AOD-9604

What AOD-9604 is

AOD-9604 is a synthetic peptide of 16 amino acids whose sequence, Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe, reproduces residues 177 to 191 of human growth hormone (hGH) with an additional tyrosine at the N-terminus [1, 4]. The name is a company code ("anti-obesity drug") from Metabolic Pharmaceuticals of Melbourne. An earlier analogue in the same series, AOD9401, is the unmodified 177-191 fragment [2]. It is also sold, loosely, as "hGH fragment 176-191"; the terminal residue differs, and a certificate should make clear which has been supplied.

The compound originates in the laboratory of Frank Ng at Monash University, which spent the 1980s and 1990s mapping which regions of the 191-residue hormone carried its activities. Their hypothesis, developed in rat adipocyte assays, was that the C-terminal region of hGH carried a lipolytic and anti-lipogenic activity that could be separated from the growth-promoting and diabetogenic activities of the full hormone [1, 2]. AOD-9604 was the synthetic embodiment of that idea: a short fragment intended to retain the effect on fat metabolism without the effect on insulin-like growth factor-1 (IGF-1) or glucose handling.

The sequence contains two cysteines at positions 7 and 14, which form an intramolecular disulphide bridge corresponding to the Cys182-Cys189 loop of the native hormone [1]. There are no non-natural residues and no lipid chain. The peptide carries two arginines and one glutamate, so it is net positively charged at neutral pH, and the N-terminal tyrosine gives it a chromophore at 275 nm. Research-grade AOD-9604 is supplied as a white lyophilised powder, usually as the acetate or trifluoroacetate salt depending on the final purification step.

How the literature describes its mechanism

The mechanism proposed for AOD-9604 has always been inferential. No receptor for the fragment has been identified, and the originating group established early that it does not bind the growth hormone receptor: in cells transfected with the hGH receptor, AOD-9604 neither competed with hGH for binding nor stimulated proliferation [5]. The published mechanism is a set of observations in rodents and rodent adipose tissue rather than a defined signalling pathway.

The Monash group's account runs as follows. In obese Zucker rats and in ob/ob mice, chronic treatment with AOD-9604 or its parent fragment AOD9401 increased the lipolytic responsiveness of isolated adipose tissue, reduced lipogenesis, raised plasma glycerol and increased whole-body fat oxidation, without the rise in blood glucose or the fall in insulin secretion seen with full-length hGH [1, 2, 3, 5]. In the Hormone Research paper of 2000, obese Zucker rats given the compound orally for 19 days gained less than half the weight of controls and showed no loss of insulin sensitivity by euglycaemic clamp [1]. Companion papers reported the cellular correlates in Zucker rat adipose tissue [2] and activity on lipid metabolism after oral administration to obese mice [3].

The most mechanistically specific paper is the 2001 Endocrinology study by Heffernan and colleagues, which looked at the β3-adrenergic receptor (β3-AR), the principal lipolytic receptor of rodent adipocytes. In obese mice, 14 days of hGH or AOD-9604 reduced body weight and body fat, increased lipolytic sensitivity and restored adipose β3-AR mRNA, which is suppressed in obesity, to lean levels. In β3-AR knockout mice, long-term treatment did not produce the weight loss or increase in lipolysis seen in wild-type animals, yet an acute dose of AOD-9604 still increased energy expenditure and fat oxidation in the knockouts. The authors concluded that the fragment's lipolytic effect does not act directly through β3-AR, but that upregulation of the receptor may contribute to the increased lipolytic sensitivity seen with chronic treatment [4]. That remains the most detailed mechanistic statement in the literature, and it is a quarter of a century old.

Two points matter for an in-vitro programme. Rodent adipocytes depend on β3-AR for lipolysis far more than human adipocytes do, so the translational relevance of these findings is uncertain. And the published assays are tissue-level readouts, principally glycerol release from adipose explants or isolated adipocytes, and whole-animal calorimetry; no cell line, reporter or binding assay specific to AOD-9604 has been published.

The research record

Preclinical. The rodent literature is small and comes almost entirely from the originating group between 1993 and 2001. The models are the obese Zucker rat, the ob/ob mouse and the β3-AR knockout mouse; the exposures are oral, intraperitoneal and by osmotic minipump; the durations are up to 19 days [1, 2, 3, 4, 5]. The consistent findings are reduced weight gain, increased fat oxidation and increased adipose lipolytic sensitivity, with no diabetogenic effect. There has been no independent replication by a group without a Monash or Metabolic Pharmaceuticals author.

A separate, later body of preclinical work on toxicology was published by the company in 2014. Moré and Kenley reported an Ames test, a chromosomal aberration assay in CHO cells, a rat bone-marrow micronucleus assay, a six-month oral study in rats, a nine-month oral study in cynomolgus monkeys, and pharmacokinetic and whole-body imaging studies in pigs and rats. The authors reported no signal of genotoxicity or general toxicity and efficient oral uptake in pigs [7]. These are the sponsor's own studies and the primary data have not been reviewed by a regulator in public.

The clinical programme. Metabolic Pharmaceuticals took AOD-9604 into human studies in 2001, which makes it unusual in this catalogue: it has been given to several hundred people under trial conditions. The company's summary, published as supplementary material to Stier and colleagues, lists six trials: a phase I single-dose intravenous study in 15 healthy men (2001); a phase IIa intravenous study in 23 obese men (2001); a phase IIa oral single-dose study in 17 obese men (2002); a seven-day oral study in 36 obese men (2003); a 12-week phase IIb oral study in 300 obese adults (2004); and a 24-week phase IIb oral tablet study in 502 obese adults with body-mass index 30 to 45 (2006) [6]. The total enrolment was 925, with sites at Medeval in Manchester and at sixteen Australian hospitals [13].

The efficacy results were never published in a peer-reviewed journal. A 2010 review in Clinical Pharmacology and Therapeutics records that in the 12-week trial subjects receiving AOD-9604 lost on average 1.8 kg more than those on placebo, and that development was halted after poor efficacy in the subsequent 24-week trial [8]. The company's own account, in an announcement to the Australian Securities Exchange in April 2013, is that the trials found the compound "very safe" but "did not show a clinically meaningful weight loss outcome across the total trial population", and that the obesity programme was terminated in February 2007 [13]. The failure was one of efficacy, not safety: a 1.8 kg difference over 12 weeks that did not hold up over 24 weeks in a larger population.

Safety data. The one peer-reviewed clinical paper is the 2013 pooled safety analysis by Stier, Vos and Kenley, in the Journal of Endocrinology and Metabolism. The authors, all affiliated with the company, report that across six randomised, double-blind, placebo-controlled trials AOD-9604 had no effect on serum IGF-1, no adverse effect on oral glucose tolerance, no detectable anti-AOD-9604 antibodies in the samples tested, and no withdrawals or serious adverse events attributed to the compound; they describe the tolerability profile as "indistinguishable from placebo" [6]. It is a rare dataset for a research peptide, but it was written by the sponsor, the number of subjects tested for antibodies is not stated, and the trials used a 1 mg oral tablet, so the data say nothing about other routes. The US Food and Drug Administration, reviewing the compound as a nominated bulk substance for pharmacy compounding, took the view that compounded AOD-9604 "may pose significant risk for immunogenicity for certain routes of administration" and that the agency had identified serious adverse events possibly associated with the compound, though causality was unclear [15].

Osteoarthritis. After 2007 the company redirected the compound towards joint and cartilage conditions; the only published work from that programme is a 2015 rabbit study by Kwon and Park. Osteoarthritis was induced in both knees of 32 New Zealand White rabbits with collagenase, and the animals were randomised to weekly intra-articular injections of saline, hyaluronic acid, AOD-9604, or AOD-9604 with hyaluronic acid, for four to seven weeks. Gross and histological cartilage scores were worse in the saline group than in the three treatment groups, and the combination group scored lowest and had the shortest period of lameness [9]. It is a single study in a chemically induced model, with no mechanism proposed; the human trials the company announced were never reported.

The GRAS announcement. In August 2014 Calzada Limited, the listed parent of Metabolic Pharmaceuticals, announced that AOD-9604 had been "designated Generally Recognised As Safe (GRAS)" in the United States, and that this would allow its use as an ingredient in foods, drinks and dietary supplements at up to 1 mg per person per day without further pre-market approval [14]. GRAS is a status under United States food law, not drug law. It can be self-determined by a company on the advice of a panel it convenes, with or without notifying the FDA, and a notification, where one is made, receives a "no questions" letter rather than an approval. The announcement does not state which route was taken [14], and the FDA's later compounding review reached a cautious view on safety [15]. GRAS status has no bearing on the compound's standing as a medicine, which is nil, and no force in the UK or EU, where a peptide of this kind would need novel-food authorisation and none has been sought.

Taking the record as a whole. AOD-9604 has a coherent but narrow preclinical rationale, a failed phase IIb obesity programme whose efficacy data were never published in full, a sponsor-authored safety analysis, one rabbit osteoarthritis study, and a 2014 food-safety designation of uncertain basis. That is a legitimate basis for in-vitro research into fragment-derived modulation of lipolysis and for analytical work. It is not a basis for therapeutic claims, and this page makes none.

Regulatory status in the United Kingdom

AOD-9604 is not licensed as a medicine in the UK or anywhere else. It has no marketing authorisation from the MHRA, the EMA, the FDA or the Australian Therapeutic Goods Administration, and no pharmacopoeial monograph; the clinical programme ended in 2007 without a submission. BuyUK Peptides supplies it as a research chemical for in-vitro laboratory use under the Terms of Sale. It is not for human or veterinary administration. Purchasers must be 18 or over and are responsible for ensuring their use of the material complies with the laws and institutional rules that apply to them. Our guide to the UK rules on research compounds sets this out in more detail.

Anti-doping. Because the compound had never been approved for human use, WADA regarded it from 2011 as prohibited under category S0, non-approved substances. That position was not explicit on the List, and in April 2013, in response to the Australian events described below, WADA issued a statement confirming that AOD-9604 fell under S0 [13]. Later Lists named it directly. The 2026 Prohibited List, in force from 1 January 2026, lists under S2.2.3 (growth hormone, its analogues and fragments) "growth hormone fragments, e.g. AOD-9604 and hGH 176-191" [12]. The S2 category is prohibited at all times, in and out of competition. UK Anti-Doping applies the WADA List in the UK without modification.

Detection methods exist. Orlovius and colleagues at the Cologne laboratory established in 2013 that AOD-9604 does not cross-react with the WADA hGH isoform immunoassay, so it cannot be detected by the test used for growth hormone itself [10]. Cox and colleagues at the Salt Lake City laboratory published a mass spectrometric method in 2015 and characterised the compound's in-vitro metabolism, identifying a stable metabolite relevant to the detection window [11].

The Essendon case. AOD-9604 is best known outside the laboratory for its part in the Essendon Football Club supplements affair, the clearest documented example of how S0 operates. From late 2011 the Australian Football League club ran a programme of injections for its players that included AOD-9604, named on player consent forms. When the programme was investigated in 2013 the compound's status was contested, since it was not then named on the List. WADA's April 2013 statement settled the point and the Australian Sports Anti-Doping Authority confirmed it had always been prohibited under S0 [13]. ASADA chose not to pursue AOD-9604 cases for use before the statement, and the proceedings turned instead on thymosin β4. The AFL Anti-Doping Tribunal cleared 34 players in March 2015; on appeal, the Court of Arbitration for Sport found in January 2016 that they had been administered thymosin β4 and imposed two-year bans [16]. The lesson is that absence of a name from the List is not evidence that a compound is permitted.

Handling, storage and stability

AOD-9604 is supplied lyophilised in a glass vial with a rubber stopper and an aluminium flip-off crimp. The disulphide is the one feature that needs thought.

Sealed vial. Store at 2–8 °C for routine use and at −20 °C or below for storage beyond a few months. Protect from light. Avoid repeated freeze–thaw cycles. Allow a refrigerated vial to reach room temperature before opening, so that moisture does not condense onto the cake.

Reconstitution. For most in-vitro work the compound is reconstituted in sterile bacteriostatic water, sterile water, or a buffer appropriate to the assay. Add the solvent down the side of the vial and swirl gently; the cake should clear within a minute. Do not vortex. The reconstitution calculator gives the volume to add for a target concentration.

Reconstituted solution. Keep at 2–8 °C and protect from light. At alkaline pH or in the presence of free thiols the Cys7-Cys14 bridge can undergo exchange or reduction, and reduced or scrambled material is distinct from the native cyclic peptide. A mildly acidic buffer (pH 4 to 6) is the conservative choice for storage, and solutions should be used within 28 days or aliquoted and frozen at −20 °C. The Cox paper on in-vitro metabolism is a reminder that the peptide is cleaved readily by proteases, so serum-containing media will consume it [11].

Solubility. AOD-9604 acetate is freely soluble in water and in common aqueous buffers at research concentrations. As a cationic peptide it may adsorb to glass and some plastics at low concentration; low-binding tubes are preferable for dilute solutions.

What a sound certificate for AOD-9604 looks like

Every batch we release carries an independent certificate of analysis, transcribed on the product page and in the certificate register. For AOD-9604 a certificate should contain the following.

Purity by RP-HPLC. Reversed-phase HPLC on a C18 column with UV detection at 214 or 220 nm reports purity as the area of the main peak as a percentage of all integrated peaks. A good batch of AOD-9604 shows a single dominant peak with purity of 98% or above. The impurities to look for are the linear reduced form, which elutes close to the native peak, and disulphide-linked dimers, which elute later; a chromatogram is more informative than a number alone.

Identity by LC-MS. Electrospray mass spectrometry confirms that the main peak has the expected mass. For AOD-9604 the average molecular weight is 1815.1 Da and the monoisotopic mass is approximately 1813.9 Da for the oxidised (cyclic) form. The peptide usually appears as the doubly charged [M+2H]2+ ion at about 908 and the triply charged [M+3H]3+ ion at about 606, and a certificate may report either or a deconvoluted mass. A mass 2 Da higher than theoretical indicates the reduced, open-chain form; a mass about 16 Da lower would indicate a phenylalanine-terminated fragment rather than AOD-9604 and should prompt a question about identity. The observed mass should agree with the theoretical value to within about 0.5 Da.

Net peptide content. Lyophilised peptides contain bound water and counter-ions, usually trifluoroacetate from purification or acetate after an exchange step, so the mass of powder in the vial is more than the mass of peptide. Net peptide content, where reported, expresses the fraction that is actual peptide, and it matters for preparing solutions of accurate concentration.

Endotoxin. Where the batch has been tested, a limulus amoebocyte lysate (LAL) result is reported in endotoxin units per milligram. This matters for adipocyte and explant work, where endotoxin itself alters lipolysis and can confound the readouts the compound is studied for.

Our guide to reading a certificate of analysis goes through a complete report line by line.

Related compounds

AOD-9604 sits in the catalogue alongside BPC-157 and TB-500 as a peptide fragment of a larger native protein, and its later osteoarthritis work places it in the same cartilage-and-joint literature as those two. The comparison is instructive: BPC-157 and TB-500 have almost no human data, whereas AOD-9604 has a 925-subject clinical programme behind it, and its lesson was that a clean rodent signal did not translate. TB-500 shares with AOD-9604 a place in the Essendon record, since the thymosin β4 on which the Court of Arbitration for Sport's decision turned is the parent protein of that fragment [16].

Frequently asked questions

Is AOD-9604 the same as "hGH fragment 176-191"? Not quite. AOD-9604 is residues 177-191 with an added N-terminal tyrosine; the native 176-191 fragment has phenylalanine at that position. They differ by about 16 Da, which an LC-MS certificate will distinguish.

Does it act through the growth hormone receptor? No. It neither binds the hGH receptor nor stimulates proliferation in receptor-transfected cells, and the clinical trials found no effect on IGF-1 [5, 6]. No receptor for the fragment has been identified [4].

Why was it abandoned as a drug? Because the 24-week phase IIb trial in 502 obese adults did not show clinically meaningful weight loss; the company closed the obesity programme in February 2007 [8, 13]. The failure was one of efficacy, not safety.

What does the GRAS claim mean? It is a 2014 company announcement of a United States food-ingredient status, whose basis (self-affirmed or notified) the announcement does not state [14]. It does not make the compound a medicine anywhere, and it has no force in the UK or EU.

Is it on the WADA list? Yes. It was treated as prohibited under S0 (non-approved substances) from 2011, confirmed in April 2013, and is now named explicitly under S2.2.3 as a growth hormone fragment, prohibited at all times [12, 13].

Is the material for human use? No. It is supplied for in-vitro research only.

How long does a sealed vial last? Short lyophilised peptides of this kind are stable for years at −20 °C and for many months at 2–8 °C. The batch certificate reports the test date; the storage guidance on this page applies from receipt.

References

1. Ng FM, Sun J, Sharma L, Libinaka R, Jiang WJ, Gianello R. Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone. Hormone Research. 2000;53(6):274–278. doi:10.1159/000053183. PMID 11146367.
2. Ng FM, Jiang WJ, Gianello R, Pitt S, Roupas P. Molecular and cellular actions of a structural domain of human growth hormone (AOD9401) on lipid metabolism in Zucker fatty rats. Journal of Molecular Endocrinology. 2000;25(3):287–298. doi:10.1677/jme.0.0250287.
3. Heffernan MA, Jiang WJ, Thorburn AW, Ng FM. Effects of oral administration of a synthetic fragment of human growth hormone on lipid metabolism. American Journal of Physiology-Endocrinology and Metabolism. 2000;279(3):E501–E507. doi:10.1152/ajpendo.2000.279.3.E501.
4. Heffernan M, Summers RJ, Thorburn A, et al. The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and β3-AR knock-out mice. Endocrinology. 2001;142(12):5182–5189. doi:10.1210/endo.142.12.8522. PMID 11713213.
5. Heffernan MA, Thorburn AW, Fam B, et al. 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. 2001;25(10):1442–1449. doi:10.1038/sj.ijo.0801740. PMID 11673763.
6. Stier H, Vos E, Kenley D. Safety and tolerability of the hexadecapeptide AOD9604 in humans. Journal of Endocrinology and Metabolism. 2013;3(1–2):7–15. doi:10.4021/jem157w.
7. Moré MI, Kenley D. Safety and metabolism of AOD9604, a novel nutraceutical ingredient for improved metabolic health. Journal of Endocrinology and Metabolism. 2014;4(3):64–77. doi:10.14740/jem213w.
8. Valentino MA, Lin JE, Waldman SA. Central and peripheral molecular targets for antiobesity pharmacotherapy. Clinical Pharmacology & Therapeutics. 2010;87(6):652–662. doi:10.1038/clpt.2010.57.
9. Kwon DR, Park GY. Effect of intra-articular injection of AOD9604 with or without hyaluronic acid in rabbit osteoarthritis model. Annals of Clinical and Laboratory Science. 2015;45(4):426–432. PMID 26275694.
10. Orlovius AK, Thomas A, Schänzer W, Thevis M. AOD-9604 does not influence the WADA hGH isoform immunoassay. Drug Testing and Analysis. 2013;5(11–12):850–852. doi:10.1002/dta.1557.
11. Cox HD, Smeal SJ, Hughes CM, Cox JE, Eichner D. Detection and in vitro metabolism of AOD9604. Drug Testing and Analysis. 2015;7(1):31–38. doi:10.1002/dta.1715. PMID 25208511.
12. World Anti-Doping Agency. The Prohibited List 2026: International Standard. In force 1 January 2026. Section S2.2.3. wada-ama.org/en/prohibited-list.
13. Calzada Limited. Announcement to the Australian Securities Exchange concerning AOD9604. 26 April 2013. announcements.asx.com.au.
14. Lab Online (Life Scientist). AOD9604 awarded safe status in US. Published 6 August 2014. labonline.com.au.
15. US Food and Drug Administration. Certain bulk drug substances for use in compounding that may present significant safety risks. fda.gov.
16. Australian Sports Anti-Doping Authority. Court of Arbitration for Sport decision: Essendon players. Press release, 11 January 2016. Reproduced at lawinsport.com.

This monograph summarises the published literature for laboratory researchers. It is not medical advice, and nothing on this site is for human or veterinary use.