Understanding the Impact of Resistance to Influenza Antivirals

A Phase 3 Safety and Efficacy Study of Baloxavir Marboxil in Children Less Than 1 Year Old With Suspected or Confirmed Influenza

BACKGROUND

Baloxavir marboxil (baloxavir) inhibits influenza virus cap-dependent endonuclease and has demonstrated safety and efficacy in children 1-<12 years of age. This study assessed the safety and efficacy of baloxavir in children <1 year old.

METHODS

miniSTONE-1 (NCT03653364) was a Phase III, global, multicenter, single-arm study to evaluate patients <1 year of age who received a single dose of baloxavir (age ≥3 months: 2 mg/kg; <3 months 1 mg/kg). The primary endpoint was safety; secondary endpoints included pharmacokinetics and efficacy (time to alleviation of signs and symptoms, duration of fever and symptoms, antibiotic use and cessation of viral shedding).

RESULTS

Overall, 48/49 enrolled patients received baloxavir, of whom 15 had positive centralized influenza reverse transcription polymerase chain reaction tests and comprised the intent-to-treat influenza-infected population. The median age was 6 months and 79.2% of patients were not influenza-vaccinated. Overall, 51 adverse events (AEs) were reported in 23 patients; most were grade 1-2. The most common AEs were diarrhea (16.7%) and vomiting (12.5%). Two patients experienced serious AEs unrelated to treatment. In the intent-to-treat influenza-infected population, median time to alleviation of signs and symptoms was 163.7 hours [95% confidence interval (CI): 122.5-not estimable], median duration of fever was 23.1 hours (95% CI: 22.3-44.6) and median time to cessation of viral shedding was 24.5 hours (95% CI: 24.2-68.6).

CONCLUSIONS

Baloxavir was well tolerated in children <1 year of age, with no new safety signals identified. Clinical, virological and safety outcomes were consistent with established profiles in adults, adolescents and children 1-<12 years old.

Efficacy of Baloxavir Treatment in Preventing Transmission of Influenza

BACKGROUND

Baloxavir marboxil (baloxavir) rapidly reduces influenza virus shedding, which suggests that it may reduce transmission. Studies of treatment with neuraminidase inhibitors have not shown sufficient evidence that they prevent transmission to contacts.

METHODS

We conducted a multicountry, phase 3b trial to assess the efficacy of single-dose baloxavir treatment to reduce influenza transmission from index patients to household contacts. Influenza-positive index patients 5 to 64 years of age were randomly assigned in a 1:1 ratio to receive baloxavir or placebo within 48 hours after symptom onset. The primary end point was transmission of influenza virus from an index patient to a household contact by day 5. The first secondary end point was transmission of influenza virus by day 5 that resulted in symptoms.

RESULTS

Overall, 1457 index patients and 2681 household contacts were enrolled across the 2019-2024 influenza seasons; 726 index patients were assigned to the baloxavir group, and 731 to the placebo group. By day 5, transmission of laboratory-confirmed influenza was significantly lower with baloxavir than with placebo (adjusted incidence, 9.5% vs. 13.4%; adjusted odds ratio, 0.68; 95.38% confidence interval [CI], 0.50 to 0.93; P = 0.01), with an adjusted relative risk reduction of 29% (95.38% CI, 12 to 45). The adjusted incidence of transmission of influenza virus by day 5 that resulted in symptoms was 5.8% with baloxavir and 7.6% with placebo; however, the difference was not significant (adjusted odds ratio, 0.75; 95.38% CI, 0.50 to 1.12; P = 0.16). Emergence of drug-resistant viruses during the follow-up period occurred in 7.2% (95% CI, 4.1 to 11.6) of the index patients in the baloxavir group; no resistant viruses were detected in household contacts. No new safety signals were identified.

CONCLUSIONS

Treatment with a single oral dose of baloxavir led to a lower incidence of transmission of influenza virus to close contacts than placebo. (Funded by F. Hoffmann-La Roche and others; CENTERSTONE ClinicalTrials.gov number, NCT03969212.).

Neutralizing monoclonal antibodies as effective therapeutics and prophylactics against lethal H10N7 avian influenza infection in a mouse model

The H10 subtype of avian influenza virus (AIV) is widespread in poultry worldwide and poses a significant threat to animal health. With the emergence of sporadic and fatal cases in humans infected with H10 subtype AIVs in recent years, it is imperative to develop neutralizing monoclonal antibodies (mAbs) to treat influenza clinically. In this study, BALB/c mice were immunized with A/chicken/Zhejiang/2CP8/2014 (H10N7) haemagglutinin (HA) protein, and eight HA-specific mAbs were subsequently screened. The characteristics of the mAbs were tested and evaluated using haemagglutination inhibition and microneutralization assays in vitro. We selected two mAbs (1E10 and 2A9) to further study their characteristics and functions, including their affinity and specificity of binding to antigens via enzyme-linked immunosorbent assays and immunofluorescence assays. We identified the mutant epitopes (K165E and N170D) of the H10N7 strain produced under the immune pressure of the two mAbs. Furthermore, we infected mice with the H10N7 virus and conducted prophylactic and therapeutic trials using the two mAbs. The results indicated that both mAbs have obvious neutralization ability in vivo. Compared with those in the isotype IgG control group, the weights of the mice in the experimental groups were greater in the prophylactic and therapeutic experiments. In conclusion, the mAbs produced in this study are expected to be effective drugs for clinical antiviral therapy against lethal infection by H10 AIVs.

Ensitrelvir treatment-emergent amino acid substitutions in SARS-CoV-2 3CLpro detected in the SCORPIO-SR phase 3 trial

The impact of treatment-emergent amino acid substitutions (TEAASs) in severe acute respiratory syndome coronavirus 2 (SARS-CoV-2) 3C-like protease (3CLpro) on clinical and virologic outcomes was evaluated in patients with mild-to-moderate coronavirus disease 2019 (COVID-19) who received ensitrelvir 125 mg in the SCORPIO-SR trial. Individuals were randomised to ensitrelvir or matched placebo once daily for 5 days (first dose <72 h after disease onset). 3CLpro-TEAASs were identified by sequencing nsp5 encoding 3CLpro from pre- and post-treatment nasopharyngeal swabs. Time to resolution of a composite of five characteristic COVID-19 symptoms (TTR) was compared between patients with and without the most common 3CLpro-TEAASs in the ensitrelvir arm. The ensitrelvir and placebo intention-to-treat populations comprised 345 and 341 patients, respectively. 3CLpro-TEAASs were detected in 19/204 (9.3%) ensitrelvir-treated and 3/137 (2.2%) placebo-treated patients with paired sequence data. The most common 3CLpro-TEAASs in the ensitrelvir arm were M49L (n = 12), M49I (n = 3) and S144A (n = 2). In the placebo arm, all 3CLpro-TEAASs occurred in ≤1 patient. Median (95% confidence interval) TTR was comparable between patients with and without those TEAASs (158.8 h [112.1-281.9] vs 189.7 h [151.4-234.4]). Mean viral RNA levels declined more slowly in patients with M49L/I or S144A versus those without. Reductions in viral titre were unaffected by these TEAASs. The characteristics of recombinant SARS-CoV-2 with 3CLpro mutations were explored in vitro. Recombinant viruses with some 3CLpro mutations had reduced susceptibility to ensitrelvir in vitro, with limited effects on viral and competitive fitness. Continued surveillance is warranted to monitor the spread of viruses with 3CLpro mutations.

Patchouli alcohol from Pogostemon cablin Benth inhibits H1N1 infection by repressing inflammasome and proptosis by targeting ubiquitin specific peptidase 18

Influenza virus infection can cause lung inflammation and viral pneumonia in patients. Patchouli alcohol (PA), a tricyclic sesquiterpene derived from Pogostemonis Herba, has been shown to alleviate inflammation in various diseases. However, the molecular mechanism by which patchouli exerts its anti-inflammatory effects, particularly its role in mitigating influenza virus induced inflammation and pneumonia during H1N1 viral infection, remains largely unclear. Herein, we found that PA considerably reduced body weight loss, lung pathological index and attenuated lung histological damage in H1N1-infected mice. Mechanistically, PA reduced the production and secretion of inflammatory cytokines via inhibition of the NF-κB-signaling pathway and blocking inflammasome-mediated proptosis. Additionally, proteomic analysis identified several potential targets of PA, with ubiquitin-specific peptidase 18 (USP18) emerging as a key candidate. Further investigation revealed that PA binds to USP18, enhancing its stability and increasing its transcriptional and translational expression. Overall, our results emphasize the anti-inflammatory effects of PA during influenza virus infection. PA may alleviate lung inflammation and damage by targeting USP18, offering a potential therapeutic strategy for treating influenza-induced lung complications.

A meta-analysis highlights the idiosyncratic nature of tradeoffs in laboratory models of virus evolution

Different theoretical frameworks have been invoked to guide the study of virus evolution. Three of the more prominent ones are (i) the evolution of virulence, (ii) life history theory, and (iii) the generalism-specialism dichotomy. All involve purported tradeoffs between traits that define the evolvability and constraint of virus-associated phenotypes. However, as popular as these frameworks are, there is a surprising paucity of direct laboratory tests of the frameworks that support their utility as broadly applicable theoretical pillars that can guide our understanding of disease evolution. In this study, we conduct a meta-analysis of direct experimental evidence for these three frameworks across several widely studied virus-host systems: plant viruses, fungal viruses, animal viruses, and bacteriophages. We extracted 60 datasets from 28 studies and found a range of relationships between traits in different analysis categories (e.g., frameworks, virus-host systems). Our work demonstrates that direct evidence for relationships between traits is highly idiosyncratic and specific to the host-virus system and theoretical framework. Consequently, scientists researching viral pathogens from different taxonomic groups might reconsider their allegiance to these canons as the basis for expectation, explanation, or prediction. Future efforts could benefit from consistent definitions, and from developing frameworks that are compatible with the evidence and apply to particular biological and ecological contexts.

Exploring potential of graphene oxide as an alternative antiviral approach for influenza A H1N1

Aim: Graphene oxide (GO), known for its distinctive physicochemical properties, shows promise as a nanomaterial capable of combating infectious agents. This study investigates the efficacy of GO nanoparticles in restricting influenza A H1N1 replication in MDCK cells.Methods: GO nanoparticles were synthesized. After evaluating the toxicity of GO nanoparticles, the antiviral activity of the highest nontoxic concentration of GO against influenza A H1N1 in MDCK cells was studied.Results: GO treatments resulted in substantial decreases in virus titers, as shown via hemagglutination assay, TCID50 assay and real-time PCR analysis.Conclusion: This study emphasizes that GO nanoparticles have a high level of effectiveness against influenza A H1N1 viruses, making them an intriguing option for various antiviral uses.

Drug resistance and possible therapeutic options against influenza A virus infection over past years

Influenza A virus infection, commonly known as the flu, has persisted in the community for centuries. Although we have yearly vaccinations to prevent seasonal flu, there remains a dire need for antiviral drugs to treat active infections. The constantly evolving genome of the influenza A virus limits the number of effective antiviral therapeutic options. Over time, antiviral drugs become inefficient due to the development of resistance, as seen with adamantanes, which are now largely ineffective against most circulating strains of the virus. Neuraminidase inhibitors have long been the drug of choice, but due to selection pressure, strains are becoming resistant to this class of drugs. Baloxavir marboxil, a drug with a novel mode of action, can be used against strains resistant to other classes of drugs but is still not available in many countries. Deep research into nanoparticles has shown they are effective as antiviral drugs, opening a new avenue of research to use them as antiviral agents with novel modes of action. As this deadly virus, which has killed millions of people in the past, continues to develop resistance, there is an urgent need for new therapeutic agents with novel modes of action to halt active infections in patients. This review article covers the available therapeutic antiviral drug options with different modes of action, their effectiveness, and resistance to various strains of influenza A virus.

Ruhao Dashi granules exert therapeutic effects on H1N1 influenza virus infection by altering intestinal microflora composition

Objective

Antiviral medications for influenza could be ineffective due to the emergence of resistant influenza virus strains. Ruhao Dashi (RHDS) granules possess anti-inflammatory and antibacterial effects. The present study aimed to determine the efficacy of RHDS granules in treating influenza-infected mice and the mechanism underlying this treatment as well as its effect on the intestinal flora composition of the infected mice.

Methods

The HPLC-UV method was used to identify the active components of RHDS granules. ICR mice were infected with influenza A virus (IAV) H1N1 subtype through a nasal drip. After the influenza mice model was successfully established, the pathological changes in the lungs were observed for 5 days after gavage treatment with 0.9% sterile saline and low, medium, and high doses (0.07, 0.14, and 0.28 g/mL, respectively) of RHDS granules. The serum levels of the cytokines IL-6 and TNF-α and sIgA were detected by ELISA. Real-time fluorescence quantitative PCR and western blotting assay were performed to determine the expression levels of the tight junction (TJ) proteins claudin-1, occludin, and zonula occludens-1 (ZO-1) in colon tissues. Furthermore, 16S rRNA gene sequencing of feces samples was conducted to assess the effect of RHDS granules on the gut microbiota.

Results

RHDS granules exerted a protective effect on the lung tissues of IAV-infected mice; moreover, the granules reduced the synthesis of proinflammatory cytokines and increased the relative expression levels of claudin-1, occludin, and ZO-1 in colon tissues. Furthermore, RHDS granule treatment increased the relative abundance of Lactobacillus, Akkermansia, and Faecalibaculum and decreased the relative abundance of Muribaculaceae; thus, RHDS granules could stabilize the intestinal microbiota to some extent.

Conclusion

RHDS granules exert a therapeutic effect on IAV-infected mice probably by modifying the structural composition of their intestinal microbiota.

Targeted recruitment of immune effector cells for rapid eradication of influenza virus infections

Despite much research, considerable data suggest that influenza virus remains a serious health problem because i) the effectiveness of current vaccines ranges only from 19% to 60%, ii) available therapies remain ineffective in advanced stages of disease, iii) death rates vary between 25,000 and 72,000/year in the United States, and iv) avian influenza strains are now being transmitted to dairy cattle that in turn are infecting humans. To address these concerns, we have developed zanDR, a bispecific small molecule that binds and inhibits viral neuraminidase expressed on both free virus and virus-infected cells and recruits naturally occurring anti-rhamnose and anti-dinitrophenyl (DNP) antibodies with rhamnose and DNP haptens. Because the neuraminidase inhibition replicates the chemotherapeutic mechanism of zanamivir and oseltamivir, while rhamnose and DNP recruit endogenous antibodies much like an anti-influenza vaccine, zanDR reproduces most of the functions of current methods of protection against influenza virus infections. Importantly, studies on cells in culture demonstrate that both of the above protective mechanisms remain highly functional in the zanDR conjugate, while studies in lethally infected mice with advanced-stage disease establish that a single intranasal dose of zanDR not only yields 100% protection but also reduces lung viral loads faster and ~1,000× more thoroughly than current antiviral therapies. Since zanDR also lowers secretion of proinflammatory cytokines and protects against virus-induced damage to the lungs better than current therapies, we suggest that combining an immunotherapy with a chemotherapy in single pharmacological agent constitutes a promising approach for treating the more challenging forms of influenza.

Interplay between Lung Diseases and Viral Infections: A Comprehensive Review

The intricate relationship between chronic lung diseases and viral infections is a significant concern in respiratory medicine. We explore how pre-existing lung conditions, including chronic obstructive pulmonary disease, asthma, and interstitial lung diseases, influence susceptibility, severity, and outcomes of viral infections. We also examine how viral infections exacerbate and accelerate the progression of lung disease by disrupting immune responses and triggering inflammatory pathways. By summarizing current evidence, this review highlights the bidirectional nature of these interactions, where underlying lung diseasesincrease vulnerability to viral infections, while these infections, in turn, worsen the clinical course. This review underscores the importance of preventive measures, such as vaccination, early detection, and targeted therapies, to mitigate adverse outcomes in patients with chronic lung conditions. The insights provided aim to inform clinical strategies that can improve patient management and reduce the burden of chronic lung diseases exacerbated by viral infections.

Genotypic and phenotypic susceptibility of emerging avian influenza A viruses to neuraminidase and cap-dependent endonuclease inhibitors

Avian influenza outbreaks, including ones caused by highly pathogenic A(H5N1) clade 2.3.4.4b viruses, have devastated animal populations and remain a threat to humans. Risk elements assessed for emerging influenza viruses include their susceptibility to approved antivirals. Here, we screened >20,000 neuraminidase (NA) or polymerase acidic (PA) protein sequences of potentially pandemic A(H5Nx), A(H7Nx), and A(H9N2) viruses that circulated globally in 2010-2023. The frequencies of NA or PA substitutions associated with reduced inhibition (RI) or highly reduced inhibition (HRI) by NA inhibitors (NAIs) (oseltamivir, zanamivir) or a cap-dependent endonuclease inhibitor (baloxavir) were low: 0.60% (137/22,713) and 0.62% (126/20,347), respectively. All tested subtypes were susceptible to NAIs and baloxavir at sub-nanomolar concentrations. A(H9N2) viruses were the most susceptible to oseltamivir, with IC50s 3- to 4-fold lower than for other subtypes (median IC50: 0.18 nM; n = 22). NA-I222M conferred RI of A(H5N1) viruses by oseltamivir (with a 26-fold IC50 increase), but NA-S246N did not reduce inhibition. PA-E23G, PA-K34R, PA-I38M/T, and the previously unreported PA-A36T caused RI by baloxavir in all subtypes tested. Avian A(H9N2) viruses endemic in Egyptian poultry predominantly acquired PA-I38V, which causes only a <3-fold decrease in the baloxavir EC50 and fails to meet the RI criteria. PA-E199A/D in A(H7Nx) and A(H9N2) viruses caused a 2- to 4-fold decrease in EC50 (close to the borderline for RI) and should be closely monitored. Our data indicate antiviral susceptibility is high among avian influenza A viruses with pandemic potential and present novel markers of resistance to existing antiviral interventions.

Covalent Organic Framework-Based Theranostic Platforms for Restricting H1N1 Influenza Virus Infection

Background

Influenza A (H1N1) virus is a highly contagious respiratory disease that causes severe illness and death. Vaccines and antiviral drugs are limited by viral variation and drug resistance, so developing efficient integrated theranostic options appears significant in anti-influenza virus infection.

Methods

In this study, we designed and fabricated covalent organic framework (COF) based theranostic platforms (T705@DATA-COF-Pro), which was composed of an RNA polymerase inhibitor (favipiravir, T705), the carboxyl-enriched COF (DATA-COF) nano-carrier and Cy3-labeled single DNA (ssDNA) probe.

Results

The multi-porosity COF core provided an excellent micro-environment and smooth delivery for T705. The ssDNA probe coating bound to the nucleic acids of H1N1 selectively, thus controlling drug release and allowing fluorescence imaging. The combination of COF and probe triggered the synergism, promoting drug further therapeutic outcomes. With the aid of T705@DATA-COF-Pro platforms, the H1N1-infected mouse models lightly achieved diagnosis and significantly prolonged survival.

Conclusion

This research underscores the distinctive benefits and immense potential of COF materials in nano-preparations for virus infection, offering novel avenues for the detection and treatment of H1N1 virus infection.

Low antiviral resistance in Influenza A and B viruses isolated in Mexico from 2010 to 2023

The most widely used class of antivirals available for Influenza treatment are the neuraminidase inhibitors (NAI) Oseltamivir and Zanamivir. However, amino acid (AA) substitutions in the neuraminidase may cause reduced inhibition or high antiviral resistance. In Mexico, the current state of knowledge about NAI susceptibility is scarce, in this study we report the results of 14 years of Influenza surveillance by phenotypic and genotypic methods. A total of 255 isolates were assessed with the NAI assay, including Influenza A(H1N1)pdm09, A(H3N2) and Influenza B (IBV). Furthermore, 827 sequences contained in the GISAID platform were analyzed in search of relevant mutations.Overall, five isolates showed highly reduced inhibition or reduced inhibition to Oseltamivir, and two showed reduced inhibition to Zanamivir in the NAI assays. Additionally, five A(H1N1)pdm09 sequences from the GISAID possessed AA substitutions associated to reduced inhibition to Oseltamivir and none to Zanamivir. Oseltamivir resistant A(H1N1)pdm09 harbored the H275Y mutation. No genetic mutations were identified in Influenza A(H3N2) and IBV. Overall, these results show that in Mexico the rate of NAI resistance is low (0.6%), but it is essential to continue the Influenza surveillance in order to understand the drug susceptibility of circulating strains.

Multicountry Spread of Influenza A(H1N1)pdm09 Viruses with Reduced Oseltamivir Inhibition, May 2023-February 2024

Since May 2023, a novel combination of neuraminidase mutations, I223V + S247N, has been detected in influenza A(H1N1)pdm09 viruses collected in countries spanning 5 continents, mostly in Europe (67/101). The viruses belong to 2 phylogenetically distinct groups and display ≈13-fold reduced inhibition by oseltamivir while retaining normal susceptibility to other antiviral drugs.

Intranasal neomycin evokes broad-spectrum antiviral immunity in the upper respiratory tract

Respiratory virus infections in humans cause a broad-spectrum of diseases that result in substantial morbidity and mortality annually worldwide. To reduce the global burden of respiratory viral diseases, preventative and therapeutic interventions that are accessible and effective are urgently needed, especially in countries that are disproportionately affected. Repurposing generic medicine has the potential to bring new treatments for infectious diseases to patients efficiently and equitably. In this study, we found that intranasal delivery of neomycin, a generic aminoglycoside antibiotic, induces the expression of interferon-stimulated genes (ISGs) in the nasal mucosa that is independent of the commensal microbiota. Prophylactic or therapeutic administration of neomycin provided significant protection against upper respiratory infection and lethal disease in a mouse model of COVID-19. Furthermore, neomycin treatment protected Mx1 congenic mice from upper and lower respiratory infections with a highly virulent strain of influenza A virus. In Syrian hamsters, neomycin treatment potently mitigated contact transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In healthy humans, intranasal application of neomycin-containing Neosporin ointment was well tolerated and effective at inducing ISG expression in the nose in a subset of participants. These findings suggest that neomycin has the potential to be harnessed as a host-directed antiviral strategy for the prevention and treatment of respiratory viral infections.

Changing and Evolution of Influenza Virus: Is It a Trivial Flu?

BACKGROUND

Influenza viruses are etiological agents which cause contagious respiratory, seasonal epidemics and, for influenza A subtypes, pandemics. The clinical picture of influenza has undergone continuous change over the years, due to intrinsic viral evolution as well as "reassortment" of its genomic segments. The history of influenza highlights its ability to adapt and to rapidly evolve, without specific circumstances. This reflects the complexity of this pathology and poses the fundamental question about its assumption as a "common illness" and its impact on public health.

SUMMARY

The global influenza epidemics and pandemics claimed millions of deaths, leaving an indelible mark on public health and showing the need for a better comprehension of the influenza virus. The clear understanding of genetic variations during the influenza seasonal epidemics is a crucial point for developing effective strategies for prevention, treatment, and vaccine design. The recent advance in next-generation sequencing approaches, model systems to virus culture, and bioinformatics pipeline played a key role in the rapid characterization of circulating influenza strains. In particular, the increase in computational power allowed the performance of complex tasks in healthcare settings through machine learning algorithms, which analyze different variables, such as medical and laboratory outputs, to optimize medical research and improve public health systems. The early detection of emerging and reemerging pathogens is a matter of importance to prevent future pandemics.

KEY MESSAGES

The perception of influenza as a "trivial flu" or a more serious public health concern is a subject of ongoing debate, reflecting the multifaceted nature of this infectious disease. The variability in the severity of influenza sheds light on the unpredictability of the viral characteristics, coupled with the challenges in accurately predicting circulating strains. This adds complexity to the public health burden of influenza and highlights the need for targeted interventions.

Co-evolution of immunity and seasonal influenza viruses

Seasonal influenza viruses cause recurring global epidemics by continually evolving to escape host immunity. The viral constraints and host immune responses that limit and drive the evolution of these viruses are increasingly well understood. However, it remains unclear how most of these advances improve the capacity to reduce the impact of seasonal influenza viruses on human health. In this Review, we synthesize recent progress made in understanding the interplay between the evolution of immunity induced by previous infections or vaccination and the evolution of seasonal influenza viruses driven by the heterogeneous accumulation of antibody-mediated immunity in humans. We discuss the functional constraints that limit the evolution of the viruses, the within-host evolutionary processes that drive the emergence of new virus variants, as well as current and prospective options for influenza virus control, including the viral and immunological barriers that must be overcome to improve the effectiveness of vaccines and antiviral drugs.

Efficacy and safety of zapnometinib in hospitalised adult patients with COVID-19 (RESPIRE): a randomised, double-blind, placebo-controlled, multicentre, proof-of-concept, phase 2 trial

Background

Zapnometinib is an oral, non-ATP-competitive, small-molecule inhibitor of MEK1/MEK2 with immunomodulatory and antiviral properties. We aimed to investigate the safety and efficacy of zapnometinib in patients with COVID-19.

Methods

In this randomised, double-blind, placebo-controlled, multicentre, proof-of-concept, phase 2 trial, we recruited hospitalised adults with moderate or severe COVID-19 from 18 hospitals in Germany, India, Romania, South Africa, and Spain. Those requiring ICU admission or ventilator support at screening or randomisation were excluded. Patients were randomly assigned (1:1) to receive oral zapnometinib (900 mg on Day 1; 600 mg on Days 2-6) or matching placebo, on top of standard of care. Randomisation, stratified by baseline clinical severity status (CSS 3 or 4, measured on a 7-point ordinal scale), was done using Interactive Response Technology. Patients, investigators, and the sponsor were masked to treatment allocation. The primary endpoint was CSS at Day 15 and was conducted on the full analysis set (FAS: all patients who were randomised to the study, received at least one dose of study medication and had at least one post-dose assessment of CSS, as randomised). Safety analyses were conducted on the safety analysis set (all study participants who received at least one dose of study medication, as treated). This study is registered at ClinicalTrials.gov (NCT04776044) and EudraCT (2020-004206-59).

Findings

The trial was terminated early as the emergence of the Omicron variant impacted recruitment. Between 12th April 2021 and 9th August 2022, 104 of the planned 220 patients were enrolled and randomly assigned, 103 were treated, and 101 were included in the FAS (zapnometinib: n = 50; placebo: n = 51). The primary outcome was not significantly different between the two groups, but patients on zapnometinib had higher odds of improved CSS versus placebo (odds ratio [OR] 1.54 [95% CI 0.72-3.33]; p = 0.26). Predefined subgroup analyses identified trends for improved CSS in patients with severe disease at baseline (OR 2.57 [0.76-8.88]; p = 0.13) and non-Omicron variants (OR 2.36 [0.85-6.71]; p = 0.10); the p value of the CSS subgroup by Treatment interaction term in the model was p = 0.28. The frequency and intensity of adverse events was low and similar between arms. Twenty (39.2%) patients treated with zapnometinib experienced adverse events compared with eighteen (34.6%) patients treated with placebo. One patient receiving zapnometinib and two patients receiving placebo died during the study. None of the deaths were considered related to study medication.

Interpretation

These results provide proof-of-concept for the innovative approach of targeting the Raf/MEK/ERK pathway in patients with hospitalised moderate/severe COVID-19. Further clinical studies will be required to evaluate the clinical benefit of zapnometinib in this and other indications.

Funding

Atriva Therapeutics GmbH and the Federal Ministry of Education and Research, Germany.

Influenza in Children and Adolescents: Epidemiology, Management, and Prevention

EDUCATION GAP

Influenza is among the most common infectious causes of pediatric emergency department visits and hospitalizations. Clinicians should use evidence-based guidelines to learn how to identify, manage, prevent, and treat influenza cases. Disease caused by influenza virus can be mitigated with appropriate treatment and prevention efforts.

OBJECTIVES After completing this article, readers should be able to:

1. Describe the virology and epidemiology of influenza.

2. List the clinical features and complications of influenza infections.

3. List the benefits and limitations of testing modalities for the diagnosis of influenza.

4. Appropriately apply American Academy of Pediatrics, Infectious Diseases Society of America, and Centers for Disease Control and Prevention (CDC) treatment guidelines for influenza or suspected influenza.

5. Describe the importance of influenza vaccination.

Conformation of influenza AM2 membrane protein in nanodiscs and liposomes

The influenza A M2 protein (AM2) is a multifunctional membrane-associated homotetramer that orchestrates several essential events in the viral infection cycle including viral assembly and budding. An atomic-level conformational understanding of this key player in the influenza life cycle could inform new antiviral strategies. For conformational studies of complex systems like the AM2 membrane protein, a multipronged approach using different biophysical methods and different model membranes is a powerful way to incorporate complementary data and achieve a fuller, more robust understanding of the system. However, one must be aware of how the sample composition required for a particular method impacts the data collected and how conclusions are drawn. In that spirit, we systematically compared the properties of AM2 in two different model membranes: nanodiscs and liposomes. Electron paramagnetic spectroscopy of spin-labeled AM2 showed that the conformation and dynamics were strikingly similar in both AM2-nanodiscs and AM2-liposomes consistent with similar conformations in both model membranes. Analysis of spin labeled lipids embedded in both model membranes revealed that the bilayer in AM2-liposomes was more fluid and permeable to oxygen than AM2-nanodiscs with the same lipid composition. Once the difference in the partitioning of the paramagnetic oxygen relaxation agent was taken into account, the membrane topology of AM2 appeared to be the same in both liposomes and nanodiscs. Finally, functionally relevant AM2 conformational shifts previously seen in liposomes due to the addition of cholesterol were also observed in nanodiscs.

The evolution of SARS-CoV-2

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused millions of deaths and substantial morbidity worldwide. Intense scientific effort to understand the biology of SARS-CoV-2 has resulted in daunting numbers of genomic sequences. We witnessed evolutionary events that could mostly be inferred indirectly before, such as the emergence of variants with distinct phenotypes, for example transmissibility, severity and immune evasion. This Review explores the mechanisms that generate genetic variation in SARS-CoV-2, underlying the within-host and population-level processes that underpin these events. We examine the selective forces that likely drove the evolution of higher transmissibility and, in some cases, higher severity during the first year of the pandemic and the role of antigenic evolution during the second and third years, together with the implications of immune escape and reinfections, and the increasing evidence for and potential relevance of recombination. In order to understand how major lineages, such as variants of concern (VOCs), are generated, we contrast the evidence for the chronic infection model underlying the emergence of VOCs with the possibility of an animal reservoir playing a role in SARS-CoV-2 evolution, and conclude that the former is more likely. We evaluate uncertainties and outline scenarios for the possible future evolutionary trajectories of SARS-CoV-2.

Antiviral Approaches against Influenza Virus

Preventing and controlling influenza virus infection remains a global public health challenge, as it causes seasonal epidemics to unexpected pandemics. These infections are responsible for high morbidity, mortality, and substantial economic impact. Vaccines are the prophylaxis mainstay in the fight against influenza. However, vaccination fails to confer complete protection due to inadequate vaccination coverages, vaccine shortages, and mismatches with circulating strains. Antivirals represent an important prophylactic and therapeutic measure to reduce influenza-associated morbidity and mortality, particularly in high-risk populations. Here, we review current FDA-approved influenza antivirals with their mechanisms of action, and different viral- and host-directed influenza antiviral approaches, including immunomodulatory interventions in clinical development. Furthermore, we also illustrate the potential utility of machine learning in developing next-generation antivirals against influenza.

Broadly Protective Neuraminidase-Based Influenza Vaccines and Monoclonal Antibodies: Target Epitopes and Mechanisms of Action

Neuraminidase (NA) is an important surface protein on influenza virions, playing an essential role in the viral life cycle and being a key target of the immune system. Despite the importance of NA-based immunity, current vaccines are focused on the hemagglutinin (HA) protein as the target for protective antibodies, and the amount of NA is not standardized in virion-based vaccines. Antibodies targeting NA are predominantly protective, reducing infection severity and viral shedding. Recently, NA-specific monoclonal antibodies have been characterized, and their target epitopes have been identified. This review summarizes the characteristics of NA, NA-specific antibodies, the mechanism of NA inhibition, and the recent efforts towards developing NA-based and NA-incorporating influenza vaccines.

Natural killer cells for antiviral therapy

Natural killer (NK) cell-based immunotherapy is being explored for treating infectious diseases, including viral infections. Here, we discuss evidence of NK cell responses to different viruses, ongoing clinical efforts to treat such infections with NK cell products, and review platforms to generate NK cell products.

Alloferon and Zanamivir Show Effective Antiviral Activity against Influenza A Virus (H1N1) Infection In Vitro and In Vivo

The use of vaccines is the most effective and reliable method for the prevention of viral infections. However, research on evaluation of effective therapeutic agents for use in treatment after infection is necessary. Zanamivir was administered through inhalation for treatment of pandemic influenza A/H1N1 in 2009. However, the emergence of drug-resistant strains can occur rapidly. Alloferon, an immunomodulatory drug developed as an NK cell activator, exerts antiviral effects against various viruses, particularly influenza viruses. Therefore, alloferon and zanamivir were administered in combination in an effort to improve the antiviral effect of zanamivir by reducing H1N1 resistance. First, we confirmed that administration of combined treatment would result in effective inhibition of viral proliferation in MDCK and A549 cells infected with H1N1. Production of IL-6 and MIP-1α in these cells and the activity of p38 MAPK and c-Jun that are increased by H1N1 were inhibited by combined treatment. Mice were then infected intranasally with H1N1, and examination of the antiviral efficacy of the alloferon/zanamivir combination was performed. The results showed that combined treatment after infection with H1N1 prevented weight loss, increased the survival rate, and improved lung fibrosis. Combined treatment also resulted in reduced infiltration of neutrophils and macrophages into the lungs. Combined treatment effectively inhibited the activity of p38 MAPK and c-Jun in lung tissue, which was increased by infection with H1N1. Therefore, the combination of alloferon/zanamivir effectively prevents the development of H1N1-mediated inflammation in the lungs by inhibiting the production of inflammatory mediators and migration of inflammatory cells into lung tissue.

Assessing the fitness of a dual-antiviral drug resistant human influenza virus in the ferret model

Influenza antivirals are important tools in our fight against annual influenza epidemics and future influenza pandemics. Combinations of antivirals may reduce the likelihood of drug resistance and improve clinical outcomes. Previously, two hospitalised immunocompromised influenza patients, who received a combination of a neuraminidase inhibitor and baloxavir marboxil, shed influenza viruses resistant to both drugs. Here-in, the replicative fitness of one of these A(H1N1)pdm09 virus isolates with dual resistance mutations (NA-H275Y and PA-I38T) was similar to wild type virus (WT) in vitro, but reduced in the upper respiratory tracts of challenged ferrets. The dual-mutant virus transmitted well between ferrets in an airborne transmission model, but was outcompeted by the WT when the two viruses were co-administered. These results indicate the dual-mutant virus had a moderate loss of viral fitness compared to the WT virus, suggesting that while person-to-person transmission of the dual-resistant virus may be possible, widespread community transmission is unlikely.

Evaluation of cytotoxicity and antiviral activity of Rhazya stricta Decne leaves extract against influenza A/PR/8/34 (H1N1)

Influenza viruses have developed resistance to the current classes of drugs, which means they could eventually become more virulent and cause more mortality and hospitalization. Our study aims to investigate the antiviral activity of Rhazya stricta Decne leaves extract in vitro and search for new promising drugs from R. stricta identified compounds in silico. The study was performed in vitro by utilizing Madin-Darby Canine Kidney cell line (MDCK) as a substrate for the influenza virus and estimating the inhibition performance of the plant leaves extract. Additionally, in silico screening was conducted to explore the antiviral activity of R. stricta phytochemicals. We investigated the cytotoxicity of R. stricta leaves extract and its antiviral activity against influenza virus (A/Puerto Rico/8/34 (H1N1)) using the MTT assay. The mode of action of the plant leaves extract during the viral life cycle was tested using time-of-addition assay. In silico analyses were performed, including molecular docking, drug-likeness analysis, and toxicity risk assessment, to state the leading compounds to be developed into an anti-influenza virus drug. The 50% cytotoxicity concentration of the leaves extract was CC50: 184.6 µg/mL, and the 50% inhibition concentration was CI50: 19.71 µg\mL. The time of addition assay revealed that R. stricta leaves extract exerted its activity in the late step of the influenza virus replication cycle. In comparison to Oseltamivir, the leading compounds showed better binding affinity and can be developed into oral drugs with low toxicity risk. Isolation and purification of the leading compounds and testing their antiviral activity in vitro and in vivo are required.

Assessment of influenza A (H1N1, H3N2) oseltamivir resistance during 2017-2019 in Iran

Background and Objectives

Neuraminidase inhibitors (NAIs) as an imperative antiviral for influenza prophylaxis and treatment are being consumed worldwide. Increasing use of these antivirals might be associated with drug resistance. Regarding the significance of these variations, this study aimed to investigate the mutations occurring in the NA gene of influenza A viruses leading to oseltamivir resistance during 2017-2019 in Iran.

Materials and Methods

In this cross-sectional study, 40 influenza A (H1N1, H3N2) strains, isolated in National Influenza Center (NIC) from patients with Severe Acute Respiratory Infection (SARI) during 2017-2019 were subjected to RT-PCR and sequencing of NA complete gene. The frequency of oseltamivir resistance and variation of NA amino acids in these strains were investigated.

Results

No significant mutation conferring oseltamivir resistance was detected. However, NA antigenic sites in these strains depicted minor changes compared to the vaccine strains. Among H3N2 isolates, mutations at 329, 344, 346 and 385 and among H1N1 isolates mutations at 143 and 188 residues occurred in NA antigenic regions.

Conclusion

Evaluation of NA gene sequences, showed no resistant viruses to oseltamivir. Given that the viruses in the present study were the last viruses circulating in Iran before COVID-19 pandemic, the results will be beneficial to have a worthy comparison with the strains circulating after the pandemic. Constant monitoring for the emergence of drug-resistant variants and antigenic changes are crucial for all countries.

Identification of cytochrome c oxidase subunit 4 isoform 1 as a positive regulator of influenza virus replication

Human infection with highly pathogenic H5N1 influenza virus causes severe respiratory diseases. Currently, the drugs against H5N1 are limited to virus-targeted inhibitors. However, drug resistance caused by these inhibitors is becoming a serious threat to global public health. An alternative strategy to reduce the resistance risk is to develop antiviral drugs targeting host cell proteins. In this study, we demonstrated that cytochrome c oxidase subunit 4 isoform 1 (COX41) of host cell plays an important role in H5N1 infection. Overexpression of COX41 promoted viral replication, which was inhibited by silencing or knockout the expression of COX41 in the host cell. The ribonucleoproteins (RNPs) of H5N1 were retained in the cell nucleus after knockout cellular COX41. Strikingly, inhibition of cellular COX41 by lycorine, a small-molecule compound isolated from Amaryllidaceae plants, reduced the levels of COX41-induced ROS and phosphorylation of extracellular signal-regulated kinase (ERK) in cells, thus resulting in the blockage of nuclear export of vRNP and inhibition of viral replication. In H5N1-infected mice that were treated with lycorine, we observed a reduction of viral titers and inhibition of pathological changes in the lung and trachea tissues. Importantly, no resistant virus was generated after culturing the virus with the continuous treatment of lycorine. Collectively, these findings suggest that COX41 is a positive regulator of H5N1 replication and might serve as an alternative target for anti-influenza drug development.

Nanomaterials for Photocatalytic Degradations of Analgesic, Mucolytic and Anti-Biotic/Viral/Inflammatory Drugs Widely Used in Controlling SARS-CoV-2

The COVID-19 pandemic has been transformed into one of the main worldwide challenges, in recent years. For controlling symptoms that are caused by this disease (e.g., chills or fever, shortness of breath and/or difficulty in breathing, cough, sore throat, fatigue, headache, muscle aches, the new loss of tastes and/or smells, congestion or runny nose, nausea, vomiting and/or diarrhea), lots of medicines including analgesics, mucolytics, and anti-biotic/viral/inflammatory drugs have been frequently prescribed. As these medicines finally contaminate terrestrial and aquatic habitats by entering surface waterways through pharmaceutical production and excreting trace amounts of waste after human usage, they have negative impacts on wildlife’s health and ecosystem. Residual drugs in water have the potential to harm aquatic creatures and disrupt their food chain as well as the breeding cycle. Therefore, proper degradation of these broadly used medicines is highly crucial. In this work, the use of nanomaterials applicable in photocatalytic degradations of analgesics (e.g., acetaminophen, aspirin, ibuprofen, and naproxen), mucolytics (e.g., ambroxol), antibiotics (e.g., azithromycin and quinolones including hydroxychloroquine and chloroquine phosphate), anti-inflammatory glucocorticoids (e.g., dexamethasone and cortisone acetate), antihistamines (e.g., diphenhydramine), H2 blockers (e.g., famotidine), anthelmintics (e.g., praziquantel), and finally antivirals (e.g., ivermectin, acyclovir, lopinavir/ritonavir, favipiravir, nitazoxanide, and remdesivir) which widely used in controlling/treating the coronavirus have been reviewed and discussed.

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

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

Intermolecular Mechanism and Dynamic Investigation of Avian Influenza H7N9 Virus' Susceptibility to E119V-Substituted Peramivir-Neuraminidase Complex

The H7N9 virus attaches itself to the human cell receptor protein containing the polysaccharide that terminates with sialic acid. The mutation of neuraminidase at residue E119 has been explored experimentally. However, there is no adequate information on the substitution with E119V in peramivir at the intermolecular level. Therefore, a good knowledge of the interatomic interactions is a prerequisite in understanding its transmission mode and subsequent effective inhibitions of the sialic acid receptor cleavage by neuraminidase. Herein, we investigated the mechanism and dynamism on the susceptibility of the E119V mutation on the peramivir-neuraminidase complex relative to the wildtype complex at the intermolecular level. This study aims to investigate the impact of the 119V substitution on the neuraminidase-peramivir complex and unveil the residues responsible for the complex conformations. We employed molecular dynamic (MD) simulations and extensive post-MD analyses in the study. These extensive computational investigations were carried out on the wildtype and the E119V mutant complex of the protein for holistic insights in unveiling the effects of this mutation on the binding affinity and the conformational terrain of peramivir-neuraminidase E119V mutation. The calculated total binding energy (ΔGbind) for the peramivir wildtype is -49.09 ± 0.13 kcal/mol, while the E119V mutant is -58.55 ± 0.15 kcal/mol. The increase in binding energy (9.46 kcal/mol) is consistent with other post-MD analyses results, confirming that E119V substitution confers a higher degree of stability on the protein complex. This study promises to proffer contributory insight and additional knowledge that would enhance future drug designs and help in the fight targeted at controlling the avian influenza H7N9 virus. Therefore, we suggest that experimentalists collaborate with computational chemists for all investigations of this topic, as we have done in our previous studies.

Efficacy and Safety of SARS-CoV-2 Neutralizing Antibody JS016 in Hospitalized Chinese Patients with COVID-19: A Phase 2/3, Multicenter, Randomized, Open-label, Controlled Trial

Recombinant human severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) monoclonal antibody JS016 showed neutralizing and therapeutic effects in preclinical studies. The clinical efficacy and safety of the therapy needed to be evaluated. In this phase 2/3, multicenter, randomized, open-label, controlled trial, hospitalized patients with moderate or severe coronavirus disease 2019 (COVID-19) were randomly assigned in a 1:1 ratio to receive standard care or standard care plus a single intravenous infusion of JS016. The primary outcome was a six-level ordinal scale of clinical status on day 28 since randomization. Secondary outcomes include adverse events, 28-day mortality, ventilator-free days within 28 days, length of hospital stay, and negative conversion rate of SARS-CoV-2 nucleic acid on day 14. A total of 199 patients were randomized, and 197 (99 in the JS016 group and 98 in the control group) were analyzed. Most patients, 95 (96%) in the JS016 group and 97 (99%) in the control group were in the best category on day 28 since randomization. The odds ratio of being in a better clinical status was 0.31 (95% confidence interval [CI], 0.03 to 3.19; P = 0.33). Few adverse events occurred in both groups (3% in the JS016 group and 1% in the control group, respectively; P = 0.34). SARS-CoV-2 neutralizing antibody JS016 did not show clinical efficacy among hospitalized Chinese patients with moderate to severe COVID-19 disease. Further studies are needed to assess the efficacy of the neutralizing antibody to prevent disease deterioration and its benefits among groups of patients specified by disease course and severity. (This study has been registered at ClinicalTrials.gov under identifier NCT04931238.)

Influenza Management During the COVID-19 Pandemic: A Review of Recent Innovations in Antiviral Therapy and Relevance to Primary Care Practice

Seasonal influenza requires appropriate management to protect public health and resources. Decreasing the burden of influenza will depend primarily on increasing vaccination rates as well as prompt initiation of antiviral therapy within 48 hours of symptom onset, especially in the context of the current coronavirus disease 2019 pandemic. A careful approach is required to prevent health services from being overwhelmed by a surge in demand that could exceed capacity. This review highlights the societal burden of influenza and discusses the prevention, diagnosis, and treatment of influenza as a complicating addition to the challenges of the coronavirus disease 2019 pandemic. The importance of vaccination for seasonal influenza and the role of antiviral therapy in the treatment and prophylaxis of seasonal influenza, including the most up-to-date recommendations from the Centers for Disease Control and Prevention for influenza management, will also be reviewed.

Baloxavir Treatment Delays Influenza B Virus Transmission in Ferrets and Results in Limited Generation of Drug-Resistant Variants

Clinical efficacy of the influenza antiviral baloxavir marboxil (baloxavir) is compromised by treatment-emergent variants harboring a polymerase acidic protein I38T (isoleucine-38-threonine) substitution. However, the fitness of I38T-containing influenza B viruses (IBVs) remains inadequately defined. After the pharmacokinetics of the compound were confirmed in ferrets, animals were injected subcutaneously with 8 mg/kg of baloxavir acid (BXA) at 24 h postinoculation with recombinant BXA-sensitive (BXA-Sen, I38) or BXA-resistant (BXA-Res, I38T) B/Brisbane/60/2008 (Victoria lineage) virus. BXA treatment of donor ferrets reduced virus replication and delayed transmission of the BXA-Sen but not the BXA-Res IBV. The I38 genotype remained dominant in the BXA-Sen-infected animals, even with BXA treatment. In competitive-mixture experiments, no transmission to aerosol contacts was seen from BXA-treated donors coinfected with the BXA-Sen and BXA-Res B/Brisbane/60/2008 viruses. However, in parallel mixed infections with the B/Phuket/3073/2013 (Yamagata lineage) virus background, BXA treatment failed to block airborne transmission of the BXA-Res virus, and the I38T genotype generally predominated. Therefore, the relative fitness of BXA-Res IBVs is complex and dependent on the virus backbone and within-host virus competition. BXA treatment of single-virus-infected ferrets hampers aerosol transmission of the BXA-Sen virus and does not readily generate BXA-Res variants, whereas mixed infections may result in propagation of BXA-Res IBVs of the Yamagata lineage. Our findings confirm the antiviral potency of baloxavir against IBVs, while supporting optimization of the dosing regimen to maximize clinical benefit.

Evidence that two instead of one defective interfering RNA in influenza A virus-derived defective interfering particles (DIPs) does not enhance antiviral activity

Influenza A virus (IAV) infection constitutes a significant health threat. Defective interfering particles (DIPs) can arise during IAV infection and inhibit spread of wild type (WT) IAV. DIPs harbor defective RNA segments, termed DI RNAs, that usually contain internal deletions and interfere with replication of WT viral RNA segments. Here, we asked whether DIPs harboring two instead of one DI RNA exert increased antiviral activity. For this, we focused on DI RNAs derived from segments 1 and 3, which encode the polymerase subunits PB2 and PA, respectively. We demonstrate the successful production of DIPs harboring deletions in segments 1 and/or 3, using cell lines that co-express PB2 and PA. Further, we demonstrate that DIPs harboring two instead of one DI RNA do not exhibit increased ability to inhibit replication of a WT RNA segment. Similarly, the presence of two DI RNAs did not augment the induction of the interferon-stimulated gene MxA and the inhibition of IAV infection. Collectively, our findings suggest that the presence of multiple DI RNAs derived from genomic segments encoding polymerase subunits might not result in increased antiviral activity.

Neutralizing Antibody Therapeutics for COVID-19

The emergence of SARS-CoV-2 and subsequent COVID-19 pandemic has resulted in a significant global public health burden, leading to an urgent need for effective therapeutic strategies. In this article, we review the role of SARS-CoV-2 neutralizing antibodies (nAbs) in the clinical management of COVID-19 and provide an overview of recent randomized controlled trial data evaluating nAbs in the ambulatory, hospitalized and prophylaxis settings. Two nAb cocktails (casirivimab/imdevimab and bamlanivimab/etesevimab) and one nAb monotherapy (bamlanivimab) have been granted Emergency Use Authorization by the US Food and Drug Administration for the treatment of ambulatory patients who have a high risk of progressing to severe disease, and the European Medicines Agency has similarly recommended both cocktails and bamlanivimab monotherapy for use in COVID-19 patients who do not require supplemental oxygen and who are at high risk of progressing to severe COVID-19. Efficacy of nAbs in hospitalized patients with COVID-19 has been varied, potentially highlighting the challenges of antiviral treatment in patients who have already progressed to severe disease. However, early data suggest a promising prophylactic role for nAbs in providing effective COVID-19 protection. We also review the risk of treatment-emergent antiviral resistant "escape" mutants and strategies to minimize their occurrence, discuss the susceptibility of newly emerging SARS-COV-2 variants to nAbs, as well as explore administration challenges and ways to improve patient access.