Repurposed pharmacological agents for the potential treatment of COVID-19: a literature review

Unveiling the "Template-Dependent" Inhibition on the Viral Transcription of SARS-CoV-2

Remdesivir is one nucleotide analogue prodrug capable to terminate RNA synthesis in SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) by two distinct mechanisms. Although the "delayed chain termination" mechanism has been extensively investigated, the "template-dependent" inhibitory mechanism remains elusive. In this study, we have demonstrated that remdesivir embedded in the template strand seldom directly disrupted the complementary NTP incorporation at the active site. Instead, the translocation of remdesivir from the +2 to the +1 site was hindered due to the steric clash with V557. Moreover, we have elucidated the molecular mechanism characterizing the drug resistance upon V557L mutation. Overall, our studies have provided valuable insight into the "template-dependent" inhibitory mechanism exerted by remdesivir on SARS-CoV-2 RdRp and paved venues for an alternative antiviral strategy for the COVID-19 pandemic. As the "template-dependent" inhibition occurs across diverse viral RdRps, our findings may also shed light on a common acting mechanism of inhibitors.

The Synergistic Inhibition of Coronavirus Replication and Induced Cytokine Production by Ciclesonide and the Tylophorine-Based Compound Dbq33b

Ciclesonide is an inhaled corticosteroid used to treat asthma and has been repurposed as a treatment for mildly ill COVID-19 patients, but its precise mechanism of action is unclear. Herein, we report that ciclesonide blocks the coronavirus-induced production of the cytokines IL-6, IL-8, and MCP-1 by increasing IκBα protein levels and significantly decreasing p65 nuclear translocation. Furthermore, we found that the combination of ciclesonide and dbq33b, a potent tylophorine-based coronavirus inhibitor that affects coronavirus-induced NF-κB activation a little, additively and synergistically decreased coronavirus-induced IL-6, IL-8, and MCP-1 cytokine levels, and synergistically inhibited the replication of both HCoV-OC43 and SARS-CoV-2. Collectively, the combination of ciclesonide and dbq33b merits consideration as a treatment for COVID-19 patients who may otherwise be overwhelmed by high viral loads and an NF-κB-mediated cytokine storm.

Bisacodyl Limits Chikungunya Virus Replication In Vitro and Is Broadly Antiviral

Identifying novel antivirals requires significant time and resource investment, and the continuous threat of viruses to human health necessitates commitment to antiviral identification and development. Developing antivirals requires years of research and validation, and recent outbreaks have highlighted the need for preparedness in counteracting pandemics. One way to facilitate development is to repurpose molecules already used clinically. By screening such compounds, we can accelerate antiviral development. Here, we screened compounds from the National Institutes of Health's Developmental Therapeutic Program for activity against chikungunya virus, an alphavirus that is responsible for a significant outbreak in the Americas in 2013. Using this library, we identified several compounds with known antiviral activity, as well as several novel antivirals. Given its favorable in vitro activity and well-described in vivo activity, as well as its broad availability, we focused on bisacodyl, a laxative used for the treatment of constipation, for follow-up studies. We find that bisacodyl inhibits chikungunya virus infection in a variety of cell types, over a range of concentrations, and over several rounds of replication. We find that bisacodyl does not disrupt chikungunya virus particles or interfere with their ability to attach to cells, but, instead, bisacodyl inhibits virus replication. Finally, we find that bisacodyl is broadly antiviral against a variety of RNA viruses, including enteroviruses, flaviviruses, bunyaviruses, and alphaviruses; however, it exhibited no activity against the DNA virus vaccinia virus. Together, these data highlight the power of compound screening to identify novel antivirals and suggest that bisacodyl may hold promise as a broad-spectrum antiviral.

Effective Reduction of SARS-CoV-2 RNA Levels Using a Tailor-Made Oligonucleotide-Based RNA Inhibitor

In only two years, the coronavirus disease 2019 (COVID-19) pandemic has had a devastating effect on public health all over the world and caused irreparable economic damage across all countries. Due to the limited therapeutic management of COVID-19 and the lack of tailor-made antiviral agents, finding new methods to combat this viral illness is now a priority. Herein, we report on a specific oligonucleotide-based RNA inhibitor targeting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). It displayed remarkable spontaneous cellular uptake, >94% efficiency in reducing RNA-dependent RNA polymerase (RdRp) RNA levels in transfected lung cell lines, and >98% efficiency in reducing SARS-CoV-2 RNA levels in samples from patients hospitalized with COVID-19 following a single application.

COVID-19 scenario and recommendations on the continuity of immunobiological therapy in patients with atopic asthma in Brazil and Latin America

INTRODUCTION

With the abrupt establishment of the COVID-19 pandemic, treatment for immunological diseases may be influenced by the SARS-CoV-2 infection, including asthma and other allergies. Immunobiologics play a pivotal role in the management of severe symptoms of allergy and an opinion regarding the continuity of this treatment during the COVID-19 pandemic must be issued.

AREAS COVERED

In Brazil and other countries, patients with severe asthma were included in the priority groups for COVID-19 vaccination, even those who are undergoing immunobiological therapy. Data are insufficient to support the influence of this therapy on severe COVID-19 as targeting molecules may play a role in the physiopathology of the infection. Therapeutic strategies for asthma and guidelines/statements of the main societies of Allergy in Latin America on the continuity of treatment with immunobiologics during the COVID-19 pandemic were obtained from the institutional websites, PubMed, Scielo, Google Scholar, and CINAHL electronic platforms by searching for papers published up to September 2021.

EXPERT OPINION

Although the association between asthma and COVID-19 has been under investigation, immunobiological treatment should follow the consensus-based statements recommending the maintenance of the therapy unless the patient is infected by the SARS-CoV-2. However, it must be closely followed by the medical assistant.

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.