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

Anti-SARS-CoV-2 gapmer antisense oligonucleotides targeting the main protease region of viral RNA

Given the worldwide risk for the outbreak of emerging/re-emerging respiratory viruses, establishment of new antiviral strategies is greatly demanded. In this study, we present a scheme to identify gapmer antisense oligonucleotides (ASOs) targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA that efficiently inhibit viral replication. We synthesized approximately 300 gapmer ASOs designed to target various SARS-CoV-2 RNA regions and evaluated their activity in cell-based assays. Through a multistep screening in cell culture systems, we identified that ASO#41, targeting the coding region for viral main protease, reduced SARS-CoV-2 RNA levels in infected cells and inhibited virus-induced cytopathic effects. Antiviral effect of ASO#41 was also observed in iPS cell-derived human lung organoids. ASO#41 depleted intracellular viral RNAs during genome replication in an endogenous RNaseH-dependent manner. ASO#41 showed a wide range of antiviral activity against SARS-CoV-2 variants of concern including Alpha, Delta, and Omicron. Intranasal administration to mice exhibited intracellular accumulation of ASO#41 in the lung and significantly reduced the viral infectious titer, with milder body weight loss due to SARS-CoV-2 infection. Further chemical modification with phosphoryl guanidine-containing backbone linkages provided an elevation of anti-SARS-CoV-2 activity, with 23.4 nM of 50% antiviral inhibitory concentration, one of the strongest anti-SARS-CoV-2 ASOs reported so far. Our study presents an approach to identify active ASOs against SARS-CoV-2, which is potentially useful for establishing an antiviral strategy by targeting genome RNA of respiratory viruses.

A path from synthesis to emergency use authorization of molnupiravir as a COVID-19 therapy

Coronaviruses are a group of enveloped viruses with non-segmented, single-stranded, and positive-sense RNA genomes. It belongs to the 'Coronaviridae family', responsible for various diseases, including the common cold, SARS, and MERS. The COVID-19 pandemic, which began in March 2020, has affected 209 countries, infected over a million people, and claimed over 50,000 lives. Significant efforts have been made by repurposing several approved drugs including antiviral, to combat the COVID-19 pandemic. Molnupiravir is found to be the first orally acting efficacious drug to treat COVID-19 cases. It was approved for medical use in the UK in November 2021 and other countries, including USFDA, which granted approval an emergency use authorization (EUA) for treating adults with mild to moderate COVID-19 patients. Considering the importance of molnupiravir, the present review deals with its various synthetic strategies, pharmacokinetics, bio-efficacy, toxicity, and safety profiles. The comprehensive information along with critical analysis will be very handy for a wide range of audience including medicinal chemists in the arena of antiviral drug discovery especially anti-viral drugs against any variant of COVID-19.

Safety, tolerability, and pharmacokinetics of the novel RdRp inhibitor SHEN26 against SARS-CoV-2: a randomized, placebo-controlled, double-blind Phase I study in healthy subjects

BACKGROUND

SHEN26, an oral broad-spectrum antiviral drug, possesses potent preclinical activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and has a favorable safety profile.

METHODS

We report safety, tolerability, and pharmacokinetic data from a randomized, double-blind, placebo-controlled phase I study of SHEN26. Eighty-six healthy subjects were enrolled in the three studies: a single ascending-dose study (SAD), a multiple ascending-dose study (MAD), and a food-effect study (FE).

RESULTS

In the SAD trial, the maximum observed plasma concentration (Cmax) and area under the curve (AUC) of the SHEN26 rapid metabolite SHEN26-69-0 increased approximately dose-proportionally in the 50-400 mg fasting dose range. In the 800 mg dose group, standard meals increased the Cmax and AUC of SHEN26-69-0. In the MAD trial, the accumulation ratios of Cmax and AUC indicated slight accumulation upon repeated SHEN26 dosing. In the FE trial, a high-fat meal prolonged the time to maximum plasma concentration (Tmax) and increased the Cmax and AUC of SHEN26-69-0 compared with fasting administration. Most treatment-related adverse events were mild and resolved without treatment.

CONCLUSION

SHEN26 demonstrated satisfactory safety and tolerability in healthy subjects, which supports the continued study of SHEN26 against SARS-CoV-2.

TRIAL REGISTRATION

The trial is registered in ClinicalTrials.gov (CT. gov identifier: NCT05504746).

Adverse events related to drug-drug interactions in COVID-19 patients. A persistent concern in the post-pandemic era: a systematic review

INTRODUCTION

Since COVID-19 patients are often polytreated, monitoring drug-drug interaction (DDIs) is necessary. We evaluated whether drugs used after the second COVID-19 pandemic wave were associated with DDI-related adverse events and the role of drug interaction checkers in identifying them.

METHODS

The study (PROSPERO-ID: CRD42024507634) included: 1) consulting the drug interaction checkers Drugs.com, Liverpool COVID-19 Interactions, LexiComp, Medscape, and Micromedex; 2) systematic review; 3) reviewed studies analysis; 4) evaluating drug interaction checkers potential to anticipate DDI-related adverse events.The systematic review was performed searching PubMed, Scopus, ScienceDirect, and Cochrane databases from 1 March 2022 to 11 November 2023. Observational studies, and clinical trials were included. Article without reporting direct association between DDIs and adverse events were excluded. The risk of bias was assessed by Newcastle-Ottawa scale.

RESULTS

The most frequent DDIs involved nirmatrelvir/ritonavir (N/R) and fluvoxamine. Fifteen studies, including 150 patients and 35 DDI-related outcomes, were analyzed. The most frequent DDIs involved tacrolimus with N/R, resulting in creatinine increase.Eighty percent of reported DDI-related adverse events would have been identified by all drug-interaction checkers, while the remaining 20% by at least 2 of them.

CONCLUSIONS

Drug interaction checkers are useful but show inconsistencies. Multiple sources are needed to tailor treatment in the context of COVID-19.

Cathepsin-Targeting SARS-CoV-2 Inhibitors: Design, Synthesis, and Biological Activity

Cathepsins (Cats) are proteases that mediate the successful entry of SARS-CoV-2 into host cells. We designed and synthesized a tailored series of 21 peptidomimetics and evaluated their inhibitory activity against human cathepsins L, B, and S. Structural diversity was realized by combinations of different C-terminal warhead functions and N-terminal capping groups, while a central Leu-Phe fragment was maintained. Several compounds were identified as promising cathepsin L and S inhibitors with Ki values in the low nanomolar to subnanomolar range, for example, the peptide aldehydes 9a and 9b (9a, 2.67 nM, CatL; 0.455 nM, CatS; 9b, 1.76 nM, CatL; 0.512 nM, CatS). The compounds' inhibitory activity against the main protease of SARS-CoV-2 (Mpro) was additionally investigated. Based on the results at CatL, CatS, and Mpro, selected inhibitors were subjected to investigations of their antiviral activity in cell-based assays. In particular, the peptide nitrile 11e exhibited promising antiviral activity with an EC50 value of 38.4 nM in Calu-3 cells without showing cytotoxicity. High metabolic stability and favorable pharmacokinetic properties make 11e suitable for further preclinical development.

An active metabolite of the anti-COVID-19 drug molnupiravir impairs mouse preimplantation embryos at clinically relevant concentrations

Molnupiravir is a nucleoside analog antiviral that is authorized for use in the treatment of COVID-19. For its therapeutic action, molnupiravir is converted after ingestion to the active metabolite N4-hydroxycytidine, which is incorporated into the viral genome to cause lethal mutagenesis. Molnupiravir is not recommended for use during pregnancy, because preclinical animal studies suggest that it is hazardous to developing embryos. However, the mechanisms underlying the embryotoxicity of molnupiravir are currently unknown. To gain mechanistic insights into its embryotoxic action, the effects of molnupiravir and N4-hydroxycytidine were examined on the in vitro development of mouse preimplantation embryos. Molnupiravir did not prevent blastocyst formation even at concentrations that were much higher than the therapeutic plasma levels. By contrast, N4-hyroxycytidine exhibited potent toxicity, as it interfered with blastocyst formation and caused extensive cell death at concentrations below the therapeutic plasma levels. The adverse effects of N4-hydroxycytidine were dependent on the timing of exposure, such that treatment after the 8-cell stage, but not before it, caused embryotoxicity. Transcriptomic analysis of N4-hydroxycytidine-exposed embryos, together with the examination of eIF-2a protein phosphorylation level, suggested that N4-hydroxycytidine induced the integrated stress response. The adverse effects of N4-hydroxycytidine were significantly alleviated by the co-treatment with S-(4-nitrobenzyl)-6-thioinosine, suggesting that the embryotoxic potential of N4-hydroxycytidine requires the activity of nucleoside transporters. These findings show that the active metabolite of molnupiravir impairs preimplantation development at clinically relevant concentrations, providing mechanistic foundation for further studies on the embryotoxic potential of molnupiravir and other related nucleoside antivirals.

Preclinical discovery and development of nirmatrelvir/ritonavir combinational therapy for the treatment of COVID-19 and the lessons learned from SARS-COV-2 variants

INTRODUCTION

Nirmatrelvir/ritonavir (Paxlovid®) represent an oral antiviral therapy approved for the treatment of COVID-19. Extensive in vitro and in vivo studies have reported the promising activity of nirmatrelvir/ritonavir against numerous emerging viruses. This combination consists of nirmatrelvir, a protease reversible inhibitor of coronavirus 3CLpro mainly metabolized by cytochrome P450 (CYP)3A4, and ritonavir, an inhibitor of the CYP3A isoforms that enhances the efficacy of nirmatrelvir by fixing its suboptimal pharmacokinetic properties.

AREAS COVERED

This review comprehensively examines the efficacy of nirmatrelvir/ritonavir through rigorous analysis of in vitro and in vivo studies. Moreover, it thoroughly assesses its safety, tolerability, pharmacokinetics, and antiviral efficacy against SARS-COV-2 infection, based on the main pre-authorization randomized controlled trials.

EXPERT OPINION

Nirmatrelvir/ritonavir has a good tolerability profile. Its administration during the early stages of mild-to-moderate COVID-19 holds potential benefits, as it can help prevent the onset of an aberrant immune response that could lead to pulmonary and extra-pulmonary complications. However, its drug - drug interactions can be a factor limiting its use, at least in populations on some chronic therapies, along with the risk of infection relapse after treatment.

BIOEQUIVALENCE STUDY OF GENERIC MOLNUPIRAVIR IN HEALTHY VOLUNTEERS

Molnupiravir is one of the drugs for the etiotropic therapy of a new coronavirus infection COVID-19. It has confirmed its clinical efficacy in the treatment of patients with mild and moderate COVID-19, including those who are at high risk of progressing to severe disease.

The aim of the study was to evaluate bioequivalence of the generic drug molnupiravir ALARIO-TL and the original drug Lagevrio with a single oral administration in healthy volunteers.

Materials and methods. This bioequivalence study was an open, randomized, two-period crossover study. In each of the two periods, volunteers received a single dose of the test drug, or reference drug molnupiravir, in the form of capsules at the dose of 200 mg. The washout period between the doses was 3 days. To determine pharmacokinetic (PK) parameters and bioequivalence, the concentration the concentration of N-hydrozycytidine (NHC), the main molnupiravir metabolit in the blood plasma of volunteers was evaluated. The blood plasma sampling was carried out in the range from 0 to 16 hours in each of the study periods. Bioequivalence was assessed by comparing 90% confidence intervals (CIs) for the ratio of geometric means of AUC(0–16) and Cmax of the test drug and reference drugs with the established equivalence limits of 80.00 – 125.00%.

Results. A total of 28 healthy male volunteers were included in the study. According to the results of the statistical analysis, after the administration of the test and reference drugs, the 90% CIs for the ratio of the geometric means of AUC (0–16) and Cmax were 96.31% – 113.64% and 91.37% – 114.8%, respectively. These intervals fit within the established limits of 80.00–125.00%, which confirms the bioequivalence of the drugs. When comparing the frequency of the individual adverse events registration, no significant differences were found out after the administration of the test and reference drugs.

Conclusion. Based on the results of this study, it can be concluded that the test and reference drugs of molnupiravir are bioequivalent. In addition, the data obtained indicate that the drugs have similar safety profiles.