The pandemic of COVID-19 has ignited a global race to locate effective therapies with drug repositioning emerging as a leading strategy due to its cost-effectiveness and established safety profiles. Remdesivir, Favipiravir, Hydroxychloroquine, and Chloroquine have been the focus of rigorous clinical trials to determine their therapeutic potential against SARS-CoV-2. This article delves into the innovative synthetic strategies behind these drugs, providing a blueprint for researchers navigating the complex landscape of antiviral development. Beyond synthesis, we explore the fascinating mechanisms of action: hydroxychloroquine and chloroquine elevate lysosomal pH to impede autophagy and viral replication; favipiravir, a nucleoside analogue, induces lethal mutagenesis or RNA chain termination and remdesivir disrupts viral RNA synthesis through delayed chain termination. By merging synthetic methodologies with mechanistic insights, this article offers a comprehensive resource aimed at accelerating the development of potent COVID-19 therapies and underscores the crucial part that chemistry in addressing global health emergencies. It also underscores the vital function of chemistry in addressing global health emergencies and highlights how innovative drug design and repurposing can provide rapid responses to emerging infectious diseases. This fusion of chemistry and virology not only advances our understanding of drug action but also paves the way for the discovery of new therapeutic agents crucial in future pandemics.

Nipah virus disease is a bat-borne zoonosis with person-to-person transmission, a case-fatality rate of 38-75%, and well recognised potential to cause a pandemic. The first reported outbreak of Nipah virus disease occurred in Malaysia and Singapore in 1998, which has since been followed by multiple outbreaks in Bangladesh and India. To date, no therapeutics or vaccines have been approved to treat Nipah virus disease, and only few such candidates are in development. In this Review, we aim to assess the safety and efficacy of the therapeutic options (monoclonal antibodies and small molecules) for Nipah virus disease and other henipaviral diseases to support prioritisation of drug candidates for further evaluation in clinical trials. At present, sufficient evidence exists to suggest trialling 1F5, m102.4, and remdesivir (alone or in combination) for prophylaxis and early treatment of Nipah virus disease. In addition to well designed clinical efficacy trials, in-vivo pharmacokinetic-pharmacodynamic studies are needed to optimise the selection and dosing of therapeutic candidates in animal challenge and natural human infection.

In response to outbreaks of (re)emerging highly pathogenic RNA viruses, simple and scalable antiviral screening methods are urgently needed. Using established and validated diagnostic methods like RT-PCR for antiviral screening offers a rapid readout of viral replication. This becomes particular important when other traditional viral replication readouts, such as TCID50 or plaque assays cannot be used due to the absence of cytopathic effects, lack of reporter gene-containing recombinant viruses or unavailability of appropriate antibodies - the latter two common challenges when so far unknown viruses emerge. This study evaluated semi-automated diagnostic RT-PCR in a 96-well approach for antiviral compound screening using Marburg virus serving as a case study. Remdesivir, a prodrug that exhibits antiviral activities against multiple RNA viruses, was used as positive control inhibiting replication of filoviruses. Applicability of the protocol to other members of the filovirus family was feasible using the same settings, while for other viruses like Middle East respiratory syndrome coronavirus (MERS-CoV) or Crimean-Congo hemorrhagic fever virus (CCHFV) adaptations to optimal infection settings were necessary. Our results demonstrate a high reproducibility and highlight the rapid adaptability of semi-automated RT-PCR assays as an accelerated antiviral screening assay with high scalability against a wide range of newly or (re)emerging RNA viruses. This is critical especially during outbreak situations where timely antiviral assessments are urgently needed.

Respiratory syncytial virus (RSV) is one of the most common viruses leading to lower respiratory tract infections (LRTIs) in children and elderly individuals worldwide. Although significant progress in the prevention and treatment of RSV infection was made in 2023, with two anti-RSV vaccines and one monoclonal antibody approved by the FDA, there is still a lack of postinfection therapeutic drugs in clinical practice, especially for the pediatric population. In recent years, with an increasing understanding of the pathogenic mechanisms of RSV, drugs and drug candidates, have shown great potential for clinical application. In this review, we categorize and discuss promising anti-RSV drug candidates that have been in preclinical or clinical development over the last five years.

SUMMARYHenipaviruses were first identified 30 years ago and have since been associated with over 30 outbreaks of disease in humans. Highly pathogenic henipaviruses include Hendra virus (HeV) and Nipah virus (NiV), classified as biosafety level 4 pathogens. In addition, NiV has been listed as a priority pathogen by the World Health Organization (WHO), the Coalition for Epidemic Preparedness Innovations (CEPI), and the UK Vaccines Research and Development Network (UKVN). Here, we re-examine epidemiological, ecological, clinical, and pathobiological studies of HeV and NiV to provide a comprehensive guide of the current knowledge and application to identify and evaluate countermeasures. We also discuss therapeutic and vaccine development efforts. Furthermore, with case identification, prevention, and treatment in mind, we highlight limitations in research and recognize gaps necessitating additional studies.

Tick-borne encephalitis (TBE) is a neurological disease caused by the tick-borne encephalitis virus (TBEV). Despite available vaccines, breakthrough infections occur, some fatal.

As no antiviral therapy for TBE is currently approved, this study evaluated the in vitro activity of already licenced remdesivir (RDV) and sofosbuvir (SOF) for possible drug repurposing against TBEV.

TBEV was cultured in A549 cells, and the inhibitory effects of RDV (GS-5734), its parent nucleotide GS-441524, and SOF (GS-7977) were assessed.

After 78 h, RDV demonstrated significantly lower EC50 values than SOF (0.14 vs. 11 µM) based on TBEV RNA levels measured by RT-qPCR. RDV also had a lower mean EC50 (0.55 µM) compared to GS-441524 and SOF (>8.9 and 13.1 µM, respectively) using crystal violet staining after 5 days. After 11 passages of TBEV in the presence of RDV, emergence of virus with a higher EC50 (1.32 vs. 0.55 µM) was detected with two mutations (L3122F and Y3278F) in NS5, the viral RNA-dependent RNA polymerase (RdRp), and one substitution in envelope (E) protein (E402G). Similarly, SOF resistance appeared after 20 passages, increasing EC50 values (35.5 vs. 10 µM).

RDV exhibits potent in vitro antiviral activity against TBEV via specific targeting of the viral RdRp as confirmed by the emergence of resistance-associated double NS5 substitutions in vitro in the presence of RDV. While the potential in vivo implications of the observed RDV resistance remain to be determined, these in vitro data support further assessment of RDV for the treatment of TBEV infection.

Remdesivir inhibits the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp; Nsp12). Here, we conducted viral resistance analyses from the Phase 3 PINETREE trial of remdesivir in nonhospitalized participants at risk of severe COVID-19. Nasopharyngeal swabs (collected at baseline [Day 1], Days 2, 3, 7, and 14) were eligible for analysis if their viral load was above the lower limit of quantification for the RT-qPCR assay (2228 copies/mL). The SARS-CoV-2 genome was sequenced for all remdesivir participants and 50% of placebo participants (baseline, Days 3, 7, and 14) and for participants who progressed to COVID-19-related hospitalization or all-cause death (all time points). Emergent substitutions in Nsp12 and other replication complex proteins were phenotyped using site-directed mutagenesis in a SARS-CoV-2 subgenomic replicon system. Overall, emergent Nsp12 substitutions were detected in 8/115 (7.0%) remdesivir participants and 7/129 (5.4%) placebo participants (1 substitution overlap between groups). Based on a structural analysis, none of the emergent Nsp12 substitutions were in direct contact with the incoming nucleoside triphosphate substrate, the RNA, or the RNA template 5' overhang. One substitution (A376V) showed reduced susceptibility to remdesivir (12.6-fold change in remdesivir half-maximal concentration [EC50]); it also showed reduced fitness when introduced in the SARS-CoV-2 replicon and virus in vitro. Other substitutions had <1.1-fold change in remdesivir EC50. None of the emergent substitutions in Nsp8, Nsp10, Nsp13, or Nsp14 (remdesivir, 10/115 [8.7%]; placebo, 10/129 [7.8%]) showed reduced remdesivir susceptibility. In conclusion, emergent substitutions in the SARS-CoV-2 RdRp complex with reduced remdesivir susceptibility were uncommon, indicating a high barrier to remdesivir resistance.CLINICAL TRIALSThis study is registered with ClinicalTrials.gov as NCT04501952.

The core subunits of the KV7.2, KV7.3, and KV7.5 channels, encoded by the KCNQ2, KCNQ3, and KCNQ5 genes, are expressed across various cell types and play a key role in generating the M-type K+ current (IK(M)). This current is characterized by an activation threshold at low voltages and displays slow activation and deactivation kinetics. Variations in the amplitude and gating kinetics of IK(M) can significantly influence membrane excitability. Notably, IK(M) demonstrates distinct voltage-dependent hysteresis when subjected to prolonged isosceles-triangular ramp pulses. In this review, we explore various small-molecule modulators that can either inhibit or enhance the amplitude of IK(M), along with their perturbations on its gating kinetics and voltage-dependent hysteresis. The inhibitors of IK(M) highlighted here include bisoprolol, brivaracetam, cannabidiol, nalbuphine, phenobarbital, and remdesivir. Conversely, compounds such as flupirtine, kynurenic acid, naringenin, QO-58, and solifenacin have been shown to enhance IK(M). These modulators show potential as pharmacological or therapeutic strategies for treating certain disorders linked to gain-of-function or loss-of-function mutations in M-type K+ (KV7x or KCNQx) channels.

Human parainfluenza virus type 3 (HPIV-3) can cause severe respiratory diseases, particularly in young children, the elderly and immunocompromised. There are no approved antiviral drugs against this virus. We report that the combination of ribavirin with either remdesivir or its parent nucleoside GS-441524 results in a pronounced antiviral effect against HPIV-3 in LLC-MK2 cells and in human airway epithelial cells grown at the air-liquid interface. In AG129 mice intranasally inoculated with HPIV-3, the combined treatment with ribavirin and GS-441524 decreased infectious viral lung titers by >2.5 log10 to undetectable levels in 4 out of 11 mice and by 1.6 log10 in the remaining 7 mice as compared with the vehicle. The lungs of all mice that received the combined treatment appeared histologically normal or virtually normal, whereas 8 of 11 vehicle-treated mice presented with bronchopneumonia. By contrast, ribavirin alone did not result in a reduction in infectious viral lung titers; GS-441524 alone reduced infectious viral lung titers by 1.2 log10. Moreover, several mice in the single-treatment groups exhibited severe lung pathology. These findings may warrant exploring this combination in patients with severe HPIV-3 infections and possibly also against infections with other viruses that are susceptible in vitro to these two drugs.

As new SARS-CoV-2 variants continue to emerge, it is important to evaluate the potency of antiviral drugs to support their continued use. Remdesivir (RDV; VEKLURY®) an approved antiviral treatment for COVID-19, and obeldesivir (ODV) are inhibitors of the SARS-CoV-2 RNA-dependent RNA polymerase Nsp12. Here we show these two compounds retain antiviral activity against the Omicron variants BA.2.86, BF.7, BQ.1, CH.1.1, EG.1.2, EG.5.1, EG.5.1.4, FL.22, HK.3, HV.1, JN.1, JN.1.7, JN.1.18, KP.2, KP.3, LB.1, XBB.1.5, XBB.1.5.72, XBB.1.16, XBB.2.3.2, XBC.1.6, and XBF when compared with reference strains. Genomic analysis identified 29 Nsp12 polymorphisms in these and previous Omicron variants. Phenotypic analysis of these polymorphisms confirmed no impact on the antiviral activity of RDV or ODV and suggests Omicron variants containing these Nsp12 polymorphisms remain susceptible to both compounds. These data support the continued use of RDV in the context of circulating SARS-CoV-2 variants and the development of ODV as an antiviral therapeutic.

Canine distemper is a severe and lethal viral disease of dogs and wild carnivores with an urgent need for the identification of effective antiviral agents against canine distemper virus (CDV). We assessed multiple agents for their ability to block the replication of three different lineages of CDV isolated from wild carnivores in the United States. Six antiviral compounds were selected after preliminary experiments that excluded ribavirin, hesperidin and rutin: a protease inhibitor (nirmatrelvir), a polymerase inhibitor (favipiravir) and four nucleoside analogs (remdesivir, GS-441524, EIDD2801 and EIDD1931). Antiviral efficacy was determined by the attenuation of the cytopathic effect in a CDV-susceptible cell line and the inhibition of viral RNA replication. The nucleoside analog GS-441524 effectively blocked the replication of CDV at pharmacologically relevant concentrations. Four other antiviral agents inhibited CDV replication to a lesser degree (remdesivir, nirmatrelvir, EIDD2801 and EIDD1931). The replication of different viral lineages was differentially inhibited by the antivirals. Several of the nucleoside analogs have been safely used previously in carnivore species for the treatment of other viral diseases, suggesting that they may be promising candidates for the treatment of canine distemper in dogs. Our results emphasize the need to consider different viral lineages in the screening of antiviral compounds.

Viral diseases have been present throughout human history, with early examples including influenza (1500 B.C.), smallpox (1000 B.C.), and measles (200 B.C.). The term "virus" was first used in the late 1800s to describe microorganisms smaller than bacteria, and significant milestones include the discovery of the polio virus and the development of its vaccine in the mid-1900s, and the identification of HIV/AIDS in the latter part of the 20th century. The 21st century has seen the emergence of new viral diseases such as West Nile Virus, Zika, SARS, MERS, and COVID-19. Human activities, including crowding, travel, poor sanitation, and environmental changes like deforestation and climate change, significantly influence the spread of these diseases. Conversely, viral diseases can impact the environment by polluting water resources, contributing to deforestation, and reducing biodiversity. These environmental impacts are exacerbated by disruptions in global supply chains and increased demands for resources. This review highlights the intricate relationship between viral diseases and environmental factors, emphasizing how human activities and viral disease progression influence each other. The findings underscore the need for integrated approaches to address the environmental determinants of viral diseases and mitigate their impacts on both health and ecosystems.

Nipah virus (NiV), a highly pathogenic Henipavirus in humans, has been responsible for annual outbreaks in recent years. Experiments involving live NiV are highly restricted to biosafety level 4 (BSL-4) laboratories, which impedes NiV research. In this study, we developed transcription and replication-competent NiV-like particles (trVLP-NiV) lacking N, P, and L genes. This trVLP-NiV exhibited the ability to infect and continuously passage in cells ectopically expressing N, P, and L proteins while maintaining stable genetic characteristics. Moreover, the trVLP-NiV displayed a favourable safety profile in hamsters. Using the system, we found the NiV nucleoprotein residues interacting with viral RNA backbone affected viral replication in opposite patterns. This engineered system was sensitive to well-established antiviral drugs, innate host antiviral factors, and neutralizing antibodies. We then established a high-throughput screening platform utilizing the trVLP-NiV, leading to the identification of tunicamycin as a potential anti-NiV compound. Evidence showed that tunicamycin inhibited NiV replication by decreasing the infectivity of progeny virions. In conclusion, this trVLP-NiV system provided a convenient and versatile molecular tool for investigating NiV molecular biology and conducting antiviral drug screening under BSL-2 conditions. Its application will contribute to the development of medical countermeasures against NiV infections.

Nipah virus causes highly lethal disease, with case-fatality rates ranging from 40% to 100% in recognised outbreaks. No treatments or licensed vaccines are currently available for the prevention and control of Nipah virus infection. In 2019, WHO published an advanced draft of a research and development roadmap for accelerating development of medical countermeasures, including diagnostics, therapeutics, and vaccines, to enable effective and timely emergency response to Nipah virus outbreaks. This Personal View provides an update to the WHO roadmap by defining current research priorities for development of Nipah virus medical countermeasures, based primarily on literature published in the last 5 years and consensus opinion of 15 subject matter experts with broad experience in development of medical countermeasures for Nipah virus or experience in the epidemiology, ecology, or public health control of outbreaks of Nipah virus. The research priorities are organised into four main sections: cross-cutting issues (for those that apply to more than one category of medical countermeasures), diagnostics, therapeutics, and vaccines. The strategic goals and milestones identified in each section focus on key achievements that are needed over the next 6 years to ensure that the necessary tools are available for rapid response to future outbreaks of Nipah virus or related henipaviruses.

The AYUSH 64 formulation helps to treat mild to moderate cases of COVID-19. Although several drugs have been proposed to combat COVID-19, no medication is available for SARS-CoV-2 infection. The RNA-dependent RNA polymerase (RdRp) is the pivotal enzyme of SARS-CoV-2 replication, so it could be considered a better drug target for experimental studies.

The AYUSH-64 formulation plants exhibited multiple therapeutic properties; thus, the present study aims to screen the phytocompounds of these plants against SARS CoV2 RdRp to identify specific compounds that could potentially affect COVID-19 infection.

PatchDock and AutoDock tools were used for docking experiments. MD simulations and Density Functional Theory (DFT) calculations of protein-ligand Picroside-I and Remdesivir complexes were carried out in GROMACS v2019.4 and Gaussian 09 software, respectively.

Among the tested, five phytocompounds (Picroside I, Oleanolic acid, Arvenin I, II, and III) from AYUSH-64 medicinal plants showed possible binding with RdRp catalytic residues (Ser759, Asp760, and Asp761). Of these, Picroside I exhibited hydrogen bond interactions with NTP entry channel residues (Arg553 and Arg555). The MM-PBSA free energy, RMSD, Rg, PCA, and RMSF analysis suggested that the Picroside I complex showed stable binding interactions with RdRp in the 50 ns simulation. In addition to this, Picroside I revealed its robust and attractive nature toward the target protein, as confirmed by DFT.

The results of this study have proposed that Picroside I from AYUSH 64 medicinal plant compounds was the selective binder of catalytic and NTP entry channel residues of SARS-CoV2 RdRp thereby; it may considered as a potential inhibitor of SARS-CoV2 RdRp.

Cyclodextrin (CD) derivatives have gained significant attention in biomedical applications due to their remarkable biocompatibility, unique inclusion capabilities, and potential for functionalization. This review focuses on recent advancements in CD-based assemblies, specifically their role in improving drug delivery, emphasizing remdesivir (RMD). The review introduces CD materials and their versatile applications in self-assembly and supramolecular assembly. CD materials offer immense potential for designing drug delivery systems with enhanced activity. Their inherent inclusion capabilities enable the encapsulation of diverse therapeutic agents, including RMD, resulting in improved solubility, stability, and bioavailability. The recent advances in CD-based assemblies, focusing on their integration with RMD have been concentrated here. Various strategies for constructing these assemblies are discussed, including physical encapsulation, covalent conjugation, and surface functionalization techniques. Furthermore, exploring future directions in these fields has also been provided. Ongoing research efforts are directed toward developing novel CD derivatives with enhanced properties, such as increased encapsulation efficiency and improved release kinetics. Moreover, the integration of CD-based assemblies with advanced technologies such as nanomedicine and gene therapy holds tremendous promise for personalized medicine and precision therapeutics.

Human parainfluenza virus type 3 (HPIV-3) can cause severe respiratory tract infections. There are no convenient small-animal infection models. Here, we show viral replication in the upper and lower airways of AG129 mice (double IFNα/β and IFNγ receptor knockout mice) upon intranasal inoculation. By multiplex fluorescence RNAscope and immunohistochemistry followed by confocal microscopy, we demonstrate viral tropism to ciliated cells and club cells of the bronchiolar epithelium. HPIV-3 causes a marked lung pathology. No virus transmission of the virus was observed by cohousing HPIV-3-infected AG129 mice with other mice. Oral treatment with GS-441524, the parent nucleoside of remdesivir, reduced infectious virus titers in the lung, with a relatively normal histology. Intranasal treatment also affords an antiviral effect. Thus, AG129 mice serve as a robust preclinical model for developing therapeutic and prophylactic strategies against HPIV-3. We suggest further investigation of GS-441524 and its prodrug forms to treat HPIV-3 infection in humans.

The coronavirus disease 2019 (COVID-19), the disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), represents the most disastrous infectious disease pandemic of the past century. As a member of the Betacoronavirus genus, the SARS-CoV-2 genome encodes a total of 29 proteins. The spike protein, RNA-dependent RNA polymerase, and proteases play crucial roles in the virus replication process and are promising targets for drug development. In recent years, structural studies of these viral proteins and of their complexes with antibodies and inhibitors have provided valuable insights into their functions and laid a solid foundation for drug development. In this review, we summarize the structural features of these proteins and discuss recent progress in research regarding therapeutic development, highlighting mechanistically representative molecules and those that have already been approved or are under clinical investigation.

The development of safe and effective broad-spectrum antivirals that target the replication machinery of respiratory viruses is of high priority in pandemic preparedness programs. Here, we studied the mechanism of action of a newly discovered nucleotide analog against diverse RNA-dependent RNA polymerases (RdRps) of prototypic respiratory viruses. GS-646939 is the active 5'-triphosphate metabolite of a 4'-cyano modified C-adenosine analog phosphoramidate prodrug GS-7682. Enzyme kinetics show that the RdRps of human rhinovirus type 16 (HRV-16) and enterovirus 71 incorporate GS-646939 with unprecedented selectivity; GS-646939 is incorporated 20-50-fold more efficiently than its natural ATP counterpart. The RdRp complex of respiratory syncytial virus and human metapneumovirus incorporate GS-646939 and ATP with similar efficiency. In contrast, influenza B RdRp shows a clear preference for ATP and human mitochondrial RNA polymerase does not show significant incorporation of GS-646939. Once incorporated into the nascent RNA strand, GS-646939 acts as a chain terminator although higher NTP concentrations can partially overcome inhibition for some polymerases. Modeling and biochemical data suggest that the 4'-modification inhibits RdRp translocation. Comparative studies with GS-443902, the active triphosphate form of the 1'-cyano modified prodrugs remdesivir and obeldesivir, reveal not only different mechanisms of inhibition, but also differences in the spectrum of inhibition of viral polymerases. In conclusion, 1'-cyano and 4'-cyano modifications of nucleotide analogs provide complementary strategies to target the polymerase of several families of respiratory RNA viruses.

Remdesivir (REM) and molnupiravir (MOL) are commonly used to treat lung transplant recipients (LTRs) with COVID-19; however, the clinical efficacy of these medications is yet to be compared. In this retrospective cohort study, we compared the clinical outcomes between LTRs with mild-to-moderate COVID-19 treated with REM and those treated with MOL.

Between March 2020 and August 2022, 195 LTRs developed COVID-19 at our center. After excluding 82 who presented with severe disease requiring hospitalization, the remaining 113 were included in the analysis: 54 did not receive antiviral treatment, 30 were treated with REM, and 29 were treated with MOL. Adjusted multivariable logistic regression analysis showed similar rates of hospitalization (adjusted odds ratio (aOR) 1.169, [95% confidence interval (95% CI) 0.105-12.997, p = 0.899], ICU admission (aOR 0.822, 95% CI 0.042-16.220, p = 0.898), mechanical ventilation (aOR 0.903, 95% CI 0.015-55.124, p = 0.961), and COVID-19-related mortality (aOR 0.822, 95% CI 0.042-16.220, p = 0.898) between LTRs treated with REM and those treated with MOL for mild-to-moderate COVID-19, irrespective of SARS-CoV-2 strain.

MOL may be a suitable alternative to REM to treat LTRs with mild-to-moderate COVID-19, and the choice of antiviral therapy can be driven by practical considerations such as route of administration and drug availability.

There are many pharmacologic therapies that are being used or considered for treatment of coronavirus disease 2019 (COVID-19), with rapidly changing efficacy and safety evidence from trials. The objective was to develop evidence-based, rapid, living guidelines intended to support patients, clinicians, and other healthcare professionals in their decisions about treatment and management of patients with COVID-19. In March 2020, the Infectious Diseases Society of America (IDSA) formed a multidisciplinary guideline panel of infectious disease clinicians, pharmacists, and methodologists with varied areas of expertise to regularly review the evidence and make recommendations about the treatment and management of persons with COVID-19. The process used a living guideline approach and followed a rapid recommendation development checklist. The panel prioritized questions and outcomes. A systematic review of the peer-reviewed and grey literature was conducted at regular intervals. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used to assess the certainty of evidence and make recommendations. Based on the most recent search conducted on 31 May 2022, the IDSA guideline panel has made 32 recommendations for the treatment and management of the following groups/populations: pre- and postexposure prophylaxis, ambulatory with mild-to-moderate disease, and hospitalized with mild-to-moderate, severe but not critical, and critical disease. As these are living guidelines, the most recent recommendations can be found online at: https://idsociety.org/COVID19guidelines. At the inception of its work, the panel has expressed the overarching goal that patients be recruited into ongoing trials. Since then, many trials were conducted that provided much-needed evidence for COVID-19 therapies. There still remain many unanswered questions as the pandemic evolved, which we hope future trials can answer.

Ebola virus (EBOV) and Marburg virus (MARV), members of the Filoviridae family, are highly pathogenic and can cause hemorrhagic fevers, significantly impacting human society. Bats are considered reservoirs of these viruses because related filoviruses have been discovered in bats. However, due to the requirement for maximum containment laboratories when studying infectious viruses, the characterization of bat filoviruses often relies on pseudoviruses and minigenome systems. In this study, we used RACE technology to sequence the 3'-leader and 5'-trailer of Měnglà virus (MLAV) and constructed a minigenome. Similar to MARV, the transcription activities of the MLAV minigenome are independent of VP30. We further assessed the effects of polymorphisms at the 5' end on MLAV minigenome activity and identified certain mutations that decrease minigenome reporter efficiency, probably due to alterations in the RNA secondary structure. The reporter activity upon recombination of the 3'-leaders and 5'-trailers of MLAV, MARV, and EBOV with those of the homologous or heterologous minigenomes was compared and it was found that the polymerase complex and leader and trailer sequences exhibit intrinsic specificities. Additionally, we investigated whether the polymerase complex proteins from EBOV and MARV support MLAV minigenome RNA synthesis and found that the homologous system is more efficient than the heterologous system. Remdesivir efficiently inhibited MLAV as well as EBOV replication. In summary, this study provides new information on bat filoviruses and the minigenome will be a useful tool for high-throughput antiviral drug screening.

Viruses are a real threat to every organism at any stage of life leading to extensive infections and casualties. N-heterocycles can affect the viral life cycle at many points, including viral entrance into host cells, viral genome replication, and the production of novel viral species. Certain N-heterocycles can also stimulate the host's immune system, producing antiviral cytokines and chemokines that can stop the reproduction of viruses. This review focused on recent five- or six-membered synthetic N-heterocyclic molecules showing antiviral activity through SAR analyses. The review will assist in identifying robust scaffolds that might be utilized to create effective antiviral drugs with either no or few side effects.

Over four years have passed since the beginning of the COVID-19 pandemic. The scientific response has been rapid and effective, with many therapeutic monoclonal antibodies and small molecules developed for clinical use. However, given the ability for viruses to become resistant to antivirals, it is perhaps no surprise that the field has identified resistance to nearly all of these compounds. Here, we provide a comprehensive review of the resistance profile for each of these therapeutics. We hope that this resource provides an atlas for mutations to be aware of for each agent, particularly as a springboard for considerations for the next generation of antivirals. Finally, we discuss the outlook and thoughts for moving forward in how we continue to manage this, and the next, pandemic.

Existing pharmacodynamic (PD) mathematical models for drug combinations discriminate antagonistic, additive, multiplicative, and synergistic effects, but fail to consider how concentration-dependent drug interaction effects may vary across an entire dose-response matrix. We developed a two-way pharmacodynamic (TWPD) model to capture the PD of two-drug combinations. TWPD captures interactions between upstream and downstream drugs that act on different stages of viral replication, by quantifying upstream drug efficacy and concentration-dependent effects on downstream drug pharmacodynamic parameters. We applied TWPD to previously published in vitro drug matrixes for repurposed potential anti-Ebola and anti-SARS-CoV-2 drug pairs. Depending on the drug pairing, the model recapitulated combined efficacies as or more accurately than existing models and can be used to infer efficacy at untested drug concentrations. TWPD fits the data slightly better in one direction for all drug pairs, meaning that we can tentatively infer the upstream drug. Based on its high accuracy, TWPD could be used in concert with PK models to estimate the therapeutic effects of drug pairs in vivo.

Malaysia reported the first human case of Nipah virus (NiV) in late September 1998 with encephalitis and respiratory symptoms. As a result of viral genomic mutations, two main strains (NiV-Malaysia and NiV-Bangladesh) have spread around the world. There are no licensed molecular therapeutics available for this biosafety level 4 pathogen. NiV attachment glycoprotein plays a critical role in viral transmission through its human receptors (Ephrin-B2 and Ephrin-B3), so identifying small molecules that can be repurposed to inhibit them is crucial to developing anti-NiV drugs. Consequently, in this study annealing simulations, pharmacophore modeling, molecular docking, and molecular dynamics were used to evaluate seven potential drugs (Pemirolast, Nitrofurantoin, Isoniazid Pyruvate, Eriodictyol, Cepharanthine, Ergoloid, and Hypericin) against NiV-G, Ephrin-B2, and Ephrin-B3 receptors. Based on the annealing analysis, Pemirolast for efnb2 protein and Isoniazid Pyruvate for efnb3 receptor were repurposed as the most promising small molecule candidates. Furthermore, Hypericin and Cepharanthine, with notable interaction values, are the top Glycoprotein inhibitors in Malaysia and Bangladesh strains, respectively. In addition, docking calculations revealed that their binding affinity scores are related to efnb2-pem (- 7.1 kcal/mol), efnb3-iso (- 5.8 kcal/mol), gm-hyp (- 9.6 kcal/mol), gb-ceph (- 9.2 kcal/mol). Finally, our computational research minimizes the time-consuming aspects and provides options for dealing with any new variants of Nipah virus that might emerge in the future.

Remdesivir (RDV) is a broad-spectrum nucleotide analog prodrug approved for the treatment of COVID-19 in hospitalized and non-hospitalized patients with clinical benefit demonstrated in multiple Phase 3 trials. Here we present SARS-CoV-2 resistance analyses from the Phase 3 SIMPLE clinical studies evaluating RDV in hospitalized participants with severe or moderate COVID-19 disease. The severe and moderate studies enrolled participants with radiologic evidence of pneumonia and a room-air oxygen saturation of ≤94% or >94%, respectively. Virology sample collection was optional in the study protocols. Sequencing and related viral load data were obtained retrospectively from participants at a subset of study sites with local sequencing capabilities (10 of 183 sites) at timepoints with detectable viral load. Among participants with both baseline and post-baseline sequencing data treated with RDV, emergent Nsp12 substitutions were observed in 4 of 19 (21%) participants in the severe study and none of the 2 participants in the moderate study. The following 5 substitutions emerged: T76I, A526V, A554V, E665K, and C697F. The substitutions T76I, A526V, A554V, and C697F had an EC50 fold change of ≤1.5 relative to the wildtype reference using a SARS-CoV-2 subgenomic replicon system, indicating no significant change in the susceptibility to RDV. The phenotyping of E665K could not be determined due to a lack of replication. These data reveal no evidence of relevant resistance emergence and further confirm the established efficacy profile of RDV with a high resistance barrier in COVID-19 patients.

Subacute sclerosing panencephalitis (SSPE) is a rare but fatal late neurological complication of measles, caused by persistent measles virus (MeV) infection of the central nervous system. There are no drugs approved for the treatment of SSPE. Here, we followed the clinical progression of a 5-year-old SSPE patient after treatment with the nucleoside analog remdesivir, conducted a post-mortem evaluation of the patient's brain, and characterized the MeV detected in the brain. The quality of life of the patient transiently improved after the first two courses of remdesivir, but a third course had no further clinical effect, and the patient eventually succumbed to his condition. Post-mortem evaluation of the brain displayed histopathological changes including loss of neurons and demyelination paired with abundant presence of MeV RNA-positive cells throughout the brain. Next-generation sequencing of RNA isolated from the brain revealed a complete MeV genome with mutations that are typically detected in SSPE, characterized by a hypermutated M gene. Additional mutations were detected in the polymerase (L) gene, which were not associated with resistance to remdesivir. Functional characterization showed that mutations in the F gene led to a hyperfusogenic phenotype predominantly mediated by N465I. Additionally, recombinant wild-type-based MeV with the SSPE-F gene or the F gene with the N465I mutation was no longer lymphotropic but instead efficiently disseminated in neural cultures. Altogether, this case encourages further investigation of remdesivir as a potential treatment of SSPE and highlights the necessity to functionally understand SSPE-causing MeV.IMPORTANCEMeasles virus (MeV) causes acute, systemic disease and remains an important cause of morbidity and mortality in humans. Despite the lack of known entry receptors in the brain, MeV can persistently infect the brain causing the rare but fatal neurological disorder subacute sclerosing panencephalitis (SSPE). SSPE-causing MeVs are characterized by a hypermutated genome and a hyperfusogenic F protein that facilitates the rapid spread of MeV throughout the brain. No treatment against SSPE is available, but the nucleoside analog remdesivir was recently demonstrated to be effective against MeV in vitro. We show that treatment of an SSPE patient with remdesivir led to transient clinical improvement and did not induce viral escape mutants, encouraging the future use of remdesivir in SSPE patients. Functional characterization of the viral proteins sheds light on the shared properties of SSPE-causing MeVs and further contributes to understanding how those viruses cause disease.

Acute Respiratory Distress Syndrome (ARDS) is a heterogeneous form of lung injury with severe hypoxemia and bilateral infiltrates after an inciting event that results in diffuse lung inflammation with a high mortality rate. While research in COVID-related ARDS has resulted in several pharmacotherapeutic agents that have undergone successful investigation, non-COVID ARDS studies have not resulted in many widely accepted pharmacotherapeutic agents despite exhaustive research.

The aim of this review is to discuss adjuvant pharmacotherapies targeting non-COVID Acute Lung Injury (ALI)/ARDS and novel therapeutics in COVID associated ALI/ARDS. In ARDS, variable data may support selective use of neuromuscular blocking agents, corticosteroids and neutrophil elastase inhibitors, but are not yet universally used. COVID-ALI/ARDS has data supporting the use of IL-6 monoclonal antibodies, corticosteroids, and JAK inhibitor therapy.

Although ALI/ARDS modifying pharmacological agents have been identified in COVID-related disease, the data in non-COVID ALI/ARDS has been less compelling. The increased use of more specific molecular phenotyping based on physiologic parameters and biomarkers, will ensure equipoise between groups, and will likely allow more precision in confirming pharmacological agent efficacy in future studies.

Decoration of nucleoside analogues with lipophilic groups often leads to compounds with improved antiviral activity. For example, N6-benzyladenosine derivatives containing elongated lipophilic substituents in the benzyl core efficiently inhibit reproduction of tick-borne encephalitis virus (TBEV), while N6-benzyladenosine itself potently inhibits reproduction of human enterovirus A71 (EV-A71). We have extended a series of N6-benzyladenosine analogues using effective synthetic methods of CC bond formation based on Pd-catalyzed cross-coupling reactions (Sonogashira and Suzuki) in order to study the influence of bulky lipophilic substituents in the N6 position of adenosine on the antiviral activity against flaviviruses, such as TBEV, yellow fever virus (YFV) and West Nile virus (WNV), as well as a panel of enteroviruses including EV-A71, Echovirus 30 (E30), and poliovirus type 2 (PV2). Reproduction of tested flaviviruses appeared to be inhibited by the micromolar concentrations of the compounds, while cytotoxicity in most cases was beyond the detection limit. Time-of-addition studies demonstrated that the hit compounds inhibited the stage of viral RNA synthesis, but not the stages of the viral entry or protein translation. As a result, several new promising antiflaviviral leads have been identified. On the other hand, none of the synthesized compounds inhibited enterovirus reproduction, indicating a possibility of involvement of flavivirus-specific pathways in their mechanism of action.

During the last forty years, significant progress has been made in the development of novel antiviral drugs, mainly crystallizing in the establishment of potent antiretroviral therapies and the approval of drugs eradicating hepatitis C virus infection. Although major targets of antiviral intervention involve intracellular processes required for the synthesis of viral proteins and nucleic acids, a number of inhibitors blocking virus assembly, budding, maturation, entry, or uncoating act on virions or viral capsids. In this review, we focus on the drug discovery process while presenting the currently used methodologies to identify novel antiviral drugs by means of computer-based approaches. We provide examples illustrating structure-based antiviral drug development, specifically neuraminidase inhibitors against influenza virus (e.g., oseltamivir and zanamivir) and human immunodeficiency virus type 1 protease inhibitors (i.e., the development of darunavir from early peptidomimetic compounds such as saquinavir). A number of drugs acting against hepatitis B virus and human immunodeficiency virus and their mechanism of action are presented to show how viral capsids can be exploited as targets of antiviral therapy. The recent approval of the antiretroviral drug lenacapavir illustrates the successful application of this knowledge.

Nipah virus (NiV) is a deadly zoonotic pathogen with high potential to cause another pandemic. Owing to biosafety concerns, studies on living NiV must be performed in biosafety level 4 (BSL-4) laboratories, which greatly hinders the development of anti-NiV drugs. To overcome this issue, minigenome systems have been developed to study viral replication and screen for antiviral drugs. This study aimed to develop two minigenome systems (transient and stable expression) based on a helper cell line expressing the NiV P, N and L proteins required to initiate NiV RNA replication. Stable minigenome cells were resistant to ribavirin, remdesivir and favipiravir but sensitive to interferons. Cells of the transient replication system were sensitive to ribavirin and favipiravir and suitable for drug screening. Our study demonstrates a feasible and effective platform for studying NiV replication and shows great potential for high-throughput drug screening in a BSL-2 laboratory environment.