Abstract: The present disclosure relates to compounds. and to their pharmaceutical compositions. that inhibit dipeptidyl peptidase IV (DPP4). Hie compounds selectively promote the proliferation of alveolar type 2 cells (AEC2s) and are useful in therapeutic methods of treating diseases whose etiology. for example. derives from epithelial degeneration and maladaptive remodeling, such as pulmonary' diseases like idiopathic pulmonary fibrosis (IFF), acute respiratory' distress syndrome (ARDS), and infant respiratory' distress syndromes (IRDS).