AOD 9604 (Anti-Obesity Drug 9604) is a synthetic 16-amino-acid peptide corresponding to the C-terminal region of human growth hormone (hGH), specifically residues 177–191, with an additional tyrosine residue added at the N-terminus. This fragment was identified by researchers at Metabolic Pharmaceuticals as retaining the lipolytic activity of full-length hGH while lacking the anabolic and insulin-desensitizing properties associated with the intact hormone — properties attributed primarily to the N-terminal domain and its interactions with the IGF-1 axis.
In research settings, AOD 9604 has been studied as a tool for dissecting the lipolytic signaling pathways activated by GH's C-terminal domain independently of the GH receptor-mediated IGF-1 axis, making it a useful probe for adipocyte biology research and metabolic pathway studies.
Biochemical Identity & Structural Properties
| Property | Value |
|---|---|
| Full Name | AOD 9604 / hGH Fragment 177-191 |
| Sequence | Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe (with disulfide bond) |
| Molecular Weight | ~1,817.1 g/mol |
| CAS Number | 221231-10-3 |
| Classification | hGH C-terminal fragment; selective lipolytic peptide |
| Key Structural Feature | Disulfide bond between Cys7 and Cys16 (critical for activity) |
| Solubility | Water-soluble; 0.1% acetic acid may aid reconstitution |
| Storage (lyophilized) | −20°C, desiccated, protected from light |
Proposed Mechanisms of Action
β3-Adrenergic Receptor Pathway Research
Research by Heffernan et al. (2001) and subsequent studies have implicated the β3-adrenergic receptor (ADRB3) pathway in AOD 9604's apparent lipolytic activity in adipocyte models. The β3-AR is expressed predominantly in adipose tissue and plays a central role in catecholamine-stimulated lipolysis. Research has documented that AOD 9604 stimulated lipid mobilization in adipocyte cell assays in a manner partially inhibited by β3-AR antagonists, suggesting β3-AR involvement in its mechanism. This finding positioned AOD 9604 as a research tool distinct from classical cAMP-elevating lipolytic agents.
Independence from IGF-1 Axis
A critical research finding distinguishing AOD 9604 from intact hGH is its apparent lack of significant GH receptor binding affinity and consequently its failure to stimulate IGF-1 production in hepatocyte research models. Published studies have documented no significant changes in serum IGF-1 levels in animal model administrations, and no insulin resistance effects — contrasting sharply with intact hGH effects. This selectivity profile has been studied in the context of understanding which domains of the hGH molecule are responsible for distinct biological activities.
Adipocyte Differentiation Research
Research in preadipocyte cell models (3T3-L1 cells) has examined AOD 9604's effects on adipocyte differentiation and lipid accumulation during adipogenesis. Studies have examined whether the compound influences expression of key adipogenic transcription factors (PPARγ, C/EBPα) and lipogenic gene programs during preadipocyte-to-adipocyte differentiation in cell culture systems.
Summary of Published Research Findings
- Adipocyte lipolysis assays: In-vitro studies using isolated adipocytes and adipocyte cell lines documented AOD 9604-stimulated glycerol release (a marker of triglyceride hydrolysis) at concentrations comparable to full-length hGH in lipolysis assays, establishing its in-vitro lipolytic activity profile.
- Animal model metabolic studies: Rodent research examined AOD 9604 effects on body fat composition in diet-induced obese animal models, providing data on the in-vivo effects of GH fragment administration on adipose depot characteristics.
- Disulfide bond structure-activity research: Studies have examined linear vs. cyclic (disulfide-bridged) forms of hGH(177-191) to characterize the contribution of the disulfide bond to lipolytic activity, establishing structure-activity relationships for this peptide class.
- Oral bioavailability research: Metabolic Pharmaceuticals' development program examined AOD 9604 in oral formulations for anti-obesity applications, generating pharmacokinetic data in human clinical research subjects — though the program was ultimately discontinued without regulatory approval.
Key Published References
Heffernan M, Summers RJ, Thorburn A, et al. (2001). The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knockout mice. Endocrinology, 142(12), 5182–5189. PMID: 11713213
Ng FM, Sun J, Sharma L, Libinaka R, Jiang WJ, Gianello R. (2000). Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone. Hormone Research, 53(6), 274–278. PMID: 11044803
Stier H, Vos E, Kenley D. (2013). Safety and tolerability of the hexadecapeptide AOD9604 in humans. Journal of Endocrinology and Metabolism, 3(1–2), 7–15. Available via journal archives.
Storage & Laboratory Handling
- Lyophilized powder: −20°C in desiccated, light-protected conditions. Stable for 24+ months.
- Reconstitution: Dissolve in sterile water or dilute acetic acid (0.1%). The disulfide bond is stable under normal aqueous conditions but susceptible to strong reducing agents — avoid DTT or β-ME in working buffers.
- Working solutions: Store at 2–8°C; use within 14 days. Ensure disulfide bond integrity is maintained — reducing conditions will inactivate the compound.
