AOD-9604

AOD-9604 has been tested in people more than most compounds sold beside it. Six double-blind, placebo-controlled trials run between 2001 and 2006 enrolled 893 adults, all but one group of them clinically obese, and the two largest followed 300 and 502 participants for 12 and 24 weeks. Every one of those trials was paid for by Metabolic Pharmaceuticals, the Australian company developing the peptide as an obesity drug, and the published summaries were written by the company and its consultants.

What those trials measured carefully was safety. IGF-1 did not rise, glucose tolerance did not worsen, and no antibodies against the peptide appeared. What they did not produce was a weight-loss result that held. The company's own 2014 paper says weight loss seen in the initial trials was not seen in the last study, the one that added an intensive diet and exercise regime, and the weight figures themselves do not appear in any of the papers cited here.

AOD-9604 is not an FDA-approved drug, and WADA names it on the Prohibited List as a growth hormone fragment.

A 16-amino-acid peptide copied from the C-terminal tail of human growth hormone. It reproduces residues 177 to 191 of the hormone with one extra tyrosine added at the front end to stabilise it, which is why the literature writes it as Tyr-hGH 177-191. The two cysteines in the chain are linked by a disulphide bond, so the peptide is held in a loop, and its 3D shape resembles the same region inside the intact hormone.

The fragment came out of work by Professor Frank Ng and colleagues at Monash University, and Metabolic Pharmaceuticals took it through toxicology and human trials. The trial material was made under cGMP conditions by a contract peptide manufacturer. WADA lists AOD-9604 and hGH 176-191 as two separate examples of growth hormone fragments, so the two names are not interchangeable, and results for one do not carry over to the other. The peptide is now offered on several websites, and US investigators have found it in confiscated vials.

Why a Fragment of Growth Hormone

Full growth hormone breaks down stored fat, and treatment with it reduces body fat mass. It also raises IGF-1 and can cause glucose intolerance, insulin resistance, oedema and hypertension, which is why it was never a workable long-term obesity treatment. Earlier research had mapped different jobs to different parts of the hormone, and the stretch from residue 177 to 191 looked like a lipid-mobilising domain that inhibited acetyl-CoA carboxylase in fat and liver cells. AOD-9604 was the attempt to keep that piece and leave the rest behind.

What Is Known, and What Is Not

Growth hormone switches on its receptor by binding two receptor molecules at once through two separate sites. AOD-9604 contains only part of the first site and none of the second, and in cell experiments it neither competed with growth hormone for receptor binding nor drove growth-factor-dependent cell proliferation. That is the basis for the claim that it does not touch the IGF-1 axis, and the human IGF-1 measurements agree with it.

How it reduces fat is a different matter. In obese mice treated for 14 days, AOD-9604 lowered body weight and body fat and raised beta-3 adrenergic receptor RNA back toward lean-mouse levels. In mice lacking that receptor, chronic treatment no longer changed body weight or lipolysis, yet a single acute dose still raised energy expenditure and fat oxidation. The authors concluded the effect is not mediated directly through the beta-3 receptor. The company's own 2014 paper states flatly that the mechanism of action is not understood.

A clean safety record is being sold as proof that it works. The trials showed IGF-1 staying flat, glucose tolerance staying normal and adverse events matching placebo. Those are reasons the peptide was considered safe to test further. None of them is evidence of fat loss, and the trial built to confirm fat loss did not.

The early weight-loss signal is quoted without the result that followed it. Weight loss in the initial trials is real in the sense that the sponsor reported it, but no figures were published in the cited sources, and the larger, longer trial with a structured diet and exercise program did not reproduce it. A signal that disappears when the comparison gets stricter is not a finding to build a purchase on.

The beta-3 receptor story is tidier than the mouse study. The study usually cited for it found that the receptor's RNA went up, that the chronic effect vanished without the receptor, and that an acute effect survived anyway. Its authors concluded the action is not directly through beta-3, and the developer later wrote that the mechanism is not understood.

The glucose trend is being promoted as a diabetes benefit. It was a non-significant trend in one 12-week trial, and the authors themselves called it a hypothesis needing a separate trial.

Tested athletes have no grey area. WADA lists AOD-9604 by name under S2.2.3 among growth hormone fragments, prohibited at all times. A validated urine test detects it at 50 pg/mL, and a stable metabolite found in serum may extend the detection window.

Safety data come from 893 trial participants on pharmaceutical-grade material, with the longest exposure at 24 weeks. Across the trials, IGF-1 did not change compared with placebo, oral glucose tolerance tests showed no deterioration, and no anti-AOD-9604 antibodies were detected.

Adverse events were common in every arm, including placebo. In the 24-week trial, 78.7 percent of participants reported at least one during treatment, ranging from 75.6 percent on the lowest dose to 83.2 percent on placebo, and 18 people (3.6 percent) had a serious adverse event, spread similarly across groups. Headache, diarrhoea, nasopharyngitis and back pain led the list. The highest oral dose tested produced more headache, diarrhoea and flatulence. In the intravenous study in obese men, 5 of 23 reported mild or moderate euphoria during AOD-9604 periods and none on placebo, and one severe episode of chest tightness was judged possibly related.

The 12-week trial had five serious adverse events, four of them cancers (basal cell carcinoma, squamous cell carcinoma, breast cancer and melanoma) and one a lipoma, all in AOD-9604 groups. The investigator judged none related, citing no dose pattern and background cancer rates in an obese Australian population. The summary also states that no treatment-related serious event occurred in any study, although its own results describe a case of diarrhoea at the highest oral dose rated possibly related.

AOD-9604 is a rare case of a body-composition peptide that went through a proper sequence of human trials, so its story can be told with some precision. It was tolerated about as well as placebo for up to 24 weeks, it did not raise IGF-1, and it did not deliver weight loss in its most rigorous trial. Anyone weighing it is weighing a safety record without an established benefit, and anyone in tested sport is weighing an outright ban.

Not an approved drug. The FDA has not approved AOD-9604 for any use. It was developed as an obesity drug, and the company later repositioned it as a nutraceutical ingredient.

Not validated by its GRAS status. AOD-9604 was declared Generally Recognized As Safe by a panel of experts for intended use in foods, conditional on publishing pre-existing safety data. At most that is a self-affirmed food-ingredient determination. It is not a drug approval and is not evidence that the compound works.

Not cleared by leaving the compounding lists. AOD-9604 is on neither FDA compounding category list. It left Category 2 on or about 2026-04-22 because the nominators withdrew the nomination, not because FDA resolved its safety concerns, and those concerns remain published.

Not permitted in tested sport. WADA names it under S2.2.3 as a growth hormone fragment, and labs have a validated urine test for it.

Not the trial material. The 893 trial participants received peptide made under cGMP conditions. Vials sold online come with no such record.

I find AOD-9604 more useful to learn from than most compounds in this library, because the question it was built to answer actually got answered.

A company had a sensible idea: keep the fat-mobilising piece of growth hormone and drop the parts that raise IGF-1 and wreck glucose control. It tested that idea in close to 900 people under placebo control. The safety half of the idea held up well. The fat-loss half did not survive the trial designed to confirm it. That is how drug development is supposed to work, and it is a better outcome than a compound nobody ever checked.

What bothers me is how the result gets used. The safety data and the early signal are quoted together as if they were a recommendation, and the trial that failed is left out. I would rather you know all three. I will not tell anyone to take it, I will not publish doses, and if you compete in tested sport the decision has already been made for you.