Design, Synthesis, and Biological Evaluation of Trisubstituted Piperazine Derivatives as Noncovalent Severe Acute Respiratory Syndrome Coronavirus 2 Main Protease Inhibitors with Improved Antiviral Activity and Favorable Druggability

Abstract

The ongoing transmission of SARS-CoV-2 necessitates the development of additional potent antiviral agents capable of combating the current highly infectious variants and future coronaviruses. Here, we present the discovery of potent nonpeptide main protease (M^pro) inhibitors with prominent antiviral activity and improved pharmacokinetic properties. Three series of 1,2,4-trisubstituted piperazine derivatives were designed and synthesized, and the optimal <b>GC-78-HCl</b> demonstrated high enzyme-inhibitory potency (IC₅₀ = 0.19 μM) and exhibited excellent antiviral activity (EC₅₀ = 0.40 μM), reaching the same level as Nirmatrelvir (EC₅₀ = 0.38 μM). Additionally, <b>GC-78-HCl</b> displayed potent antiviral activities against various SARS-CoV-2 variants as well as HCoV-OC43 and HCoV-229E, indicating its potential broad-spectrum anticoronaviral activity. Notably, the pharmacokinetic properties of <b>GC-78-HCl</b> were somewhat enhanced compared to those of the lead compound. Furthermore, the cocrystal and molecular docking elucidated the mechanism of action. In conclusion, we discovered a novel nonpeptidic M^pro inhibitor with promising antiviral activity and a favorable pharmacokinetic profile.