Is fragment 176-191 FDA-approved, and what does the research show?

What is fragment 176-191?

Fragment 176-191 is a short synthetic peptide, a chain of amino acids, copied from one end of human growth hormone. The hormone is 191 amino acids long ¹. The fragment is its last sixteen, numbered 176 to 191 ¹. Rat experiments in the 1970s and 1990s studied this end of the molecule for the hormone's effects on blood sugar and on body fat ¹, ¹².

AOD9604, the name under which the fragment went into human trials, is a modified form. A 2015 anti-doping paper describes it as amino acids 177 to 191 of growth hormone "with an additional tyrosine residue at the N-terminus," the start of the chain ². It is sixteen amino acids long and is also labeled hGH 176-191 ³. The developer, Metabolic Pharmaceuticals, took it into obesity trials ⁹.

Is fragment 176-191 FDA-approved?

Fragment 176-191 is not FDA-approved: Drugs@FDA lists no approved AOD-9604 or growth hormone fragment product as of November 9, 2026 ⁴. It is a development compound whose obesity program ended in 2007, and no source opened names an approval by any regulator ⁹. The whole hormone, somatropin, has approved products in Drugs@FDA; the fragment has none ⁴.

Compounding is the other route by which an unapproved substance reaches patients, and no source opened shows it open for this one. Section 503A of the Federal Food, Drug, and Cosmetic Act governs pharmacy compounding. A licensed pharmacy may compound from a "bulk drug substance," a raw ingredient, only if it meets one of the law's conditions. One of those conditions is a place on FDA's 503A list. The Act's wording for that condition is bulk drug substances "that appear on a list developed by the Secretary through regulations" ¹³.

AOD-9604 was nominated for that list and sat in Category 2, "Bulk Drug Substances that Raise Significant Safety Risks," until the nominators withdrew it. FDA's September 27, 2024 edition records that AOD-9604 "has been removed from Category 2 because the nominations were withdrawn by the nominators" ⁶. The current edition, updated May 14, 2026, does not name AOD-9604 in any category ⁵. The other list, under section 503B, which covers outsourcing facilities, updated March 21, 2025, does not name it either ⁷.

FDA then asked its Pharmacy Compounding Advisory Committee, the outside experts who advise it on compounding, whether AOD-9604 should go on the 503A list for obesity. At the meeting of December 4, 2024, FDA proposed that AOD-9604 "NOT be included on the 503A Bulks List" ⁸. The committee voted 12 to 0 against listing it ⁸.

No final rule naming AOD-9604 had appeared in the Federal Register when it was searched on November 9, 2026. HHS's October 2026 draft, interim enforcement-discretion policy on peptide compounding does not name it ¹⁴. No source opened for this page names a lawful route for compounding fragment 176-191 in the United States.

One FDA warning letter names a compounded AOD-9604 product. Dated January 26, 2022, it went to Innoveix Pharmaceuticals of Addison, Texas, after an inspection found "serious deficiencies in your practices for producing sterile drug products" ¹⁰. The letter records that the firm "voluntarily recalled" a compounded AOD-9604 "for subcutaneous or intramuscular injection due to a lack of sterility assurance" ¹⁰.

FDA's GRAS Notice Inventory is its public record of "generally recognized as safe" food-ingredient notices. Searched on November 9, 2026 for AOD9604, 9604 and growth hormone, it returned no record. A GRAS notice, had one existed, would record a food status, not a drug approval.

See the FDA status of every peptide, updated weekly.

How does fragment 176-191 work?

The mechanism rests on animal and cell work. In rats, the 177-191 piece blocked fat formation, an antilipogenic effect, as well as the whole hormone did ¹². It showed no fat-breaking, or lipolytic, effect in rat fat pads ¹².

The modified form, AOD9604, behaved differently. In obese Zucker rats, a strain bred to be obese, 19 days of AOD9604 by mouth cut body-weight gain by more than half against controls ¹⁵. The animals' fat tissue showed more lipolytic activity ¹⁵. In obese mice, 14 days of AOD9604 reduced weight gain and raised fat oxidation ¹⁶. Unlike the whole hormone, it did not raise blood glucose or cut insulin secretion ¹⁶.

The same mouse study showed in cells that AOD9604 does not bind the growth hormone receptor and does not drive cell proliferation ¹⁶. The authors propose that it acts by a pathway other than the hormone's receptor ¹⁶. Whether that pathway works in people has not been shown in any source opened.

What does the research show?

In animals, AOD9604 reduced weight gain and increased fat breakdown in obese rats in 2000 ¹⁵ and obese mice in 2001 ¹⁶. The 1993 rat study found the 177-191 piece blocked fat formation without breaking fat down ¹². A 2015 study gave 32 rabbits knee osteoarthritis with an enzyme, then weekly injections into the joint ¹⁷. Rabbits given AOD9604, with or without hyaluronic acid, showed less cartilage damage than rabbits given saline ¹⁷. That is the only joint evidence found, and it is in rabbits.

In people, AOD9604 was tested in six randomized placebo-controlled trials, five in obese adults, reported in a paper two of whose three authors list the developer as their affiliation ¹¹. A 2013 review of obesity drugs reports a 12-week randomized trial of AOD9604 taken by mouth once a day ⁹, ³. Participants on one daily dose lost an average of 2.6 kg against 0.8 kg on placebo ⁹. The six-trial paper describes one 12-week trial, which randomized 300 "healthy obese males and females" with a body mass index, a weight-for-height measure, of 35 or more ¹¹.

The same review reports a 24-week trial in which the drug "failed to induce significant weight loss," after which the developer ended the program in 2007 ⁹. That trial randomized 502 participants ³.

A 2026 narrative review of growth-hormone-axis peptides places AOD9604 in its evidence tier "B/C," meaning "small short-term human trials with limited body-composition signals; predominantly preclinical mechanistic data" ³. The review adds that the trials found no meaningful rise in IGF-1, the growth factor that growth hormone normally raises ³.

No human study of fragment 176-191 or AOD9604 for joints, injury or anything other than obesity was found in PubMed on November 9, 2026. ClinicalTrials.gov held no record under either name on that date. No published human study of the unmodified 176-191 sequence was found.

What are the side effects?

FDA's words are the fullest safety statement. On its page of bulk substances that may present significant safety risks, FDA lists AOD-9604 among substances "nominated but withdrawn" and writes: "Compounded drugs containing AOD-9604 may pose significant risk for immunogenicity for certain routes of administration and may have complexities with regard to peptide-related impurities and API characterization. FDA has identified no, or only limited, safety-related information. Therefore, the agency lacks sufficient information to know whether the drug would cause harm when administered to humans. FDA has also identified serious adverse events that may be associated with AOD-9604, though causality is not clear" ¹⁸.

Immunogenicity means the body may mount an immune reaction against the peptide. API is the active pharmaceutical ingredient. FDA does not say what the serious adverse events were ¹⁸.

In the human obesity trials, as the 2026 review summarizes them, AOD9604 was "generally well tolerated" ³. The review summarizes oral trials and a single-dose intravenous infusion study ³. Across them, reported effects were mild and transient headache, fatigue and injection reactions, with no significant change in glucose tolerance or IGF-1 ³. The review adds that no long-term safety data exist ³.

In rats, the unmodified 176-191 and 177-191 fragments produced "a short-lived rise in blood glucose and a more sustained rise in plasma insulin" in a 1978 study ¹. AOD9604 did not raise blood glucose in mice ¹⁶ or impair insulin sensitivity in obese rats ¹⁵. The compounded product FDA named in 2022 was recalled for lack of sterility assurance; the same letter records "serious deficiencies in your practices for producing sterile drug products" ¹⁰.

In sport

WADA, the World Anti-Doping Agency, names the fragment twice on its 2026 Prohibited List. Section S2.2.3 prohibits "Growth hormone (GH), its analogues and fragments including, but not limited to: ... growth hormone fragments, e.g. AOD-9604 and hGH 176-191" ¹⁹. Class S2, peptide hormones, growth factors, related substances and mimetics, is prohibited at all times, in and out of competition ¹⁹. A 2015 anti-doping paper notes that AOD9604 "was recently identified in confiscated vials in the USA" and describes a urine test for it ².

What JumpstartMD offers

JumpstartMD does not prescribe fragment 176-191. Our peptide library covers it so you have the facts on its FDA status and the evidence, current as of November 10, 2026.

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Compounded medications are not FDA-approved, and FDA does not review their safety, effectiveness, or quality before they are marketed. A licensed clinician decides after an evaluation whether a peptide is appropriate for you, and not every patient will qualify.