disease to severe disease requiring hospital admission and mechanical ventilation. Moreover, the role of viruses in hospital-acquired pneumonia and ventilator-associated pneumonia as causative agents or as co-pathogens and the effect of virus detection on clinical outcome are being investigated.More than 20 viruses have been linked to CAP. Clinical presentation, laboratory findings, biomarkers, and radiographic patterns are not characteristic to specific viral etiology. Currently, laboratory confirmation is most commonly done by detection of viral nucleic acid by reverse transcription-PCR of respiratory secretions.Apart from the US Food and Drug Administration-approved medications for treatment of influenza pneumonia, the treatment of non-influenza respiratory viruses is limited. Moreover, the evidence supporting the use of available antivirals to treat immunocompromised patients is modest at best. With the widespread use of molecular diagnostics, an aging population, and advancement in cancer therapy, physicians will face a bigger challenge in managing viral respiratory tract infections. Emphasis on infection control measures to prevent the spread of respiratory viruses especially in healthcare settings is extremely important.

Exploring Ugi-Azide Four-Component Reaction Products for Broad-Spectrum Influenza Antivirals with a High Genetic Barrier to Drug Resistance

Influenza viruses are respiratory pathogens that are responsible for seasonal influenza and sporadic influenza pandemic. The therapeutic efficacy of current influenza vaccines and small molecule antiviral drugs is limited due to the emergence of multidrug-resistant influenza viruses. In response to the urgent need for the next generation of influenza antivirals, we utilized a fast-track drug discovery platform by exploring multi-component reaction products for antiviral drug candidates. Specifically, molecular docking was applied to screen a small molecule library derived from the Ugi-azide four-component reaction methodology for inhibitors that target the influenza polymerase PAC-PB1N interactions. One hit compound 5 was confirmed to inhibit PAC-PB1N interactions in an ELISA assay and had potent antiviral activity in an antiviral plaque assay. Subsequent structure-activity relationship studies led to the discovery of compound 12a, which had broad-spectrum antiviral activity and a higher in vitro genetic barrier to drug resistance than oseltamivir. Overall, the discovery of compound 12a as a broad-spectrum influenza antiviral with a high in vitro genetic barrier to drug resistance is significant, as it offers a second line of defense to combat the next influenza epidemics and pandemics if vaccines and oseltamivir fail to confine the disease outbreak.

In Vitro Pharmacokinetic Optimizations of AM2-S31N Channel Blockers Led to the Discovery of Slow-Binding Inhibitors with Potent Antiviral Activity against Drug-Resistant Influenza A Viruses

Influenza viruses are respiratory pathogens that are responsible for both seasonal influenza epidemics and occasional influenza pandemics. The narrow therapeutic window of oseltamivir, coupled with the emergence of drug resistance, calls for the next-generation of antivirals. With our continuous interest in developing AM2-S31N inhibitors as oral influenza antivirals, we report here the progress of optimizing the in vitro pharmacokinetic (PK) properties of AM2-S31N inhibitors. Several AM2-S31N inhibitors, including compound 10b, were discovered to have potent channel blockage, single to submicromolar antiviral activity, and favorable in vitro PK properties. The antiviral efficacy of compound 10b was also synergistic with oseltamivir carboxylate. Interestingly, binding kinetic studies (K_d, K_on, and K_off) revealed several AM2-S31N inhibitors that have similar K_d values but significantly different K_on and K_off values. Overall, this study identified a potent lead compound (10b) with improved in vitro PK properties that is suitable for the in vivo mouse model studies.