Novel
peptidic glucagon receptor (GCGR) and glucagon-like peptide
1 receptor (GLP-1R) dual agonists are reported to have increased efficacy
over GLP-1R monoagonists for the treatment of diabetes and obesity.
We identified a novel Xenopus GLP-1-based
dual GLP-1R/GCGR agonist (xGLP/GCG-13) designed with a proper activity
ratio favoring the GLP-1R versus the GCGR. However, the clinical utility
of xGLP/GCG-13 is limited by its short in vivo half-life.
Starting from xGLP/GCG-13, dual Cys mutation was performed, followed
by covalent side-chain stapling and serum albumin binder incorporation,
resulting in a stabilized secondary structure, enhanced agonist potency
at GLP-1R and GCGR, and improved stability. The lead peptide 2c (stapled xGLP/GCG-13 analogue with a palmitic acid albumin
binder) exhibits balanced GLP-1R and GCGR activations and potent,
long-lasting effects on in vivo glucose control. 2c was further explored pharmacologically in diet-induced
obesity and db/db rodent models. Chronic administration
of 2c potently induced body weight loss and hypoglycemic
effects, improved glucose tolerance, increased energy expenditure,
and normalized lipid metabolism and adiposity in relevant animal models.
These results indicated that 2c has potential for development
as a novel antidiabetic and/or antiobesity drug. Furthermore, we propose
that the incorporation of a proper serum protein-binding motif into
a di-Cys staple is an effective method for improving the stabilities
and bioactivities of peptides. This approach is likely applicable
to other therapeutic peptides, such as glucose-dependent insulin-tropic
peptide receptor (GIPR) and GLP-1R dual agonists or GLP-1R/GCGR/GIPR
triagonists.