Design, synthesis and biological evaluation of peptidomimetic benzothiazolyl ketones as 3CL pro inhibitors against SARS-CoV-2.

A series of peptidomimetic compounds containing benzothiazolyl ketone and [2.2.1] azabicyclic ring was designed, synthesized and evaluated in the hope of obtaining potent oral 3CLpro inhibitors with improved pharmacokinetic properties. Among the target compounds, 11b had the best enzymatic potency (IC50  = 0.110 μM) and 11e had the best microsomal stability (t1/2  > 120 min) and good enzyme activity (IC50  = 0.868 μM). Therefore, compounds 11b and 11e were chosen for further evaluation of pharmacokinetics in ICR mice. The results exhibited that the AUC(0-t) of 11e was 5143 h*ng/mL following single-dose oral administration of 20 mg/kg, and the F was 67.98%. Further structural modification was made to obtain compounds 11g-11j based on 11e. Among them, 11j exhibited the best enzyme inhibition activity against SARS-CoV-2 3CLpro (IC50  = 1.646 μM), the AUC(0-t) was 32473 h*ng/mL (20 mg/kg, po), and the F was 48.1%. In addition, 11j displayed significant anti-SARS-CoV-2 activity (EC50  = 0.18 μM) and low cytotoxicity (CC50  > 50 μM) in Vero E6 cells. All of the above results suggested that compound 11j was a promising lead compound in the development of oral 3CLpro inhibitors and deserved further research.