AmycretinvsAOD-9604

Amycretin is a unimolecular co-agonist that simultaneously activates both the GLP-1 receptor and the amylin (AMY) receptor — the first peptide engineered to combine these two complementary satiety pathways in a single molecule rather than as a two-drug combination. The design philosophy is to deliver the additive weight-loss benefit demonstrated by CagriSema (semaglutide + cagrilintide) without the manufacturing, dosing, and patient-acceptance complexities of co-formulating two separate drugs.

The GLP-1 component drives appetite suppression centrally through hypothalamic POMC/CART activation and NPY/AgRP inhibition, slows gastric emptying via vagal signalling, and stimulates glucose-dependent insulin secretion from pancreatic beta cells. The amylin component activates calcitonin-receptor/RAMP heterodimer complexes concentrated in the area postrema and nucleus tractus solitarius — brainstem regions outside the blood-brain barrier that form a parallel satiety circuit reducing meal size and food-seeking behaviour through neuroanatomically distinct pathways.

Because GLP-1 and amylin signal through different receptor families and target different neurons in the appetite control network, their effects are additive rather than redundant. Phase 1b/2a data showed up to 22% body weight reduction at 36 weeks for the subcutaneous form — comparable to CagriSema with a simpler one-molecule profile. A particularly notable feature is the parallel development of an oral formulation, which would be the first oral peptide combination therapy for obesity if approved. Novo Nordisk's branded development name is zenagamtide, and the molecule is positioned as the company's strategic answer to retatrutide and tirzepatide.

AOD-9604 is a modified fragment of human growth hormone comprising amino acids 176-191 with an additional tyrosine residue at the N-terminus. This specific region of the GH molecule contains the lipolytic (fat-burning) domain while lacking the receptor binding regions responsible for growth-promoting and diabetogenic effects. The result is a peptide that mimics the fat metabolism effects of growth hormone without stimulating IGF-1 production, bone growth, or insulin resistance.

The primary mechanism involves stimulation of beta-3 adrenergic receptors on adipocytes, which activates hormone-sensitive lipase (HSL) through a cAMP-dependent pathway. HSL catalyzes the hydrolysis of stored triglycerides into free fatty acids and glycerol, which are then released into the bloodstream for oxidation by muscle and liver tissue. Simultaneously, AOD-9604 appears to inhibit lipogenesis — the synthesis of new fatty acids from non-lipid precursors — by downregulating acetyl-CoA carboxylase and fatty acid synthase activity in adipocytes.

Unlike full-length growth hormone, AOD-9604 does not bind to the GH receptor or stimulate JAK2/STAT5 signaling, which is why it avoids the IGF-1 elevation, water retention, and insulin resistance associated with exogenous GH use. However, it should be noted that AOD-9604 failed to show significant weight loss compared to placebo in Phase II/III clinical trials, raising questions about whether its in vitro lipolytic activity translates to meaningful clinical effects at the doses tested.