(R)-MDL-101146 is the R-isomer of MDL-101146. MDL-101146 is an orally active, competitive and reversible inhibitor against human neutrophil elastase ( HNE ) with a K i value of 25 nM. MDL-101146 inhibits HNE -induced hemorrhage in hamsters. MDL-101146 is promising for research of emphysema, rheumatoid arthritis, chronic bronchitis, cystic fibrosis, adult respiratory distress syndrome and glomerulonephritis.