Overview
AOD-9604 is a modified synthetic fragment of human growth hormone (HGH), corresponding to the C-terminal amino acid sequence 176-191 with an added tyrosine residue to stabilise the molecule. It was developed specifically to isolate the fat-metabolising (lipolytic) region of the HGH molecule while removing the growth-promoting and insulin-resistance-inducing effects associated with full-length HGH. The compound was researched by Melbourne-based Metabolic Pharmaceuticals in a long-running programme targeting obesity and metabolic research applications.
AOD-9604 does not bind to the growth hormone receptor in the same manner as full-length HGH and, critically, was designed not to stimulate the GH/IGF-1 axis. Research therefore focuses narrowly on lipolysis (fat breakdown) and inhibition of lipogenesis (fat storage), rather than on tissue growth, bone density, or anabolic outcomes typically associated with HGH research. This guide is for educational and research purposes only. Not medical advice.
Clinical & Research Status
| Evidence Type |
Status |
| Human RCT |
✔ |
| Observational |
✗ |
| Animal Studies |
✔ |
| In Vitro |
✔ |
| Regulatory Approval |
✗ |
Mechanism of Action
AOD-9604 is theorised to act on fat cells (adipocytes) in a manner similar to the lipolytic domain of endogenous growth hormone, promoting the breakdown of stored triglycerides into free fatty acids for use as an energy substrate, while simultaneously inhibiting the process of lipogenesis (the conversion of nutrients into stored fat). This activity has been studied primarily in adipose tissue models, with particular research interest in visceral fat.
Because AOD-9604 lacks the specific region of the HGH molecule responsible for binding to the growth hormone receptor with high affinity, research models have consistently reported no measurable increase in IGF-1 or fasting blood glucose — a key distinguishing feature from full-length HGH research, where insulin resistance and unwanted tissue growth are recognised confounds. This narrow mechanism was the basis of Metabolic Pharmaceuticals' rationale for advancing the compound through obesity-focused clinical trials.
Research Areas & Reported Effects
Lipolysis and Fat Metabolism
The majority of AOD-9604 research centres on its reported ability to has been observed to support lipolysis in adipocyte models, both in vitro and in animal studies. Rodent studies reported reductions in fat mass without corresponding changes in lean body mass, consistent with a fat-selective mechanism rather than a general metabolic or anabolic effect.
Human Obesity Trials
Metabolic Pharmaceuticals progressed AOD-9604 through Phase I and Phase II human trials for obesity, and the compound reached a Phase IIb trial involving several hundred participants. While earlier, smaller studies reported statistically significant weight loss relative to placebo over 12-week periods, the pivotal Phase IIb trial did not demonstrate a clinically meaningful difference from placebo, and the programme was discontinued as a result. This outcome is an important and well-documented part of the compound's research history.
Glucose and IGF-1 Safety Profile
A specific and consistent research finding across AOD-9604 trials is the absence of any measurable effect on fasting blood glucose, insulin sensitivity, or IGF-1 levels — parameters that are reliably altered by full-length HGH. This safety profile was one of the more robust and reproducible findings across the compound's clinical programme, even though the primary efficacy endpoint (significant fat loss versus placebo) was not met in the largest trial.
Research Data Summary
| Study / Model |
Reported Effect |
| Rodent Adipocyte Model (Heffernan et al., 2001) |
Reported lipolytic activity localised to the 176-191 HGH fragment region, with no growth-promoting activity detected. |
| Ng FM et al. Preclinical Studies |
Identified the C-terminal fragment as responsible for fat-metabolising effects independent of the GH receptor growth-promoting domain. |
| Metabolic Pharmaceuticals Phase II (obesity) |
Reported statistically significant reduction in body fat versus placebo over 12 weeks in early trial stages. |
| Metabolic Pharmaceuticals Phase IIb (pivotal, ~300 participants) |
Did not demonstrate a clinically or statistically meaningful weight-loss difference from placebo; programme subsequently discontinued. |
| Glucose/IGF-1 Monitoring (across trials) |
No significant change in fasting glucose, insulin sensitivity, or IGF-1 reported at any dose studied. |
Stack Combinations Studied
- AOD-9604 + GHRP-class peptides → Research rationale: Explored in some independent (non-Metabolic Pharmaceuticals) research contexts to examine whether combining a lipolytic HGH fragment with a GH secretagogue produces additive effects on fat metabolism, though this combination was not part of the original sponsor's clinical programme.
- AOD-9604 + Caloric restriction models → Research rationale: Used in some animal studies to isolate whether AOD-9604's lipolytic effect is additive to, or independent of, diet-induced fat loss.
⚠️ Stack combinations listed for research reference only. Not safety or efficacy guidance.
Research Protocol Reference
experimental research protocols only — not dosing recommendations.
| Protocol |
Dose (experimental model only) |
Duration (experimental model only) |
Frequency (experimental model only) |
Research Context |
| Low-Range Research Protocol |
250-300 mcg |
4-8 weeks |
Once daily |
Baseline lipolytic response, glucose safety monitoring. |
| Standard Research Protocol (as trialled) |
500 mcg |
12 weeks |
Once daily, subcutaneous |
Matches Metabolic Pharmaceuticals Phase II/IIb trial design. |
| Extended Research Protocol |
500 mcg |
16 weeks+ |
Once daily |
Long-duration fat mass and safety marker studies in animal models. |
Observed Side Effects in Research
- Injection site reactions (redness, mild irritation)
- Headache (infrequent)
- No reported changes in blood glucose or IGF-1 across trials
- No reported growth-promoting or acromegaly-type effects
The Phase IIb trial reported that AOD-9604 was generally well tolerated, with an adverse event profile similar to placebo; the trial's limitation was efficacy versus placebo, not safety.
Compound Data
- CAS Number
- 221231-10-3
- Molecular Formula
- C78H123N23O23S2
- Molecular Weight
- Approximately 1815.1 g/mol
- Half-Life
- Short (minutes range); precise in vivo half-life varies by administration route and model
- Synonyms
- hGH Fragment 177-191 (Tyr-hGH Fragment), Metabolic Pharmaceuticals AOD-9604, Anti-Obesity Drug 9604
- Research Classification
- Modified Human Growth Hormone Fragment, Lipolytic Peptide (non-growth-promoting)
Scientific References
- [Heffernan MA et al. 2001] — 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 — [Animal]
- [Ng FM et al. 2000] — Analysis of the growth-hormone-releasing region of the human growth hormone molecule and its lipolytic fragment. — Endocrinology — [In vitro / Animal]
- [Heffernan MA et al. 2000] — The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice. — Endocrinology — [Animal]
- [Metabolic Pharmaceuticals Ltd, ASX/Company Disclosures 2004-2008] — Phase I/II/IIb clinical trial results for AOD9604 in obesity. — Company Clinical Trial Reports — [Human RCT]
- [Nørrelund H et al. 2000 — background GH fragment context] — Modulation of GH action by fragments of the GH molecule. — Growth Hormone & IGF Research — [Review context]
Research base note: AOD-9604's largest and most rigorous trial (Phase IIb, pivotal) did not beat placebo on its primary efficacy endpoint, and the development programme was discontinued as a result. Independent, non-sponsor peer-reviewed literature on AOD-9604 beyond the original Metabolic Pharmaceuticals-funded studies is limited. This should be read as a compound with a documented but ultimately negative pivotal efficacy trial, not as an established fat-loss agent.
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