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Aims: To describe the in vitro characteristics and antidiabetic in vivo efficacy of the novel glucagon-like peptide-1 receptor agonist (GLP-1RA) GL0034. Materials and Methods: Glucagon-like peptide-1 receptor (GLP-1R) kinetic binding parameters, cyclic adenosine monophosphate (cAMP) signalling, endocytosis and recycling were measured using HEK293 and INS-1832/3 cells expressing human GLP-1R. Insulin secretion was measured in vitro using INS-1832/3 cells, mouse islets and human islets. Chronic administration studies to evaluate weight loss and glycaemic effects were performed in db/db and diet-induced obese mice. Results: Compared to the leading GLP-1RA semaglutide, GL0034 showed increased binding affinity and potency-driven bias in favour of cAMP over GLP-1R endocytosis and β-arrestin-2 recruitment. Insulin secretory responses were similar for both ligands. GL0034 (6 nmol/kg) led to at least as much weight loss and lowering of blood glucose as did semaglutide at a higher dose (14 nmol/kg). Conclusions: GL0034 is a G protein-biased agonist that shows powerful antidiabetic effects in mice, and may serve as a promising new GLP-1RA for obese patients with type 2 diabetes.

Mini-G proteins are engineered thermostable variants of Gα subunits designed to specifically stabilise G protein-coupled receptors (GPCRs) in their active conformation for structural analyses. Due to their smaller size and ease of use, they have become popular tools in recent years to assess specific GPCR behaviours in cells, both as reporters of receptor coupling to each G protein subtype and for in-cell assays designed to quantify compartmentalised receptor signalling from a range of subcellular locations. Here, we describe a previously unappreciated consequence of the co-expression of mini-G proteins with their cognate GPCRs, namely a profound disruption in GPCR trafficking and intracellular signalling caused by the co-expression of the specific mini-G subtype coupled to the affected receptor. We studied the Gαs-coupled pancreatic beta cell class B GPCR glucagon-like peptide-1 receptor (GLP-1R) as a model to describe in detail the molecular consequences derived from this effect, including a complete halt in β-arrestin-2 recruitment and receptor internalisation, despite near-normal levels of receptor GRK2 recruitment and lipid nanodomain segregation, as well as the disruption of endosomal GLP-1R signalling by mini-Gs co-expression. We also extend our analysis to a range of other prototypical GPCRs covering the spectrum of Gα subtype coupling preferences, to unveil a widely conserved phenomenon of GPCR internalisation blockage by specific mini-G proteins coupled to a particular receptor. Our results have important implications for the design of methods to assess intracellular GPCR signalling. We also present an alternative adapted bystander intracellular signalling assay for the GLP-1R in which we substitute the mini-Gs by a nanobody, Nb37, with specificity for active Gαs:GPCR complexes and no deleterious effect on the capacity for GLP-1R internalisation.

Background and Aims: To characterize a novel incretin analogue which engages glucagon-like peptide-1 (GLP1R) and glucose-dependent insulinotropic peptide (GIPR) receptors. Methods: Potencies for cAMP production were determined at GLP-1R and GIPR in Flp-In T-REx-293 cells. Assessment of SNAP-tagged GLP-1R internalisation by confocal microscopy, incorporation of GLP-1R into lipid rafts, Gs recruitment to GLP-1R and GIPR with NanoBiT™ used INS-1(832/3) beta cells. Ca2+ responses were recorded in mouse islets by time-lapse confocal microscopy using Cal520 AM. Results: HISHS-2001 displayed higher potency versus tirzepatide for cAMP production at both receptors (Table). GLP-1R beta arrestin-2 recruitment was lower with HISHS-2001, indicating increased bias. Efficacy and potency of recruitment of Gs protein to the GLP-1R were lower for HISHS-2001 vs. tirzepatide (Table). HISHS-2001 showed increased potency for Gs recruitment to the GIPR. GLP-1R endocytosis was lower for HISHS-2001 vs. tirzepatide but both agonists showed increased recruitment of GLP-1R to lipid rafts vs. semaglutide. Ca2+ responses, and potentiation of insulin secretion from mouse islets tended to be higher for HISHS-2001 vs. tirzepatide. Both displayed enhanced insulin secretion from human islets vs. semaglutide (Table). Conclusions: HISHS-2001 may provide a useful new GLP1R-GIP dual agonist. Disclosure Y. Manchanda: None. G. A. Rutter: Advisory Panel; Self; Sun Pharmaceutical Industries Ltd. B. Jones: Research Support; Self; Sun Pharmaceutical Industries Ltd. G. Carrat: None. Z. Ramchunder: None. P. Marchetti: Consultant; Self; Menarini Group. I. Leclerc: Consultant; Spouse/Partner; Sun Pharmaceutical Industries Ltd. R. Thennati: None. V. S. Burade: None. A. Tomas: Other Relationship; Self; Sun Pharmaceutical Industries Ltd. Funding Sun Pharmaceutical Industries Ltd. (P79787)