In Vitro Selection of Remdesivir-Resistant SARS-CoV-2 Demonstrates High Barrier to Resistance

Oral pharmacokinetics and efficacy of oral phospholipid remdesivir nucleoside prodrugs against SARS-CoV-2 in mice

Oral broad-spectrum antivirals are urgently needed for the treatment of many emerging and contemporary RNA viruses. We previously synthesized 1-O-octadecyl-2-O-benzyl-sn-glyceryl-P-RVn (ODBG-P-RVn, V2043), a phospholipid prodrug of GS-441524 (remdesivir nucleoside, RVn), and demonstrated its in vivo efficacy in a SARS-CoV-2 mouse model. Structure-activity relationship studies focusing on the prodrug scaffold identified two modifications, 3-fluoro-4-methoxy-benzyl (V2053) and 4-cyano-benzyl (V2067), that significantly enhanced the in vitro broad-spectrum antiviral activity against multiple RNA viruses when compared to V2043. Here, we demonstrate that V2043, V2053, and V2067 are all orally bioavailable, well-tolerated, and achieve high sustained plasma levels after single oral daily dosing. All three phospholipid prodrugs are significantly more active than RVn in vitro and significantly reduce SARS-CoV-2 lung titers in prophylaxis and treatment mouse models of SARS-CoV-2 B.1.351 infection. On a molar basis, V2043 and V2067 are substantially more active than obeldesivir/GS-5245 and molnupiravir in vivo. Together, these data support the continued development of phospholipid RVn prodrugs for the treatment of SARS-CoV-2 and other RNA viruses of clinical concern.

Limited Short-Term Evolution of SARS-CoV-2 RNA-Dependent RNA Polymerase under Remdesivir Exposure in Upper Respiratory Compartments

BACKGROUND

The extent of the SARS-CoV-2 short-term evolution under Remdesivir (RDV) exposure and whether it varies across different upper respiratory compartments are not fully understood.

METHODS

Patients hospitalized for COVID-19, with or without RDV therapy, were enrolled and completed up to three visits, in which they provided specimens from four respiratory compartments. Near full-length genome SARS-CoV-2 sequences were obtained from viral RNA, standard lineage and variant assignments were performed, and viral mutations in the RNA-dependent RNA polymerase (RdRp) region-the RDV target gene-were detected and compared between participants with and without RDV, across the four compartments, within participants across visits, and versus a larger sequence dataset. The statistical analysis used a generalized linear mixed-effects model.

RESULTS

A total of 139 sequences were obtained from 37 out of the 44 (84%) enrolled participants. The genotyping success varied across respiratory compartments, which ranged from 42% with oropharyngeal specimens to 67% with nasopharyngeal specimens and showed improvement with higher viral loads. No RdRp mutations known to be associated with RDV resistance were identified, and for 34 detected mutations at 32 amino acid positions that are not known as RDV-associated, there was no evidence of any associations with the RDV exposure, respiratory compartment, or time. At least 1 of these 34 mutations were detected in all participants, and some differed from the larger sequence dataset.

CONCLUSIONS

This study highlighted the SARS-CoV-2 short-term genomic stability within hosts and across upper respiratory compartments, which suggests a lack of evolution of RDV resistance over time. This contributes to our understanding of SARS-CoV-2 genomic dynamics.

SRX3177, a CDK4/6-PI3K-BET inhibitor, in combination with an RdRp inhibitor, Molnupiravir, or an entry inhibitor MU-UNMC-2, has potent antiviral activity against the Omicron variant of SARS-CoV-2

Despite considerable progress in developing vaccines and antivirals to combat COVID-19, the rapid mutations of the SARS-CoV-2 genome have limited the durability and efficacy of the current vaccines and therapeutic interventions. Hence, it necessitates the development of novel therapeutic approaches or repurposing existing drugs that target either viral life cycle, host factors, or both. Here, we report that SRX3177, a potent triple-activity CDK4/6-PI3K-BET inhibitor, blocks replication of the SARS-CoV-2 Omicron variant with IC50 values at sub-micromolar concentrations without any impact on the cell proliferation of Calu-3 cells at and below its IC50 concentration. When SRX3177 is combined with EIDD-1931 (active moiety of a small-molecule prodrug Molnupiravir) or MU-UNMC-2 (a SARS-CoV-2 entry inhibitor) at a fixed doses matrix, a synergistic effect was observed, leading to the significant reduction in the dose of the individual compounds to achieve similar inhibition of SARS-CoV-2 replication. Herein, we report that the combination of SRX3177/MPV or SRX3177/UM-UNMC-2 has the potential for further development as a combinational therapy against SARS-CoV-2 and in any future outbreak of beta coronavirus.

SARS-CoV-2 resistance to monoclonal antibodies and small-molecule drugs

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.

No Remdesivir Resistance Observed in the Phase 3 Severe and Moderate COVID-19 SIMPLE Trials

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.

Emergence of SARS-CoV-2 with Dual-Drug Resistant Mutations During a Long-Term Infection in a Kidney Transplant Recipient

Introduction

Various therapeutic agents are being developed for the treatment of coronavirus disease 2019 (COVID-19). Therefore, it is crucial to accumulate information regarding the features of drug-resistant viruses to these antiviral drugs.

Methods

We investigated the emergence of dual-drug resistance in a kidney transplant recipient who received sotrovimab (from day 0) and remdesivir (RDV) (from day 8 to day 17). We sequenced the whole viral genomes from nasopharyngeal swabs taken on day 0 and seven points after starting treatment (on days 12, 19, 23, 37, 43, 48, and 58). The genetic traits of the wild-type (day 0) and descendant viruses (after day 12) were determined by comparing the genomes with those of a Wuhan strain and the day 0 wild-type strain, respectively. Three viral isolates (from samples collected on days 0, 23, and 37) were investigated for their escape ability and growth kinetics in vitro.

Results

The sotrovimab resistant mutation (S:E340K) and the RDV resistant mutation RdRp:V792I (nt: G15814A) emerged within 12 days (day 12) and 11 days (day 19) after the treatment, respectively. The day 23 isolate harboring S:E340K/RdRp:V791I was resistant to both sotrovimab and RDV, showing 364- and 2.73-fold higher resistance respectively, compared with the wild-type. Moreover, compared with the day 23 isolate, the day 37 isolate accumulated multiple additional mutations and had a higher level of resistance to both drugs.

Conclusion

Drug-resistant variants with double mutations (S:E340K/RdRp:V791I) became dominant within 23 days after starting treatment, suggesting that even a combination therapy involving sotrovimab and RDV, dual-drug resistant viruses may emerge rapidly in immunocompromised patients. The dual-resistant variants had lower virus yields than those of the wild-type virus in vitro, suggesting that they paid a fitness cost.

SARS-CoV-2 genomics and impact on clinical care for COVID-19

The emergence and worldwide spread of SARS-CoV-2 during the COVID-19 pandemic necessitated the adaptation and rapid deployment of viral WGS and analysis techniques that had been previously applied on a more limited basis to other viral pathogens, such as HIV and influenza viruses. The need for WGS was driven in part by the low mutation rate of SARS-CoV-2, which necessitated measuring variation along the entire genome sequence to effectively differentiate lineages and characterize viral evolution. Several WGS approaches designed to maximize throughput and accuracy were quickly adopted by surveillance labs around the world. These broad-based SARS-CoV-2 genomic sequencing efforts revealed ongoing evolution of the virus, highlighted by the successive emergence of new viral variants throughout the course of the pandemic. These genomic insights were instrumental in characterizing the effects of viral mutations on transmissibility, immune escape and viral tropism, which in turn helped guide public health policy, the use of monoclonal antibody therapeutics and vaccine development strategies. As the use of direct-acting antivirals for the treatment of COVID-19 became more widespread, the potential for emergence of antiviral resistance has driven ongoing efforts to delineate resistance mutations and to monitor global sequence databases for their emergence. Given the critical role of viral genomics in the international effort to combat the COVID-19 pandemic, coordinated efforts should be made to expand global genomic surveillance capacity and infrastructure towards the anticipation and prevention of future pandemics.

Multidrug-resistant mutations to antiviral and antibody therapy in an immunocompromised patient infected with SARS-CoV-2

BACKGROUND

Antiviral and antibody therapies for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are being recommended for high-risk patients, but the potential for the development of multidrug-resistant mutations in immunocompromised patients is unclear.

METHODS

To investigate the treatment course in cases of prolonged viral shedding in an immunocompromised patient with SARS-CoV-2 infection, we conducted longitudinal measurements of laboratory tests, chest computed tomography (CT) image evaluations, antibody titers, and antigen levels in nasopharyngeal swabs. Furthermore, we performed whole-genome sequencing and digital PCR analysis to examine the mechanisms of drug resistance.

FINDINGS

We present a case of a 65-year-old man with a history of malignant lymphoma who was treated with multiple antiviral and antibody therapies, including sotrovimab, remdesivir, paxlovid (nirmatrelvir/ritonavir), and molnupiravir. Initially, viral antigen levels decreased after treatments. However, after the virus rebounded, the patient showed no virologic response. The viral genome analysis revealed a single Omicron subvariant (BA.1.1), which evolved within the host during the disease progression. The viruses had acquired multiple resistance mutations to nirmatrelvir (3 chymotrypsin-like protease [3CLpro] E166 A/V), sotrovimab (spike P337L and E340K), and remdesivir (RNA-dependent RNA polymerase [RdRp] V166L).

CONCLUSIONS

Our results indicate that viruses with multidrug-resistant mutations and survival fitness persist in the infected subpopulation after drug selection pressure.

FUNDING

This study was supported by the JSPS KAKENHI Early-Career Scientists 18K16292 (Y.H.), Grant-in-Aid for Scientific Research (B) 20H03668 and 23H02955 (Y.H.), the YASUDA Medical Foundation (Y.H.), the Uehara Memorial Foundation (Y.H.), the Takeda Science Foundation (Y.H.), and Kato Memorial Bioscience Foundation (Y.H.).

Viral Resistance Analyses From the Remdesivir Phase 3 Adaptive COVID-19 Treatment Trial-1 (ACTT-1)

BACKGROUND

Remdesivir is approved for treatment of coronavirus disease 2019 (COVID-19) in nonhospitalized and hospitalized adult and pediatric patients. Here we present severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) resistance analyses from the phase 3 ACTT-1 randomized placebo-controlled trial conducted in adult participants hospitalized with COVID-19.

METHODS

Swab samples were collected at baseline and longitudinally through day 29. SARS-CoV-2 genomes were sequenced using next-generation sequencing. Phenotypic analysis was conducted directly on participant virus isolates and/or using SARS-CoV-2 subgenomic replicons expressing mutations identified in the Nsp12 target gene.

RESULTS

Among participants with both baseline and postbaseline sequencing data, emergent Nsp12 substitutions were observed in 12 of 31 (38.7%) and 12 of 30 (40.0%) participants in the remdesivir and placebo arms, respectively. No emergent Nsp12 substitutions in the remdesivir arm were observed in more than 1 participant. Phenotyping showed low to no change in susceptibility to remdesivir relative to wild-type Nsp12 reference for the substitutions tested: A16V (0.8-fold change in EC50), P323L + V792I (2.2-fold), C799F (2.5-fold), K59N (1.0-fold), and K59N + V792I (3.4-fold).

CONCLUSIONS

The similar rate of emerging Nsp12 substitutions in the remdesivir and placebo arms and the minimal change in remdesivir susceptibility among tested substitutions support a high barrier to remdesivir resistance development in COVID-19 patients. Clinical Trials Registration. NCT04280705.

Substitutions in SARS-CoV-2 Mpro Selected by Protease Inhibitor Boceprevir Confer Resistance to Nirmatrelvir

Nirmatrelvir, which targets the SARS-CoV-2 main protease (Mpro), is the first-in-line drug for prevention and treatment of severe COVID-19, and additional Mpro inhibitors are in development. However, the risk of resistance development threatens the future efficacy of such direct-acting antivirals. To gain knowledge on viral correlates of resistance to Mpro inhibitors, we selected resistant SARS-CoV-2 under treatment with the nirmatrelvir-related protease inhibitor boceprevir. SARS-CoV-2 selected during five escape experiments in VeroE6 cells showed cross-resistance to nirmatrelvir with up to 7.3-fold increased half-maximal effective concentration compared to original SARS-CoV-2, determined in concentration-response experiments. Sequence analysis revealed that escape viruses harbored Mpro substitutions L50F and A173V. For reverse genetic studies, these substitutions were introduced into a cell-culture-infectious SARS-CoV-2 clone. Infectivity titration and analysis of genetic stability of cell-culture-derived engineered SARS-CoV-2 mutants showed that L50F rescued the fitness cost conferred by A173V. In the concentration-response experiments, A173V was the main driver of resistance to boceprevir and nirmatrelvir. Structural analysis of Mpro suggested that A173V can cause resistance by making boceprevir and nirmatrelvir binding less favorable. This study contributes to a comprehensive overview of the resistance profile of the first-in-line COVID-19 treatment nirmatrelvir and can thus inform population monitoring and contribute to pandemic preparedness.

Remdesivir: A Review in COVID-19

Remdesivir (Veklury®), a nucleotide analogue prodrug with broad-spectrum antiviral activity, is approved for the treatment of coronavirus disease 2019 (COVID-19), the illness caused by severe acute respiratory syndrome coronavirus 2 infection. Unlike some antivirals, remdesivir has a low potential for drug-drug interactions. In the pivotal ACTT-1 trial in hospitalized patients with COVID-19, daily intravenous infusions of remdesivir significantly reduced time to recovery relative to placebo. Subsequent trials provided additional support for the efficacy of remdesivir in hospitalized patients with moderate or severe COVID-19, with a greater benefit seen in patients with minimal oxygen requirements at baseline. Clinical trials also demonstrated the efficacy of remdesivir in other patient populations, including outpatients at high risk for progression to severe COVID-19, as well as hospitalized paediatric patients. In terms of mortality, results were equivocal. However, remdesivir appeared to have a small mortality benefit in hospitalized patients who were not already being ventilated at baseline. Remdesivir was generally well tolerated in clinical trials, but pharmacovigilance data found an increased risk of hepatic, renal and cardiovascular adverse drug reactions in the real-world setting. In conclusion, remdesivir represents a useful treatment option for patients with COVID-19, particularly those who require supplemental oxygen.

A mutation in the coronavirus nsp13-helicase impairs enzymatic activity and confers partial remdesivir resistance

Coronaviruses (CoVs) encode nonstructural proteins 1-16 (nsps 1-16) which form replicase complexes that mediate viral RNA synthesis. Remdesivir (RDV) is an adenosine nucleoside analog antiviral that inhibits CoV RNA synthesis. RDV resistance mutations have been reported only in the nonstructural protein 12 RNA-dependent RNA polymerase (nsp12-RdRp). We here show that a substitution mutation in the nsp13-helicase (nsp13-HEL A335V) of the betacoronavirus murine hepatitis virus (MHV) that was selected during passage with the RDV parent compound confers partial RDV resistance independently and additively when expressed with co-selected RDV resistance mutations in the nsp12-RdRp. The MHV A335V substitution did not enhance replication or competitive fitness compared to WT MHV and remained sensitive to the active form of the cytidine nucleoside analog antiviral molnupiravir (MOV). Biochemical analysis of the SARS-CoV-2 helicase encoding the homologous substitution (A336V) demonstrates that the mutant protein retained the ability to associate with the core replication proteins nsps 7, 8, and 12 but had impaired helicase unwinding and ATPase activity. Together, these data identify a novel determinant of nsp13-HEL enzymatic activity, define a new genetic pathway for RDV resistance, and demonstrate the importance of surveillance for and testing of helicase mutations that arise in SARS-CoV-2 genomes. IMPORTANCE Despite the development of effective vaccines against COVID-19, the continued circulation and emergence of new variants support the need for antivirals such as RDV. Understanding pathways of antiviral resistance is essential for surveillance of emerging variants, development of combination therapies, and for identifying potential new targets for viral inhibition. We here show a novel RDV resistance mutation in the CoV helicase also impairs helicase functions, supporting the importance of studying the individual and cooperative functions of the replicase nonstructural proteins 7-16 during CoV RNA synthesis. The homologous nsp13-HEL mutation (A336V) has been reported in the GISAID database of SARS-CoV-2 genomes, highlighting the importance of surveillance of and genetic testing for nucleoside analog resistance in the helicase.

Assessment of the frequency of SARS-CoV-2 Omicron variant escape from RNA-dependent RNA polymerase inhibitors and 3C-like protease inhibitors

The emergence and spread of antiviral-resistant SARS-CoV-2 is of great concern. In this study, we evaluated the propensity of Omicron variants to escape from RNA-dependent RNA polymerase (RdRP) inhibitors and 3C-like protease (3CLpro) inhibitors. SARS-CoV-2 Delta and Omicron variants were serially passaged in vitro in the presence of RdRP inhibitors (remdesivir and molnupiravir) and 3CLpro inhibitors (nirmatrelvir and lufotrelvir) to detect SARS-CoV-2 escape mutants. After five passages with 3CLpro inhibitors, mutant viruses that escaped from 3CLpro inhibitors emerged; however, in the presence of RdRP inhibitors all variants disappeared within 2-4 passages. Our findings suggest that the frequency of SARS-CoV-2 mutant escape from RdRP inhibitors is lower than that from 3CLpro inhibitors. We also found that Delta variants were more likely to acquire amino acid substitutions associated with resistance to 3CLpro inhibitors under the selective pressure of this drug compared with Omicron variants.

In vitro and in vivo characterization of SARS-CoV-2 strains resistant to nirmatrelvir

Nirmatrelvir, an oral antiviral agent that targets a SARS-CoV-2 main protease (3CLpro), is clinically useful against infection with SARS-CoV-2 including its omicron variants. Since most omicron subvariants have reduced sensitivity to many monoclonal antibody therapies, potential SARS-CoV-2 resistance to nirmatrelvir is a major public health concern. Several amino acid substitutions have been identified as being responsible for reduced susceptibility to nirmatrelvir. Among them, we selected L50F/E166V and L50F/E166A/L167F in the 3CLpro because these combinations of substitutions are unlikely to affect virus fitness. We prepared and characterized delta variants possessing Nsp5-L50F/E166V and Nsp5-L50F/E166A/L167F. Both mutant viruses showed decreased susceptibility to nirmatrelvir and their growth in VeroE6/TMPRSS2 cells was delayed. Both mutant viruses showed attenuated phenotypes in a male hamster infection model, maintained airborne transmissibility, and were outcompeted by wild-type virus in co-infection experiments in the absence of nirmatrelvir, but less so in the presence of the drug. These results suggest that viruses possessing Nsp5-L50F/E166V and Nsp5-L50F/E166A/L167F do not become dominant in nature. However, it is important to closely monitor the emergence of nirmatrelvir-resistant SARS-CoV-2 variants because resistant viruses with additional compensatory mutations could emerge, outcompete the wild-type virus, and become dominant.

Sequential intrahost evolution and onward transmission of SARS-CoV-2 variants

Persistent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have been reported in immune-compromised individuals and people undergoing immune-modulatory treatments. Although intrahost evolution has been documented, direct evidence of subsequent transmission and continued stepwise adaptation is lacking. Here we describe sequential persistent SARS-CoV-2 infections in three individuals that led to the emergence, forward transmission, and continued evolution of a new Omicron sublineage, BA.1.23, over an eight-month period. The initially transmitted BA.1.23 variant encoded seven additional amino acid substitutions within the spike protein (E96D, R346T, L455W, K458M, A484V, H681R, A688V), and displayed substantial resistance to neutralization by sera from boosted and/or Omicron BA.1-infected study participants. Subsequent continued BA.1.23 replication resulted in additional substitutions in the spike protein (S254F, N448S, F456L, M458K, F981L, S982L) as well as in five other virus proteins. Our findings demonstrate not only that the Omicron BA.1 lineage can diverge further from its already exceptionally mutated genome but also that patients with persistent infections can transmit these viral variants. Thus, there is, an urgent need to implement strategies to prevent prolonged SARS-CoV-2 replication and to limit the spread of newly emerging, neutralization-resistant variants in vulnerable patients.

Remdesivir Use in the Real-World Setting: An Overview of Available Evidence

In the years of Coronavirus Disease 2019 (COVID-19), various treatment options have been utilized. COVID-19 continues to circulate in the global population, and the evolution of the Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has posed significant challenges to the treatment and prevention of infection. Remdesivir (RDV), an anti-viral agent with in vitro efficacy against coronaviruses, is a potent and safe treatment as suggested by a plethora of in vitro and in vivo studies and clinical trials. Emerging real-world data have confirmed its effectiveness, and there are currently datasets evaluating its efficacy and safety against SARS-CoV-2 infections in various clinical scenarios, including some that are not in the SmPC recommendations according for COVID-19 pharmacotherapy. Remdesivir increases the chance of recovery, reduces progression to severe disease, lowers mortality rates, and exhibits beneficial post-hospitalization outcomes, especially when used early in the course of the disease. Strong evidence suggests the expansion of remdesivir use in special populations (e.g., pregnancy, immunosuppression, renal impairment, transplantation, elderly and co-medicated patients) where the benefits of treatment outweigh the risk of adverse effects. In this article, we attempt to overview the available real-world data of remdesivir pharmacotherapy. With the unpredictable course of COVID-19, we need to utilize all available knowledge to bridge the gap between clinical research and clinical practice and be sufficiently prepared for the future.

Modulation of in Vitro SARS-CoV-2 Infection by Stephania tetrandra and Its Alkaloid Constituents

Botanical natural products have been widely consumed for their purported usefulness against COVID-19. Here, six botanical species from multiple sources and 173 isolated natural product compounds were screened for blockade of wild-type (WT) SARS-CoV-2 infection in human 293T epithelial cells overexpressing ACE-2 and TMPRSS2 protease (293TAT). Antiviral activity was demonstrated by an extract from Stephania tetrandra. Extract fractionation, liquid chromatography-mass spectrometry (LC-MS), antiviral assays, and computational analyses revealed that the alkaloid fraction and purified alkaloids tetrandrine, fangchinoline, and cepharanthine inhibited WT SARS-CoV-2 infection. The alkaloids and alkaloid fraction also inhibited the delta variant of concern but not WT SARS-CoV-2 in VeroAT cells. Membrane permeability assays demonstrate that the alkaloids are biologically available, although fangchinoline showed lower permeability than tetrandrine. At high concentrations, the extract, alkaloid fractions, and pure alkaloids induced phospholipidosis in 293TAT cells and less so in VeroAT cells. Gene expression profiling during virus infection suggested that alkaloid fraction and tetrandrine displayed similar effects on cellular gene expression and pathways, while fangchinoline showed distinct effects on cells. Our study demonstrates a multifaceted approach to systematically investigate the diverse activities conferred by complex botanical mixtures, their cell-context specificity, and their pleiotropic effects on biological systems.

Remdesivir Alone or in Combination with Monoclonal Antibodies as an Early Treatment to Prevent Severe COVID-19 in Patients with Mild/Moderate Disease at High Risk of Progression: A Single Centre, Real-Life Study

Early treatment with antivirals against SARS-CoV-2 infection can prevent the onset of severe COVID-19 in fragile and immunocompromised patients. In this real-life, prospective, observational study, we evaluated efficacy and safety of a 3-day early treatment with remdesivir in adult and fragile patients with a diagnosis of SARS-CoV-2 infection who referred to the COVID-19 early treatment service of Infectious Diseases Unit of University of Naples Federico from 10 January 2022 to 31 March 2022. The included patients could be treated with either remdesivir alone or with remdesivir plus a monoclonal antibody with activity against SARS-CoV-2. Among the 62 included patients, we showed low rates of hospitalization (8%), increase in oxygen supplementation (3.2%), ICU admission (1.6%) and death (1.6%). The rate of disease progression was 8% and it was similar in patients treated with remdesivir alone or in combination with monoclonal antibodies (6.7% and 9.4%, respectively; p = 0.531). The rate of adverse drug reaction was low and similar in the two groups (13.3% in patients treated with remdesivir, 15.6% in patients treated with the combination; p = 0.543). Most common adverse events were headache and fever. In conclusion, in our cohort of patients at a high risk of worse COVID-19 outcomes, an early course of remdesivir showed low rates of disease progression and adverse drug reactions.

Sierra SARS-CoV-2 sequence and antiviral resistance analysis program

INTRODUCTION

Although most laboratories are capable of employing established protocols to perform full-genome SARS-CoV-2 sequencing, many are unable to assess sequence quality, select appropriate mutation-detection thresholds, or report on the potential clinical significance of mutations in the targets of antiviral therapy METHODS: We describe the technical aspects and benchmark the performance of Sierra SARS-CoV-2, a program designed to perform these functions on user-submitted FASTQ and FASTA sequence files and lists of Spike mutations. Sierra SARS-CoV-2 indicates which sequences contain an unexpectedly large number of unusual mutations and which mutations are associated with reduced susceptibility to clinical stage mAbs, the RdRP inhibitor remdesivir, or the Mpro inhibitor nirmatrelvir RESULTS: To assess the performance of Sierra SARS-CoV-2 on FASTQ files, we applied it to 600 representative FASTQ sequences and compared the results to the COVID-19 EDGE program. To assess its performance on FASTA files, we applied it to nearly one million representative FASTA sequences and compared the results to the GISAID mutation annotation. To assess its performance on mutations lists, we applied it to 13,578 distinct Spike RBD mutation patterns and showed that exactly or partially matching annotations were available for 88% of patterns CONCLUSION: Sierra SARS-CoV-2 leverages previously published data to improve the quality control of submitted viral genomic data and to provide functional annotation on the impact of mutations in the targets of antiviral SARS-CoV-2 therapy. The program can be found at https://covdb.stanford.edu/sierra/sars2/ and its source code at https://github.com/hivdb/sierra-sars2.

Combinations of Host- and Virus-Targeting Antiviral Drugs Confer Synergistic Suppression of SARS-CoV-2

Three directly acting antivirals (DAAs) demonstrated substantial reduction in COVID-19 hospitalizations and deaths in clinical trials. However, these agents did not completely prevent severe illness and are associated with cases of rebound illness and viral shedding. Combination regimens can enhance antiviral potency, reduce the emergence of drug-resistant variants, and lower the dose of each component in the combination. Concurrently targeting virus entry and virus replication offers opportunities to discover synergistic drug combinations. While combination antiviral drug treatments are standard for chronic RNA virus infections, no antiviral combination therapy has been approved for SARS-CoV-2. Here, we demonstrate that combining host-targeting antivirals (HTAs) that target TMPRSS2 and hence SARS-CoV-2 entry, with the DAA molnupiravir, which targets SARS-CoV-2 replication, synergistically suppresses SARS-CoV-2 infection in Calu-3 lung epithelial cells. Strong synergy was observed when molnupiravir, an oral drug, was combined with three TMPRSS2 (HTA) oral or inhaled inhibitors: camostat, avoralstat, or nafamostat. The combination of camostat plus molnupiravir was also effective against the beta and delta variants of concern. The pyrimidine biosynthesis inhibitor brequinar combined with molnupiravir also conferred robust synergistic inhibition. These HTA+DAA combinations had similar potency to the synergistic all-DAA combination of molnupiravir plus nirmatrelvir, the protease inhibitor found in paxlovid. Pharmacodynamic modeling allowed estimates of antiviral potency at all possible concentrations of each agent within plausible therapeutic ranges, suggesting possible in vivo efficacy. The triple combination of camostat, brequinar, and molnupiravir further increased antiviral potency. These findings support the development of HTA+DAA combinations for pandemic response and preparedness. IMPORTANCE Imagine a future viral pandemic where if you test positive for the new virus, you can quickly take some medicines at home for a few days so that you do not get too sick. To date, only single drugs have been approved for outpatient use against SARS-CoV-2, and we are learning that these have some limitations and may succumb to drug resistance. Here, we show that combinations of two oral drugs are better than the single ones in blocking SARS-CoV-2, and we use mathematical modeling to show that these drug combinations are likely to work in people. We also show that a combination of three oral drugs works even better at eradicating the virus. Our findings therefore bode well for the development of oral drug cocktails for at home use at the first sign of an infection by a coronavirus or other emerging viral pathogens.

Remdesivir resistance in transplant recipients with persistent COVID-19

The medical community currently lacks robust data regarding the incidence, prevalence, and clinical significance of mutations associated with resistance to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) therapeutics. This report describes two renal transplant recipients who, after remdesivir exposure, developed a de novo V792I RNA-dependent RNA polymerase (RdRp) mutation that has recently been found to confer resistance to remdesivir in vitro . To the best of our knowledge, this publication is the first to document the emergence of V792I in patients treated with remdesivir. Our work underscores the critical need for augmented efforts to identify concerning mutations and address their clinical implications.