Closantel, an FDA-approved veterinary drug, suppresses PEDV replication via targeting main protease.

Porcine epidemic diarrhea virus (PEDV) continues to pose a global threat to the swine industry, causing fatal neonatal diarrhea with a mortality rate approaching 100%. Currently, no effective targeted drugs have been approved. The coronavirus main protease (Mpro), a conserved enzyme essential for viral replication, represents a promising target for antiviral development. Here, we demonstrate that Closantel, an FDA-approved veterinary drug, acts as a potent pan-coronavirus Mpro inhibitor via enzymatic inhibition assays. Moreover, Closantel potently suppresses PEDV replication in Vero-E6 and IPEC-J2 cells, with EC50 values of 1.49 ± 0.38 μM and 4.32 ± 0.53 μM, respectively, and exhibits minimal cytotoxicity. Remarkably, Closantel triggers interferon secretion and activates JAK-STAT signaling pathways via phosphorylation of STAT1 and STAT2, establishing a dual antiviral mechanism. In summary, Closantel holds promise as a potential lead compound for developing targeted therapies against PEDV infection.