CTSL and pulmonary fibrosis: In combination with cathepsin inhibition, this effectwould then hinder endosomal cell entry even stronger and should beinvestigated for its potential to reduce pulmonary fibrosis originatingfrom a SARS-CoV-2 infection.33 The potentialto inhibit both CatL and calpain using inhibitors originally designedfor calpain inhibition is also explained by the structural similarityof human CatL and the human μ-calpain (Figure S8D).