AOD-9604

What Is AOD-9604?

AOD-9604 is a synthetic peptide derived from the far C-terminal end of human growth hormone (hGH), developed as a candidate anti-obesity drug. Its name is short for anti-obesity drug 9604^[1]. The sequence copies hGH residues 177-191 and adds a tyrosine at the N-terminus, which is why it is also written Tyr-hGH(177-191).

It is closely related to HGH Fragment 176-191, which carries the native phenylalanine at the first position. The two are easily confused, but they are distinct molecules with different formulas. Peer-reviewed data indexed specifically under the AOD-9604 name are limited, and much of what is available comes from drug-development summaries and narrative reviews.

Chemical Structure and Molecular Identity

AOD-9604 is a 16-residue peptide, YLRIVQCRSVEGSCGF, with one intramolecular disulfide bond and the molecular formula C78H123N23O23S2. PubChem lists a molecular weight of 1815.1 g/mol under CID 71300630, CAS number 221231-10-3 and InChIKey GVIYUKXRXPXMQM-BPXGDYAESA-N.

The PubChem structure shows a disulfide bridge linking the cysteines at positions 7 and 14, which closes an eight-residue ring, with a free N-terminal amine and a free C-terminal carboxylic acid. The formula matches this sequence exactly when the disulfide is formed. The two sulfur atoms in the formula come from those cysteines.

• Length: 16 amino acids, all standard L-residues
• Disulfide: Cys7-Cys14
• Basic residues: Arg3 and Arg8
• Acidic residue: Glu12
• Difference from HGH Fragment 176-191: Tyr instead of Phe at position 1, adding one oxygen atom (C78H123N23O23S2 versus C78H123N23O22S2)

What the Published Literature Covers

Indexed literature on AOD-9604 by name is sparse and consists mainly of a drug-development summary and recent narrative reviews. No primary trial report or detailed preclinical study under the AOD-9604 name was among the PubMed records available for this page.

Clinical development

A 2004 drug-development profile reported that the company Metabolic was developing AOD-9604 for the potential treatment of obesity and that phase IIa trials were under way by February 2002^[2]. The profile’s abstract does not report trial outcomes, and no approved product followed.

Reviews

A 2026 narrative review in Sports Medicine listed AOD-9604 among prominent unapproved peptides marketed directly to patients through a gray market operating largely outside regulatory oversight. It concluded that many such peptides show favorable outcomes in animal models but that rigorous human safety data are scarce, with potential for serious harm^[1].

A 2026 orthopaedic review grouped AOD-9604 with peptides acting on growth hormone and IGF-1 signaling and stated that, although preclinical studies are promising, clinical trials are currently lacking^[3]. Neither review reports new experimental data on AOD-9604.

Because AOD-9604 and HGH Fragment 176-191 differ by a single residue, researchers typically confirm identity by mass spectrometry and purity by HPLC.

Because AOD-9604 and HGH Fragment 176-191 differ by a single residue, researchers typically confirm identity by mass spectrometry and purity by HPLC.

Regulatory and Research Status

AOD-9604 is not an FDA-approved drug. Its clinical program reached phase IIa for obesity^[2], and recent reviews classify it as an unapproved peptide^[1].

In sport, the World Anti-Doping Agency Prohibited List names AOD-9604 and hGH 176-191 as examples of prohibited growth hormone fragments. The current edition of that list is the authoritative reference.

For researchers, the main limitation is the small body of indexed, peer-reviewed data under this name. Studies should state whether they used AOD-9604 or the native-sequence HGH Fragment 176-191, since the literature does not always distinguish them.