Inhibition of human neutrophil elastase and cathepsin G by a biphenyl disulfonic acid copolymer.

The sulfated polymer MDL 101,028 was found to be a potent-inhibitor of both human neutrophil elastase (HNE) and human neutrophil cathepsin G (CatG). Cleavage of synthetic substrate by HNE was inhibited by MDL 101,028 with an IC50 of 40 nM, while CatG was inhibited with an IC50 of 80 nM. Degradation of a macromolecular connective tissue substrate (cartilage proteoglycan) by HNE or CatG was inhibited by MDL 101,028 with an IC50 of approximately 10 microM. MDL 101,028 at concentrations of 4, 10 and 25 microM inhibited degradation of cartilage proteoglycan by human neutrophil lysate or stimulated human neutrophils by 54%, 70% and 79%, and 31%, 47% and 73%, respectively. Acute pulmonary injury resulting from the intratracheal (i.t.) instillation of HNE in rats was inhibited by 48%, 90% and 90% at concentrations of MDL 101,028 of 1.1 mg/kg, 2.8 mg/kg and 11 mg/kg. The duration of action of the compound after i.t. instillation was between 2 and 4 h. These results suggest that sulfated polymers such as MDL 101,146 may be useful as inhibitors of HNE-mediated lung injury.