Site-selective modification of exendin 4 with variable molecular weight dextrans by oxime-ligation chemistry for improving type 2 diabetic treatment

Dextrans, as natural and biocompatible polysaccharides, are a promising candidate as PEG alternatives to improve the therapeutic profiles of biotherapeuticals. In this work, we chemically mutated the lysine residue in native Ex4 to aminooxyl containing lysine (K*) and three Ex4 analogs (Ex4-12K*, Ex4-27K*, Ex4-12K*-27K*) were synthesized and site-selectively modified with variable Mw of dextrans by facile oxime-ligation chemistry. The biological activities of six dextran-Ex4 conjugates were studied by in vitro and in vivo experiment. It was demonstrated that dextranylation at the 12-site of Ex4 determined the in vitro potency as GLP-1R agonist and the in vivo acute glucose-lowering activity. Furthermore, the in vivo long-acting antidiabetic experiment demonstrated that hypoglycemic effect was strongly dependent on the dextranylation site of Ex4 as well as the size of dextran. And Dextran-Ex4-12K*(20,000) exhibited the best long acting hypoglycemic activity in STZ/HFD-induced T2D mice and is a promising once daily reagent for T2D treatment.