HGH fragment 176-191 · Anti-Obesity Drug 9604 · Lipolytic peptide
A synthetic fragment of human growth hormone — specifically residues 176–191 of the C-terminal. Developed at Monash University by Frank Ng to isolate the fat-burning properties of HGH without its growth-promoting and diabetogenic effects. Completed Phase 2 trials with mixed results. Received FDA GRAS designation as a food ingredient — a safety evaluation few research peptides have undergone. The drug development program was halted in 2007 after the pivotal trial failed to meet its primary endpoint.
01 — Research Summary
AOD-9604 has a more complete clinical development history than most research peptides — it went through Phase 1 and Phase 2 randomised controlled trials under the drug development program at Metabolic Pharmaceuticals. That history also includes the most important finding: the pivotal Phase IIb trial failed.
Statistically significant fat loss in 12-week RCT. The METAOD005 study (1mg/day) showed approximately 2.6kg fat loss versus 0.8kg for placebo — a statistically significant result that warranted the larger pivotal trial.
Failed to replicate. Development halted. The larger, more rigorous follow-up trial did not demonstrate statistically significant weight loss versus placebo — the primary endpoint was not met. Metabolic Pharmaceuticals halted the formal drug development program in 2007. This is the central clinical data point often omitted in marketing materials.
Consistent fat loss without muscle loss in obese animal models. Multiple independent rodent studies confirm dose-dependent reductions in body fat via beta-adrenergic lipolysis, without affecting lean mass or raising IGF-1. The animal mechanistic data is compelling; the human translation is where the evidence base weakens.
AOD-9604 then received GRAS (Generally Recognized as Safe) designation from the FDA as a food ingredient — a distinct regulatory category from drug approval, but a meaningful safety evaluation. Its Category 2 nomination was withdrawn as of April 2026, meaning standard compounding regulations now apply.
The pivotal human trial failed. Anyone claiming reliable, significant fat loss from AOD-9604 alone in humans is overstating what the controlled trial evidence supports. The compound has a plausible mechanism, a clean safety profile, and a genuine failure at the most important clinical test. That combination — interesting preclinical data, failed human translation — is more common than the marketing suggests.
02 — Mechanism of Action
AOD-9604 was specifically engineered to isolate the fat-mobilising properties of growth hormone from its other metabolic effects. Full HGH stimulates both fat loss and growth — raising IGF-1, promoting cell division, and causing insulin resistance at therapeutic doses. The 176-191 fragment retains the lipolytic activity while having minimal effect on IGF-1, insulin sensitivity, or growth.
AOD-9604 activates beta-3 adrenergic receptors on adipose tissue, triggering a cAMP-dependent cascade that activates hormone-sensitive lipase (HSL) — the primary enzyme responsible for breaking down stored triglycerides into free fatty acids for use as energy.
Simultaneously, AOD-9604 downregulates acetyl-CoA carboxylase (ACC) — a key enzyme in new fat synthesis. This dual action (stimulating breakdown, inhibiting formation) is the mechanistic basis for its targeted lipolytic profile.
Unlike full HGH, AOD-9604 does not activate the classical GH receptor pathway that drives IGF-1 production, cell proliferation, and insulin resistance. This independence from the GH receptor is what gives it the selective lipolytic profile without growth-promoting side effects.
03 — Dosing Context
Protocol extrapolated from the Phase 2 clinical trials and community practice.
| Protocol | Dose | Frequency | Timing | Notes |
|---|---|---|---|---|
| Standard | 300–500 mcg | Daily | Fasted — AM preferred | Most common community protocol |
| Phase 2 trial dose | 1 mg | Daily | Oral (trial) / SubQ (community) | Higher than typical community use |
The fasted administration is important — insulin suppresses lipolysis, so the fat-mobilising mechanism of AOD-9604 is blunted in the fed state. Morning fasted injection is the standard approach. Results, where experienced at all, are typically modest — this is not a GLP-1 class compound. Any fat loss is best understood as a complement to caloric deficit and exercise, not a standalone intervention.
04 — Community
Community sentiment for AOD-9604 is notably more mixed than for most peptides in the metabolic category. Users who report positive outcomes describe modest fat loss as part of a caloric deficit, with the peptide providing a marginal additional lipolytic signal. Users who report no effect are equally common — consistent with the pivotal trial's failure to replicate the smaller trial's results. The compound sits in the "worth trying at low cost" category for many community members rather than the "confident evidence" tier.
It is frequently stacked with GLP-1 drugs (semaglutide, tirzepatide) as a complementary mechanism — the GLP-1 suppresses appetite and improves glycaemic control while AOD-9604 theoretically targets fat cell lipolysis directly. No controlled data exists for this combination.