Metabolic Homeostasis: Glucagon Receptor Profiles of Survodutide & Mazdutide

 

The reemergence of glucagon from a counterregulatory villain to a therapeutic ally represents one of the most compelling shifts in metabolic pharmacology. 

Long regarded solely as the hormone responsible for driving hyperglycemia in diabetes, glucagon is now deliberately harnessed through balanced co-agonism with GLP-1 to exploit its broader metabolic actions without compromising glycaemic control. Within this therapeutic renaissance, survodutide and mazdutide stand as distinct examples of how molecular architecture shapes receptor engagement and ultimately clinical potential.

Molecular Pharmacology of Glucagon Receptor Activation

The pharmacological rationale for incorporating glucagon receptor (GCGR) agonism into anti-obesity therapeutics rests on glucagon’s capacity to increase energy expenditure—an effect that complements GLP-1 receptor (GLP-1R)-mediated reductions in energy intake. Beyond stimulating hepatic glucose production, glucagon coordinates energy homeostasis during fasting by promoting hepatic fatty acid β-oxidation, ketogenesis, amino acid catabolism, and ureagenesis. This broader regulatory role positions GCGR as a vigilant metabolic gatekeeper rather than merely a counterregulatory hormone.

Survodutide (BI 456906) exemplifies a specifically engineered dual agonist. It is a 29-amino acid peptide based on native glucagon, with strategic substitutions at positions 18, 20, and 23 to GLP-1 residues and position 16 to an exendin-4 residue. Position 2 carries a novel unnatural amino acid (Ac4c), and position 24 is linked to a fatty diacid for half-life extension. This structural design yields a distinct receptor engagement profile: survodutide demonstrates subnanomolar potency at both receptors, with EC50 values of 0.33 nM at GLP-1R and 0.52 nM at GCGR in CHO-K1 cells. The balance between these activities is notable—survostide is approximately 4-fold less potent than native GLP-1 at GLP-1R and 22-fold less potent than native glucagon at GCGR. This engineered balance distinguishes it from endogenous peptides and positions it as a deliberate dual agonist rather than an opportunistic cross-reactant.

Mazdutide: An Oxyntomodulin-Derived Approach

Mazdutide (IBI362/LY3305677) emerges from a different molecular lineage, synthesised as a long-acting analogue of the endogenous peptide oxyntomodulin. Oxyntomodulin naturally exhibits dual GLP-1R/GCGR activity, though with relatively modest potency at both receptors. Mazdutide’s binding profile reflects this heritage: it binds human GCGR with a Ki of 17.7 nM and human GLP-1R with a Ki of 28.6 nM, demonstrating a modest preference for GCGR. Its functional potency in stimulating insulin secretion from mouse islets (EC50: 5.2 nM) underscores its capacity to engage metabolic pathways despite binding affinities that are orders of magnitude lower than the engineered survodutide.

The clinical translation of this receptor profile has been substantial. In a US phase 2 trial involving 179 adults with overweight or obesity, mazdutide at 16 mg achieved a mean bodyweight reduction of 18.1% from baseline at week 32, with approximately 50% of participants on 10 mg or 16 mg showing 20% or greater weight reduction by week 48. These benefits were accompanied by broad cardiometabolic improvements, including placebo-adjusted reductions in systolic blood pressure (up to 9.4 mm Hg), LDL cholesterol (16.0%), and triglycerides (23.6%), without evidence that glucagon receptor activation compromised glycaemic control in non-diabetic populations.

Divergent Central Mechanisms

The central nervous system actions of these dual agonists reveal important distinctions that extend beyond receptor binding affinities. Recent transcriptomic mapping of human and mouse circumventricular organs demonstrated that GCGR is virtually undetectable in the area postrema and arcuate nucleus of the hypothalamus—regions critical for appetite regulation. In contrast, GLP-1R is expressed in these tissues, though at relatively low levels (0.4–1.5% of nuclei). This expression pattern suggests that the anorectic effects of dual agonists may be predominantly GLP-1R-dependent.

Indeed, survodutide labelled with a fluorophore was observed to access circumventricular organs and adjacent hypothalamic and hindbrain nuclei, activating multiple regions that are associated with food intake control. Consistent with the hypothesis that intake suppression is GLP-1R-dependent, a long-acting GCGR agonist did not induce neuronal activation in satiety-mediating regions or reduce food intake, though it did produce weight loss attributed to increased energy expenditure. These findings support a division of labour: GLP-1R engagement suppresses intake, while GCGR activation drives energy expenditure.

Metabolic Consequences Beyond Weight Loss

The metabolic benefits of GCGR co-agonism extend to hepatic and systemic parameters. Preclinical studies with mazdutide in diet-induced obese mice demonstrated significant reductions in systemic fat mass, remodelling of energy metabolism, and improvements in systemic glucose tolerance and insulin sensitivity. Multi-omics analysis revealed that mazdutide reprogrammed hepatic lipid metabolism by suppressing lipid uptake, de novo lipogenesis, and lipid droplet formation, primarily through modulation of the PPAR signalling pathway. Notably, pair-feeding experiments indicated that these benefits were not solely attributable to reduced food intake, confirming that dual receptor activation confers metabolic benefits beyond those achievable through GLP-1R agonism alone.

Mazdutide has also shown neuroprotective properties in models of diabetes-associated cognitive dysfunction, with balanced GCGR co-activation enhancing neurocognitive benefits compared to GLP-1R agonism alone. This finding suggests that GCGR activation may uniquely counteract glutamate excitotoxicity, a pathway less targeted by existing GLP-1R-selective agents.

Clinical Implications and Therapeutic Positioning

The clinical trajectories of these two agents reflect their distinct pharmacological profiles. Survodutide is undergoing Phase III studies for obesity and metabolic dysfunction-associated steatohepatitis (MASH), with reported weight loss up to 19% and 64.5% fibrosis reduction in F2-F3 patients. Mazdutide has already received regulatory approval in China for diabetes and obesity and has demonstrated efficacy in diverse populations through the GLORY and DREAMS clinical development programmes.

A critical consideration across the dual agonist class is the potential for glucagon-mediated hyperglycaemia. However, clinical evidence to date suggests that balanced co-agonism can circumvent this risk. Mazdutide’s phase 2 data showed reductions in fasting plasma glucose and HbA1c without evidence of glycaemic compromise. This favourable profile likely reflects the integration of GLP-1R-mediated insulin sensitisation with GCGR-driven energy expenditure, achieving superior weight reduction while mitigating the hyperglycaemic liability inherent to isolated GCGR activation.

Conclusion

Survodutide and mazdutide represent distinct solutions to the same pharmacological challenge: harnessing glucagon’s catabolic and thermogenic actions while preserving glycaemic control through concurrent GLP-1R engagement. Survodutide achieves this through a highly engineered peptide with balanced subnanomolar potency at both receptors, while mazdutide leverages the natural dual activity of oxyntomodulin with a moderate preference for GCGR. Both agents demonstrate that glucagon receptor co-agonism can deliver metabolic benefits—including weight loss, hepatic lipid remodelling, and cardiometabolic risk reduction—that exceed those of GLP-1R monotherapy. The continued clinical development of these agents and their entry into a crowded therapeutic landscape will ultimately determine whether their pharmacological distinctions translate into meaningful differences in efficacy, tolerability, and organ-specific outcomes.