AOD-9604 (Anti-Obesity Drug-9604) is a synthetic peptide fragment corresponding to amino acids 177-191 of human growth hormone (hGH), with the addition of a tyrosine residue at the N-terminus. It was developed by researchers at Monash University in Australia with the aim of isolating the lipolytic (fat-burning) activity of hGH without its anabolic and diabetogenic effects.
Mechanism of Action
The C-terminal fragment of hGH (residues 177-191) has been shown to stimulate lipolysis and inhibit lipogenesis through a mechanism that is independent of the growth hormone receptor. This region of the hGH molecule does not bind to the classical GH receptor but instead appears to interact with a distinct receptor or signalling pathway that specifically mediates metabolic effects.
In adipocyte studies, AOD-9604 has been shown to activate β3-adrenergic receptors, which are expressed on adipose tissue and mediate lipolysis. It also appears to inhibit the enzyme acetyl-CoA carboxylase, which is involved in the first committed step of fatty acid synthesis, thereby reducing lipogenesis.
Animal Model Studies
The most compelling preclinical evidence for AOD-9604’s metabolic effects comes from studies in obese rodent models. Heffernan et al. (2001) demonstrated that chronic administration of AOD-9604 to obese mice resulted in significant reductions in body weight and fat mass compared to controls, without affecting lean mass, blood glucose, or insulin levels — a profile that distinguished it from full-length hGH.
“AOD-9604 reduces body weight and fat mass in obese mice without affecting lean body mass, blood glucose, or insulin sensitivity, suggesting a selective lipolytic mechanism distinct from the full-length growth hormone molecule.” — Heffernan et al., 2001
Subsequent studies in various rodent models have generally replicated these findings, showing reductions in adipose tissue mass with AOD-9604 treatment. The peptide has also been studied in models of osteoarthritis, where it has shown potential cartilage-protective effects — an area of research that is mechanistically distinct from its metabolic effects.
Human Clinical Trial Data
AOD-9604 is one of the few research peptides to have progressed to human clinical trials. Phase IIb trials conducted in the early 2000s examined its effects on body weight in obese adults. While early results were promising, a large Phase III trial (METRO) failed to demonstrate statistically significant weight loss compared to placebo, leading to the discontinuation of its development as an obesity drug.
The METRO trial results highlight the challenges of translating preclinical metabolic findings to human clinical outcomes, and serve as an important reminder that positive animal model data does not guarantee clinical efficacy.
AOD-9604 is available from The Bio Edit for laboratory and in-vitro research purposes only. The clinical trial data referenced in this article relates to pharmaceutical development programs and does not constitute evidence for any specific use.
Conclusion
AOD-9604 has a well-characterised preclinical profile as a selective lipolytic agent, with a mechanism of action that is distinct from full-length growth hormone. Its progression to human clinical trials — and the mixed results obtained — provides a valuable case study in the translation of metabolic peptide research from bench to bedside.