Dynamic evolution of the sofosbuvir-associated variant A1343V in HEV-infected patients under concomitant sofosbuvir-ribavirin treatment.

Background & Aims: In the absence of a hepatitis E virus (HEV)-specific antiviral treatment, sofosbuvir has recently been shown to have antiviral activity against HEV in vivo. However, a variant, A1343V, that is strongly associated with viral relapse impedes treatment success. In this study, we investigated the occurrence of variants during sofosbuvir and ribavirin treatment in vivo and assessed the sensitivity of resistance-associated variants to concurrent treatment in cell culture. Methods: Two patients with chronic HEV infection that did not clear infection under ribavirin treatment were subsequently treated with a combination of sofosbuvir and ribavirin. We determined response to treatment by measuring liver enzymes and viral load in blood and stool. Moreover, we analyzed viral evolution using polymerase-targeted high-throughput sequencing and assessed replication fitness of resistance-associated variants using a HEV replicon system. Results: Combination treatment was successful in decreasing viral load towards the limit of quantification. However, during treatment sustained virological response was not achieved. Variants associated with sofosbuvir or ribavirin treatment emerged during treatment, including A1343V and G1634R. Moreover, A1343V, as a single or double mutation with G1634R, was associated with sofosbuvir resistance during concomitant treatment in vitro. Conclusions: These results highlight the importance of variant profiling during antiviral treatment of patients with chronic infection. Understanding how intra-host viral evolution impedes treatment success will help guide the design of next-generation antivirals. Impact and implications: The lack of hepatitis E virus (HEV)-specific antivirals to treat chronic infection remains a serious health burden. Although ribavirin, interferon and sofosbuvir have been reported as anti-HEV drugs, not all patients are eligible for treatment or clear infection, since resistant-associated variants can rapidly emerge. In this study, we analyzed the efficacy of sofosbuvir and ribavirin combination treatment in terms of HEV suppression, the emergence of resistance-associated variants and their ability to escape treatment inhibition in vitro. Our results provide novel insights into evolutionary dynamics of HEV during treatment and thus will help guide the design of next-generation antivirals.

Systematic identification and repurposing of FDA-approved drugs as antibacterial agents against Streptococcus pyogenes: In silico and in vitro studies.

Streptococcus pyogenes (Group A Streptococcus - GAS) is a human pathogen causing wide range of infections and toxin-mediated diseases in human beings of all age groups with fatality of 10-30 %. The limited success of antibiotics and the non-availability of vaccines makes GAS a global burden. The multi-subunit RNA polymerase (RNAP) is a validated bacterial therapeutic target as it is involved in transcription and can arrest growth. Of the five subunits of this enzyme complex, the ß-subunit (RpoC) has attracted specific attention as a drug target, particularly in the switch region. Here we attempt to repurpose non-antimicrobial drugs to act as RpoC inhibitors against S. pyogenes. In this study, 1826 FDA approved drugs have been identified through high-throughput virtual screening. Free Energy Perturbation (FEP) based binding free energy calculations have been performed at the final step of the virtual screening funnel to ensure high accuracy in silico results. Three compounds identified have been tested for susceptibility of S. pyogenes MTCC 442 strain and two antibiotic-resistant clinical isolates of S. pyogenes using microdilution assay. Among the three, two drugs Amlodipine Besylate (Amd) and Ranitidine hydrochloride (Rnt) have shown inhibition against all the tested strains and its mechanism of interaction with RpoC has been studied. The docked complexes were analyzed to understand the binding mode of the drugs to the target. Classical Molecular Dynamics studies for RpoC-Rnt complex and the two stable conformations of RpoC-Amd complex was carried out. Root Mean Square Deviation (RMSD), Root Mean Square Fluctuation (RMSF), Radius of Gyration (RoG) and Solvent Accessible Surface Area (SASA) of the complexes were plotted and studied. The thermodynamic parameters of protein-drug were experimentally determined using Isothermal Titration Calorimetry (ITC). Infrared spectroscopic studies and Fluorescence quenching studies provided insights into the secondary structural changes in RpoC on binding to the drugs.

New Route to the Synthesis of Novel Pyrazolo[1,5-a]pyrimidines and Evaluation of their Antimicrobial Activity as RNA Polymerase Inhibitors.

AIMS: The current study aimed to synthesize novel pyrazolo[1,5-a]pyrimidines based on 5- aminopyrazoles 3, evaluate their antimicrobial activity, and study the minimum inhibitory concentration (MIC) for the most active compounds. In addition, molecular docking studies and RNA polymerase inhibitory activity were determined. BACKGROUND: Starting with our previously reported 5-aminopyrazoles 3, a number of novel pyrazolo[1,5- a]pyrimidines were synthesized. Due to the similarity of pyrazolopyrimidine derivatives with the purine systems, pyrazolopyrimidines are important in many different biological applications, most notably as anti-tumor, antibacterial, and hepatitis C virus inhibitors. The pharmaceutical applications of the pyrazolopyrimidine derivatives were explained in several approved drugs like Indiplon, Zaloplan, and Ocinaplon. OBJECTIVE: To prepare a novel antimicrobial agent, namely pyrazolo[1,5-a]pyrimidine, reveal their structures using different spectral data, the minimum inhibitory concentration (MIC) for the most active compounds was evaluated, and both the molecular docking and the RNA polymerase inhibitory activity were determined. METHODS: A number of different pyrazolopyrimidines namely 2-(phenylamino)-6,11-dihydrobenzo[g]pyrazolo [1,5-a]quinazoline-3-carboxamides (5a-c), (E)-5,7-dimethyl-2-(phenylamino)-6-(phenyldiazenyl)pyrazolo-[1,5- a]pyrimidine-3-carboxamides (7a-c), 7-amino-2-(phenylamino) pyrazolo[1,5-a]pyrimidine-3-carboxamides (11af), 7-amino-2-(phenylamino)-5-(2-thienyl)pyrazolo[1,5-a]pyrimidine-3-carboxamides (14-f) and ethyl 7-amino-3- carbamoyl-2-(phenylamino)-5-(4-pyridyl)pyrazolo[1,5-a]pyrimidine-6-carboxylate derivatives (14g-i) were synthesized through the reaction of 5-aminopyrazoles 3 with a variety of chemical reagents. On the other hand, the evaluation of the antimicrobial activity for all the prepared compounds was screened through different strains as Gram-positive bacteria, such as staphylococcus aureus and Streptococcus mutans, and Gram-negative bacteria, such as Escherichia coli, Pseudomonas aeruginosa, and klebsiella. The antifungal activity was determined by Candids Albicans fungal strain, and the MIC of the most active compounds was measured. The molecular docking was recorded, and the RNA polymerase inhibitory activity was estimated for the high docking score compounds. RESULTS: Compounds 5a, 5b, 5c, 7a, 7b, 7c, 11d, 14b, and 14h were the most active compounds against some of the bacterial and fungal tested strains. MIC was determined for the most active tested compounds. As an antimicrobial agent, compound 7b was the most potent, with a high docking score and RNA polymerase inhibitory activity (IC50= 0.213 µg/ml) compared to Rifampicin (IC50= 0.244 µg/ml). The reactivity of the latter compound was attributed to the presence of 4-Br-C6H4 moiety. The results demonstrated that docking studies on the most active compounds in the RNA polymerase active site were consistent with in vitro assays. CONCLUSION: The resultant novel bioactive pyrazolo[1,5-a]pyrimidine derivatives were synthesized based on 5- aminopyrazole derivatives 3. The current study evaluated the antimicrobial activity for all the prepared compounds, followed by the determination of the MIC for the most potent active compounds. The molecular docking study was performed, and it was appropriate with the in vitro activity. The RNA polymerase inhibitory activity was assessed for the most active antimicrobial compounds with a high docking score (7b, 7c, 14a, 14b, 14e, 14i). Compound 7b was the most potent compound inhibiting RNA polymerase enzyme compared to the reference drug Rifampicin. Other: The novel prepared heterocyclic systems are extremely important in a variety of domains, especially biological and pharmacological ones.

Screening of potential inhibitors of COVID-19 with repurposing approach via molecular docking.

SARS-CoV-2 (COVID-19) is the causative organism for a pandemic disease with a high rate of infectivity and mortality. In this study, we aimed to assess the affinity between several available small molecule and proteins, including Abl kinase inhibitors, Janus kinase inhibitor, dipeptidyl peptidase 4 inhibitors, RNA-dependent RNA polymerase inhibitors, and Papain-like protease inhibitors, using binding simulation, to test whether they may be effective in inhibiting COVID-19 infection through several mechanisms. The efficiency of inhibitors was evaluated based on docking scores using AutoDock Vina software. Strong ligand-protein interactions were predicted among some of these drugs, that included: Imatinib, Remdesivir, and Telaprevir, and this may render these compounds promising candidates. Some candidate drugs might be efficient in disease control as potential inhibitors or lead compounds against the SARS-CoV-2. It is also worth highlighting the powerful immunomodulatory role of other drugs, such as Abivertinib that inhibits pro-inflammatory cytokine production associated with cytokine release syndrome (CRS) and the progression of COVID-19 infection. The potential role of other Abl kinase inhibitors, including Imatinib in reducing SARS-CoV and MERS-CoV viral titers, immune regulatory function and the development of acute respiratory distress syndrome (ARDS), indicate that this drug may be useful for COVID-19, as the SARS-CoV-2 genome is similar to SARS-CoV.

Myxopyronin B inhibits growth of a Fidaxomicin-resistant Clostridioides difficile isolate and interferes with toxin synthesis.

The anaerobic, gastrointestinal pathogen Clostridioides difficile can cause severe forms of enterocolitis which is mainly mediated by the toxins it produces. The RNA polymerase inhibitor Fidaxomicin is the current gold standard for the therapy of C. difficile infections due to several beneficial features including its ability to suppress toxin synthesis in C. difficile. In contrast to the Rifamycins, Fidaxomicin binds to the RNA polymerase switch region, which is also the binding site for Myxopyronin B. Here, serial broth dilution assays were performed to test the susceptibility of C. difficile and other anaerobes to Myxopyronin B, proving that the natural product is considerably active against C. difficile and that there is no cross-resistance between Fidaxomicin and Myxopyronin B in a Fidaxomicin-resistant C. difficile strain. Moreover, mass spectrometry analysis indicated that Myxopyronin B is able to suppress early phase toxin synthesis in C. difficile to the same degree as Fidaxomicin. Conclusively, Myxopyronin B is proposed as a new lead structure for the design of novel antibiotics for the therapy of C. difficile infections.

Comparison of remdesivir and favipiravir - the anti-Covid-19 agents mimicking purine RNA constituents.

By December 2019, humanity was challenged by a new infectious respiratory disease named coronavirus disease of 2019 or COVID-19. This is a viral infection based on the presence of the previously non-problematic coronavirus with assigned number 2. This virus causes severe acute respiratory distress and is known now as SARS-CoV2. Since SARS-CoV2 is an RNA virus, remdesivir and favipiravir, both broad-spectrum RNA polymerase inhibitors, were repurposed for treating COVID-19 patients. Remdesivir and favipiravir are antimetabolites, and they are structurally related to the naturally occurring structural elements of RNA. Both agents are prodrugs and must be activated intracellularly to exert their effects through numerous and different mechanisms of action. Efforts have been exerted to determine their efficacy and safety against COVID-19 through clinical trials. Clinical trials have shown an association of remdesivir with increased frequency of adverse effects (in comparison to favipiravir). Nevertheless, the data obtained with remdesivir resulted in its approval by the FDA on the 22nd of October 2020 for COVID-19 treatment. At present, remdesivir is being recommended by several treatment guidelines for the treatment of COVID-19 patients. The evidence in favor of favipiravir is compromised by the small number and low-quality of trials conducted. Favipiravir has shown various benefits when administered in mild and moderate cases of COVID-19, while remdesivir was more beneficial in more severe cases of the disease. Since the two agents are suitable for different groups of patients, both drugs can play a significant role in fighting this pandemic. The goal of this work is to summarize the information available on two antimetabolites - remdesivir and favipiravir - and to compare clinical experience obtained so far with these two agents in COVID-19 patients.

Anti-influenza A virus activity and structure-activity relationship of a series of nitrobenzoxadiazole derivatives.

Influenza viruses represent a major threat to human health and are responsible for seasonal epidemics, along with pandemics. Currently, few therapeutic options are available, with most drugs being at risk of the insurgence of resistant strains. Hence, novel approaches targeting less explored pathways are urgently needed. In this work, we assayed a library of nitrobenzoxadiazole derivatives against the influenza virus A/Puerto Rico/8/34 H1N1 (PR8) strain. We identified three promising 4-thioether substituted nitrobenzoxadiazoles (12, 17, and 25) that were able to inhibit viral replication at low micromolar concentrations in two different infected cell lines using a haemagglutination assay. We further assessed these molecules using an In-Cell Western assay, which confirmed their potency in the low micromolar range. Among the three molecules, 12 and 25 displayed the most favourable profile of activity and selectivity and were selected as hit compounds for future optimisation studies.

Tenofovir, Another Inexpensive, Well-Known and Widely Available Old Drug Repurposed for SARS-COV-2 Infection.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is spreading worldwide with different clinical manifestations. Age and comorbidities may explain severity in critical cases and people living with human immunodeficiency virus (HIV) might be at particularly high risk for severe progression. Nonetheless, current data, although sometimes contradictory, do not confirm higher morbidity, risk of more severe COVID-19 or higher mortality in HIV-infected people with complete access to antiretroviral therapy (ART). A possible protective role of ART has been hypothesized to explain these observations. Anti-viral drugs used to treat HIV infection have been repurposed for COVID-19 treatment; this is also based on previous studies on severe acute respiratory syndrome virus (SARS-CoV) and Middle East respiratory syndrome virus (MERS-CoV). Among them, lopinavir/ritonavir, an inhibitor of viral protease, was extensively used early in the pandemic but it was soon abandoned due to lack of effectiveness in clinical trials. However, remdesivir, a nucleotide analog that acts as reverse-transcriptase inhibitor, which was tested early during the pandemic because of its wide range of antiviral activity against several RNA viruses and its safety profile, is currently the only antiviral medication approved for COVID-19. Tenofovir, another nucleotide analog used extensively for HIV treatment and pre-exposure prophylaxis (PrEP), has also been hypothesized as effective in COVID-19. No data on tenofovir's efficacy in coronavirus infections other than COVID-19 are currently available, although information relating to SARS-CoV-2 infection is starting to come out. Here, we review the currently available evidence on tenofovir's efficacy against SARS-CoV-2.

Repositioning HIV protease inhibitors and nucleos(t)ide RNA polymerase inhibitors for the treatment of SARS-CoV-2 infection and COVID-19.

AIMS: SARS-CoV-2 is a single-stranded RNA virus which is part of the ß-coronavirus family (like SARS 2002 and MERS 2012). The high prevalence of hospitalization and mortality, in addition to the lack of vaccines and therapeutics, forces scientists and clinicians around the world to evaluate new therapeutic options. One strategy is the repositioning of already known drugs, which were approved drugs for other indications. SUBJECT AND METHOD: SARS-CoV-2 entry inhibitors, RNA polymerase inhibitors, and protease inhibitors seem to be valuable targets of research. At the beginning of the pandemic, the ClinicalTrials.gov webpage listed n=479 clinical trials related to the antiviral treatment of SARS-CoV-2 (01.04.2020, "SARS-CoV-2," "COVID-19," "antivirals," "therapy"), of which n=376 are still accessible online in January 2021 (10.01.2021). Taking into account further studies not listed in the CTG webpage, this narrative review appraises HIV protease inhibitors and nucleos(t)ide RNA polymerase inhibitors as promising candidates for the treatment of COVID-19. RESULTS: Lopinavir/ritonavir, darunavir/cobicistat, remdesivir, tenofovir-disoproxilfumarate, favipriravir, and sofosbuvir are evaluated in clinical studies worldwide. Study designs show a high variability and results often are contradictory. Remdesivir is the drug, which is deployed in nearly 70% of the reviewed clinical trials, followed by lopinavir/ritonavir, favipiravir, ribavirine, and sofosbuvir. DISCUSSION: This review discusses the pharmacological/clinical background and questions the rationale and study design of clinical trials with already approved HIV protease inhibitors and nucleos(t)ide RNA polymerase inhibitors which are repositioned during the SARS-CoV-2 pandemic worldwide. Proposals are made for future study design and drug repositioning of approved antiretroviral compounds.

Serious bradycardia and remdesivir for coronavirus 2019 (COVID-19): a new safety concerns.

OBJECTIVES: In recent clinical trials some cardiac arrhythmias were reported with use of remdesivir for COVID-19. To address this safety concern, we investigated whether use of remdesivir for COVID-19 is associated with an increased risk of bradycardia. METHODS: Using VigiBase®, the World Health Organization Global Individual Case Safety Reports database, we compared the cases of bradycardia reported in COVID-19 patients exposed to remdesivir with those reported in COVID-19 patients exposed to hydroxychloroquine, lopinavir/ritonavir, tocilizumab or glucocorticoids. All reports of patients with COVID-19 registered up to the 23 September 2020 were included. We conducted disproportionality analyses allowing the estimation of reporting odds ratios (RORs) with 95% CI. RESULTS: We found 302 cardiac effects including 94 bradycardia (31%) among the 2603 reports with remdesivir prescribed in COVID-19 patients. Most of the 94 reports were serious (75, 80%), and in 16 reports (17%) evolution was fatal. Compared with hydroxychloroquine, lopinavir/ritonavir, tocilizumab or glucocorticoids, the use of remdesivir was associated with an increased risk of reporting bradycardia (ROR 1.65; 95% CI 1.23-2.22). Consistent results were observed in other sensitivity analyses. DISCUSSION: This post-marketing study in a real-world setting suggests that the use of remdesivir is significantly associated with an increased risk of reporting bradycardia and serious bradycardia when compared with the use of with hydroxychloroquine, lopinavir/ritonavir, tocilizumab or glucocorticoids. This result is in line with the pharmacodynamic properties of remdesivir.

Insights into RNA-dependent RNA Polymerase Inhibitors as Antiinfluenza Virus Agents.

BACKGROUND: Influenza is a seasonal disease that affects millions of people every year and has a significant economic impact. Vaccines are the best strategy to fight this viral pathology, but they are not always available or administrable, prompting the search for antiviral drugs. RNA-dependent RNA polymerase (RdRp) recently emerged as a promising target because of its key role in viral replication and its high conservation among viral strains. DISCUSSION: This review presents an overview of the most interesting RdRp inhibitors that have been discussed in the literature since 2000. Compounds already approved or in clinical trials and a selection of inhibitors endowed with different scaffolds are described, along with the main features responsible for their activity. RESULTS: RdRp inhibitors are emerging as a new strategy to fight viral infections and the importance of this class of drugs has been confirmed by the FDA approval of baloxavir marboxil in 2018. Despite the complexity of the RdRp machine makes the identification of new compounds a challenging research topic, it is likely that in the coming years, this field will attract the interest of a number of academic and industrial scientists because of the potential strength of this therapeutic approach.

Current pharmacological modalities for management of novel coronavirus disease 2019 (COVID-19) and the rationale for their utilization: A review.

SARS-CoV-2 has caused a pandemic which is putting strain on the health-care system and global economy. There is much pressure to develop both preventative and curative therapies for SARS-CoV-2 as there is no evidence to support therapies to improve outcomes in patients with SARS-CoV-2. Medications that inhibit certain steps of virus life cycle that are currently used to treat other illnesses such as Malaria, Ebola, HIV and Hepatitis C are being studied for use against SARS-CoV-2. To date, data is limited for medications that facilitate clinical improvement of COVID-19 infections.

Synthesis, docking and antibacterial studies of more potent amine and hydrazone rifamycin congeners than rifampicin.

New rifamycin congeners (1-33) with incorporated amine and hydrazone substituents leading to lipophilic and/or basic nature and altered rigidity of modified C(3) arm were synthesized and structurally characterized in detail. NMR spectroscopic studies at different temperatures indicate two types of structures of rifamycin congeners that are realized in solution: zwitterionic and non-ionic forms in dependence of the basicity of modified C(3) arm. The presence of rifamycin congeners in these two possible forms has a significant impact on the physico-chemical parameters such as lipophilicity (clogP) and water solubility and different binding mode of the C(3) arm of antibiotic at RNAP binding pocket (molecular target) leading to different antibacterial potency. The highest antibacterial potency against S. aureus (including MRSA and MLSB strains) and S. epidermidis strains, even higher than reference rifampicin (Rif) and rifaximin (Rifx) antibiotics, was found for rifamycin congeners bearing at the C(3) arm relatively rigid and basic substituents (bipiperidine and guanidine groups). These modifications provide favorable docking mode and excellent water solubility resulting in high potency (MICs 0.0078 µg/mL what gives ∼ 8.5 nM), irrespective whether rifamycin congener is a tertiary amine (15) or hydrazone (29). In turn, for a higher antibacterial potency of rifamycin congeners against E. faecalis strain (MICs 0.5 µg/mL that is 0.6 µM) as compared to Rif and Rifx, the most crucial factors are: bulkiness and the lipophilic character of the end of the C(3) rebuilt arm.

Orientia tsutsugamushi Is Highly Susceptible to the RNA Polymerase Switch Region Inhibitor Corallopyronin A In Vitro and In Vivo.

Scrub typhus is a potentially lethal infection caused by the obligate intracellular bacterium Orientia tsutsugamushi Reports on the emergence of doxycycline-resistant strains highlight the urgent need to develop novel antiinfectives against scrub typhus. Corallopyronin A (CorA) is a novel α-pyrone compound synthesized by the myxobacterium Corallococcus coralloides that was characterized as a noncompetitive inhibitor of the switch region of the bacterial RNA polymerase (RNAP). We investigated the antimicrobial action of CorA against the human-pathogenic Karp strain of O. tsutsugamushiin vitro and in vivo The MIC of CorA against O. tsutsugamushi was remarkably low (0.0078 µg/ml), 16-fold lower than that against Rickettsia typhi In the lethal intraperitoneal O. tsutsugamushi mouse infection model, a minimum daily dose of 100 µg CorA protected 100% of infected mice. Two days of treatment were sufficient to confer protection. In contrast to BALB/c mice, SCID mice succumbed to the infection despite treatment with CorA or tetracycline, suggesting that antimicrobial treatment required synergistic action of the adaptive immune response. Similar to tetracycline, CorA did not prevent latent infection of O. tsutsugamushiin vivo However, latency was not caused by acquisition of antimicrobial resistance, since O. tsutsugamushi reisolated from latently infected BALB/c mice remained fully susceptible to CorA. No mutations were found in the CorA-binding regions of the ß and ß' RNAP subunit genes rpoB and rpoC Inhibition of the RNAP switch region of O. tsutsugamushi by CorA is therefore a novel and highly potent target for antimicrobial therapy for scrub typhus.

Novel RNA polymerase inhibitor found in soil extracts provides hope for future antibacterial drugs.

Richard H Ebright talks to Rachel Coleby, Commissioning Editor: Ebright is at Rutgers University (New Brunswick, NJ, USA), where he performs research on the structure, mechanism, and regulation of bacterial transcription and on antibacterial drug discovery targeting bacterial transcription. He has received research awards, including the Searle Scholar Award, the Walter J Johnson Prize, the Schering-Plough Award of the American Society for Biochemistry and Molecular Biology, the Waksman Award of the Theobold Smith Society, the MERIT Award of the National Institutes of Health, and membership in the American Academy of Arts and Science. He has more than 130 publications in peer-reviewed journals and more than 30 issued and pending patents.

Structural Basis of Mycobacterium tuberculosis Transcription and Transcription Inhibition.

Mycobacterium tuberculosis (Mtb) is the causative agent of tuberculosis, which kills 1.8 million annually. Mtb RNA polymerase (RNAP) is the target of the first-line antituberculosis drug rifampin (Rif). We report crystal structures of Mtb RNAP, alone and in complex with Rif, at 3.8-4.4 Å resolution. The results identify an Mtb-specific structural module of Mtb RNAP and establish that Rif functions by a steric-occlusion mechanism that prevents extension of RNA. We also report non-Rif-related compounds-Nα-aroyl-N-aryl-phenylalaninamides (AAPs)-that potently and selectively inhibit Mtb RNAP and Mtb growth, and we report crystal structures of Mtb RNAP in complex with AAPs. AAPs bind to a different site on Mtb RNAP than Rif, exhibit no cross-resistance with Rif, function additively when co-administered with Rif, and suppress resistance emergence when co-administered with Rif.

Progress of small molecular inhibitors in the development of anti-influenza virus agents.

The influenza pandemic is a major threat to human health, and highly aggressive strains such as H1N1, H5N1 and H7N9 have emphasized the need for therapeutic strategies to combat these pathogens. Influenza anti-viral agents, especially active small molecular inhibitors play important roles in controlling pandemics while vaccines are developed. Currently, only a few drugs, which function as influenza neuraminidase (NA) inhibitors and M2 ion channel protein inhibitors, are approved in clinical. However, the acquired resistance against current anti-influenza drugs and the emerging mutations of influenza virus itself remain the major challenging unmet medical needs for influenza treatment. It is highly desirable to identify novel anti-influenza agents. This paper reviews the progress of small molecular inhibitors act as antiviral agents, which include hemagglutinin (HA) inhibitors, RNA-dependent RNA polymerase (RdRp) inhibitors, NA inhibitors and M2 ion channel protein inhibitors etc. Moreover, we also summarize new, recently reported potential targets and discuss strategies for the development of new anti-influenza virus drugs.

From the Cover: Investigative Nonclinical Cardiovascular Safety and Toxicology Studies with BMS-986094, an NS5b RNA-Dependent RNA Polymerase Inhibitor.

BMS-986094, a 2'-C-methylguanosine prodrug that was in development for treatment of chronic hepatitis C infection was withdrawn from Phase 2 clinical trials because of unexpected cardiac and renal adverse events. Investigative nonclinical studies were conducted to extend the understanding of these findings using more comprehensive endpoints. BMS-986094 was given orally to female CD-1 mice (25 and 150 mg/kg/d) for 2 weeks (53/group) and to cynomolgus monkeys (15 and 30 mg/kg/d) for up to 6 weeks (2-3/sex/group for cardiovascular safety, and 5/sex/group for toxicology). Endpoints included toxicokinetics; echocardiography, telemetric hemodynamics and electrocardiography, and tissue injury biomarkers (monkey); and light and ultrastructural pathology of heart, kidney, and skeletal muscle (mouse/monkey). Dose-related and time-dependent findings included: severe toxicity in mice at 150 mg/kg/d and monkeys at 30 mg/kg/d; decreased left ventricular (LV) ejection fraction, fractional shortening, stroke volume, and dP/dt; LV dilatation, increased QTc interval, and T-wave flattening/inversion (monkeys at ≥ 15 mg/kg/d); cardiomyocyte degeneration (mice at 150 mg/kg/d and monkeys at ≥ 15 mg/kg/d) with myofilament lysis/myofbril disassembly; time-dependent proteinuria and increased urine ß-2 microglobulin, calbindin, clusterin; kidney pallor macroscopically; and tubular dilatation (monkeys); tubular regeneration (mice 150 mg/kg/d); and acute proximal tubule degeneration ultrastructurally (mice/monkeys); and skeletal muscle degeneration with increased urine myoglobin and serum sTnI. These studies identified changes not described previously in studies of BMS-986094 including premonitory cardiovascular functional changes as well as additional biomarkers for muscle and renal toxicities. Although the mechanism of potential toxicities observed in BMS-986094 studies was not established, there was no evidence for direct mitochondrial toxicity.

Hepatitis C virus infection treatment: An era of game changer direct acting antivirals and novel treatment strategies.

Chronic hepatitis C virus infection and associated liver diseases represent a major health care burden all over the world. The current standard of care, i.e. peginterferon-alfa (PEG-IFNα) plus ribavirin (RBV) are associated with frequent and sometimes serious adverse effects and contraindications, which further limit their therapeutic efficacy. The approval of first and second generation HCV protease inhibitors represents a major breakthrough in the development of novel direct acting antivirals (DAAs) against different HCV genotypes and establishes a new standard of care for chronically infected HCV genotypes 1 patients. Similarly, next generation protease inhibitors and HCV RNA polymerase inhibitors have shown better pharmacokinetics and pharmacodynamics in terms of broader HCV genotypes coverage, better safety profile, fewer drug interactions and possible once daily administration than first generation direct acting antivirals. The testing of adenovirus-based vector vaccines, which escalates the innate and acquired immune responses against the most conserved regions of the HCV genome in chimpanzees and humans, may be a promising therapeutic approach against HCV infection in coming future. This review article presents up-to-date knowledge and recent developments in HCV therapeutics, insights the shortcomings of current HCV therapies and key lessons from the therapeutic potential of improved anti-HCV treatment strategies.