Pharmacological characterization and antidiabetic activity of a long‐acting glucagon‐like peptide‐1 analogue conjugated to an antithrombin III ‐binding pentasaccharide

Aims To examine the biological characteristics of a novel glucagon‐like peptide‐1 ( GLP ‐1) conjugate, in which an antithrombin III ( ATIII )‐binding pentasaccharide is conjugated to d ‐ Ala 8 GLP ‐1 using a tetraethylene glycol linker. Methods We assessed GLP ‐1 receptor binding, cAMP generation and insulin secretory activity of the GLP ‐1 conjugate in vitro . Circulating half‐life, glucose homeostatic and subchronic therapeutic effectiveness were then examined in vivo . Results The half‐life of the GLP ‐1 conjugate in mice was ∼11 h. In vitro insulin secretion from clonal β cells and islets was increased (p < 0.001) by the conjugate. The conjugate had half maximum effective concentration values of 1.3 × 10 −7 and 9.9 × 10 −8  M for displacement of 125 I‐GLP ‐1 in competitive GLP ‐1 receptor binding and cAMP generation, respectively. Glucose tolerance in normal mice, immediately and 4 h after conjugate injection, resulted in significant (p < 0.001) improvements in blood glucose. These effects persisted for >48 h after administration. Daily treatment (21 days) of high‐fat‐fed and ob/ob mice with 25 nmol/kg conjugate resulted in significant improvement in glucose tolerance (p < 0.001) and reductions in glycated haemoglobin ( HbA1c ; p < 0.01) equivalent to or better than with exenatide or liraglutide. Treatment of C57BL / KsJ db/db mice for 15 days with 100 nmol/kg conjugate significantly (p < 0.001) reduced glucose and raised plasma insulin. Oral glucose tolerance was significantly (p < 0.001) improved and both 24‐h glucose profile (p < 0.001) and HbA1c levels (p < 0.001) were reduced. Islet size (p < 0.001) and pancreatic insulin content were increased without change of islet cell proliferation or apoptosis. Conclusion These data show that d ‐ Ala 8 GLP‐1 ( Lys 37 ) pentasaccharide exerts significant antidiabetic actions and has a projected pharmacokinetic/pharmacodynamic profile that merits further evaluation in humans for a possible once‐weekly dosing regimen.