The effect of 2-mercaptoacetyl-L-phenylalanyl-L-leucine, a specific inhibitor of Pseudomonas aeruginosa elastase, on experimental Pseudomonas keratitis in rabbit eyes.

The compound 2-mercaptoacetyl-L-phenylalanyl-L-leucine (HS-Ac-Phe-Leu) is a potent and specific inhibitor of Pseudomonas aeruginosa elastase, effectively inhibiting the elastase activity both, in vitro and within the rabbit cornea. This inhibitor was therefore evaluated as an adjunct to antibiotics (gentamicin) treatment in experimentally induced Pseudomonas keratitis in rabbits. Twenty eight hours after infection, the eyes that received both, gentamicin and HS-Ac-Phe-Leu showed significantly less corneal melting than those treated with the antibiotics alone, demonstrating the beneficial effect of the inhibitor. Forty eight hours after infection, the difference in clinical appearance between the two treatment groups diminished and was statistically insignificant. No adverse effects were noted in the eyes that received the inhibitor in spite of its frequent application. The protective effect of HS-Ac-Phe-Leu, seen on the first day of the experiment suggests further exploration of the therapeutic potential of this or other, similarly structured, specific and potent inhibitors of Pseudomonas elastase.