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 makes you burn fat. It also raises IGF-1 (a hormone that drives tissue growth), causes insulin resistance, and triggers joint pain. The Monash team thought they'd isolated the fat-burning piece without the rest. Mice agreed. Humans, eventually, did not (Heffernan et al., 2000).

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 breakdown of stored fat into fatty acids). The effect partly disappeared in mice missing the β3 adrenergic receptor (a fat-cell signal that turns on lipolysis), suggesting AOD-9604 works through that pathway (Ng et al., 2001).

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 fat-burning effect didn't reproduce in cell culture. A 2008 study found no fat-burning 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 “targets the right receptor, skips the wrong ones,” not knowing the receptor is a problem. It means 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 weight loss at therapeutic doses.

The trial failed. According to the sponsor's 2005 Inpharma Weekly writeup, AOD-9604 didn't produce clinically meaningful weight loss compared to placebo (Inpharma Weekly, 2005). That ended the obesity clinical-development program. The drug was never tested in Phase III.

Metabolic Pharmaceuticals pivoted. First they tried osteoarthritis (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. Lots of 2000s obesity programs ended this way. Any honest review of AOD-9604 has to include the Phase IIb result. Anything that skips it is selling.

AOD-9604 research alternative

hGH fragment 16 aa Failed Phase IIb

AOD-9604 is on the Peptriva research-content roadmap, but we don't currently stock the hGH 176-191 fragment — the Phase IIb obesity trial was negative and the clinical-development program ended. For weight-loss research, our most-evidenced compounds are in the GLP-1 / incretin class (semaglutide, tirzepatide, retatrutide), which have decisive Phase III human efficacy data.

Browse weight-loss catalog

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 weight loss versus placebo. The obesity program ended (Inpharma Weekly, 2005). The early mouse signal from Heffernan et al., 2000 did not translate.

Osteoarthritis (the pivot)

After the obesity failure, Metabolic Pharmaceuticals pivoted to joint repair. A 2009 Bone paper tested whether AOD-9604 builds bone in mice. It didn't (Brennan et al., 2009). No osteoarthritis program ever reached approval.

Recent research (2020 to 2026)

The only AOD-9604 paper on PubMed in the last six years is a 2022 drug-delivery study. The authors used the peptide as a homing molecule on chitosan-coated chemotherapy nanoparticles aimed at breast cancer cells (Habibullah et al., 2022). That's a lab-tool application, not a therapy study. The 2026 Sports Medicine review grouped AOD-9604 with grey-market peptides where “rigorous human safety data are scarce” (Mendias & Awan, 2026).

Co-investigation with other compounds

Some grey-market literature has described AOD-9604 in combination with other growth-hormone-axis peptides. No published clinical data supports any such combination. The premise is further complicated by the fact that compounds such as CJC-1295 and Ipamorelin elevate endogenous GH and IGF-1 — the effects AOD-9604 was specifically designed to avoid, making any theoretical rationale for co-use difficult to sustain. Co-administration of AOD-9604 with GLP-1 / incretin-class compounds has been proposed in lay literature; however, no peer-reviewed trial has evaluated the combination. Any attributable effect in such a scenario would be expected to derive from the GLP-1 compound, which has extensive Phase III human efficacy data, rather than from AOD-9604.

Reconstitution and storage

1. Draw bacteriostatic water (1 to 2 mL of 0.9% benzyl alcohol bacteriostatic water) into a syringe.
2. Inject the water slowly down the side of the vial, not directly onto the freeze-dried peptide. Don't make foam.
3. Swirl gently until fully dissolved. Don't shake. Shaking can denature peptides.
4. Storage: Sealed vials keep at −20°C for 12+ months. Reconstituted solution lasts 14 to 28 days refrigerated at 2 to 8°C. Consult the vendor-provided stability data for the specific lot.
5. Don't freeze reconstituted solution. Freeze-thaw cycles degrade peptides faster than the fridge alone.

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 weight-loss 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?

AOD-9604 does not appear on the WADA Prohibited List by name. It is not specifically banned in major sports leagues. That reflects how rarely it has been studied in competitive sport, not an endorsement of its use.

The S2 category of the WADA Prohibited List (Peptide Hormones, Growth Factors, Related Substances) covers “growth hormone, its fragments and releasing factors.” AOD-9604 is structurally a growth hormone fragment. The class may therefore apply even where the compound is not named explicitly. Researchers and study participants subject to anti-doping regulations should consult their relevant governing body before any use.

Browse weight-loss research peptides

Semaglutide Tirzepatide Retatrutide

AOD-9604 is on the research-content roadmap but not currently stocked — the Phase IIb obesity trial was negative and the obesity-indication clinical program ended. For research peptides with decisive human weight-loss data, the GLP-1 / incretin class (semaglutide, tirzepatide, retatrutide) is on a categorically different evidence tier. Research-grade reference compound, COA per lot.

Browse the catalog

Frequently asked questions

Can AOD-9604 be purchased legally in the US?

AOD-9604 is not FDA-approved as a drug. It may be sold in the United States as a research reference compound labeled for laboratory use only. The 2014 GRAS food-ingredient status does not change that framework. Selling it with weight-loss claims for human use falls outside the research-compound channel and would be subject to FDA enforcement. Supply labeled for research use only is the compliant channel.

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 weight loss versus placebo. That ended the obesity program. The sponsor pivoted to GRAS food-ingredient status in 2014 instead of running another drug trial.

Does it burn fat in people?

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 weight loss versus placebo. No PubMed-indexed randomized trial published from 2020 to 2026 has demonstrated human fat-loss efficacy for AOD-9604.

How does it compare to tirzepatide or retatrutide?

The evidence bases are not comparable. Tirzepatide produced 22.5% mean weight loss in SURMOUNT-1 (Phase III). Retatrutide produced 24.2% in a Phase II NEJM trial. Semaglutide produced 14.9% in STEP-1 (Phase III). AOD-9604 did not meet its Phase IIb endpoint. The GLP-1 / incretin class has decisive human Phase III data; AOD-9604 has a single 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 view that the compound is safe for 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 research-grade AOD-9604 typically retail for?

Research-grade AOD-9604 retails at approximately $30 to $60 per 5 mg vial from research-compound vendors. That is roughly $6 to $12 per milligram. The low price reflects synthesis economics: the 16-residue sequence has no fatty-acid modifications, no cyclization, and a relatively simple SPPS route. Price reflects manufacturing cost, not therapeutic value.

Is it banned by WADA?

Not by name. The S2 category (Peptide Hormones, Growth Factors, Related Substances) covers “growth hormone, its fragments and releasing factors.” AOD-9604 is structurally a 16-residue fragment of human growth hormone. The class prohibition may therefore apply even without an explicit name listing. Study participants subject to anti-doping regulations should consult their governing body.