An intranasally active glucagon-like peptide-1 (GLP-1) formulation would have great advantages over conventional injectable therapies for the treatment of diabetic patients. The purpose of this study was to investigate the biological potentials of PEGylated exendin-4 (PEG-Ex4) analogs administered intranasally and the effects of polyethylene glycol (PEG) molecular weight (1, 2, 5 kDa) on nasal absorption. Initially, PEGEx4 analogs were site-specifically PEGylated to Lys 27 -amine, and their bioactivities and stabilities were studied in vitro. The hypoglycemic effects and pharmacokinetics of these analogs after nasal administration were evaluated in type 2 diabetic animal models. PEG-Ex4 analogs had 3.1-, 3.8-, and 5.9-fold increased stabilities in rat nasal homogenates than Ex4. However, Lys 27 -PEG 1k -Ex4 was found to have well-preserved bioactivities (83.3% potency vs. Ex4), and other analogs were found to have much lower bioactivities than Lys 27 -PEG 1k -Ex4. In particular, the in vivo pharmacokinetic parameters of Lys 27 -PEG 1k -Ex4 in intranasally administered rats were significantly improved by PEGylation. Area under the curve (AUC) values of Lys 27 -PEG 1k -Ex4 were 33.6-fold higher and circulating t 1/2 values was 27.1-fold higher than Ex4. But, other analogs were not effectively absorbed via the intranasal route, because the higher molecular weight PEG (over 2 kDa) limited intranasal absorption. Finally, in vivo hypoglycemic experiment showed that Lys 27 -PEG 2k -, Lys 27 -PEG 5k -Ex4 had significantly lower hypoglycemic efficacies than Lys 27 -PEG 1k -Ex4, probably because of their lower intrinsic bioactivities and intranasal absorptions. Taken together, our findings suggest that the site-specific conjugation of appropriately sized PEG (1 kDa) substitution onto peptides like Ex4 offers two advantages for delivery via the intranasal route, namely, increased stability and extended circulating half-life.Key words exendin-4; hypoglycemic effect; intranasal administration; PEGylation; type 2 diabetes Non-invasive delivery systems are much more convenient for diabetic patients because they alleviate the discomfort and pain associated with injections.

This method has been successfully applied to the pharmacokinetic study of meloxicam and 5-carboxymeloxicam after oral administration of meloxicam (15 mg) to 30 volunteers.