Compound profile
AOD-9604
Limited human dataAlso known as: hGH fragment 176-191
A fragment of the C-terminal region of human growth hormone historically investigated for fat metabolism without full GH receptor agonism claims.
Overview
AOD-9604 is a synthetic 16-amino-acid peptide corresponding to a fragment of the C-terminal region of human growth hormone, specifically amino acids 176 through 191, modified with an added tyrosine at the N-terminus. It was developed in the 1990s by Metabolic Pharmaceuticals, an Australian biotechnology company, working with researchers at Monash University in Melbourne. Its name is short for "Anti-Obesity Drug, compound 9604," reflecting the goal behind it: isolating the fat-metabolizing effects of growth hormone while stripping out the growth-promoting and blood-sugar-raising effects associated with full-length hGH.
AOD-9604 actually went through a substantial formal clinical development program, six human trials involving more than 900 participants, along with preclinical toxicology work, which is more extensive than most research peptides discussed online can claim. Early studies reported lipolytic and anti-lipogenic signals consistent with the underlying hypothesis. However, the largest and most important trial, a phase IIb study, failed to meet its primary weight-loss efficacy endpoint, and Metabolic Pharmaceuticals discontinued development around 2007.
Since then, AOD-9604 has circulated only as a research chemical, moving in and out of regulatory attention. It was nominated for the FDA's Category 2 restricted compounding list at one point but that nomination was later withdrawn, leaving it in an unsettled regulatory position rather than either approved or explicitly restricted. It has never received FDA approval for any indication.
Mechanism (plain language)
Derived from hGH 176-191 region; researched for lipolytic signaling distinct from intact GH’s broader anabolic profile, with mechanistic details that remain debated.
How it works
The hypothesis behind AOD-9604 is that growth hormone's various effects, tissue growth, blood sugar changes, and fat metabolism among them, can be separated by isolating the specific region of the hGH molecule responsible for lipolysis, the breakdown of stored fat. The C-terminal fragment (176-191) was identified in earlier research as carrying much of hGH's fat-metabolizing activity without triggering growth hormone receptor activation the way the intact hormone does, which is the basis for claims that it avoids the growth-promoting and glucose-raising effects associated with full GH therapy.
In practice, the mechanistic details have remained somewhat debated. Because AOD-9604 does not act through the classical growth hormone receptor in the way intact hGH does, researchers have had to characterize its activity through more indirect metabolic studies rather than confirming a single clean receptor-based mechanism, and the extensive human trial program that followed was aimed at establishing whether the lipolytic hypothesis held up in practice, a question the phase IIb failure ultimately answered in the negative for the doses and population tested.
What research suggests
Some early human and preclinical work explored fat-loss endpoints. Effect sizes and consistency have not matched modern incretin therapeutics in large modern RCTs.
Reported benefits
What studies, case reports, and the research literature describe, not guaranteed outcomes. The trials behind these findings are in the studies below.
Early metabolic signals
Early human and preclinical research reported effects on carbohydrate and lipid metabolism consistent with the lipolytic hypothesis behind the compound's design.
Favorable tolerability in trials
The extensive clinical safety database, drawn from more than 900 trial participants across six controlled studies, found AOD-9604 was generally well tolerated with minimal adverse effects reported.
Absence of GH-like side effects
Consistent with its design goal, trial data did not report the growth-promoting or blood-sugar-raising effects associated with intact growth hormone administration.
Uncertainties & risks
Evidence base is older and mixed. Not a substitute for lifestyle or approved obesity therapies. Product authenticity in gray markets is a recurring diligence issue.
The central fact to weigh with AOD-9604 is that its largest and most decisive trial failed. Despite an unusually large human safety database for a research peptide, the phase IIb obesity trial did not demonstrate statistically significant weight-loss efficacy, and that result is why formal drug development stopped rather than continued toward approval. That distinguishes it from compounds that simply haven't been tested in large human trials yet: AOD-9604 was tested at scale and did not clear the efficacy bar that mattered most. The evidence base is also older, largely dating to the 1990s and 2000s, and has not been revisited with the kind of modern, larger randomized trial methodology used for today's incretin-based obesity drugs, so its effect sizes and consistency simply have not kept pace with what newer compounds have shown. It is not a substitute for lifestyle changes or approved obesity therapies, and product authenticity is a recurring practical concern in the gray market where it is sold today, on top of the underlying efficacy question the phase IIb trial already raised.
STACKD study summaries
Start with our in-house roundups, plain-language synthesis of the research, with primary sources cited at the bottom of each.
Primary sources
Secondary citations for verification. Prefer the STACKD summary above for context before opening these.