Review on molnupiravir as a promising oral drug for the treatment of COVID-19

Small Molecule Drugs Targeting Viral Polymerases

Small molecules that specifically target viral polymerases-crucial enzymes governing viral genome transcription and replication-play a pivotal role in combating viral infections. Presently, approved polymerase inhibitors cover nine human viruses, spanning both DNA and RNA viruses. This review provides a comprehensive analysis of these licensed drugs, encompassing nucleoside/nucleotide inhibitors (NIs), non-nucleoside inhibitors (NNIs), and mutagenic agents. For each compound, we describe the specific targeted virus and related polymerase enzyme, the mechanism of action, and the relevant bioactivity data. This wealth of information serves as a valuable resource for researchers actively engaged in antiviral drug discovery efforts, offering a complete overview of established strategies as well as insights for shaping the development of next-generation antiviral therapeutics.

Rapid development and mass production of SARS-CoV-2 neutralizing chicken egg yolk antibodies with protective efficacy in hamsters

Despite the record speed of developing vaccines and therapeutics against the SARS-CoV-2 virus, it is not a given that such success can be secured in future pandemics. In addition, COVID-19 vaccination and application of therapeutics remain low in developing countries. Rapid and low cost mass production of antiviral IgY antibodies could be an attractive alternative or complementary option for vaccine and therapeutic development. In this article, we rapidly produced SARS-CoV-2 antigens, immunized hens and purified IgY antibodies in 2 months after the SARS-CoV-2 gene sequence became public. We further demonstrated that the IgY antibodies competitively block RBD binding to ACE2, neutralize authentic SARS-CoV-2 virus and effectively protect hamsters from SARS-CoV-2 challenge by preventing weight loss and lung pathology, representing the first comprehensive study with IgY antibodies. The process of mass production can be easily implemented in most developing countries and hence could become a new vital option in our toolbox for combating viral pandemics. This study could stimulate further studies, optimization and potential applications of IgY antibodies as therapeutics and prophylactics for human and animals.

Peptidomimetics as potent dual SARS-CoV-2 cathepsin-L and main protease inhibitors: In silico design, synthesis and pharmacological characterization

In this paper we present the design, synthesis, and biological evaluation of a new series of peptidomimetics acting as potent anti-SARS-CoV-2 agents. Starting from our previously described Main Protease (MPro) and Papain Like Protease (PLPro) dual inhibitor, CV11, here we disclose its high inhibitory activity against cathepsin L (CTSL) (IC50 = 19.80 ± 4.44 nM), an emerging target in SARS-CoV-2 infection machinery. An in silico design, inspired by the structure of CV11, led to the development of a library of peptidomimetics showing interesting activities against CTSL and Mpro, allowing us to trace the chemical requirements for the binding to both enzymes. The screening in Vero cells infected with 5 different SARS-CoV-2 variants of concerns, highlighted sub-micromolar activities for most of the synthesized compounds (13, 15, 16, 17 and 31) in agreement with the enzymatic inhibition assays results. The compounds showed lack of activity against several different RNA viruses except for the 229E and OC43 human coronavirus strains, also characterized by a cathepsin-L dependent release into the host cells. The most promising derivatives were also evaluated for their chemical and metabolic in-vitro stability, with derivatives 15 and 17 showing a suitable profile for further preclinical characterization.

Antivirals for Broader Coverage against Human Coronaviruses

Coronaviruses (CoVs) are enveloped positive-sense single-stranded RNA viruses with a genome that is 27-31 kbases in length. Critical genes include the spike (S), envelope (E), membrane (M), nucleocapsid (N) and nine accessory open reading frames encoding for non-structural proteins (NSPs) that have multiple roles in the replication cycle and immune evasion (1). There are seven known human CoVs that most likely appeared after zoonotic transfer, the most recent being SARS-CoV-2, responsible for the COVID-19 pandemic. Antivirals that have been approved by the FDA for use against COVID-19 such as Paxlovid can target and successfully inhibit the main protease (MPro) activity of multiple human CoVs; however, alternative proteomes encoded by CoV genomes have a closer genetic similarity to each other, suggesting that antivirals could be developed now that target future CoVs. New zoonotic introductions of CoVs to humans are inevitable and unpredictable. Therefore, new antivirals are required to control not only the next human CoV outbreak but also the four common human CoVs (229E, OC43, NL63, HKU1) that circulate frequently and to contain sporadic outbreaks of the severe human CoVs (SARS-CoV, MERS and SARS-CoV-2). The current study found that emerging antiviral drugs, such as Paxlovid, could target other CoVs, but only SARS-CoV-2 is known to be targeted in vivo. Other drugs which have the potential to target other human CoVs are still within clinical trials and are not yet available for public use. Monoclonal antibody (mAb) treatment and vaccines for SARS-CoV-2 can reduce mortality and hospitalisation rates; however, they target the Spike protein whose sequence mutates frequently and drifts. Spike is also not applicable for targeting other HCoVs as these are not well-conserved sequences among human CoVs. Thus, there is a need for readily available treatments globally that target all seven human CoVs and improve the preparedness for inevitable future outbreaks. Here, we discuss antiviral research, contributing to the control of common and severe CoV replication and transmission, including the current SARS-CoV-2 outbreak. The aim was to identify common features of CoVs for antivirals, biologics and vaccines that could reduce the scientific, political, economic and public health strain caused by CoV outbreaks now and in the future.

After the Hurricane: Anti-COVID-19 Drugs Development, Molecular Mechanisms of Action and Future Perspectives

Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) is a new coronavirus in the Coronaviridae family. The COVID-19 pandemic, caused by SARS-CoV-2, has undoubtedly been the largest crisis of the twenty-first century, resulting in over 6.8 million deaths and 686 million confirmed cases, creating a global public health issue. Hundreds of notable articles have been published since the onset of this pandemic to justify the cause of viral spread, viable preventive measures, and future therapeutic approaches. As a result, this review was developed to provide a summary of the current anti-COVID-19 drugs, as well as their timeline, molecular mode of action, and efficacy. It also sheds light on potential future treatment options. Several medications, notably hydroxychloroquine and lopinavir/ritonavir, were initially claimed to be effective in the treatment of SARS-CoV-2 but eventually demonstrated inadequate activity, and the Food and Drug Administration (FDA) withdrew hydroxychloroquine. Clinical trials and investigations, on the other hand, have demonstrated the efficacy of remdesivir, convalescent plasma, and monoclonal antibodies, 6-Thioguanine, hepatitis C protease inhibitors, and molnupiravir. Other therapeutics, including inhaled medicines, flavonoids, and aptamers, could pave the way for the creation of novel anti-COVID-19 therapies. As future pandemics are unavoidable, this article urges immediate action and extensive research efforts to develop potent specialized anti-COVID-19 medications.

Synthesis and Antiviral Activity of Novel β-D-N4-Hydroxycytidine Ester Prodrugs as Potential Compounds for the Treatment of SARS-CoV-2 and Other Human Coronaviruses

The spread of COVID-19 infection continues due to the emergence of multiple transmissible and immune-evasive variants of the SARS-CoV-2 virus. Although various vaccines have been developed and several drugs have been approved for the treatment of COVID-19, the development of new drugs to combat COVID-19 is still necessary. In this work, new 5'-O-ester derivatives of N4-hydroxycytidine based on carboxylic acids were developed and synthesized by Steglich esterification. The antiviral activity of the compounds was assessed in vitro-inhibiting the cytopathic effect of HCoV-229E, and three variants of SARS-CoV-2, on huh-7 and Vero E6 cells. Data have shown that most synthesized derivatives exhibit high activity against coronaviruses. In addition, the relationship between the chemical structure of the compounds and their antiviral effect has been established. The obtained results show that the most active compound was conjugate SN_22 based on 3-methyl phenoxyacetic acid. The results of this study indicate the potential advantage of the chemical strategies used to modify NHC as a promising avenue to be explored in vivo, which could lead to the development of drugs with improved pharmacological properties that potently inhibit SARS-CoV-2.

A sensitive UPLC-MS/MS method for the simultaneous assay and trace level genotoxic impurities quantification of SARS-CoV-2 inhibitor-Molnupiravir in its pure and formulation dosage forms using fractional factorial design

Two potential genotoxic impurities were identified (PGTIs)-viz. 4-amino-1-((2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)pyrimidin-2(1H)-one (PGTI-1), and 1-(2R,3R,4S,5R)-3,4-dihydroxy-5-(hydroxymethyl)tetrahydrofuran-2-yl)pyrimidin-2,4(1H,3H)-one (PGTI-II) in the Molnupiravir (MOPR) synthetic routes. COVID-19 disease was treated with MOPR when mild to moderate symptoms occurred. Two (Q)-SAR methods were used to assess the genotoxicity, and projected results were positive and categorized into Class-3 for both PGTIs. A simple, accurate and highly sensitive ultra-performance liquid chromatography-mass spectrometry (UPLC-MS/MS) method was optimized for the simultaneous quantification of the assay, and these impurities in MOPR drug substance and formulation dosage form. The multiple reaction monitoring (MRM) technique was utilized for the quantification. Prior to the validation study, the UPLC-MS method conditions were optimised using fractional factorial design (FrFD). The optimized Critical Method Parameters (CMPs) include the percentage of Acetonitrile in MP B, Concentration of Formic acid in MP A, Cone Voltage, Capillary Voltage, Collision gas flow and Desolvation temperature were determined from the numerical optimization to be 12.50 %, 0.13 %, 13.6 V, 2.6 kV, 850 L/hr and 375 °C, respectively. The optimized chromatographic separation achieved on Waters Acquity HSS T3 C18 column (100 mm × 2.1 mm, 1.8 µm) in a gradient elution mode with 0.13% formic acid in water and acetonitrile as mobile phases, column temperature kept at 35 °C and flow rate at 0.5 mL/min. The method was successfully validated as per ICH guidelines, and demonstrated excellent linearity over the concentration range of 0.5-10 ppm for both PGTIs. The Pearson correlation coefficient of each impurity and MOPR was found to be higher than 0.999, and the recoveries were in between the range of 94.62 to 104.05% for both PGTIs and 99.10 to 100.25% for MOPR. It is also feasible to utilise this rapid method to quantify MOPR accurately in biological samples.

What are the current anti-COVID-19 drugs? From traditional to smart molecular mechanisms

BACKGROUND

Coronavirus disease 19 (COVID-19) is the disease caused by SARS-CoV-2, a highly infectious member of the coronavirus family, which emerged in December 2019 in "Wuhan, China". It induces respiratory illness ranging from mild symptoms to severe disease. It was declared a "pandemic" by the World Health Organization (WHO) in March 2020. Since then, a vast number of clinical and experimental studies have been conducted to identify effective approaches for its prevention and treatment.

MAIN BODY

The pathophysiology of COVID-19 represents an unprecedented challenge; it triggers a strong immune response, which may be exacerbated by "a cytokine storm syndrome". It also induces thrombogenesis and may trigger multi-organ injury. Therefore, different drug classes have been proposed for its treatment and prevention, such as antivirals, anti-SARS-CoV-2 antibody agents (monoclonal antibodies, convalescent plasma, and immunoglobulins), anti-inflammatory drugs, immunomodulators, and anticoagulant drugs. To the best of our knowledge, this review is the first to present, discuss, and summarize the current knowledge about the different drug classes used for the treatment of COVID-19, with special emphasis on their targets, mechanisms of action, and important adverse effects and drug interactions. Additionally, we spotlight the latest "October 2023" important guidelines (NIH, IDSA, and NICE) and FDA approval or authorization regarding the use of these agents in the management of COVID-19.

CONCLUSION

Despite the wide array of therapeutic strategies introduced for the treatment of COVID-19, one of the most prominent therapeutic challenges is SARS-CoV-2 mutations and emerging new variants and subvariants. Currently, the anti-COVID-19 drug pipeline is continuously affording novel treatments to face this growing challenge.

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.

Molnupiravir: an antiviral drug against COVID-19

SARS-CoV-2, the virus responsible for COVID-19, has caused numerous deaths worldwide and poses significant challenges. Researchers have recently studied a new antiviral drug called molnupiravir for treating COVID-19. This review examines the causes and immunopathogenesis of COVID-19, as well as the role of molnupiravir in its treatment. Molnupiravir is a prodrug of β-D-N4-hydroxyctytidine (NHC) and has demonstrated activity against various viruses, including MERS-CoV, SARS-CoV, SARS-CoV-2, and influenza virus. The active form of molnupiravir, NHC triphosphate, acts as a nucleoside analog that disrupts viral replication by causing mutations in the viral RNA, thereby inhibiting viral growth. This review summarizes the results of multiple clinical trials that have evaluated the effectiveness of molnupiravir against SARS-CoV-2 and its variants. Animal studies have also shown that molnupiravir significantly reduces the viral load and prevents transmission to other animals. Overall, molnupiravir has demonstrated strong efficacy and reasonable safety, reducing hospitalization rates by nearly 50% among COVID-19-positive individuals at risk of complications. Patients in clinical settings have tolerated molnupiravir well and experienced positive outcomes, such as clearance of viral RNA, decreased viral load, and reduced hospitalization rates. Additionally, compared to a placebo, molnupiravir has been associated with lower mortality rates. Therefore, molnupiravir can be a beneficial drug to treat patients suffering from SARS-CoV-2, and further studies can provide more information about its safety and efficacy.

Structure-Based Drug Design of RdRp Inhibitors against SARS-CoV-2

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has caused a worldwide pandemic since 2019, spreading rapidly and posing a significant threat to human health and life. With over 6 billion confirmed cases of the virus, the need for effective therapeutic drugs has become more urgent than ever before. RNA-dependent RNA polymerase (RdRp) is crucial in viral replication and transcription, catalysing viral RNA synthesis and serving as a promising therapeutic target for developing antiviral drugs. In this article, we explore the inhibition of RdRp as a potential treatment for viral diseases, analysing the structural information of RdRp in virus proliferation and summarizing the reported inhibitors' pharmacophore features and structure-activity relationship profiles. We hope that the information provided by this review will aid in structure-based drug design and aid in the global fight against SARS-CoV-2 infection.

Synthesis and evaluation of NHC derivatives and 4'-fluorouridine prodrugs

β-D-N4-Hydroxycytidine (NHC) derivatives with structural modifications at the C4', O4' or C6 position and 4'-fluorouridine prodrugs were synthesized and evaluated for their antiviral activities against respiratory syncytial virus (RSV) or influenza virus (IFV) in vitro. The NHC derivatives were found inactive, but 4'-fluorouridine and its prodrugs had potent anti-RSV and anti-IFV activities. 4'-Fluorouridine was proved to be a nucleoside with poor stability, but the tri-ester prodrugs exhibited enhanced stability, especially tri-isobutyrate ester 1a. This prodrug also showed excellent oral pharmacokinetic properties in rats, with potential to be an oral antiviral candidate.

Broad-spectrum coronavirus 3C-like protease peptidomimetic inhibitors effectively block SARS-CoV-2 replication in cells: Design, synthesis, biological evaluation, and X-ray structure determination

Despite the approval of vaccines, monoclonal antibodies and restrictions during the pandemic, the demand for new efficacious and safe antivirals is compelling to boost the therapeutic arsenal against the COVID-19. The viral 3-chymotrypsin-like protease (3CL^pro) is an essential enzyme for replication with high homology in the active site across CoVs and variants showing an almost unique specificity for Leu-Gln as P2-P1 residues, allowing the development of broad-spectrum inhibitors. The design, synthesis, biological activity, and cocrystal structural information of newly conceived peptidomimetic covalent reversible inhibitors are herein described. The inhibitors display an aldehyde warhead, a Gln mimetic at P1 and modified P2-P3 residues. Particularly, functionalized proline residues were inserted at P2 to stabilize the β-turn like bioactive conformation, modulating the affinity. The most potent compounds displayed low/sub-nM potency against the 3CL^pro of SARS-CoV-2 and MERS-CoV and inhibited viral replication of three human CoVs, i.e. SARS-CoV-2, MERS-CoV, and HCoV 229 in different cell lines. Particularly, derivative 12 exhibited nM-low μM antiviral activity depending on the virus, and the highest selectivity index. Some compounds were co-crystallized with SARS-CoV-2 3CL^pro validating our design. Altogether, these results foster future work toward broad-spectrum 3CL^pro inhibitors to challenge CoVs related pandemics.

Molnupiravir: A Versatile Prodrug against SARS-CoV-2 Variants

The nucleoside analog β-D-N4-hydroxycytidine is the active metabolite of the prodrug molnupiravir and is accepted as an efficient drug against COVID-19. Molnupiravir targets the RNA-dependent RNA polymerase (RdRp) enzyme, which is responsible for replicating the viral genome during the replication process of certain types of viruses. It works by disrupting the normal function of the RdRp enzyme, causing it to make mistakes during the replication of the viral genome. These mistakes can prevent the viral RNA from being transcribed, converted into a complementary DNA template, translated, or converted into a functional protein. By disrupting these crucial steps in the viral replication process, molnupiravir can effectively inhibit the replication of the virus and reduce its ability to cause disease. This review article sheds light on the impact of molnupiravir and its metabolite on SARS-CoV-2 variants of concern, such as delta, omicron, and hybrid/recombinant variants. The detailed mechanism and molecular interactions using molecular docking and dynamics have also been covered. The safety and tolerability of molnupiravir in patients with comorbidities have also been emphasized.

Theranostics for COVID-19 Antiviral Drugs: Prospects and Challenges for Worldwide Precision/Personalized Medicine

Coronavirus disease 2019 (COVID-19) is a systemic disease that impacts multiple organ systems with a complex clinical presentation and outcomes that can vary from person to person and between populations. To optimize COVID-19 treatment outcomes, and in light of the availability of antiviral drugs, there is a need for greater attention to the field of theranostics, the fusion of therapeutics and diagnostics. Theranostics tests would be invaluable, we suggest in this expert review, so as to optimize the efficacy and safety of current and future antiviral drugs against COVID-19. Theranostics would also assist in the design and implementation of clinical trials with antiviral drug candidates. We discuss here theranostics considering drugs such as remdesivir, Paxlovid™, and molnupiravir. All in all, we underscore that theranostics as a concept and practice is essential for efficient and safe health interventions against COVID-19 and other ecological crises in the 21st century.

An Overview of Repurposed Drugs for Potential COVID-19 Treatment

The COVID-19 pandemic caused by SARS-CoV-2 has placed severe constraints on healthcare systems around the globe. The SARS-CoV-2 virus has caused upheaval in the healthcare and economic sectors worldwide. On the 20th of May 2020, the World Health Organisation declared COVID-19 a global pandemic due to the unprecedented number of cases reported around the globe. As of the 4th of November 2022, there were 637,117,429 coronavirus cases reported globally by Worldometer stats, with 6,602,572 related deaths. In South Africa, there were approximately 4,029,496 coronavirus cases and 102,311 associated deaths. As such, there is a need for efficacious therapeutic regimes. There has been a paucity of knowledge encompassing the use of effective and specific antiviral drug therapies for treating COVID-19 since the outbreak. In this review, we provide valuable insights into the repurposing of current drugs for COVID-19. Drug repurposing provides a suitable option for the discovery of efficacious drugs for COVID-19, thereby decreasing the costs and turnaround times of drug development strategies. This review provides an overview of ten drugs, including antimalarial, antiparasitic, anti-inflammatory, nucleoside analogue, monoclonal-antibody drugs, that were repurposed for the potential treatment of COVID-19.

The MEK1/2 Inhibitor ATR-002 (Zapnometinib) Synergistically Potentiates the Antiviral Effect of Direct-Acting Anti-SARS-CoV-2 Drugs

The coronavirus disease 2019 (COVID-19) represents a global public health burden. In addition to vaccination, safe and efficient antiviral treatment strategies to restrict the viral spread within the patient are urgently needed. An alternative approach to a single-drug therapy is the combinatory use of virus- and host-targeted antivirals, leading to a synergistic boost of the drugs’ impact. In this study, we investigated the property of the MEK1/2 inhibitor ATR-002’s (zapnometinib) ability to potentiate the effect of direct-acting antivirals (DAA) against SARS-CoV-2 on viral replication. Treatment combinations of ATR-002 with nucleoside inhibitors Molnupiravir and Remdesivir or 3C-like protease inhibitors Nirmatrelvir and Ritonavir, the ingredients of the drug Paxlovid, were examined in Calu-3 cells to evaluate the advantage of their combinatory use against a SARS-CoV-2 infection. Synergistic effects could be observed for all tested combinations of ATR-002 with DAAs, as calculated by four different reference models in a concentration range that was very well-tolerated by the cells. Our results show that ATR-002 has the potential to act synergistically in combination with direct-acting antivirals, allowing for a reduction in the effective concentrations of the individual drugs and reducing side effects.

Paxlovid: Mechanism of Action, Synthesis, and In Silico Study

In this work, the discovery and description of PF-07321332, a major bioavailable oral SARS-CoV-2 protease inhibitor with in vitro human coronavirus antiviral activity, and excellent selection of off-target and in vivo immune profiles are reported. Various drugs and novel compound candidates for the treatment of the COVID-19 pandemic have been developed. PF-07321332 (or nirmatrelvir) is a new oral antiviral drug developed by Pfizer. In response to the pandemic, Pfizer has developed the COVID vaccine and in 2022 will launch its new major anti-SARS-Cov-2 protease inhibitor (PI). The combination of ritonavir and nirmatrelvir is under study in phase III of the clinical trial with a brand name Paxlovid. Paxlovid is an active 3Cl protease inhibitor. Paxlovid exerts its antiviral efficacy by inhibiting a necessary protease in the viral replication procedure. Proteases of coronavirus cleave several sites in the viral polyprotein where pyrrolidone was replaced by flexible glutamine. Due to the coronavirus pandemic, there is high demand for synthesis and development of this novel drug. Herein, we report the synthetic route and the mechanism of action was recently published on nirmatrelvir. Also, a comparison of the performance of two new oral antiviruses (molnupiravir and nirmatrelvir) for the treatment of COVID-19 is described. This review will be helpful for different disciplines such as biochemistry, organic chemistry, medicinal chemistry, and pharmacology.

A review on drug repurposing in COVID-19: from antiviral drugs to herbal alternatives

Background

COVID-19 is an illness caused by severe acute respiratory syndrome coronavirus 2. Due to its rapid spread, in March 2020 the World Health Organization (WHO) declared pandemic. Since the outbreak of pandemic many governments, scientists, and institutions started to work on new vaccines and finding of new and repurposing drugs.

Main body of the abstract

Drug repurposing is an excellent option for discovery of already used drugs, effective against COVID-19, lowering the cost of production, and shortening the period of delivery, especially when preclinical safety studies have already been performed. There are many approved drugs that showed significant results against COVID-19, like ivermectin and hydrochloroquine, including alternative treatment options against COVID-19, utilizing herbal medicine.

Short conclusion

This article summarized 11 repurposing drugs, their positive and negative health implications, along with traditional herbal alternatives, that harvest strong potential in efficient treatments options against COVID-19, with small or no significant side effects. Out of 11 repurposing drugs, four drugs are in status of emergency approval, most of them being in phase IV clinical trials. The first repurposing drug approved for clinical usage is remdesivir, whereas chloroquine and hydrochloroquine approval for emergency use was revoked by FDA for COVID-19 treatment in June 2020.

Outpatient treatment options to address the SARS-CoV-2 variant Omicron

INTRODUCTION

: On November 26, 2021, the World Health Organization's Technical Advisory Group on SARS-CoV-2 Virus Evolution designated PANGO lineage B.1.1.529 a variant of concern and gave it the designation Omicron. The following day, the United Kingdom reported its first two cases of Omicron, a novel variant that was thought to be more transmissible than other variants such as Delta, Beta, and Alpha.

AREAS COVERED

: Omicron has since become the dominant variant around the world, accounting for unprecedented case counts and hospitalizations. Omicron's high rate of spread has been attributed to a variety of factors, including enhanced replication in the upper airways (bronchi) as well as immune evasion.

EXPERT OPINION

: These intrinsic factors have implications for the approach to treatment. Monoclonal antibody therapies, which were highly effective against prior SARS-CoV-2 variants, were rendered largely ineffective against Omicron, and other antiviral options remain severely limited due to supply issues. This manuscript reviews the landscape of Omicron therapeutics and looks ahead to examine how these treatments and others may be used in the future to address the expanding threat of the Omicron variant.

Industrially Relevant Enzyme Cascades for Drug Synthesis and Their Ecological Assessment

Environmentally friendly and sustainable processes for the production of active pharmaceutical ingredients (APIs) gain increasing attention. Biocatalytic synthesis routes with enzyme cascades support many stated green production principles, for example, the reduced need for solvents or the biodegradability of enzymes. Multi-enzyme reactions have even more advantages such as the shift of the equilibrium towards the product side, no intermediate isolation, and the synthesis of complex molecules in one reaction pot. Despite the intriguing benefits, only a few enzyme cascades have been applied in the pharmaceutical industry so far. However, several new enzyme cascades are currently being developed in research that could be of great importance to the pharmaceutical industry. Here, we present multi-enzymatic reactions for API synthesis that are close to an industrial application. Their performances are comparable or exceed their chemical counterparts. A few enzyme cascades that are still in development are also introduced in this review. Economic and ecological considerations are made for some example cascades to assess their environmental friendliness and applicability.

Repurposing Probenecid to Inhibit SARS-CoV-2, Influenza Virus, and Respiratory Syncytial Virus (RSV) Replication

Viral replication and transmissibility are the principal causes of endemic and pandemic disease threats. There remains a need for broad-spectrum antiviral agents. The most common respiratory viruses are endemic agents such as coronaviruses, respiratory syncytial viruses, and influenza viruses. Although vaccines are available for SARS-CoV-2 and some influenza viruses, there is a paucity of effective antiviral drugs, while for RSV there is no vaccine available, and therapeutic treatments are very limited. We have previously shown that probenecid is safe and effective in limiting influenza A virus replication and SARS-CoV-2 replication, along with strong evidence showing inhibition of RSV replication in vitro and in vivo. This review article will describe the antiviral activity profile of probenecid against these three viruses.