Hormone Analogues with Unique Signaling Profiles from Replacement of -Residue Triads with / Diads

We have applied an underexplored backbone modification strategy to generate new analogues of peptides that activate two clinically important class B1 G protein-coupled receptors (GPCRs). Most peptide modification strategies involve changing side chains or, less commonly, changing the configuration at side chain-bearing carbons (i.e., L residues replaced by D residues). In contrast, backbone modifications alter the number of backbone atoms and the identities of backbone atoms relative to a poly-a-amino acid backbone. Starting from the peptide agonists PTH(1-34) (the first 34 residues of the parathyroid hormone, used clinically as the drug teriparatide) and glucagon-like peptide-1 (7-36) (GLP-1(7-36)), we replaced native alpha-residue triads with a diad composed of a beta-amino acid residue and a gamma-amino acid residue. The beta/gamma diad retains the number of backbone atoms in the aaa triad. Because the beta and gamma residue each bear a single side chain, we implemented alpha alpha alpha -> beta gamma replacements at sites that contained a Gly residue (i.e., at alpha-residue triads that presented only two side chains). All seven of the alpha/beta/gamma-peptides derived from PTH(1-34) or GLP-1(7-36) bind to the cognate receptor (the PTHR1 or the GLP-1R), but they vary considerably in their activity profiles. Outcomes include functional mimicry of the all-alpha agonist, receptor-selective agonist activity, biased agonism, or strong binding with weak activation, which could lead to antagonist development. Collectively, these findings demonstrate that alpha alpha alpha -> beta gamma replacements, which are easily implemented via solid-phase synthesis, can generate peptide hormone analogues that display unique and potentially useful signaling behavior.