Souradip Mallick, National Institute of Technology, Rourkela
The emergence of SARS-CoV-2 virus has resulted in a worldwide pandemic killed over 1,368,000 people globally (WHO). Currently, effective treatments to inhibit SARS-CoV-2 morbidity and mortality are not available. The pharmacological screen identified several compounds capable of blocking the in vitro replication of two beta-coronaviruses. Among many ones is against OC43, which is a common human coronavirus that typically causes mild to moderate upper respiratory tract infections. To improve treatment options, high-throughput drug screening was done to reveal the compounds that block the viral activity of SARS-CoV-2.
The compounds were screened against the virus OC43 to test whether OC43 would replicate in MRC5-hT cells, which are human pulmonary fibroblasts (immortalized with human TERT) that have previously been shown to be an effective model of viral infection into non-transformed cells. The OC43 virus rapidly replicated in MRC5 cells as viral RNA and protein increased in cells upon infection. Viral replication causes cell death, known as the cytopathic effect (CPE). OC43 induced substantial CPE in MRC5 cells.
For better understanding, the pharmacologic profile for each compound the Multifunctional Approach to Pharmacologic Screening (MAPS) was developed. In that case, each drug was arrayed across 10 dose points, ranging from 20 μM to 1 nM. These multiple concentrations provided a broad picture of each drugs’ ability to block virus-induced CPE.
The maximal inhibition of viral killing in cells (at any dose) was identified as potential hits of the compound. Doramapimod (BIRB 796), lapatinib, and 17-AAG are the top inhibitor compounds. Doramapimod is a pan-inhibitor of p38 MAPKs, lapatinib is a dual inhibitor of EGFR/HER2, and 17-AAG blocks HSP90 activity. Upon validation using a larger number of drug concentrations, the hit compounds demonstrated robust inhibition of CPE.
Lapatinib inhibited SARS-CoV-2 replication by more than 50,000-fold without any toxicity and at doses readily achievable in human tissues. These findings illustrate the power of the MAPS platform, which identified hits that would have been most likely missed if the screen was performed at a single high drug concentration.
Lapatinib effectively blocked SARS-CoV-2 infection by reducing the accumulation of viral RNA. 17-AAG, inhibitor against OC43, only minimally reduced SARS-CoV-2 RNA accumulation. Although doramapimod was less effective at blocking OC43 infection, it was able to block SARS-CoV-2 infection at a low μM concentration, although it was still not as inhibitory as lapatinib or remdesivir. Nonetheless, lapatinib and doramapimod also blocked SARS-CoV-2-induced CPE and completely prevented SARS-CoV-2 protein accumulation. Both lapatinib and doramapimod were able to reduce the dose required for remdesivir required to abolish SARS-CoV-2 RNA accumulation. These findings suggest that the top hit compounds lapatinib and doramapimod, either alone or in combination with remdesivir, are potentially effective therapeutic options for patients infected with SARS-CoV-2.
Also read: Scientists discover new coronaviruses in Japan and Cambodia
Source: doi: https://doi.org/10.1101/2020.11.25.398859
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