Optimization of Truncated Glucagon Peptides to Achieve Selective, High Potency, Full Antagonists.

Antagonism of glucagon's biological action is a proven strategy for decreasing glucose in diabetic animals and patients. To achieve full, potent, and selective suppression, we chemically optimized N-terminally truncated glucagon fragments for the identification and establishment of the minimum sequence peptide, [Glu9]glucagon(6-29) amide () as a full antagonist in cellular signaling and receptor binding (IC = 36 nM). Substitution of Phe6 with l-3-phenyllactic acid (Pla) produced [Pla6, Glu9]glucagon(6-29) amide (), resulting in a 3-fold improvement in receptor binding (IC = 12 nM) and enhanced antagonist potency. Further substitution of Glu9 and Asn28 with aspartic acid yielded [Pla6, Asp28]glucagon amide (), which demonstrated a further increase in inhibitory potency (IC = 9 nM), and improved aqueous solubility. Peptide and a palmitoylated analogue, [Pla6, Lys10(γGluγGlu-C16), Asp28]glucagon(6-29) amide (), displayed sustained duration action that successfully reversed glucagon-induced glucose elevation in mice.