# What Is AOD-9604? The hGH Fragment 176-191 Peptide, Explained

> What is AOD-9604? A 16-amino-acid fragment of growth hormone built to burn fat. Antilipogenic in animals, receptor-sparing, investigational, and null in its human obesity trial. Plainly explained.

The plain answer: what it is, what it was for, what the studies found, and what to watch out for.

## The short answer

What is AOD-9604? It is a small lab-made peptide — sixteen amino acids — copied from the tail end of human growth hormone (the [hGH fragment 176-191](/hgh-fragment-176-191)). It was built to be a fat-loss drug. The idea: copy the part of growth hormone that handles fat, leave out the part that drives growth.

In fat cells it slows the building of new fat (this is called being antilipogenic) and, in animals, helps cells burn a bit more fat. It does this without acting like growth hormone: it does not switch on the growth hormone receptor and does not raise IGF-1, a growth signal — so it skips growth-hormone-style side effects. The catch is the human evidence. The main obesity trial showed no real weight loss versus a dummy pill, and the program was dropped. It is investigational, not FDA-approved, not a supplement, and banned in sport. Most of the good data is still in animals.

## AOD9604 peptide: the basics

The AOD9604 peptide is a hexadecapeptide — sixteen amino acids — modelled on human growth hormone residues 177-191 with a tyrosine added at the front, plus a disulfide bridge between two cysteines [3]. Its name is short for "Anti-Obesity Drug 9604," which tells you what it was made to do. You will also see it written AOD-9604, AOD 9604, hGH fragment 176-191, HGH frag 176-191, or Tyr-hGH(177-191) — all the same molecule.

Reported sequence: Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe. Molecular formula C78H123N23O23S2; molecular weight about 1815.1 Da; CAS 221231-10-3. It is not growth hormone and not a growth-hormone secretagogue: unlike CJC-1295, ipamorelin, or sermorelin, it does not tell the body to make more growth hormone — it acts downstream in the fat cell.

## What it was built to do, and what happened

AOD-9604 was developed by Metabolic Pharmaceuticals (Australia) as an oral anti-obesity drug, growing out of Monash University work on growth hormone's fat-metabolising C-terminal domain [9]. In obese mice, chronic dosing reduced body weight and fat and raised the beta-3 adrenergic receptor (a fat-cell switch for burning fat); the long-term effect depended on that receptor [4].

The human program is the honest centre of the story. Across roughly six trials totalling about 900 obese adults, oral AOD-9604 was as safe and tolerable as placebo [5]. But the pivotal Phase IIb obesity trial did not show statistically significant weight loss versus placebo, the program was discontinued around 2007, and the compound was never approved for any indication [9]. The mechanism is real in animals; the weight-loss promise did not hold in people.

## What to watch out for

AOD-9604 is investigational and not FDA-approved, so it has no approved dose or quality standard [9]. Its fat-loss claim is not supported by the human trials [10]. Most of its mechanism is preclinical — mouse, rat, and cell data that has not been confirmed in people [7]. There is no long-term human safety record beyond about 24 weeks. And it is prohibited in sport: as a growth-hormone fragment it falls under WADA Section S2 and is banned at all times [6]. The fuller, plain-English account of reported effects and cited cautions is on [the effects page](/effects).

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A brushed-steel worksheet on the AOD-9604 record — the antilipogenic fragment logged first, the receptor-sparing design stated as the design it is, and the failed human weight-loss trial left in plain steel; no clinic behind the console and nothing here dosed, compounded, prescribed, or sold.