Preclinical characterization of EGT710, an oral non-peptidomimetic reversible covalent SARS-CoV-2 main protease inhibitor

Stephanie A. Moquin, Suresh B. Lakshminarayana, Kamal Kumar Balavenkatraman, Hilmar Schiller, Allison Claas, Barun Bhhatarai, Ioannis Loisios-Konstantinidis, Katarina Vulic, Chaitanya Kurhade, Birte K. Kalveram, John Yun-Chung Chen, Jing Zou, Xuping Xie, Laura Tandeske, Dustin Dovala, Elizabeth Ornelas, Mark S. Knapp, Daniel Fuller, Zachary Nguyen, David T. Barkan, Lidiya Bebrevska, S. Kirk Wright, Scott A. Busby, Johanne Blais, Pei-Yong Shi, Suzanne Gaudet, Renee Bergeron, Hannah Yu, Julia Zack, Christopher Sarko, Feng Gu, James E. Bradner, John A. Tallarico, Thierry T. Diagana & Julien P. N. Papillon 

npj Drug Discov. 2, 28 (2025). 

https://doi.org/10.1038/s44386-025-00030-5

EGT710 is an orally bioavailable non-peptidomimetic reversible covalent coronavirus main protease (Mpro) inhibitor with low nM cellular activity against SARS-CoV-2. Twice daily dosing of 10 mg/kg of EGT710 decreased lung viral load in a mouse model of SARS-CoV-2 infection to below the limit of detection. Resistance selection resulted in the emergence of several Mpro mutations, with recombinant viruses containing L50F + E166A substitutions showing the largest shift in potency. Development of a viral kinetics model using viremia data from clinical trials, along with a human physiologically based pharmacokinetic model, predicted efficacy in humans with once daily oral doses of >360 mg. EGT710 displays favorable pharmacokinetic properties and an acceptable in vitro and in vivo safety profile, with human exposures at the recommended clinical dose of 600 mg predicted to be below the no adverse effect level in preclinical toxicology studies. Together, EGT710 has a promising preclinical profile and has completed a Phase I study.

Fast and Site-Specific Covalent Targeting of Proteins by Arylfluorosulfate-Modified Aptamers

 Kaining Zhang, Juan Li, Yang Shi, Sining Hou, Zichen Qin, Wenhao Shi, Yiying Zhu, Jingjing Zhang, Aijun Tong, and Yu Xiang

Journal of the American Chemical Society 2025

DOI: 10.1021/jacs.5c14374

Sulfur fluoride exchange (SuFEx) is a versatile click chemistry platform with emerging applications in covalent inhibitor development, among which arylfluorosulfate (AFS) derivatives have shown great promise because of their exclusive selectivity to target proteins. Nevertheless, due to the inherently mild electrophilicity of AFS, the high target specificity often comes at the expense of target reactivity. Here, we challenge this conventional view and show that in vitro selected AFS-modified covalent aptamers (AFS-Aps) can be both highly target selective and reactive. One such AFS-Ap is able to site-specifically modify the extracellular domain (ECD) of human epidermal growth factor receptor 3 (HER3) with a “click” reaction half-life (t1/2) as short as 1 min and covalently inhibit the protein–protein interaction (PPI) of HER3/EGFRs. Another AFS-Ap targeting human vascular endothelial growth factor (VEGF) can also rapidly cross-link VEGF165 and block the PPI of VEGF/VEGFR. The inactivation rate constants (kinact) of these AFS-Aps are one to two orders of magnitude higher than many reported AFS-based covalent molecules. This unexpectedly fast and site-specific covalent targeting requires a precisely organized aptamer–protein binding interface, where the AFS structure, rather than electrophilicity, is the decisive factor. We believe the target reactivity potential of AFS derivatives may have long been underestimated in covalent inhibitor development. AFS-adapted combinatorial techniques are therefore invaluable for discovering covalent inhibitors with both high target reactivity and selectivity.