Molnupiravir Does Not Induce Mutagenesis in Host Lung Cells during SARS-CoV-2 Treatment

Establishment of a National Surgical Tissue Biobank for Pediatric Crohn's Disease: An Implementation Feasibility Study

BACKGROUND

Crohn's disease (CD) is a lifelong gastrointestinal inflammatory condition that often requires surgery, particularly for patients diagnosed in childhood. CD has been linked to a combination of microbial, genetic, and environmental factors, but pathogenesis remains unknown. We outline a framework for multicenter surgical biobanking across a large geographic area, required to enable meaningful research, and evaluate feasibility using the 2016 Consolidated Standards of Reporting Trials (CONSORT) extension to randomized pilot and feasibility trials. We also share proof-of-concept RNA sequencing and immunohistochemistry results demonstrating adequacy to generate high-quality translational results.

METHODS

CD patients (5-17.2 years) scheduled for intestinal resection were included. Intra-abdominal sepsis was excluded. Surgeons from 10 Canadian children's hospitals underwent virtual training on tissue collection. Bowel, mesenteric fat, and lymph nodes were collected intraoperatively, fixed in formalin and RNAlater, and shipped overnight to a single lab. Feasibility was determined by protocol adherence, study recruitment efficacy, and tissue viability.

RESULTS

Tissue has been collected from 18 patients at seven sites since the study launched in 2023. The biobank is on track to bank 30-50 % of the total estimated eligible yearly case volume. Adherence to shipping protocols was impacted by the day of the week of the operation and by shipping office closures. Proof-of-concept immunohistochemistry demonstrated high-quality multiplex images. RNA sequencing identified 560 genes discriminating between inflamed and non-inflamed bowel.

CONCLUSIONS

Establishing a national biobank for surgically resected pediatric CD is feasible for translational investigations of CD pathogenesis. Preliminary experiments demonstrate functional protocols sufficient to collect research-quality tissue.

LEVEL OF EVIDENCE

Prognosis Study - Level IV.

A tale of two drugs: Molnupiravir and Paxlovid

The orally administered antiviral drug Lagevrio or molnupiravir (MOV) and the combination antiviral drug nirmatrelvir/ritonavir or Paxlovid (PAX) have been shown to reduce the likelihood of hospitalization and death for high-risk patients with COVID-19. Clinical studies, including those comparing PAX and MOV, were reviewed; both drugs are effective in reducing morbidity and mortality in COVID patients, although PAX generally appears to be more efficacious. Both drugs received Emergency Use Authorization in the United States for mild to moderate COVID-19 infection, while only PAX has subsequently been given full FDA approval. The principal disadvantage of PAX is that it interacts with many commonly used drugs, while MOV does not. The purpose of this review is to summarize current information and knowledge about these two drugs. The two drugs have completely different mechanisms of action. PAX inhibits viral replication while MOV induces viral replication errors that are expected to lead to viral inactivation. There is, however, the potential that MOV also could mutate host DNA and cause the virus to mutate into variants with new features. The package insert for MOV states that patients should be notified of relevant toxicity issues before administration. Sensitive mutation detection/analysis studies, such as error corrected Next Generation Sequencing (ecNGS) or HPRT mutation detection assays, in MOV-treated patients are needed to establish the safety of MOV.

Evaluation of N4-hydroxycytidine incorporation into nucleic acids of SARS-CoV-2-infected host cells by direct measurement with liquid chromatography-mass spectrometry

Molnupiravir, an orally administered prodrug of β-d-N4-hydroxycytidine (NHC), is incorporated into newly synthesized RNA by viral RNA-dependent RNA polymerase (RdRp). It is used for treatment of SARS-CoV-2 infections. Incorporation of NHC triphosphate into viral RNA inhibits replication of the virus, at least in part by introducing deleterious mutations. However, there is limited information on NHC incorporation into host RNA and reports on the risk of mutagenicity that molnupiravir/NHC pose to the host are conflicting. We used two liquid chromatography-mass spectrometry (LC-MS) methods to evaluate the incorporation of NHC into RNA and DNA of host Vero E6 cells in a SARS-CoV-2 infection model. To test this, host and viral RNA were degraded to their ribonucleosides, while host DNA was degraded to deoxyribonucleosides. Subsequently, nucleic acid constituents were analyzed by LC-MS, which offers specific, direct, and quantitative determination of incorporation. Our findings revealed concentration dependent NHC incorporation into host cell RNA in both infected and uninfected cell cultures, reaching a maximum of 1 in 7,093 bases. Analysis of host DNA revealed no presence of deoxy-N4-hydroxycytidine down to a detection limit of 1 in 133,000 bases. Our findings therefore suggest minimal to no NHC incorporation into host DNA, indicating a low probability of significant host cell mutagenicity associated with its use.

Shaping the future of antiviral Treatment: Spotlight on Nucleobase-Containing drugs and their revolutionary impact

Nucleobases serve as essential molecular frameworks present in both natural and synthetic compounds that exhibit notable antiviral activity. Through molecular modifications, novel nucleobase-containing drugs (NCDs) have been developed, exhibiting enhanced antiviral activity against a wide range of viruses, including the recently emerged SARS‑CoV‑2. This article provides a detailed examination of the significant advancements in NCDs from 2015 till current, encompassing various aspects concerning their mechanisms of action, pharmacology and antiviral properties. Additionally, the article discusses antiviral prodrugs relevant to the scope of this review. It fills in the knowledge gap by examining the structure-activity relationship and trend of NCDs as therapeutics against a diverse range of viral diseases, either as approved drugs, clinical candidates or as early-stage development prospects. Moreover, the article highlights on the status of this field of study and addresses the prevailing limitations encountered.

Atypical Mutational Spectrum of SARS-CoV-2 Replicating in the Presence of Ribavirin

We report that ribavirin exerts an inhibitory and mutagenic activity on SARS-CoV-2-infecting Vero cells, with a therapeutic index higher than 10. Deep sequencing analysis of the mutant spectrum of SARS-CoV-2 replicating in the absence or presence of ribavirin indicated an increase in the number of mutations, but not in deletions, and modification of diversity indices, expected from a mutagenic activity. Notably, the major mutation types enhanced by replication in the presence of ribavirin were A→G and U→C transitions, a pattern which is opposite to the dominance of G→A and C→U transitions previously described for most RNA viruses. Implications of the inhibitory activity of ribavirin, and the atypical mutational bias produced on SARS-CoV-2, for the search for synergistic anti-COVID-19 lethal mutagen combinations are discussed.

The preclinical discovery and development of molnupiravir for the treatment of SARS-CoV-2 (COVID-19)

INTRODUCTION

Molnupiravir (MOV) is a broad-spectrum oral antiviral agent approved for the treatment of COVID-19. The results from in vitro and in vivo studies suggested MOV activity against many RNA viruses such as influenza virus and some alphaviruses agents of epidemic encephalitis. MOV is a prodrug metabolized into the ribonucleoside analog β-D-N⁴-hydroxycytidine. It is incorporated into the viral RNA chain causing mutations impairing coding activity of the virus, thereby inhibiting viral replication.

AREAS COVERED

This review analyzes the in vitro and in vivo studies that have highlighted the efficacy of MOV and the main pre-authorization randomized controlled trials evaluating its safety, tolerability, and pharmacokinetics, as well as its antiviral efficacy against SARS-COV-2 infection.

EXPERT OPINION

MOV is an antiviral agent with an excellent tolerability profile with few drug-drug interactions. Treatment of mild-to-moderate COVID-19 can benefit from MOV administration in the precocious phases of the disease, prior to the trigger of an aberrant immune response responsible for the parenchymal damage to pulmonary and extrapulmonary tissues. However, its suspected mutagenic effect can be a factor limiting its use at least in selected populations and studies on its teratogen effects should be planned before it is authorized for use in the pediatric population or in pregnant women.

Quasispecies Fitness Partition to Characterize the Molecular Status of a Viral Population. Negative Effect of Early Ribavirin Discontinuation in a Chronically Infected HEV Patient

The changes occurring in viral quasispecies populations during infection have been monitored using diversity indices, nucleotide diversity, and several other indices to summarize the quasispecies structure in a single value. In this study, we present a method to partition quasispecies haplotypes into four fractions according to their fitness: the master haplotype, rare haplotypes at two levels (those present at <0.1%, and those at 0.1−1%), and a fourth fraction that we term emerging haplotypes, present at frequencies >1%, but less than that of the master haplotype. We propose that by determining the changes occurring in the volume of the four quasispecies fitness fractions together with those of the Hill number profile we will be able to visualize and analyze the molecular changes in the composition of a quasispecies with time. To develop this concept, we used three data sets: a technical clone of the complete SARS-CoV-2 spike gene, a subset of data previously used in a study of rare haplotypes, and data from a clinical follow-up study of a patient chronically infected with HEV and treated with ribavirin. The viral response to ribavirin mutagenic treatment was selection of a rich set of synonymous haplotypes. The mutation spectrum was very complex at the nucleotide level, but at the protein (phenotypic/functional) level the pattern differed, showing a highly prevalent master phenotype. We discuss the putative implications of this observation in relation to mutagenic antiviral treatment.

Real-world effectiveness of molnupiravir and nirmatrelvir plus ritonavir against mortality, hospitalisation, and in-hospital outcomes among community-dwelling, ambulatory patients with confirmed SARS-CoV-2 infection during the omicron wave in Hong Kong: an observational study

BACKGROUND

Little is known about the real-world effectiveness of oral antivirals against the SARS-CoV-2 omicron (B.1.1.529) variant. We aimed to assess the clinical effectiveness of two oral antiviral drugs among community-dwelling COVID-19 outpatients in Hong Kong.

METHODS

In this observational study, we used data from the Hong Kong Hospital Authority to identify an unselected, territory-wide cohort of non-hospitalised patients with an officially registered diagnosis of SARS-CoV-2 infection between Feb 26 and June 26, 2022, during the period in which the omicron subvariant BA.2.2 was dominant in Hong Kong. We used a retrospective cohort design as primary analysis, and a case-control design as sensitivity analysis. We identified patients with COVID-19 who received either molnupiravir (800 mg twice daily for 5 days) or nirmatrelvir plus ritonavir (nirmatrelvir 300 mg and ritonavir 100 mg twice daily for 5 days, or nirmatrelvir 150 mg and ritonavir 100 mg if estimated glomerular filtration rate was 30-59 mL/min per 1·73 m2). Outpatient oral antiviral users were matched with controls using propensity score (1:10) according to age, sex, date of SARS-CoV-2 infection diagnosis, Charlson Comorbidity Index score, and vaccination status. Study outcomes were death, COVID-19-related hospitalisation, and in-hospital disease progression (in-hospital death, invasive mechanical ventilation, or intensive care unit admission). Hazard ratios (HRs) were estimated by Cox regression for the primary analysis, and odds ratios in oral antiviral users compared with non-users by logistic regression for the sensitivity analysis.

FINDINGS

Among 1 074 856 non-hospitalised patients with COVID-19, 5383 received molnupiravir and 6464 received nirmatrelvir plus ritonavir in the community setting. Patients were followed up for a median of 103 days in the molnupiravir group and 99 days in the nirmatrelvir plus ritonavir group. Compared with nirmatrelvir plus ritonavir users, those on molnupiravir were older (4758 [85·9%] vs 4418 [88.7%] aged >60 years) and less likely to have been fully vaccinated (1850 [33·4%] vs 800 [16·1%]). Molnupiravir use was associated with lower risks of death (HR 0·76 [95% CI 0·61-0·95]) and in-hospital disease progression (0·57 [0·43-0·76]) than non-use was, whereas risk of hospitalisation was similar in both groups (0·98 [0·89-1·06]). Nirmatrelvir plus ritonavir use was associated with lower risks of death (0·34 [0·22-0·52]), hospitalisation (0·76 [0·67-0·86]), and in-hospital disease progression (0·57 [0·38-0·87]) than non-use was. We consistently found reduced risks of mortality and hospitalisation associated with early oral antiviral use among older patients. The findings from the case-control analysis broadly supported those from the primary analysis.

INTERPRETATION

During Hong Kong's wave of SARS-CoV-2 omicron subvariant BA.2.2, among non-hospitalised patients with COVID-19, early initiation of novel oral antivirals was associated with reduced risks of mortality and in-hospital disease progression. Nirmatrelvir plus ritonavir use was additionally associated with a reduced risk of hospitalisation.

FUNDING

Health and Medical Research Fund, Health Bureau, Government of Hong Kong Special Administrative Region, China.

TRANSLATION

For the Chinese translation of the abstract see Supplementary Materials section.

Repurposing Molnupiravir for COVID-19: The Mechanisms of Antiviral Activity

Molnupiravir is a β-d-N4-hydroxycytidine-5'-isopropyl ester (NHC) compound that exerts antiviral activity against various RNA viruses such as influenza, SARS, and Ebola viruses. Thus, the repurposing of Molnupiravir has gained significant attention for combatting infection with SARS-CoV-2, the etiological agent of COVID-19. Recently, Molnupiravir was granted authorization for the treatment of mild-to-moderate COVID-19 in adults. Findings from in vitro experiments, in vivo studies and clinical trials reveal that Molnupiravir is effective against SARS-CoV-2 by inducing viral RNA mutagenesis, thereby giving rise to mutated complementary RNA strands that generate non-functional viruses. To date, the data collectively suggest that Molnupiravir possesses promising antiviral activity as well as favorable prophylactic efficacy, attributed to its effective mutagenic property of disrupting viral replication. This review discusses the mechanisms of action of Molnupiravir and highlights its clinical utility by disabling SARS-CoV-2 replication, thereby ameliorating COVID-19 severity. Despite relatively few short-term adverse effects thus far, further detailed clinical studies and long-term pharmacovigilance are needed in view of its mutagenic effects.

First-generation Oral Antivirals Against SARS-CoV-2

Background

Objectives

Sources

Content

Implications

Oral antiviral treatments for COVID-19: opportunities and challenges

The use of antiviral COVID-19 medications can successfully inhibit SARS-CoV-2 replication and prevent disease progression to a more severe form. However, the timing of antiviral treatment plays a crucial role in this regard. Oral antiviral drugs provide an opportunity to manage SARS-CoV-2 infection without a need for hospital admission, easing the general burden that COVID-19 can have on the healthcare system. This review paper (i) presents the potential pharmaceutical antiviral targets, including various host-based targets and viral-based targets, (ii) characterizes the first-generation anti-SARS-CoV-2 oral drugs (nirmatrelvir/ritonavir and molnupiravir), (iii) summarizes the clinical progress of other oral antivirals for use in COVID-19, (iv) discusses ethical issues in such clinical trials and (v) presents challenges associated with the use of oral antivirals in clinical practice. Oral COVID-19 antivirals represent a part of the strategy to adapt to long-term co-existence with SARS-CoV-2 in a manner that prevents healthcare from being overwhelmed. It is pivotal to ensure equal and fair global access to the currently available oral antivirals and those authorized in the future.