Coronaviruses cause diseases in humans and livestock. The SARS-CoV-2 is infecting millions of human beings, with high morbidity and mortality worldwide. The main protease (M^pro) of coronavirus plays a pivotal role in viral replication and transcription, which, in theory, is an attractive drug target for antiviral drug development. It has been extensively discussed whether Xanthohumol is able to help COVID-19 patients. Here, we report that Xanthohumol, a small molecule in clinical trials from hops (Humulus lupulus), was a potent pan-inhibitor for various coronaviruses by targeting M^pro, for example, betacoronavirus SARS-CoV-2 (IC₅₀ value of 1.53 μM), and alphacoronavirus PEDV (IC₅₀ value of 7.51 μM). Xanthohumol inhibited M^pro activities in the enzymatical assays, while pretreatment with Xanthohumol restricted the SARS-CoV-2 and PEDV replication in Vero-E6 cells. Therefore, Xanthohumol is a potent pan-inhibitor of coronaviruses and an excellent lead compound for further drug development.

The eukaryotic translation initiation factor 4E (eIF4E) has emerged as a compelling target for cancer therapeutics due to its pivotal role in regulating cap-dependent translation of oncogenic mRNAs and its implication in various malignancies. However, the clinical potential of current eIF4E inhibitors is limited by suboptimal potency and binding affinity. Based on an analysis of the eIF4E/eIF4G binding pocket and structural features of existing inhibitors, 75 compounds were designed, synthesized, and screened. The binding affinity, molecular mechanism and antitumor activity of the most potent compound b14 were evaluated in vitro and in vivo. Through structure-activity relationship analysis, 75 thiazole derivatives were synthesized and screened for binding affinity using fluorescence polarization (FP) and surface plasmon resonance (SPR). Hit compounds were evaluated for antitumor activity using the SRB assay. The most promising compound, b14, was further investigated for its antitumor activity and molecular mechanism via Western blotting (WB), quantitative real-time PCR (qRT-PCR), immunofluorescence, co-immunoprecipitation, and proteomics. The in vivo antitumor activity and safety of b14 were assessed using HeLa xenograft models and acute/subacute toxicity models, respectively. Compound b14 emerged as a lead molecule, exhibiting a 10-fold higher binding affinity to eIF4E than the reference inhibitor 4EGI-1. Mechanistic studies revealed that b14 disrupts eIF4F complex formation by inhibiting AKT-mTOR-4EBP1 and ERK-eIF4E phosphorylation, subsequently triggering mitochondrial dysfunction and apoptosis in tumor cells, with relatively low IC₅₀ values. Moreover, proteomics analysis further demonstrated that b14 suppresses oncogenic lipogenesis by downregulating key enzymes involved in lipid metabolism. Finally, oral administration of b14 significantly inhibits HeLa xenograft growth in vivo without measurable side effects. Together, our results demonstrate that b14 is an excellent novel small-molecule inhibitor of eIF4E for future cancer therapy.

Zoonotic coronaviruses infect mammals and birds, causing pulmonary and gastrointestinal infections. Some animal coronaviruses, such as the porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV), lead to severe diarrhea and animal deaths. Gastrointestinal symptoms were also found in COVID-19 and SARS patients. However, the pathogenesis of gastrointestinal symptoms in coronavirus diseases remains elusive. In this study, the main protease-induced LPCAT3 cleavage was monitored by exogenous gene expression and protease inhibitors, and the related regulation of gene expression was confirmed by qRT-PCR and gene knockdown. Interestingly, LPCAT3 plays an important role in lipid absorption in the intestines. The Mpro of coronaviruses causing diarrhea, such as PEDV and MERS-CoV, but not the Mpro of HCoV-OC43 and HCoV-HKU1, which could induce LPCAT3 cleavage. Mutagenesis analysis and inhibitor experiments indicated that LPCAT3 cleavage was independent of the catalytic activity of Mpro. Moreover, LPCAT3 cleavage in cells boosted CHOP and GRP78 expression, which were biomarkers of ER stress. Since LPCAT3 is critical for lipid absorption in the intestines and malabsorption may lead to diarrhea in coronavirus diseases, Mpro-induced LPCAT3 cleavage might trigger gastrointestinal symptoms during coronavirus infection.

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 (M^pro), 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 M^pro 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.

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 (M ^pro ), 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 M ^pro inhibitor via enzymatic inhibition assays. Moreover, Closantel potently suppresses PEDV replication in Vero-E6 and IPEC-J2 cells, with EC ₅₀ 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.