Ursodeoxycholic acid may protect from severe acute respiratory syndrome coronavirus 2 Omicron variant by reducing angiotensin‐converting enzyme 2

The SARS‐CoV‐2 caused COVID‐19 pandemic has posed a global health hazard. While some vaccines have been developed, protection against viral infection is not perfect because of the urgent approval process and the emergence of mutant SARS‐CoV‐2 variants. Here, we employed UDCA as an FXR antagonist to regulate ACE2 expression, which is one of the key pathways activated by SARS‐CoV‐2 Delta variant infection. UDCA is a well‐known reagent of liver health supplements and the only clinically approved bile acid. In this paper, we investigated the protective efficacy of UDCA on Omicron variation, since it has previously been verified for protection against Delta variant. When co‐housing with an Omicron variant‐infected hamster group resulted in spontaneous airborne transmission, the UDCA pre‐supplied group was protected from weight loss relative to the non‐treated group at 4 days post‐infection by more than 5%–10%. Furthermore, UDCA‐treated groups had a 3‐fold decrease in ACE2 expression in nasal cavities, as well as reduced viral expressing genes in the respiratory tract. Here, the data show that the UDCA serves an alternative option for preventive drug, providing SARS‐CoV‐2 protection against not only Delta but also Omicron variant. Our results of this study will help to propose drug‐repositioning of UDCA from liver health supplement to preventive drug of SARS‐CoV‐2 infection. We found that UDCA‐fed hamsters effectively inhibited viral transmission from Omicron variant‐infected hamsters and verified UDCA‐derived downregulation of ACE2 expression in respiratory organs. As an FXR antagonist, UDCA may protect against SARS‐CoV‐2 Omicron variant.