Structure-based discovery of highly bioavailable, covalent, broad-spectrum coronavirus M<sup>Pro</sup> inhibitors with potent in vivo efficacy.

Detomasi, Tyler C; Degotte, Gilles; Huang, Sijie; Suryawanshi, Rahul K; Diallo, Amy; Lizzadro, Luca; Zapatero-Belinchón, Francisco J; Taha, Taha Y et al. · Sci Adv · 2025

basic_science · Level V

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Abstract

The main protease (M<sup>Pro</sup>) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a validated drug target. Starting with a lead-like dihydrouracil chemotype identified in a large-library docking campaign, we improved M<sup>Pro</sup> inhibition >1000-fold by engaging additional M<sup>Pro</sup> subsites and using a latent electrophile to engage Cys<sup>145</sup>. Advanced leads from this series show pan-coronavirus antiviral activity, low clearance in mice, and for <b>AVI-4773</b>, a rapid reduction in viral titers >1,000,000 after just three doses. Both compounds are well distributed in mouse tissues, including brain, where concentrations >1000× the 90% effective concentration are observed 8 hours after oral dosing for <b>AVI-4773</b>. <b>AVI-4516</b> shows minimal inhibition of major cytochrome P450s and human proteases. <b>AVI-4516</b> also exhibits synergy with the RNA-dependent RNA polymerase inhibitor, molnupiravir, in cellular infection models. Related analogs strongly inhibit nirmatrelvir-resistant M<sup>Pro</sup> mutant virus. The properties of this chemotype are differentiated from existing clinical and preclinical M<sup>Pro</sup> inhibitors and will advance therapeutic development against emerging SARS-CoV-2 variants and other coronaviruses.

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