ABSTRACT
AIMS: In human diabetes, the deleterious effects of chronic hyperglycemia are the result of excessive nonenzymatic modification of proteins and phospholipids by glucose and its by-products leading to the formation of irreversible oxidized, aromatic, and fluorescent ligands known as advanced glycation end products. This glycation process has been associated with deleterious health effects. The present invention provides the potent inhibitors of protein glycation and AGEs formation, which are particularly advantageous for eyedrop delivery in the prevention and treatment of diabetes- and age-related pathologies. MAIN METHODS AND KEY FINDINGS: We proposed a deglycation system involving removal, by transglycation of sugar or aldehyde moieties from the Schiff bases by ophthalmic aldehyde scavenger L-carnosine derived from its ocular bioactivating sustained release prodrug 1% N-acetylcarnosine (NAC) lubricant eyedrops containing a mucoadhesive cellulose compound combined with corneal absorption promoters in drug delivery system. Carnosine analogs bearing the histidyl-hydrazide moiety were synthesized and patented in ophthalmic formulations with NAC bioactivating prodrug to moderate the enzymatic hydrolysis of a dipeptide by carnosinase (inhibited by a nonhydrolyzable substrate analog so that this keeps steadier levels of the drug active principle in the aqueous humor). Leucyl-histidylhydrazide peptidomimetic demonstrated the transglycation activity more pronounced than L-carnosine accounting for the ability of either molecule to reverse pre-existing, glycation-induced, cross-linking, and checking the nonenzymatic glycation cascade in the ophthalmic pathologies. The ophthalmic drug N-acetylcarnosine eye drop formulation with sustained time- release and increased absorption of L-carnosine in the aqueous humor (a prolonged effective dose) showed follow-up treatment efficacy for age-related cataracts for enrolled patients into the randomized double blind placebo controlled crossover clinical trial, and in over 50250 various cohort patients, was demonstrated to have an efficacy, safety and good tolerability for prevention and treatment of visual impairment in the older population data base. SIGNIFICANCE: The bioactivating antioxidant NAC and histidyl-hydrazide are potent agents with the pleiotropic effects for ophthalmic therapy of senile cataracts and diabetic ocular complications.
