AOD-9604 — identity, handling and published literature

AOD-9604 is a synthetic hexadecapeptide corresponding to the C-terminal region of human growth hormone, supplied as a lyophilised solid for laboratory use.

Presentation and physical properties

AOD-9604 is a 16-residue linear peptide, YLRIVQCRSVEGSCGF (H-Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe-OH), carrying a single intramolecular disulfide bond between its two cysteine residues. It corresponds to residues 177–191 of mature human growth hormone (hGH) with an additional tyrosine at the N-terminus, and is written in the literature as Tyr-hGH(177–191).

The relationship to the separately marketed material sold as “hGH fragment 176-191” is worth stating precisely, because the two are routinely conflated. Mature hGH carries phenylalanine at position 176, so hGH(176–191) is FLRIVQCRSVEGSCGF. AOD-9604 is the same 16-residue span with tyrosine in that first position instead of phenylalanine — a single hydroxyl group’s difference, and a different molecule with a different mass, a different CAS number and a separate entry on the WADA Prohibited List.

The disulfide bond joins the cysteines at positions 7 and 14 of the fragment, which are Cys182 and Cys189 in hGH numbering. UniProt annotates Cys182–Cys189 as one of the two native disulfide bonds of mature somatropin, so the fragment reproduces the small C-terminal loop of the parent protein rather than forming a novel one.

• Appearance: white to off-white lyophilised powder or cake.
• Molecular formula: C₇₈H₁₂₃N₂₃O₂₃S₂ (free base).
• Average molecular mass: 1815.1 g/mol (free base, PubChem CID 71300630). Acetate and other salt forms carry additional counter-ion mass, so a certificate quoting a higher figure is not necessarily inconsistent.
• Solubility: readily soluble in water and in aqueous buffers at neutral pH. The sequence contains no methionine and no tryptophan, and only one aromatic residue beyond the N-terminal tyrosine.
• Net charge: two arginine residues and one glutamate; the peptide is basic at neutral pH.

Reconstitution arithmetic

Reconstitution is a division. The concentration of the resulting solution is the labelled mass of peptide in the vial divided by the volume of diluent introduced:

concentration (mg/mL) = mass in vial (mg) ÷ diluent volume (mL)

The volume drawn into a U-100 graduated syringe converts on a fixed basis: one graduation (“unit”) is 0.01 mL, so 10 graduations are 0.1 mL and 100 graduations are 1 mL. The mass contained in one graduation is therefore the concentration multiplied by 0.01.

Worked for two nominal vial masses commonly encountered in the literature and in seized-material analyses. AOD-9604 is not supplied by NovoVita and these figures are arithmetic examples, not a product specification.

Two arithmetical cautions apply. First, the calculation is performed against the nominal labelled mass; where the solid is a salt or contains residual solvent or counter-ion, the peptide content by mass is lower than the label implies and every figure in the table scales down with it. Second, lyophilised peptide occupies volume, so the final solution volume slightly exceeds the diluent volume added; at the volumes above the effect is small but it is not zero, and it makes the computed concentration a marginal overestimate.

Storage and stability

As a lyophilised solid, AOD-9604 is handled on the same basis as other small disulfide-containing peptides: stored desiccated, protected from light, and held at −20 °C or below for extended periods. Vials taken from cold storage should be equilibrated to ambient temperature before opening, since condensation onto a hygroscopic cake introduces water that the lyophilisation was performed to remove.

In solution the peptide is markedly less stable than as a solid. Aqueous solutions are typically held at 2–8 °C and repeated freeze–thaw cycling avoided; aliquoting at the point of reconstitution is the standard means of avoiding it. Three degradation routes are relevant to this particular sequence:

• Disulfide instability. The single Cys7–Cys14 bond is susceptible to reduction and to thiol–disulfide exchange, both of which accelerate above pH 7. Scrambling in a peptide with only one bond produces intermolecular dimers rather than isomers, which is detectable by size-based separation.
• Deamidation. The glutamine at position 6 is a deamidation site, converting to glutamate with a mass shift of +1 Da and a change in net charge.
• Adsorption. At the low concentrations used analytically, loss to glass and plastic surfaces is a real source of apparent instability rather than chemical degradation.

One published stability observation is specific to this compound. Cox and colleagues, incubating AOD-9604 in serum and urine in vitro, identified six candidate metabolites and reported that one of them — the nine-residue fragment CRSVEGSCG — was “significantly more stable than the other metabolites or the parent compound”, persisting in serum longer than AOD-9604 itself [8]. The parent peptide is therefore the less durable species in biological matrix, which has consequences for anything that assumes intact AOD-9604 is the analyte to look for.

Analytical identity

Identity is established by mass and by sequence, and purity separately from both.

Mass spectrometry. Electrospray ionisation of a 1815 Da peptide gives multiply charged ions rather than a single protonated species, and the charge-state envelope is itself part of the identification. Tandem MS on the peptide backbone yields the b- and y-ion series required to confirm the sequence rather than merely the mass — which matters here, because YLRIVQCRSVEGSCGF and the phenylalanine-bearing hGH(176–191) differ by 16 Da and are distinguishable on accurate mass, while several other C-terminal hGH fragments are not distinguishable on nominal mass alone.

Chromatography. Reversed-phase HPLC with UV detection at 214 nm (amide bond) and 280 nm (the tyrosine) is the routine purity method; the ratio between the two channels is a crude but useful check that the aromatic residue is present. Cox and colleagues reported a validated solid-phase extraction and LC-MS/MS method for AOD-9604 in urine with a limit of detection of 50 pg/mL, linearity, precision better than 20% and recovery of 62% [8]. Thomas and colleagues subsequently reported a direct-urine-injection screening approach using liquid chromatography with ion mobility mass spectrometry, covering peptides below 2 kDa as a class [10].

Disulfide confirmation. Ellman’s reagent quantifies free thiol; a correctly closed single-disulfide peptide gives essentially none. Comparison of masses before and after reduction gives the expected +2 Da shift.

Cross-reactivity with hGH assays. Orlovius and colleagues reported that AOD-9604 does not influence the WADA hGH isoform immunoassay [6]. Analytically this means the fragment is not detected by, and does not confound, the immunoassay used for the intact hormone — it requires its own method.

Material of uncertain provenance. Vanhee and colleagues characterised unlabelled pharmaceutical preparations seized by the Belgian authorities and identified AOD-9604 as the peptide present [7]. That case report is a reminder that the analytical question for material outside a regulated supply chain is not only “how much” but “what is actually in the vial”.

What the published literature investigated

The primary research record on AOD-9604 is small, concentrated in the years 2000–2001, and produced almost entirely by one group working with the sponsor that developed the compound. Everything published since is either analytical method development for anti-doping purposes or narrative review.

Rodent studies

Ng and colleagues administered a synthetic lipolytic domain of hGH orally to obese Zucker rats for 19 days and reported reduced body weight gain relative to controls, increased lipolytic activity in adipose tissue, and — in contrast to full-length hGH — no adverse effect on insulin sensitivity as measured by glucose clamp. The authors concluded the analogue “may have the potential to be developed into an orally usable and safe therapeutic agent for obesity” [1].

Heffernan and colleagues treated obese (ob/ob) and lean C57BL/6J mice for 14 days with hGH or with AOD-9604 and reported that both reduced weight gain and increased fat oxidation and lipolysis, with AOD-9604 doing so without the hyperglycaemic and insulin-suppressing effects reported for full hGH. They proposed that “fragments of hGH can act in a manner novel to traditional hGH-stimulated pathways” [2].

The same group then examined the mechanism in β₃-adrenoceptor knock-out mice. They reported that both hGH and AOD-9604 raised the repressed β₃-AR transcript levels of obese mice towards those of lean animals, and that in animals genetically lacking the receptor the chronic weight effect was absent although an acute increase in energy expenditure was still observed [3].

A fourth paper from the same laboratory is frequently cited in connection with AOD-9604 and should be attributed accurately: Heffernan and colleagues reported oral administration in ob/ob mice and lipolytic and antilipogenic actions in human adipose tissue in vitro, but the compound studied was AOD-9401, a different hGH fragment, not AOD-9604 [4]. It is included here because it is part of the same programme and is routinely miscited; it is not evidence about AOD-9604.

Rabbit model

Kwon and Park induced knee osteoarthritis in 32 New Zealand white rabbits with collagenase and compared intra-articular saline, hyaluronic acid, AOD-9604, and AOD-9604 with hyaluronic acid over 4–7 weeks. They reported that “combined AOD9604 and HA injections were more effective than HA or AOD9604 injections alone” on cartilage degeneration and lameness measures relative to control [9]. This is a single study, in a single species, in an indication unrelated to the compound’s original development programme, and it has not been replicated.

In vitro and analytical work

The in vitro record consists of the metabolism and detection work described under Analytical identity [6, 7, 8, 10]. None of it addresses biological activity; it exists because AOD-9604 is a prohibited substance in sport and testing laboratories required methods for it.

Human studies

Human trials of AOD-9604 itself were conducted, and their efficacy results were negative. This is the most important fact about the compound’s evidence base and it is stated here without qualification.

Six randomised, double-blind, placebo-controlled trials were run between 2001 and 2006 by the sponsor, Metabolic Pharmaceuticals, enrolling approximately 900 adults in total. The programme comprised a phase I single-dose study, three phase IIa studies, and two phase IIb studies: one of 300 obese adults over 12 weeks, and one of 502 adults over 24 weeks. The later studies evaluated an oral formulation.

The safety and tolerability findings from this programme were published by Stier, Vos and Kenley in 2013, in a journal not indexed by PubMed [13]. That paper reports that AOD-9604 “displayed a very good safety and tolerability profile indistinguishable from placebo”, that it “had no effect on serum IGF-1 levels”, that “there were no anti-AOD9604 antibodies detected in any of the patients”, and that no withdrawal or serious adverse event related to intake occurred in any of the studies.

The efficacy findings were never published in a peer-reviewed journal at all. The phase IIb studies did not meet their primary weight-loss endpoint: AOD-9604 did not separate from placebo. The sponsor discontinued development in 2007. A PubMed search for human trials of AOD-9604 returns no clinical efficacy publication, and there is no registered record of the phase IIb studies on ClinicalTrials.gov. The failure is documented in the sponsor’s own announcements and, subsequently, in the United States Food and Drug Administration’s review of the substance for its section 503A bulk drug substances list, which cited a lack of clinical effectiveness data for any use.

The asymmetry is itself the finding. The favourable safety dataset from a nine-hundred-subject programme entered the literature; the unfavourable efficacy dataset from the same programme did not. Any reading of the published record that stops at the safety paper will systematically overstate what is known.

Reviews

Wilding’s 2004 profile in Current Opinion in Investigational Drugs documents the compound at the point where “by February 2002, phase IIa trials were underway” [5], and predates the phase IIb results. Two 2026 reviews place AOD-9604 in its current context: Mendias and Awan survey approved and unapproved peptides marketed for musculoskeletal injury and athletic performance, noting that for compounds in this group “rigorous human safety data are scarce, and there is potential for serious harm to patients” [11]; Dominikowski and colleagues review peptides modulating the GH–IGF-1 axis and note the absence of regulatory approval for physique- or performance-related indications together with uncertainty over product composition [12].

Evidence gaps and limitations

Stated plainly, and without softening:

• The compound failed in humans. Two phase IIb obesity studies, one of them 24 weeks in 502 adults, did not meet their primary weight-loss endpoint. This is not an absence of evidence; it is evidence of absence of the effect that was tested for.
• No efficacy result has ever been peer-reviewed. The only published human paper reports safety. The negative efficacy data sit outside the scientific literature entirely, which means they cannot be scrutinised, re-analysed or meta-analysed, and the shape of the failure — dose–response, subgroup behaviour, time course — is not publicly available.
• The positive findings are pre-clinical, from one group, and unreplicated. The three rodent papers [1, 2, 3] share overlapping authorship with each other and with the sponsor. No independent laboratory has published a replication of the metabolic findings in any species.
• The human programme studied a formulation the current market does not use. The phase IIa and IIb studies evaluated an oral preparation. Material now in circulation is a lyophilised solid for aqueous reconstitution. The FDA’s review noted the absence of published human exposure data for the subcutaneous and topical routes proposed to it.
• The orthopaedic literature is one rabbit study. [9] The framing of AOD-9604 as a musculoskeletal repair agent rests on that single unreplicated animal experiment, and cannot be supported by the obesity programme, which tested something else entirely.
• Attribution errors are common in secondary sources. AOD-9604 is regularly conflated with hGH(176–191), which is a different molecule, and with AOD-9401, which is a different molecule studied in a different paper [4]. Findings cited for AOD-9604 should be checked back to the primary record.
• Immunogenicity of injectable preparations is uncharacterised. The clinical programme detected no anti-AOD-9604 antibodies [13], but that was in the formulations it studied. The FDA has recorded concern about immunogenicity arising from aggregation and peptide-related impurities in injectable presentations, and no published data resolve it.
• No long-term toxicology is in the public domain. The published human exposure is at most 24 weeks; there is no published carcinogenicity, reproductive or developmental dataset.

Regulatory and standards position

United Kingdom. AOD-9604 holds no marketing authorisation from the MHRA and is not an authorised medicinal product in the United Kingdom. It is not itself named in the schedules to the Misuse of Drugs Act 1971. The distinction from the parent hormone matters and should not be assumed either way: somatropin is a Class C controlled drug and sits in Schedule 4 Part II of the Misuse of Drugs Regulations 2001, but that listing names the hormone, and a 16-residue synthetic fragment is not somatropin. Supply for administration to humans would engage the Human Medicines Regulations 2012 regardless of controlled-drug status, and under MHRA Guidance Note 8 and the “medicinal product by presentation” doctrine a claim made about a substance can bring it within the definition of a medicinal product independently of what the molecule is.

European Union. No authorisation from the European Medicines Agency, and no national authorisation in any member state. Belgian federal authorities have seized unlabelled pharmaceutical preparations subsequently identified as containing AOD-9604, a case documented in the peer-reviewed analytical literature [7].

United States. Never approved by the FDA for any indication; development was discontinued in 2007 without a marketing application. The substance was nominated for inclusion on the section 503A bulk drug substances list for compounding, placed in the interim list’s Category 2 — substances the agency identified as raising significant safety risks — and reviewed by the Pharmacy Compounding Advisory Committee in December 2024. The committee did not support inclusion. The agency’s stated grounds included inadequate physicochemical characterisation, immunogenicity concerns arising from aggregation and peptide-related impurities, absence of clinical effectiveness data for any use, and no published human exposure data for the routes proposed. The compounding position has been revised more than once since 2023 and should be checked against the current FDA list rather than against any secondary summary.

Australia. Not approved for human use by the TGA. AOD-9604 was central to the 2013 Essendon Football Club supplements matter, in which ASADA stated publicly that it had at no point advised any party that AOD-9604 was permitted in sport. This remains the most fully documented enforcement episode involving the compound.

WADA. AOD-9604 is prohibited at all times, in and out of competition, under section S2.2.3 of the WADA Prohibited List — growth hormone fragments — where it is named explicitly, alongside hGH 176-191. It is not a borderline or inferred listing: the compound appears by name. A validated urine LC-MS/MS method exists [8], a broader screening method covering peptides below 2 kDa has been published [10], and AOD-9604 has been confirmed not to interfere with the hGH isoform immunoassay [6], so its detection is a separate analytical exercise from growth hormone testing rather than a byproduct of it.

Laboratory handling and safety

AOD-9604 has no comprehensive published toxicological dataset and no established occupational exposure limit. It is handled on the basis that its hazards are incompletely characterised.

• Lyophilised peptide is a fine, static-prone solid. Open and weigh vials in a ventilated enclosure to avoid generating or inhaling airborne powder.
• Nitrile gloves, safety spectacles and a laboratory coat as a minimum; change gloves after contact with the solid.
• Reconstitute and aliquot in a manner that avoids repeated entry into a single vial, which is a route to both microbial ingress and freeze–thaw damage.
• Label reconstituted solutions with the compound, the concentration as calculated, the diluent and the date. An unlabelled peptide solution of 1815 Da is not identifiable by inspection.
• Segregate from any material intended for human or veterinary administration, and store so that no such confusion is physically possible.
• Dispose of solutions and contaminated consumables as chemical waste through the institution’s route; do not discharge to drain.
• No safety data sheet supplied with research-grade material should be assumed to reflect a complete hazard assessment; the absence of listed hazards reflects the absence of testing.

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):274–8. Model: rodent (obese Zucker rats). PMID 11146367
2. Heffernan MA, Thorburn AW, Fam B, Summers R, Conway-Campbell B, Waters MJ, Ng FM. 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 and Related Metabolic Disorders. 2001;25(10):1442–9. Model: rodent (ob/ob and lean C57BL/6J mice). PMID 11673763
3. Heffernan M, Summers RJ, Thorburn A, Ogru E, Gianello R, Jiang WJ, Ng FM. The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knock-out mice. Endocrinology. 2001;142(12):5182–9. Model: rodent (obese, wild-type and β₃-adrenoceptor knock-out mice). PMID 11713213
4. 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):E501–7. Model: rodent (ob/ob mice) with human adipose tissue in vitro. Studies AOD-9401, a different hGH fragment, not AOD-9604; listed to prevent miscitation. PMID 10950816
5. Wilding J. AOD-9604 Metabolic. Current Opinion in Investigational Drugs. 2004;5(4):436–40. Model: review. PMID 15134286
6. 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):850–2. Model: in vitro (immunoassay interference). PMID 24124033
7. Vanhee C, Moens G, Deconinck E, De Beer JO. Identification and characterization of peptide drugs in unknown pharmaceutical preparations seized by the Belgian authorities: case report on AOD9604. Drug Testing and Analysis. 2014;6(9):964–8. Model: in vitro (analytical characterisation of seized material). PMID 24976118
8. Cox HD, Smeal SJ, Hughes CM, Cox JE, Eichner D. Detection and in vitro metabolism of AOD9604. Drug Testing and Analysis. 2015;7(1):31–8. Model: in vitro (serum and urine incubation; urine LC-MS/MS method). PMID 25208511
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):426–32. Model: animal (New Zealand white rabbit, collagenase-induced knee osteoarthritis; n=32). PMID 26275694
10. Thomas A, Görgens C, Guddat S, Thieme D, Dellanna F, Schänzer W, Thevis M. Simplifying and expanding the screening for peptides <2 kDa by direct urine injection, liquid chromatography, and ion mobility mass spectrometry. Journal of Separation Science. 2016;39(2):333–41. Model: in vitro (analytical method development, human urine). PMID 26578461
11. Mendias CL, Awan TM. Safety and efficacy of approved and unapproved peptide therapies for musculoskeletal injuries and athletic performance. Sports Medicine. 2026. Model: review. PMID 41966639
12. Dominikowski A, Rękoś Z, Olejarz M, Szczepanek-Parulska E, Domin R, Ruchała M. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Frontiers in Endocrinology. 2026;17:1822475. Model: review. PMID 42395176
13. 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. Model: human trials (pooled safety analysis of six randomised, double-blind, placebo-controlled studies, approximately 900 adults). DOI 10.4021/jem157w. No PubMed record — this journal is not indexed in PubMed, and this is the only peer-reviewed publication of human data on AOD-9604.

Identity data are taken from PubChem CID 71300630 and UniProt P01241 (somatotropin, for hGH residue numbering and the Cys182–Cys189 disulfide annotation). The WADA position is taken from the current Prohibited List, section S2.2.3.

Research use only

AOD-9604 is supplied and described here as a laboratory chemical for research use only. It is not a medicine, it is not authorised for human or veterinary use in the United Kingdom or anywhere else, and nothing in this entry is a statement that it does anything.

This entry reports what has been published. Where a study is described, the finding belongs to that study and is attributed to it; it is not a claim about the compound. The human efficacy programme for AOD-9604 failed, and that is reported here for the same reason the favourable rodent findings are: because it is what the record contains.

NovoVita does not supply AOD-9604. This library documents the compounds a reader is likely to encounter in the literature, which is a wider set than the catalogue. The presence of an entry is not an offer, and its absence from the shop is not an oversight.