Date of Award

2022

Embargo Period

4-22-2027

Document Type

Dissertation - MUSC Only

Degree Name

Master of Science (MS)

College

College of Graduate Studies

First Advisor

Mark T. Hamann

Second Advisor

Russell “Chip” Norris

Third Advisor

Rupak Mukherjee

Fourth Advisor

Amy Bradshaw

Abstract

Unlike the vaccines for COVID-19, which depend on the highly mutable Spike (S) protein of SARS-CoV-2, antiviral therapeutics that directly inhibit nonstructural proteins (Nsps) can be designed to be specific and efficacious for all variants of related viruses. Nsps retain genetic homology throughout closely related viruses, such as SARS and MERS viruses from the Beta-coronavirus genus, allowing all variants of SARS-CoV-2, such as Delta (Δ) and Omicron (Ο), to be directly targeted. As a result, antiviral compounds with suspected activity against highly conserved Nsps were produced to inhibit a broad-spectrum of coronaviruses. Novel classes of biphenylpyrans (BPPs), specifically chromenephenylmethanones (CPMs) and tetrahydrophenylmethanones (TPMs), were selected from a unique pool of over 1000 naturally-derived or inspired compounds. Selection of the novel BPPs was based on compelling in silico docking scores to Nsps of coronaviruses, but with high specificity to the 2’-O-methyltransferase (2’-OMTase, Nsp10-Nsp16) responsible for viral mRNA maturation and host innate immune response evasion. In silico experiments were conducted to predict the compounds’ binding affinities to Nsps, the compounds’ physicochemical parameters, and the compounds’binding interactions to the S-adenosylmethionine (SAM) binding pocket in 2’-O-MTase. BPP regioisomers with a tetrahydrodibenzopyran (TBP) or benzochromenepyran (BCP) core motif, which are found in cannabinoids and other natural products, were chemically synthesized, purified via chromatography, and structurally analyzed using nuclear magnetic resonance (NMR) and DP4+ calculations. Molecular ion networking (MoIN) was conducted via tandem mass spectrometry (MS/MS) to molecularly compare synthesized BPPs to cannabinoids that share the core motif. In vitro assays for cytotoxicity, kinetic replication, and antiviral activity were conducted using Vero (African Green Monkey Kidney), Calu-3 (Human Lung Carcinoma), and Caco-2 (Human Colorectal Adenocarcinoma) cell lines. The BPPs displayed similarly high viral inhibitory percentages (BPP 2-A: 99.3% at 10 μM) as the FDA-approved remdesivir antiviral (99.9% at 10 μM) used as a control. The BPPs also had significantly greater CC50 concentrations in PBM cells (BPP 2-A: >100 μM) in comparison to the control (2.0 μM), which indicated their potential safety as broad-spectrum coronavirus inhibitors. Future experiments have been planned to biochemically assay the BPPs predicted role as ligands for 2’-O-MTase inhibition. Further in vitro Tox/ADME studies will be conducted to screen candidate compounds prior to in vivo research.

Rights

All rights reserved. Copyright is held by the author.

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Available for download on Thursday, April 22, 2027

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