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.

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 (Mpro) 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 GC-78-HCl 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, GC-78-HCl 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 GC-78-HCl 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 Mpro inhibitor with promising antiviral activity and a favorable pharmacokinetic profile.

Discovery of novel sulfonamide substituted indolylarylsulfones as potent HIV-1 inhibitors with better safety profiles.

Indolylarylsulfones (IASs) are classical HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) with a unique scaffold and possess potent antiviral activity. To address the high cytotoxicity and improve safety profiles of IASs, we introduced various sulfonamide groups linked by alkyl diamine chain to explore the entrance channel of non-nucleoside inhibitors binding pocket. 48 compounds were designed and synthesized to evaluate their anti-HIV-1 activities and reverse transcriptase inhibition activities. Especially, compound R10L4 was endowed with significant inhibitory activity towards wild-type HIV-1 (EC50(WT) = 0.007 µmol/L, SI = 30,930) as well as a panel of single-mutant strains exemplified by L100I (EC50 = 0.017 µmol/L, SI = 13,055), E138K (EC50 = 0.017 µmol/L, SI = 13,123) and Y181C (EC50 = 0.045 µmol/L, SI = 4753) which were superior to Nevirapine and Etravirine. Notably, R10L4 was characterized with significantly reduced cytotoxicity (CC50 = 216.51 µmol/L) and showed no remarkable in vivo toxic effects (acute and subacute toxicity). Moreover, the computer-based docking study was also employed to characterize the binding mode between R10L4 and HIV-1 RT. Additionally, R10L4 presented an acceptable pharmacokinetic profile. Collectively, these results deliver precious insights for next optimization and indicate that the sulfonamide IAS derivatives are promising NNRTIs for further development.

Discovery and Crystallographic Studies of Nonpeptidic Piperazine Derivatives as Covalent SARS-CoV-2 Main Protease Inhibitors.

The spread of SARS-CoV-2 keeps threatening human life and health, and small-molecule antivirals are in demand. The main protease (Mpro) is an effective and highly conserved target for anti-SARS-CoV-2 drug design. Herein, we report the discovery of potent covalent non-peptide-derived Mpro inhibitors. A series of covalent compounds with a piperazine scaffold containing different warheads were designed and synthesized. Among them, GD-9 was identified as the most potent compound with a significant enzymatic inhibition of Mpro (IC50 = 0.18 µM) and good antiviral potency against SARS-CoV-2 (EC50 = 2.64 µM), similar to that of remdesivir (EC50 = 2.27 µM). Additionally, GD-9 presented favorable target selectivity for SARS-CoV-2 Mpro versus human cysteine proteases. The X-ray co-crystal structure confirmed our original design concept showing that GD-9 covalently binds to the active site of Mpro. Our nonpeptidic covalent inhibitors provide a basis for the future development of more efficient COVID-19 therapeutics.