DEVELOPMENT AND IN-VITRO EVALUATION OF SYSTEMS TO PROTECT PEPTIDE DRUGS FROM AMINOPEPTIDASE-N

Purpose, Develop and evaluate systems to prevent aminopeptidase N caus ed enzymatic degradation of perorally administrated peptide drugs. Met hods. Bacitracin was covalently bound to the unabsorbable carrier matr ix poly(acrylic acid) (paa) in order to avoid any dilution effects of the inhibitor in the intestine as well as systemic toxic side effects. The inhibitory effect of this conjugate, of neutralized paa and N-ace tylcysteine was evaluated using a brush border membrane model. Results , Whereas within 6 h of incubation 65.3 +/- 3.7 mu mol/l of the substr ate (L-leucine p-nitroanilide) was hydrolyzed under our assay conditio ns, this metabolism was reduced to 44.5 +/- 6.3 mu mol/l and 49.0 +/- 8.8 mu mol/l (n = 3-5; +/- S.D.) using 1.5% bacitracin-polymer conjuga te and 0.5% N-acetylcysteine, respectively. The same amount of bacitra cin as immobilized to the polymer exhibited a comparably weaker inhibi tory effect. Neutralized paa did not inhibit membrane bound aminopepti dase N. Covering the membrane with a thin mucus layer led to a signifi cantly lowered inhibitory effect of all tested agents. Conclusions. Th e immobilization of enzyme inhibitors to a carrier matrix and the use of N-acetylcysleine as a novel inhibitor are promising strategies in o rder to overcome the enzymatic barrier caused by membrane bound peptid ases. However the use of effective mucolytic agents seems to be a prer equisite.