Combining virtual screening with cis-/trans-cleavage enzymatic assays effectively reveals broad-spectrum inhibitors that target the main proteases of SARS-CoV-2 and MERS-CoV.

The main protease (Mpro) of SARS-CoV-2 is essential for viral replication, which suggests that the Mpro is a critical target in the development of small molecules to treat COVID-19. This study used an in-silico prediction approach to investigate the complex structure of SARS-CoV-2 Mpro in compounds from the United States National Cancer Institute (NCI) database, then validate potential inhibitory compounds against the SARS-CoV-2 Mpro in cis- and trans-cleavage proteolytic assays. Virtual screening of ∼280,000 compounds from the NCI database identified 10 compounds with highest site-moiety map scores. Compound NSC89640 (coded C1) showed marked inhibitory activity against the SARS-CoV-2 Mpro in cis-/trans-cleavage assays. C1 strongly inhibited SARS-CoV-2 Mpro enzymatic activity, with a half maximal inhibitory concentration (IC50) of 2.69 µM and a selectivity index (SI) of >74.35. The C1 structure served as a template to identify structural analogs based on AtomPair fingerprints to refine and verify structure-function associations. Mpro-mediated cis-/trans-cleavage assays conducted with the structural analogs revealed that compound NSC89641 (coded D2) exhibited the highest inhibitory potency against SARS-CoV-2 Mpro enzymatic activity, with an IC50 of 3.05 µM and a SI of >65.57. Compounds C1 and D2 also displayed inhibitory activity against MERS-CoV-2 with an IC50 of <3.5 µM. Thus, C1 shows potential as an effective Mpro inhibitor of SARS-CoV-2 and MERS-CoV. Our rigorous study framework efficiently identified lead compounds targeting the SARS-CoV-2 Mpro and MERS-CoV Mpro.

Effective Antiviral Activity of the Tyrosine Kinase Inhibitor Sunitinib Malate against Zika Virus.

INTRODUCTION: Zika virus (ZIKV), a mosquito-borne flavivirus, causes the outbreaks of Latin America in 2015 - 2016, with the incidence of neurological complications. Sunitinib malate, an orally bioavailable malate salt of the tyrosine kinase inhibitor, is suggested as a broad-spectrum antiviral agent against emerging viruses like severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2. MATERIALS AND METHODS: This study investigated the antiviral efficacy and antiviral mechanisms of sunitinib malate against ZIKV infection using cytopathic effect reduction, virus yield, and time-of-addition assays. RESULTS: Sunitinib malate concentration-dependently reduced ZIKV-induced cytopathic effect, the expression of viral proteins, and ZIKV yield in supernatant with 50% inhibitory concentration (IC50) value of 0.015 µM, and the selectivity index of greater than 100 against ZIKV infection, respectively. Sunitinib malate had multiple antiviral actions during entry and post-entry stages of ZIKV replication. Sunitinib malate treatment at entry stage significantly reduced the levels of ZIKV RNA replication with the reduction of (+) RNA to (-) RNA ratio and the production of new intracellular infectious particles in infected cells. The treatment at post-entry stage caused a concentration-dependent increase in the levels of ZIKV (+) RNA and (-) RNA in infected cells, along with enlarging the ratio of (+) RNA to (-) RNA, but caused a pointed increase in the titer of intracellular infectious particles by 0.01 and 0.1 µM, and a substantial decrease in the titer of intracellular infectious particles by 1 µM. CONCLUSION: The study discovered the antiviral actions of sunitinib malate against ZIKV infection, demonstrating a repurposed, host-targeted approach to identify potential antiviral drugs for treating emerging and global viral diseases.