A 16-amino-acid modified fragment of human growth hormone (residues 176-191) designed to retain GH's fat-burning properties while eliminating its growth-promoting and diabetogenic effects. Also studied for osteoarthritis and cartilage repair.
AOD-9604 (Advanced Obesity Drug) is a modified 16-amino-acid fragment corresponding to residues 176-191 of human growth hormone (hGH), with a tyrosine residue added at the C-terminus. It was developed by Metabolic Pharmaceuticals in Australia based on the observation that the C-terminal portion of GH is responsible for its lipolytic (fat-burning) effects, while the N-terminal portion mediates growth and IGF-1 stimulation.
The key innovation of AOD-9604 is that it mimics GH's fat-burning activity without increasing IGF-1 levels, without promoting bone/muscle growth, and without the diabetogenic effects (insulin resistance) associated with full-length GH therapy. This makes it potentially safer for long-term anti-obesity use.
AOD-9604 was originally developed by Metabolic Pharmaceuticals Ltd. in Australia as a potential anti-obesity drug. It represents a creative pharmacological approach: by using only the lipolytic (fat-burning) fragment of growth hormone — specifically amino acids 177-191 of the GH molecule, with an added tyrosine for stability — researchers sought to capture GH's fat-metabolizing effects without the anabolic, diabetogenic, or growth-promoting side effects that make full GH therapy problematic for obesity treatment.
The peptide reached Phase IIb clinical trials for obesity but failed to demonstrate statistically significant weight loss compared to placebo, and its development as an obesity drug was discontinued. However, it subsequently found a second life in regenerative medicine, where it has been studied for osteoarthritis and cartilage repair. In Australia, AOD-9604 received GRAS (Generally Recognized as Safe) status for use as a food ingredient — an unusual regulatory pathway for a peptide.
AOD-9604 was placed on the FDA Category 2 restricted list in late 2023 but is expected to return to Category 1 under the February 2026 HHS reclassification. See our March 2026 briefing for the latest status.
AOD-9604 acts on adipose tissue through a mechanism independent of the growth hormone receptor. It appears to activate beta-3 adrenergic signaling in fat cells, stimulating hormone-sensitive lipase (HSL) to break down stored triglycerides into free fatty acids and glycerol. Simultaneously, it inhibits fatty acid synthase, reducing new fat formation. This dual action — increased fat burning + decreased fat storage — produces a net reduction in adipose tissue.
| Pathway | Effect | Significance |
|---|---|---|
| Lipolysis stimulation | Activates HSL in adipose tissue via β3 pathways | Breaks down stored fat into free fatty acids for energy |
| Lipogenesis inhibition | Reduces fatty acid synthase activity | Prevents new fat accumulation |
| Cartilage repair | Stimulates proteoglycan and type II collagen synthesis in chondrocytes | Potential OA therapy — TGA approved in Australia for this indication |
| No IGF-1 increase | Does not bind GH receptor or stimulate hepatic IGF-1 | Avoids cancer risk and growth effects associated with GH therapy |
| No glucose effects | Does not impair insulin sensitivity | Safer metabolic profile than full-length GH |
| Study | Design | Findings | Level |
|---|---|---|---|
| Phase IIb obesity | RCT, n=300, 12 weeks | Modest but significant weight loss vs placebo. Did not meet primary endpoint for regulatory approval. | Level I-II (modest) |
| Cartilage repair | Preclinical + Phase II | Stimulated proteoglycan synthesis in animal OA models. Phase II human trials showed cartilage protection. | Level II |
| Safety/tolerability | Multiple human studies | No significant adverse effects. No changes in IGF-1, glucose, or insulin levels. | Level II |
| GRAS determination | FDA review | AOD-9604 received GRAS (Generally Recognized as Safe) status as a food ingredient in the US (2014) | Regulatory |
Favorable safety profile: In Phase I and Phase IIb clinical trials, AOD-9604 was well-tolerated with no serious drug-related adverse events. The key safety advantage over full GH therapy is that AOD-9604 does not affect blood glucose levels, IGF-1 levels, or insulin sensitivity — the metabolic side effects that limit GH use for fat loss.
No effect on growth or anabolism: Because AOD-9604 is a fragment of GH that specifically lacks the growth-promoting regions of the molecule, it does not stimulate bone or tissue growth and does not elevate IGF-1. This is both its safety advantage and its limitation — it does not provide the anabolic benefits that some users seek from GH-related peptides.
GRAS status: The Australian TGA granted AOD-9604 GRAS status for oral use as a food ingredient, indicating a high level of safety confidence from a regulatory authority. However, GRAS status for oral supplementation is distinct from safety at injectable doses, and the two should not be conflated.
Limited efficacy data: The Phase IIb obesity trial failure raises questions about whether AOD-9604 produces meaningful clinical effects at the doses typically used. The shift toward osteoarthritis applications (intra-articular injection) represents a different use case with different dose-response dynamics.
| Jurisdiction | Status |
|---|---|
| FDA | Not approved as a drug. Has GRAS status as a food ingredient (2014). |
| TGA (Australia) | Approved for intra-articular injection for knee osteoarthritis (2023) |
| WADA | Banned under S0 (non-approved substances) |