A 4-arm polyethylene glycol derivative conjugated with exendin-4 peptide and palmitylamine having dual-function of size-increase and albumin-binding for long hypoglycemic action

PEGylation and albumin binding are viewed as the most effective ways of prolonging the lifespans of short-lived peptides by delaying renal filtration. Here, we describe a derivative of exendin-4 with pharmaceutical benefits produced using both techniques. This exendin-4 derivative is based on a 4-arm PEG_20k conjugated with two exendin-4s and two palmitylamines on its arms. PEG and palmitylamine were chosen to increase molecular size and bind to albumin, respectively. This derivative (Ex4-PEG-C16) was found to have larger molecular size (169kDa) than actual (28.9kDa) by size-exclusion chromatography and acceptable binding capability (~90%) to immobilized-albumin. Although the receptor-binding of Ex4-PEG-C16 to RIN-m5F cells was significantly lower than that of exendin-4, its acute anti-hyperglycemic efficacy was equivalent to that of exendin-4 in type 2 diabetic db/db mice. Furthermore, Ex4-PEG-C16 displayed a >6-fold increase in AUC and circulating t_1/2 vs. exendin-4. Due to this improvement, its hypoglycemic duration was greatly increased to 18.6h at a dose 250nmol/kg as compared with exendin-4 (8.7h). Our results show that the combined technique of PEGylation and albumin binding was effective when applied to exendin-4. We believe that this exendin-4 derivative has considerable pharmaceutical potential as a novel type 2 anti-diabetic systemic treatment.