CTSL and chronic obstructive pulmonary disease: A previous study investigated the changes in SARS‐CoV‐2 coreceptor expression using SARS‐CoV‐2 inoculated primary bronchial epithelial cells (pBECs), demonstrating higher susceptibility to SARS‐CoV‐2 infection in COPD pBECs, with upregulation of TMPRSS2 and cathepsin B (CTSB) upon infection, as well as elevated baseline expression of CTSL in COPD donors [47].