Recently developed small molecule inhibitors of the lysosomal protease dipeptidyl peptidase 1 (DPP1), also known as cathepsin C (CatC), can suppress suppurative inflammation in vivo by blocking the processing of zymogenic (pro-) forms of the neutrophil serine proteases (NSPs), including neutrophil elastase, proteinase 3, and cathepsin G. However, DPP1 also