Identification of SARS-CoV-2 Mpro inhibitors containing P1' 4-fluorobenzothiazole moiety highly active against SARS-CoV-2

COVID-19 caused by SARS-CoV-2 has continually been serious threat to public health worldwide. While a few anti-SARS-CoV-2 therapeutics are currently available, their antiviral potency is not sufficient. Here, we identify two orally available 4-fluoro-benzothiazole-containing small molecules, TKB245 and TKB248, which specifically inhibit the enzymatic activity of main protease (Mpro) of SARS-CoV-2 and significantly more potently block the infectivity and replication of various SARS-CoV-2 strains than nirmatrelvir, molnupiravir, and ensitrelvir in cell-based assays employing various target cells. Both compounds also block the replication of Delta and Omicron variants in human-ACE2-knocked-in mice. Native mass spectrometric analysis reveals that both compounds bind to dimer Mpro, apparently promoting Mpro dimerization. X-ray crystallographic analysis shows that both compounds bind to Mpro's active-site cavity, forming a covalent bond with the catalytic amino acid Cys-145 with the 4-fluorine of the benzothiazole moiety pointed to solvent. The data suggest that TKB245 and TKB248 might serve as potential therapeutics for COVID-19 and shed light upon further optimization to develop more potent and safer anti-SARS-CoV-2 therapeutics.

Nobuyo Higashi-Kuwata, Kohei Tsuji, Hironori Hayashi, Haydar Bulut, Maki Kiso, Masaki Imai, Hiromi Ogata-Aoki, Takahiro Ishii, Takuya Kobayakawa, Kenta Nakano, Nobutoki Takamune, Naoki Kishimoto, Shin-ichiro Hattori, Debananda Das, Yukari Uemura, Yosuke Shimizu, Manabu Aoki, Kazuya Hasegawa, Satoshi Suzuki, Akie Nishiyama, Junji Saruwatari, Yukiko Shimizu, Yoshikazu Sukenaga, Yuki Takamatsu, Kiyoto Tsuchiya, Kenji Maeda, Kazuhisa Yoshimura, Shun Iida, Seiya Ozono, Tadaki Suzuki, Tadashi Okamura, Shogo Misumi, Yoshihiro Kawaoka, Hirokazu Tamamura, Hiroaki Mitsuya