AOD-9604
Growth-hormone C-terminal fragment analog studied for fat metabolism; its largest obesity trial failed to beat placebo.
Reviewed by Mei Li, PhD, Chief Science Officer
Overview
AOD-9604 is a synthetic 16-amino-acid peptide (a hexadecapeptide) modeled on the C-terminal region of human growth hormone. Its structure corresponds to hGH residues 177–191 with a tyrosine added at the N-terminus; it is often loosely marketed as the "hGH fragment 176–191," though that name more precisely describes the parent fragment. It was developed by Metabolic Pharmaceuticals under the name "Anti-Obesity Drug 9604" on the hypothesis that this hGH region could reproduce growth hormone's fat-metabolizing activity without its effects on blood glucose or IGF-1. Preclinical work in rodent models reported reduced adiposity, and early small human studies suggested modest metabolic signals. However, the published record is best characterized by a notable negative result: the compound's largest randomized, placebo-controlled obesity trial did not produce statistically significant weight loss versus placebo, and the drug-development program was discontinued around 2007. The molecule was later pursued as a food/dietary-supplement ingredient (for which it obtained a "generally recognized as safe" self-determination in the U.S. around 2014) and appeared in preclinical cartilage and joint-tissue investigations. No regulatory body has approved AOD-9604 as a weight-loss medication, and it is not on the FDA Pharmacy Compounding Advisory Committee's July 2026 bulks docket. On PepSense it is presented strictly as a research compound: the literature examines its metabolic and musculoskeletal biology, not any endorsed human application. Readers should weigh the failed pivotal obesity endpoint heavily when interpreting claims about this peptide.
Mechanism of action
Published mechanistic work proposes that AOD-9604 mimics the lipolytic (fat-mobilizing) region of human growth hormone. In preclinical models it has been reported to stimulate lipolysis and inhibit lipogenesis in adipocytes, with investigators pointing to modulation of beta-3-adrenergic receptor signaling and downstream effects on fat-cell metabolism as candidate pathways. A recurring and better-supported observation is what the peptide does not do: unlike full-length hGH, AOD-9604 does not appear to act through the growth hormone receptor, does not raise serum IGF-1, and has not shown the adverse effects on glucose tolerance or carbohydrate metabolism associated with growth hormone. This IGF-1-independent profile was central to the original therapeutic rationale. It is important to note that the precise molecular target remains undefined in the literature, and the mechanistic hypotheses derive largely from in-vitro and animal data rather than confirmed human physiology.
What published research has examined
The dominant research theme is metabolic: AOD-9604 was investigated across multiple human trials as an oral anti-obesity candidate. Early-phase studies reported a favorable tolerability profile and some suggestion of fat reduction, but the pivotal, larger and longer randomized trial did not demonstrate significant weight loss over placebo, which ended its development as a weight-loss drug around 2007. A second, smaller literature examines musculoskeletal applications: preclinical (in-vitro and animal) studies have explored AOD-9604 in the context of chondrocyte activity and cartilage-tissue biology — for example, intra-articular injection in a collagenase-induced rabbit osteoarthritis model, alone or combined with hyaluronic acid — as hypothesis-generating work on joint and connective-tissue repair. There is no published human clinical trial establishing efficacy for osteoarthritis, cartilage repair, or any orthopedic indication. The compound has also been discussed as a food-ingredient candidate. Overall, human evidence is confined to the obesity program, and the joint/cartilage narrative rests on preclinical data only.
Safety considerations in the literature
Across its clinical program of several randomized, double-blind, placebo-controlled studies involving roughly 900 participants, the published literature described AOD-9604 as well tolerated, with an adverse-event profile that investigators characterized as largely indistinguishable from placebo and no drug-related serious adverse events or drug-related withdrawals reported in those trials. Studies also reported no elevation of serum IGF-1, no negative effect on glucose tolerance, and no detectable anti-drug antibody formation — findings the authors used to argue it avoided key growth-hormone-associated risks. These observations, however, come from short-to-medium-duration trials of a compound that failed its efficacy endpoint and was never approved; long-term safety, the safety of unregulated research-grade material, and safety outside monitored trial settings are not established in the literature. Any characterization here describes what studies observed, not an assurance about human use.
Key published studies
| Study | Journal | Year | Finding |
|---|---|---|---|
| Safety and Tolerability of the Hexadecapeptide AOD9604 in Humans | Journal of Endocrinology and Metabolism (Stier, Vos, Kenley) | 2013 | Pooled review of six randomized, placebo-controlled human trials (~900 subjects); reported tolerability indistinguishable from placebo with no IGF-1 rise, no glucose impairment, and no anti-drug antibodies — human clinical safety evidence. |
| Effect of Intra-articular Injection of AOD9604 with or without Hyaluronic Acid in Rabbit Osteoarthritis Model | Annals of Clinical and Laboratory Science (Kwon et al.) | 2015 | Preclinical (animal) study in a collagenase-induced rabbit knee osteoarthritis model; reported enhanced cartilage regeneration, with AOD9604 plus hyaluronic acid more effective than either alone — hypothesis-generating musculoskeletal evidence only, no human data. |
| Randomized, double-blind, placebo-controlled, multicenter obesity trials of AOD9604 (Metabolic Pharmaceuticals phase II program) | Metabolic Pharmaceuticals clinical program (as summarized in the peer-reviewed literature) | 2007 | The larger/longer pivotal analysis did not show statistically significant weight loss over placebo, leading to program discontinuation — key negative human efficacy evidence. |
Regulatory status
Current status: Unscheduled / RUO. Unscheduled / RUO. PepSense tracks FDA filings and updates this record as the regulatory picture changes. See the FDA PCAC tracker for the July 2026 vote and what happens next.