Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone
Ng FM, Sun J, Sharma L, Libinaki R, Jiang WJ, Gianello R
Hormone Research (2000)
Nineteen days of oral 500 µg/kg/day AOD-9604 in obese Zucker rats reduced body-weight gain by more than half versus control (15.8 vs. 35.6 g), increased ex vivo adipose lipolytic activity, and produced no detectable insulin-sensitivity decrement under euglycemic clamp — the foundational preclinical paper for the molecule.
This is the foundational preclinical paper for AOD-9604, published in Hormone Research in 2000 by Frank Ng's group at Monash University. The paper introduces the synthetic hexadecapeptide derived from the C-terminal lipolytic domain of human growth hormone (hGH residues 177–191, with an N-terminal tyrosine appended for disulfide-constrained cyclization) and tests it in the obese Zucker rat, the standard rodent model for genetic obesity available to the program at the time.
The methodology is direct. Obese Zucker rats received AOD-9604 by oral gavage at 500 µg/kg/day for 19 consecutive days, with a parallel placebo arm. The headline finding is the body-weight effect: animals on AOD-9604 gained 15.8 ± 0.6 g over the dosing window versus 35.6 ± 0.8 g in controls — a more than 50% reduction in weight gain on the active compound. Ex vivo adipose tissue dissected from treated animals exhibited increased lipolytic activity relative to control adipose, consistent with the proposed mechanism that the C-terminal hGH fragment retains the lipolytic activity attributed to the parent hormone. Critically, the authors used the euglycemic clamp technique to measure insulin sensitivity in treated animals and reported no detectable decrement relative to control — the experimental separation designed to distinguish AOD-9604 from full-length hGH, which is known to induce insulin resistance and impair glucose tolerance. The paper concludes that the lipolytic domain analogue retains the fat-mobilizing activity of hGH while shedding the diabetogenic and IGF-1-elevating effects that have prevented broader therapeutic use of growth hormone itself.
This is one of the two papers (alongside Heffernan et al. 2001) on which the mechanistic case for AOD-9604 was built and on which the subsequent Metabolic Pharmaceuticals Phase I and Phase II human program was justified. The integrated safety summary in Stier et al. 2013 cites it as the originating preclinical paper.
This is a single-laboratory study in a single rodent strain. The obese Zucker rat is a genetic-leptin-receptor-mutant model whose lipid biology does not map cleanly onto polygenic human obesity, and the 19-day dosing window is short relative to any clinically meaningful weight-loss trial. The lipolysis assays are ex vivo on dissected adipose, not in vivo metabolic flux measurements, and the dose tested (500 µg/kg/day) is well above the per-kilogram exposure that the subsequent human program found ineffective at the primary efficacy endpoint. The euglycemic clamp data demonstrate the absence of an insulin-sensitivity decrement at the 19-day timepoint but cannot speak to chronic exposure. The most important caveat is replication: all of the foundational AOD-9604 preclinical pharmacology was published from the Monash group under common authorship between 1996 and 2001, and the lipolytic-domain story has not been independently reproduced at scale by an unaffiliated laboratory. The rodent-positive efficacy signal described here did not translate to the placebo-controlled 24-week Phase IIb obesity trial that ended the development program in 2007 — a translation failure the /peptides/aod-9604 page treats as the load-bearing fact of the molecule's clinical history.
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