Human leukocyte elastase (HLE) is a serine protease stored in and secreted from neutrophils that plays a determinant role in the pathogenesis of several lung diseases. 4- Oxo-β-lactams, previously reported as acylating agents of porcine pancreatic elastase, were found to be selective and potent inhibitors of HLE. Structure− activity relationship analysis showed that inhibitory activity is very sensitive to the nature of C-3 substituents, with small ...