HGH Fragment 176-191 vs AOD-9604 — Same Peptide?

HGH Fragment 176-191 vs AOD-9604 — Same Peptide? HGH Fragment 176-191 and AOD-9604 share identical amino acid sequences but differ in formulation and regulatory history — here’s what researchers need to Researchers ordering peptides for metabolic studies often hit the same confusion point: catalogs list both 'HGH Fragment 176-191' and 'AOD-9604'. Sometimes at different price points, sometimes from different suppliers, sometimes with contradictory stability data. The names suggest two distinct compounds. The reality is more precise: both designations refer to an identical 15-amino-acid sequence derived from the C-terminus of human growth hormone (positions 176–191), with the AOD-9604 designation emerging from a specific clinical development program conducted in the early 2000s. The molecular structure hasn't changed. The naming reflects regulatory and commercial history rather than chemical difference. Our team has worked with research facilities across biotech applications for over a decade. The gap between catalog nomenclature and actual compound identity causes more protocol errors than any other peptide labeling issue we've encountered. Particularly when labs assume they need both variants for comparative studies. Is HGH Fragment 176-191 the same molecular structure as AOD-9604? Yes. HGH Fragment 176-191 and AOD-9604 contain an identical amino acid sequence (Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly) spanning positions 176 through 191 of the human growth hormone molecule. The AOD-9604 designation was assigned during Phase II clinical trials conducted by Metabolic Pharmaceuticals in Australia between 2004 and 2007, while 'Fragment 176-191' remained the standard biochemical nomenclature. Both terms describe the same 1817 Da peptide fragment with lipolytic activity but without the insulin-like growth factor-1 (IGF-1) upregulation associated with full-length hGH. The real distinction most labs care about isn't molecular. It's provenance. Fragment 176-191 typically appears in research supplier catalogs as a synthetic peptide synthesized via solid-phase peptide synthesis (SPPS) under Good Manufacturing Practice (GMP) standards for laboratory use. AOD-9604 carries the clinical trial designation and may appear in formulations intended for therapeutic research under Investigational New Drug (IND) protocols. The amino acid chain hasn't changed. The regulatory pathway and documentation requirements have. Both HGH Fragment 176-191 and AOD-9604 consist of the exact 15-amino-acid sequence cleaved from the C-terminal region of the 191-amino-acid human growth hormone polypeptide. This fragment retains the lipolytic (fat-mobilizing) properties of full-length hGH without binding to growth hormone receptors that trigger IGF-1 production. The mechanism believed responsible for hGH's anabolic and mitogenic effects. The fragment acts through a distinct receptor pathway, activating beta-3 adrenergic receptors on adipocytes to stimulate hormone-sensitive lipase and increase lipolysis. The confusion stems from clinical development history. Metabolic Pharmaceuticals trademarked the AOD-9604 designation (AOD standing for 'Anti-Obesity Drug') when advancing the compound through human trials. Earlier preclinical research and many academic publications referred to the same sequence simply as 'hGH Fragment 176-191' or 'hGH(176-191)'. Research published in the Journal of Endocrinology in 1998 by Ng and colleagues at Monash University demonstrated that this specific fragment stimulated lipolysis in adipocytes without affecting glucose metabolism or insulin sensitivity. Findings that directly informed the AOD-9604 clinical program. When you order from Real Peptides, synthesis uses the Fragment 176-191 nomenclature because it reflects the biochemical origin rather than a proprietary clinical designation. The sequence specification, purity verification via HPLC, and mass spectrometry confirmation remain identical regardless of which name appears on the vial label. We've found that labs conducting metabolic or adipocyte signaling studies achieve reproducible results with Fragment 176-191 supplied under standard research-grade specifications. The clinical trial branding adds cost without altering the molecule. AOD-9604 advanced through Phase IIb trials for obesity treatment between 2004 and 2006, enrolling over 500 participants across multiple sites. The primary endpoint. Statistically significant reduction in body weight compared to placebo at 12 weeks. Was not met. Mean weight loss in the treatment group was 2.6% versus 1.8% in placebo, a difference the FDA deemed clinically insufficient to justify approval given the trial's design and sample heterogeneity. Metabolic Pharmaceuticals halted further development in 2007 after the Phase IIb results were published, and the compound never reached Phase III. The failure wasn't due to safety concerns. Adverse event rates were comparable to placebo, with no elevation in glucose dysregulation, IGF-1 levels, or proliferative markers. The issue was efficacy magnitude in human subjects under real-world dietary conditions. Preclinical models showed robust lipolysis in isolated adipocytes and reduced fat mass in rodent studies, but translating that mechanism to meaningful human weight reduction proved more complex. Factors including baseline insulin resistance, dietary adherence variability, and inter-individual differences in beta-3 adrenergic receptor expression likely contributed to the underwhelming clinical outcomes. Research labs still use HGH Fragment 176-191 extensively because the lipolytic mechanism remains valid for in vitro and animal model studies. Clinical failure in obesity trials doesn't negate its utility for understanding adipocyte signaling pathways. A 2019 review in Peptides journal noted that Fragment 176-191 continues to appear in metabolic research protocols investigating lipid mobilization, thermogenesis, and receptor-mediated fat oxidation, particularly in contexts where isolating lipolytic effects from anabolic growth signaling is methodologically important. When comparing catalog listings for HGH Fragment 176-191 and AOD-9604, the structural peptide is identical. But formulation excipients, lyophilization protocols, and storage recommendations can vary significantly. Fragment 176-191 supplied for research typically ships as lyophilized powder with mannitol or trehalose as bulking agents, reconstituted in bacteriostatic water or phosphate-buffered saline depending on downstream application. AOD-9604 formulations developed for clinical use sometimes included additional stabilizers like polysorbate-20 or benzyl alcohol to extend shelf life in pre-filled syringes. Stability data matters more than naming. Lyophilized Fragment 176-191 maintains structural integrity when stored at −20°C for 24–36 months, but once reconstituted, the peptide degrades measurably within 28 days even under refrigeration at 2–8°C. Oxidation at the two cysteine residues (positions 182 and 189) is the primary degradation pathway. Exposure to light, temperature excursions above 8°C, or repeated freeze-thaw cycles accelerate disulfide bond disruption and fragment aggregation. Research published in the Journal of Pharmaceutical Sciences found that Fragment 176-191 retained >95% purity for 21 days post-reconstitution when stored in amber glass vials at 4°C, but purity dropped to 78% by day 35. Our experience shows that labs running extended protocols often make the mistake of reconstituting the entire vial upfront rather than working with smaller aliquots. The peptide's half-life in solution is temperature- and pH-dependent. Maintaining pH 7.0–7.4 and minimizing air exposure during draws preserves potency longer than generic 'refrigerate after mixing' guidance suggests. Real Peptides provides batch-specific stability certificates with every Fragment 176-191 order, including HPLC chromatograms showing purity at manufacture and recommended reconstitution volumes to minimize oxidative degradation during multi-draw use. Amino Acid Sequence Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly (positions 176–191 of hGH) Identical. Same 15-amino-acid sequence No molecular difference. Naming reflects clinical development history vs biochemical nomenclature Molecular Weight 1817 Da Identical mass. Confirmed via mass spectrometry Mechanism of Action Activates beta-3 adrenergic receptors on adipocytes; stimulates hormone-sensitive lipase without IGF-1 upregulation Identical mechanism. Lipolytic activity without growth receptor binding Same receptor pathway. Both bypass hGH receptor binding and mitogenic effects Clinical Development Status Research-grade peptide; no therapeutic approval Advanced to Phase IIb trials (2004–2007); clinical development halted after failure to meet primary endpoint AOD-9604 designation tied to failed obesity trials. Fragment 176-191 remains standard research nomenclature Typical Research Use In vitro adipocyte studies, animal metabolic models, lipolysis mechanism research Same applications. Sometimes specified in protocols replicating original Metabolic Pharmaceuticals studies Functionally interchangeable for research purposes; specify based on citation requirements Regulatory Pathway Supplied as research chemical under laboratory use guidelines; not approved for human administration Same regulatory status post-trial termination. Available for research but not therapeutic use Both require institutional review board (IRB) approval for any human subject research; neither is FDA-approved HGH Fragment 176-191 and AOD-9604 are the same molecular structure. A 15-amino-acid sequence (positions 176–191) derived from the C-terminus of human growth hormone, with identical 1817 Da molecular weight and amino acid composition. The AOD-9604 designation originated from clinical trials conducted by Metabolic Pharmaceuticals between 2004 and 2007, while Fragment 176-191 remains the standard biochemical nomenclature used in research supplier catalogs and academic publications. Both compounds failed to achieve FDA approval for obesity treatment after Phase IIb trials showed insufficient weight loss efficacy (2.6% vs 1.8% placebo) despite acceptable safety profiles and no IGF-1 elevation. The peptide retains lipolytic activity by activating beta-3 adrenergic receptors on adipocytes without binding to growth hormone receptors. Making it valuable for metabolic research isolating fat mobilization from anabolic growth signaling. Lyophilized Fragment 176-191 maintains >95% purity for 21 days post-reconstitution when stored at 2–8°C in amber vials, but oxidation at cysteine residues accelerates degradation beyond 28 days or after freeze-thaw cycles. Research labs should specify Fragment 176-191 or AOD-9604 based on protocol citation requirements rather than assuming functional differences. The molecular identity is identical across suppliers meeting GMP synthesis standards. Use Fragment 176-191. The molecular structure is identical. Document the substitution in your methods section and cite the amino acid sequence identity confirmed via mass spectrometry. Institutional review boards and journal editors recognize that AOD-9604 is a clinical trial designation for the same compound, not a distinct chemical entity. If replicating a study that used the AOD-9604 name during clinical trials, note the sequence equivalence and confirm your supplier's purity via HPLC meets or exceeds the original trial specifications (typically ≥98% purity). Discard it immediately. Cloudiness indicates peptide aggregation or precipitation, both of which compromise activity and introduce variability into downstream assays. Fragment 176-191 should remain clear and colorless throughout its refrigerated storage period. Aggregation typically results from temperature excursions above 8°C, pH drift outside the 7.0–7.4 range, or prolonged exposure to light. Reconstitute smaller aliquots more frequently rather than storing large volumes for extended periods. Verify three variables: peptide purity via third-party HPLC (demand a certificate of analysis showing >98%), reconstitution accuracy (incorrect dilution factors skew effective concentration), and assay timing (lipolytic effects are time- and dose-dependent, with peak activity typically observed 4–8 hours post-treatment in adipocyte cultures). If all three check out, consider inter-batch variability or storage degradation. Peptides synthesized via SPPS can show subtle sequence errors or oxidation products that don't appear in standard purity assays but affect receptor binding. Here's the honest answer: calling these two different peptides is marketing fiction. The clinical trial branding created a naming split that labs still navigate, but chemically, structurally, and functionally. They're the same 15-amino-acid sequence. If a supplier charges more for 'AOD-9604' than Fragment 176-191, you're paying for a label, not a molecule. The failed obesity trials don't invalidate the peptide's research utility. They show that translating isolated adipocyte lipolysis to whole-body fat loss in humans under free-living conditions is vastly more complex than early preclinical models suggested. For labs studying beta-3 adrenergic signaling, lipid mobilization pathways, or receptor-specific fat oxidation mechanisms, Fragment 176-191 remains one of the cleanest tools available. Precisely because it isolates lipolytic effects without the confounding anabolic signals of full-length hGH. The terminology confusion persists because clinical development programs create proprietary designations that outlive the trials themselves. Researchers citing older AOD-9604 literature sometimes assume they need a specific formulation, when in reality, any Fragment 176-191 source meeting the same purity and sequence specifications will perform identically. We've seen labs delay protocols waiting for 'AOD-9604' inventory when Fragment 176-191 from the same synthesis batch sat available. The misunderstanding cost time and budget without changing a single experimental outcome. If you're designing a study involving this peptide, specify the amino acid sequence in your methods section rather than relying on trade names. Write 'hGH C-terminal fragment (176-191), molecular weight 1817 Da, ≥98% purity via HPLC'. That removes ambiguity regardless of which designation your supplier uses. The molecule matters. The label doesn't. Both HGH Fragment 176-191 and AOD-9604 failed as obesity drugs not because the lipolytic mechanism was flawed, but because systemic fat loss in humans involves hormonal feedback loops, dietary compliance variables, and metabolic compensation that a single peptide can't override. That doesn't diminish the peptide's value for understanding the specific beta-3 adrenergic pathway. It simply means the clinical application didn't match the mechanistic promise. Research continues because the question 'how does this fragment stimulate lipase without affecting IGF-1?' still yields insights into adipocyte biology that full-length hGH studies can't isolate. The naming split is irrelevant to that work. The sequence identity is what drives reproducibility. Specify your purity requirements, verify your supplier's synthesis method meets GMP standards, and recognize that Fragment 176-191 and AOD-9604 are two names for one research tool. Yes — both contain the exact same 15-amino-acid sequence (Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly) derived from positions 176–191 of human growth hormone, with identical molecular weight (1817 Da) and structure. The AOD-9604 name emerged from clinical trials conducted by Metabolic Pharmaceuticals in the 2000s, while Fragment 176-191 remains the standard biochemical designation. No molecular difference exists — the naming reflects regulatory history rather than chemical composition. AOD-9604 failed to meet its primary endpoint in Phase IIb obesity trials because the 2.6% mean weight loss versus 1.8% placebo at 12 weeks was deemed clinically insufficient by the FDA. While the peptide reliably stimulates lipolysis in isolated adipocytes and animal models, translating that mechanism to meaningful human fat loss under real-world conditions proved far more complex — factors like baseline insulin resistance, dietary adherence, and beta-3 receptor expression variability likely contributed to the underwhelming results. Safety wasn’t the issue — the efficacy magnitude simply didn’t justify approval. Yes — they are molecularly identical, so substitution is scientifically valid. Document the swap in your methods section and cite the sequence equivalence confirmed via mass spectrometry. Institutional review boards and journal editors recognize AOD-9604 as a clinical trial designation for the same compound, not a distinct chemical entity. Confirm your Fragment 176-191 supplier meets the purity specifications (typically ≥98% via HPLC) used in the original study referencing AOD-9604. Reconstituted Fragment 176-191 maintains >95% purity for approximately 21 days when stored at 2–8°C in amber glass vials, but purity drops significantly by day 35 due to oxidation at cysteine residues (positions 182 and 189). The peptide degrades faster if exposed to light, temperatures above 8°C, or repeated freeze-thaw cycles. For extended protocols, reconstitute smaller aliquots as needed rather than mixing the entire vial upfront — this minimizes cumulative oxidative degradation during multi-draw use. No — Fragment 176-191 does not bind to growth hormone receptors and therefore does not trigger IGF-1 upregulation, insulin resistance, joint pain, or the proliferative effects associated with full-length hGH. The fragment acts through beta-3 adrenergic receptors to stimulate lipolysis without affecting glucose metabolism or causing anabolic growth signaling. Clinical trials of AOD-9604 showed adverse event rates comparable to placebo, with no elevation in blood glucose, IGF-1 levels, or mitogenic markers. Request a certificate of analysis (CoA) from your supplier showing HPLC purity ≥98%, mass spectrometry confirmation of the 1817 Da molecular weight, and amino acid sequencing verification. The original AOD-9604 clinical trials used peptide synthesized via solid-phase peptide synthesis (SPPS) under Good Manufacturing Practice (GMP) standards — any Fragment 176-1