What is AOD-9604?
7 min read · Updated October 2026 · MY PEPTIDES Research Team
Key facts
AOD-9604 is a modified form of the 176-191 fragment of human growth hormone, the last sixteen residues of the hormone. The fragment itself, usually sold as HGH fragment 176-191, is that sequence alone; AOD-9604 is the same sequence with a tyrosine residue added at the N-terminus, a change made during pharmaceutical development to improve stability. The two are therefore closely related but not identical, which is a frequent source of confusion when comparing listings. Research interest centres on reports that this region of the growth hormone molecule is associated with effects on fat metabolism in preclinical models, separately from the growth-promoting activity of the full hormone. AOD-9604 was taken into clinical development for obesity and did not demonstrate the efficacy required; it holds no marketing authorisation as a medicine. MY PEPTIDES does not stock either compound. General information for laboratory context only, not medical advice.
The short answer
These are two closely related compounds separated by a single amino acid, and they are confused constantly.
Human growth hormone is a protein 191 residues long. HGH fragment 176-191 is its last sixteen residues, nothing more. AOD-9604 is that same sixteen-residue stretch with one tyrosine added at the front, a change made during pharmaceutical development to make the molecule more stable.
So they are relatives, not synonyms. If a protocol names one, the other does not substitute for it.
Why anyone cut the hormone up
Growth hormone does several different things, and for a long time the question was whether those activities could be separated. If one region of the molecule were responsible for effects on fat metabolism while other regions drove growth promotion, then isolating that region would be a way to study the first without the second.
The 176-191 fragment comes from that line of work. Reports associated this C-terminal region with effects on fat metabolism in preclinical models, apparently separately from the growth-promoting activity of the intact hormone. Whether that separation holds up as cleanly as the early framing suggested is exactly the kind of question the subsequent literature has been arguing about.
The naming is a relic of the ambition rather than the result. AOD stands for Anti-Obesity Drug, which describes what the development programme hoped to produce. It is not a description of a demonstrated property, and reading it as one is a mistake the name actively invites.
What happened in the clinic
This is the part that makes AOD-9604 genuinely unusual in this market, and it is worth stating plainly because it cuts against the way the compound is usually sold.
Most compounds discussed under the research heading have never been tested in people at all. Their status is simply unknown: the preclinical work looked interesting and nothing further happened. AOD-9604 is different. It was taken into clinical development for obesity, it was tested in humans, and it did not demonstrate the efficacy that approval would require. It holds no marketing authorisation as a medicine.
That is a more informative outcome than silence. A negative clinical result is real evidence, and it is evidence that the preclinical promise did not carry over. Marketing copy for this compound tends to cite the animal literature and the existence of clinical trials while omitting what the trials concluded, which inverts the actual weight of the evidence.
None of this means the fragment is uninteresting as a laboratory tool for studying that region of the hormone. It means the specific therapeutic hypothesis the name encodes was tested and not supported.
Handling and analytical notes
A sixteen-residue peptide is a straightforward molecule by the standards of this field: long enough to have some structure, short enough to characterise cleanly, and robust enough to handle without special precautions beyond the usual. Temperature, light and time are the variables that matter, and our guide on storing research peptides covers the general discipline.
One analytical point is specific to these two compounds and worth attention when comparing suppliers. Because AOD-9604 and the plain 176-191 fragment differ by a single residue, they differ in mass by a predictable, modest amount, and they are similar enough to be mistaken for one another by a careless analysis. A certificate that genuinely identifies the material, rather than simply asserting a purity percentage, is therefore doing more work here than usual. If a listing does not make clear which of the two it is selling, that ambiguity is itself the problem.
Where MY PEPTIDES stands
We do not stock the compounds described above. There are no Certificates of Analysis for them in our library and no product pages for them on this site, and this guide is not an offer to supply them. If that changes it will change by a product appearing in the catalogue with a batch certificate attached, not by a line in a guide.
What we do supply, and the documentation standard we hold it to, is set out in our guide on certificates of analysis.
The bottom line
HGH fragment 176-191 is the C-terminal sixteen residues of human growth hormone, and AOD-9604 is the same sequence with one tyrosine added for stability. The region was studied in the hope of separating fat-metabolism effects from growth promotion; AOD-9604 was tested clinically for obesity and did not show sufficient efficacy. Neither is an approved medicine and we supply neither.
All compounds referenced on this site are discussed strictly in the context of in-vitro laboratory research. Nothing here is a medicine, a supplement or a therapeutic product, nothing here describes administration to humans or animals, and this guide is general information rather than medical, legal or research advice.
Frequently asked questions
- What is the difference between AOD-9604 and HGH fragment 176-191?
- One residue. HGH fragment 176-191 is the sixteen-amino-acid stretch running from position 176 to position 191 of human growth hormone. AOD-9604 is that same stretch with a tyrosine added at the N-terminus, a modification introduced during pharmaceutical development to improve the molecule\u2019s stability. They are closely related and routinely conflated in listings, but a protocol specifying one is not satisfied by the other.
- What does "176-191" refer to?
- Position numbers in the human growth hormone sequence. The full hormone is 191 amino acids long, so 176-191 is its final sixteen residues, the C-terminal tail. The fragment is of research interest because that specific region has been reported to be associated with effects on fat metabolism in preclinical work, apparently separately from the growth-promoting activity attributed to other parts of the molecule.
- What does AOD stand for?
- Anti-Obesity Drug, which tells you what the development programme was aiming at rather than anything about the chemistry. The name is a historical artefact of that programme and should not be read as a description of what the compound has been shown to do. The programme did not produce an approved medicine.
- What is AOD-9604 studied for in research?
- Preclinical and in-vitro work examines it in the context of lipid metabolism, following from reports that the 176-191 region is associated with effects on fat handling in animal models. Observations depend on the model, the concentration and the exposure. It has also been studied in human clinical trials for obesity, which is unusual for a compound in this market, and those trials did not demonstrate the efficacy needed to support approval.
- Is AOD-9604 an approved medicine?
- No. It went through clinical development for obesity and did not show sufficient efficacy, and it holds no marketing authorisation as a medicine. That is a genuinely informative outcome: unlike most research compounds, this one was tested in people and the result was negative. Material sold under this name is supplied for in-vitro laboratory research only.
- Do you sell AOD-9604 or HGH fragment 176-191?
- No. We stock neither, and there are no Certificates of Analysis for them in our library. Both are documented here because they draw steady search interest and are persistently confused with one another.