Evaluation of the antiviral potential against SARS-CoV-2 of halogenated compounds derived from L-tyrosine

Abstract

ABSTRACT: Introduction: The coronavirus disease (COVID-19) caused by SARS-CoV-2 was declared a pandemic in March 2020. To date, more than 774 million people have been infected worldwide and more than 7 million deaths have been reported. Currently, there are no effective medications to combat the infection in all patients and reduce the symptoms and spread of the virus. Furthermore, vaccines are not effective against all variants or in all population groups. For this reason, there is a need to look for new treatment alternatives. Some halogenated compounds derived from L-tyrosine produced by marine sponges from “Golfo de Urabá Colombiano” have antiviral activity against arboviruses and HIV (strains X4 and R5) inhibiting different steps of the replication cycle, probably due to the interaction with viral proteins through the formation of halogen bonds that can increase their affinity, blocking their function. The above suggests an antiviral potential that could be explored in other viral models, such as SARS-CoV-2. Methodology: 15 di-halogenated compounds derived from L-tyrosines were analyzed. The in vitro cytotoxicity of each compound at different concentrations was evaluated using the MTT assay. Non-cytotoxic concentrations were used to evaluate antiviral activity using a combined strategy (pre/posttreatment) in Vero E6 cells infected with SARS-CoV-2. The viral titer was quantified using a plaque assay from the supernatants. Compounds that showed >40% antiviral activity (promising compounds) were evaluated by individual strategies (pre-, post-, and co-treatment), and RT-qPCR was performed to quantify viral RNA in infected cells. In addition, in silico tests were carried out for the toxicological evaluation of the compounds using the ADMET Predictor® v8 software from Simulation Plus. The molecular docking between the compounds with antiviral activity with the Spike protein (S protein), the RNA-dependent RNA polymerase (RdRp), the main protease (Mpro) of SARS-CoV-2, and the cellular protein ACE2 was evaluated to determine protein-ligand interaction using Autodock Vina software. Results: It was found that the compounds TODC-3M, TODI-2M and YODC-3M reduce the viral titer >40% (promising compounds) by post- and co-treatment strategies in plaque assays, without significant cytotoxicity at ≤150µM concentration. PCR results showed that TODC-3M and TODI-2M, but not YODC-3M, inhibited the replication of viral genetic material. In in silico analyses, these compounds presented low toxicity scores in ADMET risk and had significant affinity for viral (S, RdRp and Mpro) and cellular (ACE2) proteins. Conclusion: The promising compounds with significant antiviral activity were TODC-3M, TODI-2M and YODC-3M; these did not show considerable cytotoxicity in vitro and have a low in silico probability of toxicity in organs and tissues. In vitro, TODC-3M and TODI-2M inhibited viral replication in the post- and co-treatment stages and inhibited RNA replication; the mechanism of action could be the interaction with the S protein or blocking Mpro or RdRp. YODC-3M inhibited viral replication by the co-treatment strategy but did not reduce the number of copies of the viral genetic material in this same strategy, suggesting a block in generating new infectious viral particles.