Trypstatin as a Novel TMPRSS2 Inhibitor with Broad-Spectrum Efficacy Against Corona and Influenza Viruses

Respiratory viruses, such as SARS-CoV-2 and influenza, exploit host proteases like TMPRSS2 for entry, making TMPRSS2 a prime antiviral target. Here, we report the identification and characterization of Trypstatin, a 61-amino acid Kunitz-type protease inhibitor derived from human hemofiltrate. Trypstatin inhibits TMPRSS2 and related proteases, with IC ₅₀ values in the nanomolar range, comparable to the small molecule inhibitor camostat mesylate. In vitro assays demonstrated that Trypstatin effectively blocks spike-driven entry of SARS-CoV-2, SARS-CoV-1, MERS-CoV, and hCoV-NL63, as well as hemagglutinin-mediated entry of influenza A and B viruses. In primary human airway epithelial cultures, Trypstatin significantly reduced SARS-CoV-2 replication and retained activity in the presence of airway mucus. In vivo , intranasal administration of Trypstatin to SARS-CoV-2-infected Syrian hamsters reduced viral titers and alleviated clinical symptoms. These findings highlight Trypstatin’s potential as a broad-spectrum antiviral agent against TMPRSS2-dependent respiratory viruses.