AOD-9604: six human trials, one Phase IIa signal, one failed Phase IIb endpoint, and a literature that is thin but clean.

What is AOD-9604?

AOD-9604 is a synthetic 16-amino-acid peptide corresponding to the C-terminal residues 176–191 of human growth hormone, with a tyrosine substituted at the N-terminal position. Its molecular formula is C78H123N23O23S2, molecular weight 1815.1 Da. The compound was developed by Metabolic Pharmaceuticals Ltd (Melbourne, Australia) specifically to isolate the lipolytic domain of hGH — the region responsible for fat-metabolism effects — while leaving behind the growth-promoting, IGF-1-stimulating N-terminal region.

The research rationale was direct: hGH itself reduces body fat, but it also elevates IGF-1, promotes insulin resistance, and stimulates tissue growth at pharmacological doses. If the lipolytic activity resided in a separable C-terminal fragment, that fragment could potentially be studied for fat metabolism without the growth-axis side effects. The 1993 in-vitro work by Wu and Ng confirmed that the synthetic C-terminal sequence 177–191 had antilipogenic activity identical to intact hGH in adipose tissue — establishing the functional domain ^[1].

Six Phase I and Phase II randomized controlled trials were subsequently conducted in approximately 900 human participants. The compound reached FDA Generally Recognized as Safe (GRAS) status as a nutraceutical ingredient. The pharmaceutical obesity program was discontinued in 2007 after the pivotal Phase IIb trial failed its primary efficacy endpoint ^[9]. The research literature is thin but fully documented: the core preclinical evidence base is five papers from the Monash University Ng and Heffernan labs (1983–2001), the clinical evidence is captured in two 2013–2014 Journal of Endocrinology and Metabolism papers, and a 2015 rabbit osteoarthritis study and a 2022 nanoparticle paper extend the research into non-obesity contexts.

AOD-9604 Peptide: Structure and Research Background

The AOD-9604 peptide sequence is the C-terminal arm of human growth hormone, a 191-amino-acid polypeptide. Residues 176–191 form the segment experimentally identified as responsible for hGH's antilipogenic and lipolytic properties. AOD-9604 replaces phenylalanine with tyrosine at the N-terminal end of this fragment — hence it is also identified as Tyr-hGH177–191 in the literature. The modification was designed to improve stability while preserving the lipolytic function.

Critically, AOD-9604 does not bind the hGH receptor. It does not stimulate IGF-1 production. Across all six human clinical trials, no IGF-1 elevation was detected in any participant at any dose ^[10]. This receptor-independence is the property that distinguished the compound from full-length hGH as a research target for metabolic applications and gave the pharmaceutical program its rationale: a fragment that might replicate the fat-metabolism signal without activating the growth axis.

The AOD-9604 mechanism of action operates through at least two distinct pathways: inhibition of acetyl-CoA carboxylase — the rate-limiting enzyme in fatty acid synthesis — via a plasma-membrane second-messenger mechanism ^[3], and upregulation of beta-3 adrenergic receptor (ADRB3) mRNA in adipose tissue, which promotes cAMP-mediated lipolysis via hormone-sensitive lipase ^[6]. The relative contribution of each pathway to the observed fat-mass reduction in rodent models was partially resolved by beta-3 AR knockout experiments (see Research).

The six-trial record: what was measured

Six randomized, double-blind, placebo-controlled trials were completed. Phase I studies established safety at escalating doses. A 12-week Phase IIa trial in approximately 300 obese adults — the early efficacy signal — found that subjects at 1 mg/day oral lost an average of 2.6 kg versus 0.8 kg in the placebo group ^[8]. That signal did not replicate at higher doses: subjects receiving 10 mg/day showed a smaller reduction than those at 1 mg/day, indicating a non-linear dose-response relationship whose mechanism was not fully characterized in the published record ^[8].

The pivotal Phase IIb OPTIONS study enrolled 536 obese adults over 24 weeks at three oral dose levels — 0.25 mg, 0.5 mg, and 1 mg per day. It failed its primary endpoint: no statistically significant body-mass reduction was observed versus placebo ^[9]. Pharmaceutical development was halted in 2007. The compound was not approved as a drug for any indication in any jurisdiction.

Safety across all six trials was indistinguishable from placebo: no serious adverse events, no treatment-related withdrawals, no IGF-1 elevation, no glucose intolerance, no anti-AOD-9604 antibodies in any participant, and no genotoxicity signals in preclinical toxicology panels covering rat (6 months) and cynomolgus monkey (9 months) chronic exposure ^[11]. The AOD-9604 side effects and safety profile page summarizes this data in detail.

Subsequent to the obesity program, a 2015 rabbit study demonstrated cartilage regeneration effects via intra-articular injection ^[14], and an active Phase 2a human clinical trial (NCT07225829) is investigating an intra-articular AOD-9604 formulation (branded 4P004) for knee osteoarthritis as of 2025.

Regulatory status and the WADA prohibition

AOD-9604 received FDA Generally Recognized as Safe (GRAS) designation for use as a food, beverage, and dietary supplement ingredient — a nutraceutical pathway distinct from pharmaceutical drug approval ^[11]. No regulatory agency has approved the compound as a pharmaceutical drug for any human therapeutic indication.

The World Anti-Doping Agency (WADA) prohibits AOD-9604 under the S0 category (Non-Approved Substances) — any pharmacological substance not approved by any governmental regulatory health authority for human therapeutic use, including discontinued drug candidates. This prohibition applies at all times in competitive sport.

For AOD-9604 dosage protocols studied in research, including the clinical dose levels and intra-articular protocols, see the dosage page. For before and after research outcomes, see the results page. For a complete index of frequently asked questions, see the FAQ.