AOD-9604

Also known as: AOD9604, AOD 9604, hGH fragment 176-191, Tyr-hGH177-191

3 notable studies · 3 references

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TLDR

AOD-9604 is a modified C-terminal human-growth-hormone fragment developed to reproduce proposed fat-metabolism effects without the broader actions of intact HGH; although animal studies showed promising lipolytic effects, its human obesity-development program failed to demonstrate significant weight loss over placebo in a large trial and was subsequently discontinued.

 Research Supports Studied for effects on fat metabolism and lipolysis
Investigated in human clinical trials for obesity treatment
Examined for effects on glucose and insulin sensitivity relative to intact growth hormone
Studied in experimental cartilage and osteoarthritis research
 

 Observations Reported in Research Reduced body-weight gain by more than 50% and increased adipose lipolytic activity in obese Zucker rats without impairing insulin sensitivity (Ng et al., 2000)
OPTIONS trial of roughly 536 participants with obesity found weight loss too small versus placebo to reach statistical significance (2007)
FDA's 2024 review concluded evidence was insufficient to support effectiveness for obesity
Identified six potential metabolites after incubation in human serum and urine (2015 analytical study)
 

These are brief summaries of what the referenced research examined or reported — not conclusions about safety or effectiveness, and not medical advice. See Notable Studies and Sources & References below for the full context and citations.

At a Glance

Classification: Synthetic modified C-terminal human growth hormone fragment; experimental metabolic peptide

AOD-9604 is a synthetic peptide derived from the C-terminal region of human growth hormone (hGH). More precisely, it consists of hGH amino acids 177–191 with an additional N-terminal tyrosine, which is why the common shorthand “HGH Fragment 176-191” isn't a perfectly precise chemical description. It was developed to answer an appealing question: Could researchers isolate growth hormone's proposed fat-metabolism effects without producing its broader growth-promoting and diabetogenic effects? Animal experiments were encouraging. Early human development proceeded into multiple clinical studies. Then came the critical result: A large obesity trial involving more than 500 participants failed to demonstrate statistically significant weight loss versus placebo. The company subsequently terminated AOD-9604's obesity-development program. FDA reviewers summarized the evidence in 2024 as showing a lack of support for effectiveness in obesity. That's the central Aminodex story.

What Is AOD-9604?

Human growth hormone contains 191 amino acids. Researchers historically investigated whether different regions of the hormone were responsible for different biological effects. Work on its C-terminal region suggested that some shorter fragments might influence fat metabolism without reproducing the full growth-promoting actions of intact hGH. AOD-9604 was developed from this idea. Its structure corresponds to: hGH residues 177–191 + an additional N-terminal tyrosine. The intended result was essentially a selective metabolic fragment. Preclinical studies reported effects on lipolysis and body-weight gain, leading to development as an anti-obesity drug candidate.

What Are Researchers Studying?

Fat metabolism

AOD-9604 was primarily developed around the hypothesis that the C-terminal region of growth hormone contains lipolytic biological activity. Preclinical research reported increased fat breakdown and reduced fat accumulation. That gave rise to the popular description: “The fat-burning part of HGH.” It's catchy, but too simplistic. The existence of metabolic effects in animal or cellular experiments does not establish clinically meaningful fat loss in humans. And in this case we have unusually useful evidence showing exactly why that distinction matters.

Obesity

Obesity was AOD-9604's major intended clinical indication. Multiple human studies were conducted during pharmaceutical development. FDA's later review identified several clinical studies and concluded that most failed to demonstrate benefit for weight reduction compared with placebo. Most importantly, the large OPTIONS study enrolled roughly 536 participants with obesity. Participants received diet/exercise intervention plus placebo or AOD-9604. According to the company's reported results, weight loss with AOD-9604 was too small relative to placebo to reach statistical significance at the primary and secondary endpoints. Development for obesity was terminated. This makes AOD-9604 unusually instructive: The hypothesis wasn't merely “never properly tested.” It progressed far enough to encounter a substantial negative human efficacy result.

Lipolysis

In obese Zucker rats, daily AOD-9604 treatment reduced body-weight gain by more than 50% relative to controls during a 19-day experiment and increased lipolytic activity in adipose tissue. Importantly, those animals did not show the same deterioration in insulin sensitivity associated with chronic intact growth-hormone exposure. That result supported the original selective-lipolysis hypothesis. But the later human obesity program demonstrates why animal metabolic findings cannot be assumed to translate quantitatively into human weight loss.

Glucose and insulin biology

One major concern with intact growth hormone is that chronic exposure can impair insulin sensitivity. AOD-9604 was specifically interesting because researchers hoped to separate metabolic fat effects from these unwanted GH actions. Animal clamp studies did not show the same adverse effect on insulin sensitivity seen with intact hGH. Clinical development also investigated glucose-related safety. However, lack of a classic GH-like diabetogenic effect does not establish that AOD-9604 is effective for obesity. Safety hypothesis and efficacy hypothesis are separate questions.

Cartilage and musculoskeletal biology

AOD-9604 has also appeared in experimental musculoskeletal research, particularly around cartilage and osteoarthritis biology. This is mechanistically distinct from its original obesity-development program. These findings have contributed to renewed research-market interest in AOD-9604 after its obesity program ended. However, preclinical cartilage findings should not be interpreted as established treatment of osteoarthritis or tissue injury.

How Does It Work?

AOD-9604's exact human mechanism remains incompletely characterized. The original hypothesis was that the C-terminal portion of hGH could influence: Lipolysis Increasing mobilization of stored triglycerides from adipose tissue. Lipogenesis Potentially reducing formation or storage of new fat. Metabolic regulation Producing some GH-associated metabolic effects without activating the complete spectrum of growth-hormone biology. But one important Aminodex distinction is: AOD-9604 should not simply be described as a miniature growth hormone. Its biological behavior differs substantially from intact hGH.

What Does the Research Show?

Human research

This is the most important section. AOD-9604 did reach human clinical development for obesity. That differentiates it from many research-market peptides. But the overall efficacy story was disappointing. FDA's 2024 review concluded: • Most identified studies failed to show weight-loss benefit over placebo. • The large obesity study did not demonstrate significant weight loss. • Development for obesity was terminated following the failed study. • Evidence was insufficient to support effectiveness for obesity. The large OPTIONS study apparently was not published as a conventional peer-reviewed medical paper, which is itself an important evidence limitation. FDA relied partly on company disclosures when reconstructing the development history. So the correct summary is not: “AOD-9604 has no human research.” It's: “AOD-9604 was studied in humans for obesity, but the development program did not establish meaningful weight-loss efficacy.”

Animal research

Animal evidence is much more encouraging. The classic obese Zucker-rat study reported: • reduced body-weight gain, • increased adipose lipolytic activity, • and no detected deterioration in insulin sensitivity under the study conditions. Other animal research contributed to the hypothesis that the C-terminal GH region carries metabolic activity. But the human program is precisely why Aminodex should rank direct clinical evidence above animal results.

In-vitro research

Laboratory research has examined: • Adipocyte metabolism • Lipolysis • Lipogenesis • Peptide metabolism • Cartilage biology • Growth-factor-related signaling AOD-9604 has also been studied analytically because of its use in sports-doping contexts. A 2015 analytical study identified several potential AOD-9604 metabolites after incubation in human serum and urine.

Notable Studies

Metabolic Studies of a Synthetic Lipolytic Domain (AOD9604) of Human Growth Hormone

animal

Ng FM, Sun J, Sharma L, Libinaka R, Jiang WJ, Gianello R · 2000

Researchers studied AOD-9604 as a synthetic analogue of the proposed lipolytic domain of human growth hormone. Daily treatment for 19 days reduced body-weight gain by more than 50% compared with controls and increased adipose-tissue lipolytic activity. Unlike intact hGH, chronic AOD-9604 treatment did not impair insulin sensitivity in the euglycemic-clamp experiments.

Limitations: This was an obese-rat model. The promising metabolic effects did not translate into convincing weight-loss efficacy during subsequent human obesity development.

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OPTIONS Study

human

2007

The trial enrolled approximately 536 people with obesity and evaluated multiple AOD-9604 doses alongside a formal diet and exercise program. According to company information reviewed by FDA, weight loss compared with placebo was too small to reach statistical significance at the 12- or 24-week endpoints. The company subsequently concluded that the trial did not support commercial viability of AOD-9604 as an obesity treatment and terminated development for that indication.

Limitations: Detailed trial results do not appear to have been published in the peer-reviewed medical literature. Consequently, independent assessment of methodology and complete results is limited. The source packet links this study to an FDA scientific review of AOD-9604 evidence (December 2024), not a PubMed record. No public FDA URL was included in the packet, so this card has no publication link.

Detection and In Vitro Metabolism of AOD9604

in-vitro

2015

Researchers developed a method for detecting AOD-9604 in urine and investigated peptide degradation in serum and urine. Six potential metabolites were identified, with one fragment showing greater stability than the parent compound and other metabolites.

Limitations: This was an analytical/doping-detection study, not an efficacy trial. It provides information about metabolism and detection rather than fat loss or therapeutic effects.

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What We Still Don't Know

• Whether AOD-9604 has a clinically meaningful effect in any specific obesity subgroup • Exact human molecular mechanism • Whether any human fat-metabolism effect is large enough to matter clinically • Long-term safety with contemporary research-market patterns of exposure • Long-term pharmacokinetics • Clinical relevance of proposed cartilage effects • Whether musculoskeletal findings translate to humans • Whether alternative formulations materially change biological exposure • Whether benefits exist for indications unrelated to obesity • How research-market material compares with pharmaceutical-development material But one thing is considerably less uncertain: Existing evidence does not support presenting AOD-9604 as a proven human weight-loss compound. FDA's review reached essentially that conclusion.

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Sources & References

Ng FM, Sun J, Sharma L, Libinaka R, Jiang WJ, Gianello R. Metabolic Studies of a Synthetic Lipolytic Domain (AOD9604) of Human Growth Hormone. Hormone Research. 2000;53:274–278.
Detection and In Vitro Metabolism of AOD9604. Drug Testing and Analysis.
U.S. Food and Drug Administration. AOD-9604 Pharmacy Compounding Advisory Committee Scientific Review. December 2024.

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