AOD-9604 (Advanced Obesity Drug) - Modified hGH Fragment (177-191)

AOD-9604 for Research: Complete Scientific Overview

AOD-9604 (Advanced Obesity Drug-9604) is a synthetic peptide corresponding to the C-terminal region of human growth hormone (hGH), specifically amino acid residues 177-191. This 15-amino acid modified fragment was rationally designed through extensive structure-activity relationship studies at Metabolic Pharmaceuticals Ltd. to isolate and enhance the lipolytic domain of hGH while eliminating its undesirable somatogenic and diabetogenic activities. Unlike full-length hGH, which stimulates both lipolysis and IGF-1 production (leading to growth promotion and insulin resistance), AOD-9604 selectively activates the lipolytic signaling pathways in adipose tissue without binding to the classical growth hormone receptor or inducing IGF-1 secretion. This selective activity profile makes AOD-9604 a uniquely valuable tool for dissecting the metabolic versus anabolic effects of growth hormone and for studying the molecular mechanisms of adipose tissue lipolysis.

Mechanism of Action

AOD-9604 exerts its biological effects through multiple well-characterized pathways that specifically target lipid metabolism:

• Lipolysis Stimulation via HSL Activation: AOD-9604 activates hormone-sensitive lipase (HSL), the rate-limiting enzyme in triglyceride hydrolysis, in white and brown adipocytes. Activation occurs through a cAMP-dependent pathway, leading to the phosphorylation and translocation of HSL to lipid droplets, promoting the breakdown of stored triglycerides into free fatty acids (FFAs) and glycerol. This effect is independent of the classical growth hormone receptor and does not require JAK2/STAT5 signaling.
• β-Oxidation Enhancement: The peptide increases fatty acid oxidation in mitochondria through upregulation of carnitine palmitoyltransferase-1 (CPT-1) and other enzymes involved in β-oxidation. This reduces lipid accumulation in adipose tissue, liver, and skeletal muscle, improving overall metabolic profile.
• Selective hGH Fragment Activity: AOD-9604 mimics the lipolytic domain of hGH (which resides in the C-terminal region) without binding to the growth hormone receptor or stimulating IGF-1 production. This selectivity is achieved because the somatogenic domain of hGH is located in the N-terminal region, which is absent in the AOD-9604 fragment.
• AMPK Pathway Modulation: Research indicates that AOD-9604 may activate AMP-activated protein kinase (AMPK) in adipose tissue and skeletal muscle, contributing to improved energy homeostasis, increased glucose uptake, and enhanced fatty acid oxidation.
• Reduced Lipogenesis: The peptide downregulates the expression of key lipogenic enzymes in adipose tissue, including fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC), and stearoyl-CoA desaturase-1 (SCD-1), reducing de novo fatty acid synthesis and lipid accumulation.
• Adipocyte Differentiation Modulation: Studies have shown that AOD-9604 can influence adipocyte differentiation and maturation, potentially affecting the balance between white and brown adipose tissue phenotypes.

Key Advantages Over Full-Length hGH for Research Applications

• No IGF-1 Stimulation: Unlike full-length hGH, AOD-9604 does not increase insulin-like growth factor-1 (IGF-1) levels. IGF-1 is responsible for many of the growth-promoting and anabolic effects of hGH, and its absence allows for focused study of direct metabolic effects without confounding growth-related variables.
• No Hyperglycemia Risk: Does not affect blood glucose or insulin sensitivity. Full-length hGH is known to induce insulin resistance and hyperglycemia through its effects on glucose transport and gluconeogenesis. AOD-9604 lacks these effects, making it suitable for studies requiring isolated lipolytic activity without metabolic complications.
• No Growth Promotion: Lacks the somatogenic (growth-promoting) activity of full-length hGH, including effects on bone growth, organ enlargement, and tissue hyperplasia. This eliminates confounding anabolic variables in metabolic studies.
• Focused Metabolic Activity: Specifically targets lipid metabolism pathways without off-target hormonal effects on the hypothalamic-pituitary axis, thyroid function, or reproductive hormones.
• Improved Safety Profile: The selective activity profile eliminates concerns about hGH-related adverse effects, allowing for more targeted investigation of lipolytic mechanisms.

Research Applications

• Lipolysis and Fatty Acid Oxidation Studies: Investigating the molecular mechanisms of hormone-sensitive lipase (HSL) activation, fatty acid mobilization, and mitochondrial β-oxidation in adipose tissue.
• Obesity and Metabolic Syndrome Research: Studying the effects of enhanced lipolysis on adiposity, ectopic lipid deposition, insulin sensitivity, and metabolic health in various animal models.
• Adipocyte Biology and Lipid Metabolism: Examining the signaling pathways involved in adipocyte lipolysis, including cAMP/PKA, ERK, and AMPK pathways, and how they regulate triglyceride metabolism.
• Selective hGH Fragment Pharmacology: Mapping the structure-activity relationships of hGH to identify domains responsible for specific biological activities. AOD-9604 serves as a tool to study the C-terminal lipolytic domain in isolation.
• Comparative Studies with Full-Length hGH: Comparing the metabolic, anabolic, and endocrine effects of AOD-9604 versus full-length hGH to understand which effects are mediated through distinct domains of the growth hormone molecule.
• Energy Homeostasis Research: Investigating the effects of enhanced fatty acid mobilization and oxidation on whole-body energy expenditure, thermogenesis, and metabolic rate.
• Fatty Liver and Lipid Accumulation Studies: Examining the effects of AOD-9604 on hepatic steatosis, intrahepatic lipid content, and liver function in models of non-alcoholic fatty liver disease (NAFLD).
• Brown Adipose Tissue Activation: Studying the effects of AOD-9604 on brown adipose tissue (BAT) activity, including thermogenesis, uncoupling protein-1 (UCP-1) expression, and energy dissipation.
• Skeletal Muscle Lipid Metabolism: Investigating the effects of AOD-9604 on intramyocellular lipid content, fatty acid oxidation, and insulin sensitivity in skeletal muscle.
• β-Oxidation Pathway Research: Studying the regulation of carnitine palmitoyltransferase-1 (CPT-1), acyl-CoA dehydrogenase, and other enzymes involved in mitochondrial fatty acid oxidation.

Clinical Development Background

AOD-9604 has undergone extensive preclinical and clinical development. Phase I and II clinical trials involving over 600 subjects demonstrated that AOD-9604 is well-tolerated and produces measurable effects on fat metabolism without the adverse effects associated with full-length hGH, including insulin resistance, carpal tunnel syndrome, and arthralgia. Importantly, studies confirmed that AOD-9604 does not stimulate IGF-1 production or affect blood glucose levels, validating its selective activity profile. This clinical background provides confidence in the peptide's pharmacological characterization and supports its use as a reference tool in metabolic research.

Structural Characteristics

AOD-9604 is a 15-amino acid peptide with several key structural features:

• C-Terminal Fragment of hGH: Corresponds to hGH residues 177-191, which contains the lipolytic domain of the full-length hormone.
• Modified Sequence: The peptide incorporates specific modifications to enhance stability and biological activity compared to the native hGH fragment.
• Cyclized Structure: Contains a disulfide bridge between two cysteine residues (Cys-6 and Cys-14), which stabilizes the peptide's conformation and enhances receptor interaction.
• Small Molecular Size: The 15-amino acid length (1715.9 Da) allows for efficient tissue penetration and rapid distribution.
• Sequence: H-Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe-NH2

Chemical Information

CAS Number: 221231-10-3
Research Codes: AOD-9604, Advanced Obesity Drug-9604, hGH Fragment 177-191, AOD9604
Molecular Formula: C78H123N23O23
Molecular Weight: 1715.9 g/mol
Sequence: H-Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe-NH2
Disulfide Bridge: Cys6-Cys14 (cyclic structure)
Number of Amino Acids: 15
Source: Synthetic (human growth hormone fragment derivative)
Purity: >99% (HPLC)
Form: Lyophilized powder
Storage: -20°C (lyophilized), 4°C (reconstituted)
Stability: Stable at -20°C for 24 months; reconstituted solution stable at 4°C for 30 days

Reconstitution and Handling Protocols

For optimal stability and research validity, AOD-9604 should be reconstituted with sterile bacteriostatic water or sterile saline (0.9% NaCl). The peptide is highly soluble in aqueous solutions. Allow the lyophilized powder to dissolve completely without vigorous shaking to maintain peptide integrity, particularly the disulfide bridge. Gently swirl the vial until the solution is clear and free of particulates. Once reconstituted, the solution should be stored at 4°C and used within 30 days. Avoid repeated freeze-thaw cycles to preserve peptide structure and biological activity. For long-term storage, keep the lyophilized powder at -20°C away from light and moisture. Do not vortex or vigorously shake the reconstituted solution, as this may reduce the integrity of the disulfide bridge and cause aggregation.

Quality Assurance

PeptideVanta's AOD-9604 undergoes rigorous quality control including HPLC purity analysis (>99%), ESI-mass spectrometry for molecular weight confirmation (expected 1715.9 Da), disulfide bridge verification, endotoxin testing (<1.0 EU/mg), sterility testing, and residual solvent analysis. Each batch is accompanied by a Certificate of Analysis (COA) with complete testing results. The peptide is synthesized using solid-phase peptide synthesis (SPPS) with Fmoc chemistry, followed by HPLC purification and lyophilization under sterile conditions.