AOD-9604

AOD-9604 (Anti-Obesity Drug 9604) is a synthetic peptide fragment derived from the C-terminal region of human growth hormone — specifically amino acids 176–191 of the hGH sequence. This specific fragment was identified through research into the lipolytic (fat-burning) properties of growth hormone and was shown to reproduce GH's fat-metabolizing effects while being entirely separated from GH's other activities, including its insulin-like and IGF-1-raising effects.

The functional isolation of AOD-9604 from the rest of the GH molecule is its defining advantage. Full growth hormone stimulates fat breakdown, but it also raises blood glucose, elevates IGF-1 (which has its own complex biological effects), promotes muscle and tissue growth, and activates a range of anabolic pathways. AOD-9604 delivers the fat-metabolizing signal specifically — stimulating lipolysis and inhibiting lipogenesis (fat storage) through beta-3 adrenergic receptor activation and direct effects on adipocytes — without meaningful impact on glucose metabolism, IGF-1 levels, or insulin sensitivity.

AOD-9604 received FDA GRAS (Generally Recognized as Safe) designation based on its clinical safety data — a regulatory status indicating that the available evidence supports a conclusion of safety. Multiple Phase I through Phase IIb clinical trials were conducted by Metabolic Pharmaceuticals as part of an obesity drug development program in the early 2000s, with the compound showing acceptable safety profiles across all trials. The program ultimately did not advance to Phase III due to commercial rather than safety considerations, leaving AOD-9604 with an unusually robust human safety dataset for a research peptide.

The mechanism of fat-selective activity involves AOD-9604's interaction with beta-3 adrenergic receptors in adipose tissue, which triggers cAMP-mediated activation of hormone-sensitive lipase (HSL) — the enzyme that breaks down stored triglycerides in fat cells. This mimics the effect of natural catecholamine-driven lipolysis but with selective targeting via the GH receptor fragment's specific binding properties. The result is accelerated fat cell breakdown without the systemic metabolic disruption associated with stimulant-based fat-burning approaches.