Endosomal acidification inhibitors broadly inhibit influenza virus and coronavirus in vivo

Abstract Influenza virus, coronavirus, and drug-resistant viruses are long-term threats to public health because of lacking effective antivirals. Thus, chemicals with broad-spectrum antiviral activities and low possibility to induce drug resistance are urgently needed. Here, we identify a peptidic inhibitor P16 significantly inhibiting influenza A/B virus by binding to HA to block viral fusion. Moreover, P16 antagonizes endosomal acidification to suppress influenza virus and SARS-CoV-2 entry through the endocytic pathway. Importantly, endosomal acidification inhibitor P16 or chloroquine can broadly inhibit A(H1N1) virus, SARS-CoV and SARS-CoV-2 replication in mice and hamsters when administrated through intranasal inoculation or atomization inhalation, contrary to reported treatment failure by systemic route. Chloroquine can significantly inhibit SARS-CoV-2 replication in ex vivo human lung tissues. In conclusion, endosomal acidification inhibitors (P16 and chloroquine) can broadly inhibit influenza virus and coronavirus replication in vivo, which supports atomization inhalation of chloroquine for treating coronavirus and influenza patients in clinical trials.