AOD-9604: What Researchers Should Know About This hGH Fragment
AOD-9604 (hGH Fragment 176-191) for research: mechanism of action, clinical data, safety profile and how it differs from full growth hormone.
AOD-9604 is a synthetic peptide derived from amino acids 176-191 of human growth hormone (hGH). The name stands for "Anti-Obesity Drug 9604". It was developed in the 1990s at Monash University in Melbourne with the goal of isolating the lipolytic effects of hGH without triggering the growth-related and diabetogenic side effects of the full hormone.
Modified hGH fragment (176-191) studied for fat metabolism and lipolysis research. Interacts with beta-3 adrenergic receptors without growth-promoting effects.
Structure and Origin
The amino acid sequence of AOD-9604 is:
Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe
AOD-9604 consists of 16 amino acids: residues 177-191 from the C-terminal region of hGH, plus a tyrosine residue at the N-terminus for stabilisation. The disulphide bond between the two cysteine residues (positions 7 and 14) is required for biological activity.
What matters is what the fragment lacks: binding site 2 of the hGH receptor is absent from AOD-9604. This means the peptide cannot dimerise and activate the receptor the way full-length hGH does. This structural property explains why AOD-9604 does not increase IGF-1, does not cause insulin resistance, and does not promote tissue growth.
Mechanism of Action
The lipolytic effect of AOD-9604 operates through beta-3 adrenergic receptors on adipocytes. The signalling cascade leads to elevated intracellular cAMP levels, which in turn stimulates fat breakdown (lipolysis) and inhibits new fat formation (lipogenesis).
The dependence on beta-3 receptors was demonstrated in knockout mice: animals lacking functional beta-3 receptors show no lipolytic response to AOD-9604 (Ng et al., 2001, Endocrinology). This confirms that the mechanism is specifically mediated through this receptor type.
Selective Action
AOD-9604 was specifically engineered to isolate the fat-metabolising properties of hGH. Unlike the full hormone, it does not affect blood glucose, insulin sensitivity, or IGF-1 levels.
Clinical Trials
The clinical development of AOD-9604 was driven by Metabolic Pharmaceuticals (Australia). A total of six randomised, controlled studies were conducted.
Phase II Trial (12 Weeks)
In a randomised, double-blind, placebo-controlled 12-week trial, subjects receiving 1 mg/day AOD-9604 lost an average of 2.6 kg body weight, compared to 0.8 kg in the placebo group. An improvement in cholesterol profile was also observed. The safety profile was unremarkable.
Phase IIb Trial (24 Weeks, OPTIONS Study)
The larger OPTIONS study enrolled 536 obese subjects and tested lower doses than the Phase II trial. The result: at the chosen dosages, no statistically significant weight loss versus placebo could be demonstrated. Metabolic Pharmaceuticals discontinued development as an obesity therapeutic in 2007.
Interpreting the Trial Results
The clinical data show a clear pattern: AOD-9604 is well tolerated and safe (over 900 subjects across six controlled trials), but its efficacy as an oral obesity drug at the tested doses was not convincing. This does not mean the peptide is biologically inactive - rather that the chosen delivery method and dosing were insufficient for clinical approval.
Safety Profile
The safety data for AOD-9604 are unusually extensive for a research peptide. Across all six clinical trials (Phase I, IIa, and IIb) involving over 900 subjects, the following was established:
- No changes in fasting glucose or glucose tolerance
- No impact on insulin sensitivity
- No elevation of IGF-1
- No suppression of the hypothalamic-pituitary axis
- No effects on thyroid function or reproductive hormones
- Adverse event profile indistinguishable from placebo (Stier et al., Journal of Endocrinology and Metabolism)
GRAS Status
In 2021, AOD-9604 received GRAS (Generally Recognized As Safe) status from the US FDA for use as a food ingredient. This status is based on the totality of safety data from the clinical trials. Important: GRAS does not mean therapeutic approval - it is exclusively a safety classification.
TGA Approval in Australia
The Australian Therapeutic Goods Administration (TGA) approved AOD-9604 for use in cartilage repair formulations. This approval is based on preclinical cartilage regeneration data combined with the favourable safety profile from the clinical studies.
WADA Status
AOD-9604 is listed on the World Anti-Doping Agency (WADA) Prohibited List under the category "Peptide hormones, growth factors, related substances, and mimetics" (class S2). This is relevant for researchers working in sports medicine or exercise physiology contexts.
AOD-9604 vs. Full-Length hGH
| Property | AOD-9604 | hGH (full-length) |
|---|---|---|
| Structure | 16 amino acids (C-terminal fragment) | 191 amino acids |
| Lipolysis | Yes (via beta-3 receptors) | Yes |
| IGF-1 elevation | No | Yes |
| Insulin resistance | No | Yes (diabetogenic effect) |
| Tissue growth | No | Yes |
| Receptor dimerisation | No (binding site 2 absent) | Yes |
The key difference: AOD-9604 separates the lipolytic effect from the rest of hGH's actions. For research purposes, this is relevant because it allows investigation of fat metabolism pathways without the confounding effects of growth and glucose metabolism.
Cartilage Research
A lesser-known research field for AOD-9604 is cartilage regeneration. In a rabbit osteoarthritis model (collagenase-induced), intra-articular injection of AOD-9604 showed improved cartilage regeneration compared to untreated controls (Annu Clin Lab Sci, 2015).
The combination of AOD-9604 with hyaluronic acid (HA) produced better outcomes in this model than either substance alone. The authors suggest a synergistic effect: HA protects chondrocytes while AOD-9604 stimulates the production of proteoglycans and collagen in cartilage cells.
Mechanistically, the data suggest that AOD-9604 mimics developmental cascades that lead to the reformation of articular cartilage structures. Whether this effect translates to human joints is the subject of ongoing research.
Cartilage Research Status
Cartilage research on AOD-9604 is at the preclinical stage. Results are promising, but controlled human studies are lacking. The TGA approval in Australia is based on these preclinical data combined with the established safety profile.
Quality and Sourcing
Purity Testing
Research-grade AOD-9604 should have a purity of at least 98%. At PeptidesDirect, each batch is independently tested by Janoshik Analytical.
A complete Certificate of Analysis (COA) for AOD-9604 must include: HPLC purity analysis, mass spectrometry for identity confirmation, peptide content, residual moisture, and counterion determination.
Storage
Store AOD-9604 as lyophilised powder at -20 °C. After reconstitution, keep refrigerated at 2-8 °C and use within 2-4 weeks.
EU Shipping: PeptidesDirect ships from within the EU. No customs, no import fees, delivery in 2-3 working days with tracking.
Frequently Asked Questions
Order AOD-9604
Researchers sourcing AOD-9604 should look for independent purity testing, EU shipping, and transparent analytical data.
Modified hGH fragment (176-191) studied for fat metabolism and lipolysis research. Interacts with beta-3 adrenergic receptors without growth-promoting effects.