AOD-9604: Modified Growth Hormone Fragment Research
Mar 22, 2026·4 min read
Background
AOD-9604 is a synthetic peptide corresponding to the C-terminal fragment (residues 176-191) of human growth hormone (hGH) with a tyrosine-to-phenylalanine substitution at the terminal position. This modification was designed to improve metabolic stability while retaining the lipolytic properties identified in the native C-terminal sequence. The compound was developed by Metabolic Pharmaceuticals Ltd. in collaboration with Monash University, Australia.
AOD-9604 is structurally related to but distinct from the unmodified hGH Fragment 176-191. The single amino acid substitution confers enhanced resistance to enzymatic degradation, making AOD-9604 more suitable for oral administration in preclinical research models.
Preclinical Lipid Metabolism Studies
The metabolic properties of AOD-9604 were characterized in a series of publications from the Monash University research group. Ng et al. (2000), publishing in Obesity Research, reported that AOD-9604 stimulated lipolysis and inhibited lipogenesis in adipose tissue from obese Zucker rats. The study demonstrated that daily oral treatment at 500 micrograms per kilogram body weight for 19 days reduced body weight gain by over 50% compared to controls.
Heffernan et al. (2001), publishing in Endocrinology, conducted a mechanistic study examining AOD-9604 in both normal obese mice and beta-3 adrenergic receptor (beta3-AR) knockout mice. The study reported that chronic treatment with AOD-9604 increased fat oxidation and reduced body fat content in normal mice, but these effects were abolished in beta3-AR knockout animals. This established that AOD-9604's lipolytic mechanism is dependent on the beta-3 adrenergic receptor signaling pathway.
Ng et al. (2001), publishing in the International Journal of Obesity, confirmed that chronic treatment with AOD-9604 increased fat oxidation as measured by indirect calorimetry and reduced body weight in diet-induced obese mice. The publication reported that these metabolic effects occurred without the insulin resistance observed with chronic intact growth hormone administration.
Absence of GH Receptor Interaction
A consistent finding across published AOD-9604 studies is that the compound does not interact with the classical growth hormone receptor. Receptor binding assays documented that AOD-9604 has no measurable affinity for the GH receptor, distinguishing its mechanism from intact growth hormone. This accounts for the absence of GH-receptor-mediated effects such as insulin-like growth factor I (IGF-I) stimulation and the insulin resistance associated with chronic GH administration.
The dissociation between lipolytic activity and GH receptor binding was a central rationale for the development of the fragment as a research compound — it provided a tool to study the fat-metabolic effects of the GH C-terminal domain independently of GH receptor signaling.
Clinical Trial Experience
AOD-9604 advanced to human clinical trials. A 12-week randomized clinical trial reported that subjects receiving 1 mg per day of oral AOD-9604 demonstrated greater weight loss compared to placebo. However, a larger 24-week Phase IIb trial enrolling 536 subjects did not meet its primary efficacy endpoint for clinically significant weight loss, and pharmaceutical development of the compound was discontinued in 2007.
The clinical trial data demonstrated that the compound was well-tolerated at doses studied, with an adverse event profile comparable to placebo. No significant effects on glucose homeostasis, IGF-I levels, or other endocrine parameters were observed, consistent with the absence of GH receptor interaction.
Laboratory Handling Notes
AOD-9604 is supplied as a lyophilized powder and should be stored at -20°C. The peptide should be reconstituted in sterile bacteriostatic water for research applications.
All findings discussed in this article are derived from peer-reviewed investigations. This compound is intended for research applications only.
References
- Ng, F.M., et al. "Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone." Obesity Research 8.suppl 1 (2000): 91S.
- Heffernan, M.A., et al. "The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knock-out mice." Endocrinology 142.12 (2001): 5182-5189.
- Ng, F.M., et al. "Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone or a modified C-terminal fragment." International Journal of Obesity 25.10 (2001): 1442-1449.
- Heffernan, M.A., et al. "Effects of oral administration of a synthetic fragment of human growth hormone on lipid metabolism." American Journal of Physiology — Endocrinology and Metabolism 279.3 (2000): E501-E507.
