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, the identification and characterization of Trypstatin, a 61-amino acid Kunitz-type protease inhibitor derived from human hemofiltrate are reported. Trypstatin inhibits TMPRSS2 and related proteases with high potency, exhibiting half-maximal inhibitory concentration values in the nanomolar range, comparable to the small molecule inhibitor camostat mesylate. In vitro assays demonstrate 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 reduces 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 reduces viral titers and alleviates clinical symptoms. These findings highlight Trypstatin's potential as a broad-spectrum antiviral agent against TMPRSS2-dependent respiratory viruses.