Disconnect between signalling potency and in vivo efficacy of pharmacokinetically optimised biased glucagon-like peptide-1 receptor agonists

Objective To determine how pharmacokinetically advantageous acylation impacts on glucagon-like peptide-1 receptor (GLP-1R) signal bias, trafficking, anti-hyperglycaemic efficacy and appetite suppression. Methods In vitro signalling responses were measured using biochemical and biosensor assays. GLP-1 receptor trafficking was determined by confocal microscopy and diffusion-enhanced resonance energy transfer. Pharmacokinetics, glucoregulatory effects and appetite suppression were measured in acute, sub-chronic and chronic settings in mice. Results A C-terminally acylated ligand, exendin-phe1-C16, was identified with undetectable β-arrestin recruitment and GLP-1R internalisation. Depending on the cellular system used, this molecule was up to 1000-fold less potent than the comparator exendin-asp-3-C16 for cyclic AMP signalling, yet was considerably more effective in vivo , particularly for glucose regulation. Conclusions C-terminal acylation of biased GLP-1R agonists increases their degree of signal bias in favour of cAMP production and improves their therapeutic potential.