Inhibition of corneal ulceration by tetrapeptidyl hydroxamic acid

The inhibitory activity of a new peptidyl collagenase inhibitor, FN-439 or tetrapeptidyl hydroxamic acid (H2N-C6H4-CO-Gly-L-Pro-D-Leu-D-Ala-NHOH), was determined against vertebrate collagenases derived from human fibroblast, human polymorphonuclear leukocyte (PMN) and tadpole skin. In addition, the effect of FN-439 in inhibiting corneal ulceration was also investigated with alkali-burned rabbit corneas. FN-439 can block the active site of collagenase, and hydroxamic acid can chelate Zn2+ which is essential for collagenase activity. Furthermore, this compound contains D-amino acids to resist nonspecific host-derived degradative enzymes. In our experiments, corneal ulceration occurred in 5 of the 9 control eyes, but in none of the 9 eyes treated with FN-439 (P < 0.01). The only cellular elements observed at the ulcerated area were PMNs and monocytes. FN-439 appeared to act against PMN collagenase. In addition, we compared the change in the concentration of FN-439 (D-peptide) and the L-form of FN-439 (L-peptide) in aqueous humor aspirated from the rabbit eyes burned with alkali. After incubation for 3 hours, the concentration of the D-peptide was decreased by 3%, while that of the L-peptide was decreased by 60%. FN-439 may be useful for treating noninfectious corneal ulcers because of its potent activity (IC50 = 1 microM) and chemical and biological stabilities.