Biology subjects

Toba, S.

Publications and source records attributed to Toba, S..

5 recordsLinked to original sources

bioRxiv2022

2-Thiouridine is a broad-spectrum antiviral nucleoside analogue against positive-strand RNA viruses

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection causes significant morbidity and mortality worldwide, seriously impacting not only human health but also the global economy. Furthermore, over 1 million cases of newly emerging or re-emerging viral infections, specifically dengue virus (DENV), are known to occur annually. Because no virus-specific and fully effective treatments against these and many other viruses have been approved, they continue to be responsible for large-scale epidemics and global pandemics. Thus, there is an urgent need for novel, effective therapeutic agents. Here, we identified 2-thiouridine (s2U) as a broad-spectrum antiviral nucleoside analogue that exhibited antiviral activity against SARS-CoV-2 and its variants of concern, including the Delta and Omicron variants, as well as a number of other positive-sense single-stranded RNA (ssRNA+) viruses, including DENV. s2U inhibits RNA synthesis catalyzed by viral RNA-dependent RNA polymerase, thereby reducing viral RNA replication, which improved the survival rate of mice infected with SARS-CoV-2 or DENV in our animal models. Our findings demonstrate that s2U is a potential broad-spectrum antiviral agent not only against SARS-CoV-2 and DENV but other ssRNA+ viruses.

microbiology↗

bioRxiv2022

Discovery of Chlorofluoroacetamide-Based Covalent Inhibitors for SARS-CoV-2 3CL Protease

The pandemic of coronavirus disease 2019 (COVID-19) has urgently necessitated the development of antiviral agents against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The 3C-like protease (3CLpro) is a promising target for COVID-19 treatment. Here, we report the new class of covalent inhibitors for 3CLpro possessing chlorofluoroacetamide (CFA) as a cysteine reactive warhead. Based on the aza-peptide scaffold, we synthesized the series of CFA derivatives in enantiopure form and evaluated their biochemical efficiencies. The data revealed that 8a (YH-6) with R configuration at the CFA unit strongly blocks the SARS-CoV-2 replication in the infected cells and this potency is comparable to that of nirmatrelvir. The X-ray structural analysis shows that 8a (YH-6) forms a covalent bond with Cys145 at the catalytic center of 3CLpro. The strong antiviral activity and sufficient pharmacokinetics property of 8a (YH-6) suggest its potential as a lead compound for treatment of COVID-19.

biochemistry↗

bioRxiv2022

Oral administration of S-217622, a SARS-CoV-2 main protease inhibitor, decreases viral load and accelerates recovery from clinical aspects of COVID-19

In parallel with vaccination, oral antiviral agents are highly anticipated to act as countermeasures for the treatment of the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). Oral antiviral medication demands not only high antiviral activity but also target specificity, favorable oral bioavailability, and high metabolic stability. Although a large number of compounds have been identified as potential inhibitors of SARS-CoV-2 infection in vitro, few have proven to be effective in vivo. Here, we show that oral administration of S-217622, a novel inhibitor of SARS-CoV-2 main protease (Mpro, also known as 3C-like protease), decreases viral load and ameliorates the disease severity in SARS-CoV-2-infected hamsters. S-217622 inhibited viral proliferation at low nanomolar to sub-micromolar concentrations in cells. Oral administration of S-217622 demonstrated eminent pharmacokinetic properties and accelerated recovery from acute SARS-CoV-2 infection in hamster recipients. Moreover, S-217622 exerted antiviral activity against SARS-CoV-2 variants of concern (VOCs), including the highly pathogenic Delta variant and the recently emerged Omicron variant. Overall, our study provides evidence that S-217622, an antiviral agent that is under evaluation in a phase II/III clinical trial, possesses remarkable antiviral potency and efficacy against SARS-CoV-2 and is a prospective oral therapeutic option for COVID-19.

microbiology↗

bioRxiv2022

Discovery of S-217622, a Non-Covalent Oral SARS-CoV-2 3CL Protease Inhibitor Clinical Candidate for Treating COVID-19

The coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has resulted in millions of deaths and threatens public health and safety. Despite the rapid global spread of COVID-19 vaccines, effective oral antiviral drugs are urgently needed. Here, we describe the discovery of S-217622, the first oral non-covalent, non-peptidic SARS-CoV-2 3CL protease inhibitor clinical candidate. S-217622 was discovered via virtual screening followed by biological screening of an in-house compound library, and optimization of the hit compound using a structure-based drug-design strategy. S-217622 exhibited antiviral activity in vitro against current outbreaking SARS-CoV-2 variants and showed favorable pharmacokinetic profiles in vivo for once-daily oral dosing. Furthermore, S-217622 dose-dependently inhibited intrapulmonary replication of SARS-CoV-2 in mice, indicating that this novel non-covalent inhibitor could be a potential oral agent for treating COVID-19.

biochemistry↗

bioRxiv2021

SARS-CoV-2 bearing a mutation at the S1/S2 cleavage site exhibits attenuated virulence and confers protective immunity

Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) possesses a discriminative polybasic cleavage motif in its spike protein that is recognized by host furin protease. Proteolytic cleavage activates the spike protein and influences both the cellular entry pathway and cell tropism of SARS-CoV-2. Here, we investigated the impact of the furin cleavage site on viral growth and pathogensis using a hamster animal model infected with SARS-CoV-2 variants bearing mutations at the furin cleavage site (S gene mutants). In the airway tissues of hamsters, the S gene mutants exhibited a low growth property. In contrast to parental pathogenic SARS-CoV-2, hamsters infected with the S gene mutants showed no body weight loss and only a mild inflammatory response, indicating the attenuated variant nature of S gene mutants. We reproduced the attenuated growth of S gene mutants in primary differenciated human airway epithelial cells. This transient infection was enough to induce protective neutralizing antibodies crossreacting with different SARS-CoV-2 lineages. Consequently, hamsters inoculated with S gene mutants showed resistance to subsequent infection with both the parental strain and the currently emerging SARS-CoV-2 variants belonging to lineages B.1.1.7 and P.1. Together, our findings revealed that the loss of the furin cleavage site causes attenuation in the airway tissues of SARS-CoV-2 and highlights the potential benefits of S gene mutants as potential immunogens.

microbiology↗