AOD-9604: the hGH fragment that failed its Phase IIb obesity trial.

AOD-9604 is the 16-residue C-terminal fragment of human growth hormone studied for lipolytic activity. Its pivotal human trial — a 24-week Phase IIb study in over 500 obese adults — failed to beat placebo, ending the obesity-indication clinical-development program.

What is AOD-9604?

AOD-9604 stands for “Anti-Obesity Drug 9604.” That was the project name Metabolic Pharmaceuticals gave it. The Australian biotech licensed the molecule from Monash University in the 1990s.

The compound is a 16-amino-acid peptide. It matches the tail end of human growth hormone (positions 176 to 191 out of 191 total). Researchers tacked on one extra amino acid, tyrosine, at the front to keep it stable in the body.

The thesis was clever. Growth hormone stimulates lipolysis, the breakdown of stored fat. It also raises IGF-1, a hormone that drives tissue growth, and it causes insulin resistance and joint pain.

The Monash team thought they'd isolated the fat-burning fragment and left the rest behind. Mice agreed, as Heffernan and colleagues reported in 2000. Humans, eventually, did not.

How does it work in animals?

In mice, AOD-9604 burns fat by acting directly on fat cells. The 2001 papers from Ng and Heffernan reported that chronic dosing in obese mice cut fat mass and triggered lipolysis.

The effect partly disappeared in mice missing the β3 adrenergic receptor, which is the fat-cell signal that switches lipolysis on. Ng and colleagues read that as evidence AOD-9604 works through that pathway.

Two things didn't hold up.

• The receptor was never found. Twenty-five years after the first papers, nobody has identified the specific receptor that AOD-9604 binds to. The mechanism is described in terms of what it does (fat cells release fatty acids) instead of what it grips.
• The lipolytic effect didn't reproduce in cell culture. A 2008 study found no lipolytic effect from purified human growth hormone on cultured mouse fat cells (Richelsen et al., 2008). The whole rodent-lipolysis story has been tough to repeat in standardized lab systems.

For a drug whose whole pitch is targeting the right receptor and skipping the wrong ones, not knowing the receptor is a problem. We'd call it the central one. The marketing rests on what happened in mice, not on a confirmed mechanism.

What happened in the Phase IIb trial?

The pivotal study was a 24-week placebo-controlled trial in over 500 obese adults. Metabolic Pharmaceuticals ran it in the mid-2000s. The goal was simple: show meaningful body-weight reduction at therapeutic doses.

The trial failed. Per the sponsor's 2005 Inpharma Weekly writeup, AOD-9604 didn't produce clinically meaningful body-weight reduction against placebo. That ended the obesity development program, and the drug was never tested in Phase III.

Metabolic Pharmaceuticals pivoted. First they tried osteoarthritis, aiming at cartilage repair. That didn't reach approval either. Finally, in 2014, they filed for GRAS status as a food ingredient.

The pattern is familiar: positive mouse data, encouraging Phase I safety, failed Phase II efficacy, indication shuffle, food-ingredient consolation prize. Plenty of 2000s obesity programs ended this way.

Any honest review of AOD-9604 has to carry the Phase IIb result. We'd treat anything that skips it as marketing.

AOD-9604

hGH fragment 176-191 16 aa Tyr-modified

The same hGH 176-191 fragment examined across the trials in this review. third-party tested identity and ≥99% purity, third-party tested, full Certificate of Analysis with every lot.

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What does the research actually show?

Obesity (the original target)

The Phase IIb 24-week trial in over 500 obese study participants did not produce meaningful body-weight reduction versus placebo, per Inpharma Weekly in 2005. The obesity program ended there. The early mouse signal from Heffernan and colleagues never translated.

Osteoarthritis (the pivot)

After the obesity failure, Metabolic Pharmaceuticals pivoted to joint repair. A 2009 Bone paper by Brennan and colleagues tested whether AOD-9604 builds bone in mice. It didn't, and no osteoarthritis program ever reached approval.

Recent research (2020 to 2026)

We found one AOD-9604 paper on PubMed in the last six years, a 2022 drug-delivery study by Habibullah and colleagues. They used the peptide as a homing molecule on chitosan-coated chemotherapy nanoparticles aimed at breast cancer cells.

That's a lab-tool application, not a therapy study. The 2026 Sports Medicine review by Mendias and Awan grouped AOD-9604 with grey-market peptides where “rigorous human safety data are scarce.”

Should AOD-9604 be stacked with other peptides?

No. Grey-market literature describes AOD-9604 stacked with other growth-hormone-axis peptides, and no published clinical data supports any of those combinations.

The premise also argues against itself. CJC-1295 and ipamorelin raise endogenous GH and IGF-1. Those are exactly the effects AOD-9604 was designed to avoid, which makes the rationale for stacking them hard to sustain.

Pairing AOD-9604 with a GLP-1 or incretin compound gets proposed in lay writing too. No peer-reviewed trial has evaluated it. If you saw an effect from that pairing, the honest reading is that the GLP-1 compound did it, since that's the half with Phase III data behind it.

Adverse events reported in clinical studies

Commonly reported in the Phase IIb trial

• Injection-site reactions: mild redness, occasional bruising
• Appetite changes (both directions, increase and decrease)
• Brief fatigue or energy shifts in early study weeks

Less commonly reported

• Headache
• Mild gastrointestinal discomfort
• Brief skin flushing

Limitations of the available safety data

• No long-term safety data. The Phase IIb trial covered 24 weeks. No controlled human safety data beyond that window has been published.
• Purity varies by source. Grey-market sources show wide differences in identity and purity from vendor to vendor.
• GH-receptor-mediated effects are not expected. AOD-9604 was designed to bypass GH receptor signaling; claims of GH-equivalent effects on body composition or recovery lack mechanistic support.

Is AOD-9604 legal in the US?

The regulatory story is where vendor marketing gets the most creative. Here's what's actually true.

• FDA drug approval: no. AOD-9604 has never been approved as a drug for any condition. The Phase IIb obesity trial was the closest it ever came.
• GRAS food status (2014): yes, with a huge caveat. GRAS stands for “Generally Recognized as Safe.” It's a food-ingredient framework. Metabolic Pharmaceuticals filed a GRAS self-determination dossier for AOD-9604 as a food/dietary ingredient. GRAS food status is not drug approval. It doesn't validate a therapy. It doesn't authorize health claims. Marketing that calls it “FDA approved” is misleading.
• EMA (European Medicines Agency): Not approved.
• Australian TGA: Not approved, despite the Australian origin.
• Selling it as a research compound: Legal in the US if labeled “Research Use Only.”
• Selling it for human use with obesity-treatment claims: Crosses into FDA jurisdiction and draws enforcement.

If a seller calls AOD-9604 “FDA approved,” ask whether they mean drug approval or food-ingredient GRAS. They're not the same. Drug approval requires proof of efficacy. AOD-9604 doesn't have that.

Is it banned by WADA?

Not by name, and not specifically in major sports leagues either. We read that as a reflection of how rarely AOD-9604 has been studied in competitive sport, rather than any kind of endorsement.

The S2 category of the WADA Prohibited List covers peptide hormones, growth factors and related substances. That includes “growth hormone, its fragments and releasing factors,” and AOD-9604 is structurally a growth hormone fragment.

So the class ban may apply even without an explicit name listing. If you're subject to anti-doping regulations, check with your governing body before any use.

AOD-9604

5 mg ≥99% pure Lyophilized

Lipolytic hGH C-terminal fragment. The same reference compound discussed across the cited obesity and osteoarthritis trials — and note the evidence honesty above: the Phase IIb obesity-trial endpoint was negative. third-party tested, COA with every lot.

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Frequently asked questions

Can AOD-9604 be purchased legally in the US?

AOD-9604 isn't FDA-approved as a drug. It can be sold in the United States as a research reference compound labeled for laboratory use only, and the 2014 GRAS food-ingredient status doesn't change that.

Selling it with obesity-treatment claims for human use falls outside the research channel and draws FDA enforcement. Research-use-only labeling is the compliant route.

Did AOD-9604 actually work in the Phase II trial?

No. The 24-week Phase IIb obesity trial enrolled over 500 study participants. AOD-9604 did not produce meaningful body-weight reduction versus placebo. That ended the obesity program. The sponsor pivoted to GRAS food-ingredient status in 2014 instead of running another drug trial.

Did the lipolytic effect translate to humans?

The preclinical evidence has not translated to humans. Rodent studies from 2000 and 2001 reported lipolytic effects without IGF-1 elevation. The 24-week trial in obese study participants showed no meaningful body-weight reduction versus placebo. No PubMed-indexed randomized trial published from 2020 to 2026 has demonstrated human lipolytic efficacy for AOD-9604.

How does it compare to tirzepatide or retatrutide?

They aren't comparable. Tirzepatide produced 22.5% mean body-weight reduction in the Phase III SURMOUNT-1 trial. Retatrutide produced 24.2% in a Phase II NEJM trial, and semaglutide produced 14.9% in Phase III STEP-1.

AOD-9604 didn't meet its Phase IIb endpoint. The GLP-1 and incretin class has decisive human Phase III data. AOD-9604 has one failed pivotal trial.

What does “GRAS” status actually mean?

GRAS stands for “Generally Recognized as Safe.” It's a food-ingredient framework, not a drug approval. The sponsor filed a GRAS self-determination dossier for AOD-9604 as a food ingredient in 2014.

It reflects the sponsor's own view that the compound is safe in food. It doesn't say the FDA approved it as a drug. Marketing that calls GRAS “FDA approved” is using the wrong category on purpose.

What does third-party tested AOD-9604 typically retail for?

Third-party verified AOD-9604 retails at roughly $30 to $60 per 5 mg vial from research-compound vendors, or about $6 to $12 per milligram.

The low price is synthesis economics. The 16-residue sequence has no fatty-acid modifications, no cyclization and a fairly simple SPPS route. What you're paying reflects manufacturing cost, not therapeutic value.

Is it banned by WADA?

Not by name. The S2 category, covering peptide hormones, growth factors and related substances, includes “growth hormone, its fragments and releasing factors.” AOD-9604 is structurally a 16-residue fragment of human growth hormone.

So the class prohibition may apply without an explicit name listing. If you're subject to anti-doping rules, check with your governing body.