The growth hormone fat-loss fragment that fell short in trials
Injection · 503A Compounding
Educational content. This page describes AOD-9604 for informational purposes only and is not medical advice, diagnosis, or treatment. Consult a licensed provider before starting, stopping, or modifying any therapy.
Researched and maintained by the PepHookup team. Regulatory status last verified April 12, 2026.
In obese mice and rats, AOD-9604 increased lipolysis and fat oxidation and reduced body fat gain, mimicking the lipolytic action of the growth hormone C-terminal domain. These effects are well documented in rodents but were not reproduced as meaningful weight loss in people.[3][4]
A single rabbit osteoarthritis study found that intra-articular AOD-9604, especially combined with hyaluronic acid, improved cartilage repair markers. This is preliminary animal evidence only and has not been tested for joint health in people.[8]
AOD-9604 (Advanced Obesity Drug 9604) is a synthetic 16-amino-acid peptide that reproduces the C-terminal lipolytic region of human growth hormone (residues 177-191) with an extra tyrosine added at the front. It carries a disulfide bond between two cysteine residues, giving it a small cyclic structure. It was developed by Metabolic Pharmaceuticals in Australia beginning in the late 1990s with the goal of capturing growth hormone's fat-burning activity while leaving out its growth-promoting and blood-sugar effects.
The promise from early animal work did not carry over to people. Metabolic Pharmaceuticals ran six placebo-controlled human trials enrolling roughly 900 participants between 2001 and 2007. The pivotal Phase 2b OPTIONS study (502 randomized, 24 weeks of oral dosing) failed its primary endpoint, with no statistically significant weight loss over placebo, and the company terminated obesity development in February 2007.
AOD-9604 later received a self-affirmed GRAS (Generally Recognized as Safe) determination for narrow dietary-supplement use. That is a food-ingredient safety classification, not FDA approval as a drug, and it does not establish that the compound works for weight loss. It is now found mainly through compounding channels marketed by wellness clinics.
AOD-9604 is thought to act like the lipolytic tail of growth hormone, encouraging fat cells to break down stored triglycerides into free fatty acids while discouraging the laying down of new fat. In rodent studies it raised plasma glycerol (a lipolysis marker), increased fat oxidation measured by indirect calorimetry, and reduced white and brown adipose tissue without animals eating less.
What sets it apart from full-length growth hormone is what it does not do. In cell assays AOD-9604 does not compete for the growth hormone receptor and does not trigger receptor-driven cell proliferation, and in animals it left blood glucose, insulin, and IGF-1 unchanged. These properties are the basis for the claim that it separates fat metabolism from growth hormone's anabolic and diabetogenic effects.
The exact molecular target is still unresolved. The FDA, in its 2024 review, stated that the mechanism of action of AOD-9604 remains unknown. The most cited clue comes from a study in beta-3 adrenergic receptor knockout mice, where AOD-9604 lost its effect on body weight and fat, suggesting beta-3 adrenergic signaling is at least partly involved, but this is a single line of evidence rather than an established pathway.
The growth hormone fat-loss fragment that fell short in trials
AOD-9604 reproduces the lipolytic C-terminal domain of growth hormone and, in animal models, increases fat breakdown and oxidation while leaving glucose, insulin, IGF-1, and the growth hormone receptor untouched. A beta-3 adrenergic receptor knockout study suggests beta-3 signaling contributes to its effect, but the precise molecular target remains unconfirmed.
Oral AOD-9604 (0.25, 0.5, or 1 mg daily) plus a diet-and-exercise program produced no statistically significant weight loss over placebo at 12 or 24 weeks. This failure of the primary endpoint led Metabolic Pharmaceuticals to terminate obesity development in February 2007. The full study was never published in the peer-reviewed literature.
Wilding J · Current Opinion in Investigational Drugs, 5(4):436-440 (2004) · PubMed
AOD-9604 was well tolerated with a safety profile largely indistinguishable from placebo. No serious adverse events were judged related to treatment, IGF-1 was unchanged, glucose tolerance was unaffected, and no anti-AOD-9604 antibodies were detected. The trials were funded by the developer and did not establish efficacy.
Stier H, Vos E, Kenley D · Journal of Endocrinology and Metabolism, 3(1-2):7-15 (2013)
AOD-9604 reduced body fat gain and increased fat oxidation without affecting growth, IGF-1, or insulin sensitivity. The effect was lost in beta-3 receptor knockout mice, implicating beta-3 adrenergic signaling. This is animal evidence and does not translate directly to human outcomes.
Heffernan M, Summers RJ, Thorburn A, Ogru E, Gianello R, Jiang WJ, et al. · Endocrinology, 142(12):5182-5189 (2001) · PubMed
Intra-articular AOD-9604 improved cartilage repair markers, with the strongest effect when combined with hyaluronic acid. This is a single preclinical study and joint-health use has not been tested in humans.
Kwon DR, Park GY · Annals of Clinical and Laboratory Science, 45(4):426-432 (2015) · PubMed
start low, go slow
Subcutaneous Injection
Subcutaneous Injection: Clinic protocols commonly use a morning, fasted subcutaneous dose into abdominal fat. No subcutaneous human pharmacokinetic or efficacy data exist; the original trials used oral and intravenous routes.
There is no validated or FDA-approved dosing regimen for AOD-9604. Any dose, route, and cycle length must be set by a licensed provider, and protocols seen in clinics are based on practice convention rather than trial-established efficacy.
The human trials used oral tablets (0.25 to 30 mg) and intravenous infusion, not subcutaneous injection. The compound has a very short measured half-life of roughly three minutes after intravenous dosing in animals.
It is sometimes paired with growth hormone secretagogues such as CJC-1295 or Ipamorelin in clinical practice, though no controlled data support these combinations.
In human trials AOD-9604 was generally well tolerated, with an adverse-event profile close to placebo, no related serious adverse events, no IGF-1 elevation, no glucose impairment, and no detectable anti-drug antibodies. These are the strongest reassurances in the human record.
The evidence base is limited and developer-funded. The compound failed to beat placebo for weight loss, no human pharmacokinetic data exist, and there is no human safety data for the subcutaneous or transdermal routes most often used in clinics today.
Animal toxicology raised several signals the FDA flagged as potentially clinically relevant: dose-dependent changes in serum osteocalcin (a bone-turnover marker) in rats, periportal liver vacuolation in monkeys after nine months of oral dosing, and equivocal genotoxicity signals across in-vitro and in-vivo assays.
Because AOD-9604 is a 16-amino-acid peptide prone to aggregation and impurity formation, the FDA also raised concerns about immunogenicity and product quality, which depend heavily on how a given compounded batch is made.
| Peptide | Primary Use | Administration | Cycle Length | Key Differentiator |
|---|---|---|---|---|
| AOD-9604 | Fat Reduction (efficacy unproven in humans) | Injection (clinic practice); oral and IV in trials | Set by provider; no standard exists | Reproduces growth hormone's fat-burning domain without raising IGF-1 or impairing glucose, but failed to beat placebo for weight loss in human trials |
| Semaglutide | Weight Management & Metabolic Health | Injection (weekly), Oral (daily) | Ongoing | The most clinically validated GLP-1 medicine, with outcomes data spanning weight, heart, kidney, and liver disease |
| Tirzepatide | Weight Loss & Type 2 Diabetes | Injection (weekly) | Ongoing | Only dual GIP/GLP-1 agonist; the deepest weight loss of any approved obesity drug, up to about 21% of body weight |
| Tesamorelin | Visceral Fat & GHRH Signaling | Subcutaneous Injection | Ongoing daily | The only FDA-approved GHRH analog, with Phase III data in over 800 patients, documented liver-fat reduction, and physiologic pulsatile GH release |
| Ipamorelin | GH stimulation for body composition and recovery | Subcutaneous injection (1-3x daily) | Determined by provider | The most selective GH secretagogue in preclinical work: a clean GH pulse without the cortisol, prolactin, or appetite effects of older GHRPs |
The FDA placed this substance in Category 2 of the 503A bulk drug substances evaluation, flagging significant safety risks. 503A compounding carries FDA enforcement risk, so most pharmacies decline to prepare it and many physicians hesitate to prescribe it.
hGH fragment 176-191. Nomination withdrawn September 2024, then reviewed by PCAC on December 4, 2024. PCAC voted against inclusion. FDA cited immunogenicity, impurity concerns, and serious adverse events. Remains ineligible for 503A compounding. Not among the 12 peptides HHS withdrew from Category 2 in April 2026.
PCAC reviewed and recommended against inclusion on 503A bulks list
Removed from Category 2 (nomination withdrawn by nominators)
Placed in 503A Category 2 with significant safety risks identified
Last verified April 12, 2026. PepHookup tracks public FDA actions. This is not legal or medical advice.
Wu Z, Ng FM “Antilipogenic action of synthetic C-terminal sequence 177-191 of human growth hormone.” Biochemistry and Molecular Biology International, 30(1):187-196 (1993)
Heffernan MA, Thorburn AW, Fam B, Summers R, Conway-Campbell B, Waters MJ, Ng FM “Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone or a modified C-terminal fragment.” International Journal of Obesity and Related Metabolic Disorders, 25(10):1442-1449 (2001)
Moré MI, Kenley D “Safety and Metabolism of AOD9604, a Novel Nutraceutical Ingredient for Improved Metabolic Health.” Journal of Endocrinology and Metabolism, 4(3):64-77 (2014)
Stier H, Vos E, Kenley D “Safety and Tolerability of the Hexadecapeptide AOD9604 in Humans.” Journal of Endocrinology and Metabolism, 3(1-2):7-15 (2013)
Wilding J “AOD-9604 Metabolic.” Current Opinion in Investigational Drugs, 5(4):436-440 (2004)
Kwon DR, Park GY “Effect of Intra-articular Injection of AOD9604 with or without Hyaluronic Acid in Rabbit Osteoarthritis Model.” Annals of Clinical and Laboratory Science, 45(4):426-432 (2015)
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