TMPRSS2 and influenza: TMPRSS2, a transmembrane serine protease, plays a vital role in the entry of respiratory viruses such as SARS‐CoV‐2 and influenza by cleaving and activating viral glycoproteins essential for membrane fusion.[20, 21, 23, 35] We show that Trypstatin effectively blocks TMPRSS2 by binding to the S1 specificity pocket of the protease, thus inhibiting enzymatic activity and thus the cleavage step, thereby preventing viral entry.