Tsuji K, Kobayakawa T, Ishii T, Higashi-Kuwata N, Azuma C, Shinohara K, Miura Y, Yamamoto K, Nishimura S, Hattori SI, Bulut H, Mitsuya H, Tamamura H. Exploratory Studies of Effective Inhibitors against the SARS-CoV-2 Main Protease by Halogen Incorporation and Amide Bond Replacement.
Chem Pharm Bull (Tokyo) 2023;
71:879-886. [PMID:
38044140 DOI:
10.1248/cpb.c23-00562]
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Abstract
In the development of anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) drugs, its main protease (Mpro), which is an essential enzyme for viral replication, is a promising target. To date, the Mpro inhibitors, nirmatrelvir and ensitrelvir, have been clinically developed by Pfizer Inc. and Shionogi & Co., Ltd., respectively, as orally administrable drugs to treat coronavirus disease of 2019 (COVID-19). We have also developed several potent inhibitors of SARS-CoV-2 Mpro that include compounds 4, 5, TKB245 (6), and TKB248 (7), which possesses a 4-fluorobenzothiazole ketone moiety as a reactive warhead. In compounds 5 and TKB248 (7) we have also found that replacement of the P1-P2 amide of compounds 4 and TKB245 (6) with the corresponding thioamide improved their pharmacokinetics (PK) profile in mice. Here, we report the design, synthesis and evaluation of SARS-CoV-2 Mpro inhibitors with replacement of a digestible amide bond by surrogates (9-11, 33, and 34) and introduction of fluorine atoms in a metabolically reactive methyl group on the indole moiety (8). As the results, these compounds showed comparable or less potency compared to the corresponding parent compounds, YH-53/5h (2) and 4. These results should provide useful information for further development of Mpro inhibitors.
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