Membrane fusion is also the crucial step for the CoV life cycle in the nonclathrin/endosomal route, in which host proteases such as cathepsin L, TMPRSS2, and TMPRSS11D (airway trypsin‐like protease) cut the S protein at the S1/S2 cleavage site to activate the S protein for membrane fusion. 101  Interference with this process by targeting these proteases could become an attractive strategy for combating CoV infections. A recent study confirms the role of TMPRSS2 for the viral life cycle in SARS‐CoV‐2‐infected VeroE6 cells. 5  Furin (a serine endoprotease) activates MERS‐CoV to initiate the nonclathrin mediated membrane fusion event. 102