ABSTRACT
The incretin gut hormone glucagon-like peptide-1 (GLP-1) has become a household name because of its ability to induce glucose-dependent insulin release with accompanying weight loss in patients. Indeed, derivatives of the peptide exert numerous pleiotropic actions that favorably affect other metabolic functions, and consequently, such compounds are being considered as treatments for a variety of ailments. The ability of native GLP-1 to function as a clinical drug is severely limited because of its short half-life in vivo. All of the beneficial effects of GLP-1 come from its agonism at the cognate receptor, GLP-1R. In our quest for long-lived activation of the receptor, we hypothesized that an agonist that had the ability to covalently cross-link with GLP-1R would prove useful. We here report the structure-guided design of peptide analogues containing an electrophilic warhead that could be covalently captured by a resident native nucleophile on the receptor. The compounds were evaluated using washout experiments, and resistance to such washing serves as an index of prolonged activation and covalent capture, which we use to tabulate longevity and robust long-lived GLP-1R agonism. The addition of SulF (cross-linkable warhead), an N-terminal trifluoroethyl group (for protease protection), and a C18 diacid lipid (protractor) all contributed to the increased wash resistance of GLP-1. The most effective compound based on the wash resistance metric, C2K26DAC18_K34SulF, has all three elements outlined and may serve as a blueprint and a proof-of-concept scaffold for the design of clinically useful molecules.