AOD-9604 vs tirzepatide: trials, approval and status compared

Not yet medically reviewed. Fact-checked against the sources listed below on October 7, 2026.How we write and review

Last updated October 7, 2026

Tirzepatide is an approved medicine, tested in phase 3 trials of thousands of people, and Mounjaro is registered in the Philippines. AOD-9604, a growth hormone fragment, was tested as an obesity pill, but its largest trial found no significant weight difference from placebo and development stopped in 2007. The US FDA says no approved drug contains it.

Key takeaways

Tirzepatide activates the GIP and GLP-1 hormone receptors. AOD-9604 is a 16 amino acid fragment of human growth hormone that was proposed to increase fat breakdown, based on animal studies.
Tirzepatide is approved in the US (Zepbound, Mounjaro) and the EU (Mounjaro). The US FDA says no approved drug product contains AOD-9604, and a US FDA advisory committee voted 0 to 12 against adding it to the list of substances US pharmacies may use for compounding.
In SURMOUNT-1 (2,539 adults, 72 weeks), mean weight change was -15.0% to -20.9% with tirzepatide versus -3.1% with placebo. In AOD-9604's 24-week phase 2b trial (536 enrolled), the US FDA reports no significant difference from placebo.
Mounjaro and Mounjaro KwikPen are listed as registered prescription drugs in the FDA Philippines Verification Portal (checked October 7, 2026). For AOD-9604, no record was found in a portal search the same day.
WADA prohibits AOD-9604 at all times as a growth hormone fragment. USADA says tirzepatide is in the WADA 2027 Monitoring Program, which means it is not prohibited but labs test for it.

Side by side

	AOD-9604	Tirzepatide
Class	Synthetic 16 amino acid fragment of human growth hormone (the C-terminal region, with an added tyrosine); investigational, not approved as a medicine anywhere	Dual GIP and GLP-1 receptor agonist
FDA Philippines registration	No record found in an FDA Philippines Verification Portal search on October 7, 2026	Registered (Mounjaro, Mounjaro KwikPen)
Evidence	Phase 2 human trials	Approved by at least one medicines regulator (as Mounjaro, Zepbound)
Prescription needed	Not confirmed	Yes
Registration source date	Checked October 7, 2026	Checked October 7, 2026

How they work

Both have been studied for weight, but they work in different ways and reached very different stages of development.

	Tirzepatide	AOD-9604
What it is	Dual GIP and GLP-1 receptor agonist (US Zepbound label)	Synthetic 16 amino acid fragment of human growth hormone (amino acids 177 to 191, with an added tyrosine)
Proposed action	Activates the receptors for the body's own GIP and GLP-1 hormones, which are found in brain areas involved in appetite	Increases fat breakdown and fat oxidation without binding the growth hormone receptor, in animal studies
How it was given in trials	Once-weekly injection under the skin (US labels)	By mouth in the phase 2b trials. Other human studies also gave it into a vein
Brand names	Mounjaro, Zepbound	None. Also called AOD9604, Tyr-hGH 177-191 or hGH 176-191

Tirzepatide. The US Zepbound label says it lowers calorie intake, likely by affecting appetite, and increases insulin sensitivity. The US Mounjaro label says it raises insulin release and lowers glucagon, both in a glucose-dependent manner.

AOD-9604. It was designed to keep growth hormone's fat-breakdown signal while avoiding its growth effects and IGF-1. In obese mice it increased fat breakdown and fat oxidation, and unlike growth hormone it did not cause high blood sugar. In human trials summarised by the developer's authors, it had no effect on serum IGF-1. These mechanisms come from animal studies and company-funded trials.

For more on each, see the tirzepatide page and the what are peptides guide.

Development and approval status

Tirzepatide completed development and is approved in the US and the EU. AOD-9604's development for obesity stopped in 2007, and no approval was found.

Regulator or body	Tirzepatide	AOD-9604
US FDA	Zepbound approved November 8, 2023 for weight management. Mounjaro approved for type 2 diabetes	No FDA-approved drug product contains it. An FDA advisory committee voted 0 yes, 12 no on adding it to the 503A bulks list for pharmacy compounding (December 4, 2024)
European Medicines Agency	Mounjaro first authorised September 15, 2022, now for type 2 diabetes and weight management	The US FDA found no listing for it on the European Medicines Agency website
Australia	Not recorded here	Listed in Schedule 4, prescription only medicines, in the Poisons Standard (June 2026). Whether any product is on the Australian Register of Therapeutic Goods was not checked
FDA Philippines	Mounjaro and Mounjaro KwikPen listed as registered prescription drugs in the Verification Portal (checked October 7, 2026)	No record found in a Verification Portal search on October 7, 2026

Why AOD-9604 stopped. In February 2007, its developer announced that the phase 2b results "do not support the commercial viability of the drug as a treatment for obesity" and ended development for obesity. In 2024 the US FDA concluded there is "a lack of evidence to support the effectiveness" of AOD-9604 for obesity, by any route.

Evidence compared

The amount of evidence behind each is very different. Tirzepatide has several published phase 3 trials with thousands of participants. AOD-9604's phase 2b efficacy results were never published in a peer-reviewed journal. No trial has compared the two directly.

Tirzepatide results are shown by dose group. They are trial groups, not treatment advice.

Trial	Compound	Who took part	Length	Mean weight change	Placebo
SURMOUNT-1 (NEJM 2022), phase 3	Tirzepatide, 5 mg, 10 mg and 15 mg groups	2,539 adults with obesity, or overweight with a weight-related complication, without diabetes	72 weeks	-15.0%, -19.5%, -20.9%	-3.1%
SURMOUNT-2 (Lancet 2023), phase 3	Tirzepatide, 10 mg and 15 mg groups	938 adults with a BMI of 27 or more and type 2 diabetes	72 weeks	-12.8%, -14.7%	-3.2%
SURMOUNT-3 (Nat Med 2023)	Tirzepatide, maximum tolerated dose	579 adults who had already lost 5% or more in a 12-week lifestyle program	72 weeks	-18.4% (from randomization)	+2.5%
OPTIONS (METAOD006), phase 2b	AOD-9604 by mouth, three doses	536 enrolled, 502 randomized, adults with obesity, plus a diet and exercise program	24 weeks	US FDA summary: "not a significant difference in the primary endpoint of weight loss between placebo and AOD-9604"	Not reported in the sources
METAOD005, phase 2b	AOD-9604 by mouth, five doses	300 adults with obesity	12 weeks	A 2005 meeting abstract reported more weight loss than placebo on all doses. The US FDA calls the differences small, with "unclear meaningful therapeutic effects"	Not reported in the sources

Longer follow-up. In SURMOUNT-1 participants with obesity and prediabetes, mean weight change at 176 weeks (about 3 years) was -12.3%, -18.7% and -19.7% in the three tirzepatide groups, versus -1.3% with placebo. Type 2 diabetes was diagnosed in 1.3% on tirzepatide versus 13.3% on placebo. No AOD-9604 trial longer than 24 weeks is recorded.

Who ran the trials. The SURMOUNT trials were published in peer-reviewed journals. The six AOD-9604 trials summarised in 2013 were all funded by its developer, and the 2013 safety summary of six trials was written by authors who worked for or consulted for the developer. That summary does not report efficacy results.

Trials registered today. A ClinicalTrials.gov search on October 7, 2026 found no AOD-9604 studies.

Risks compared

Tirzepatide has a full US label based on large trials. AOD-9604 has no label, and the US FDA says its human safety is largely unknown.

	Tirzepatide	AOD-9604
Most common side effects	Nausea 25% to 29% vs 8% placebo, diarrhea 19% to 23% vs 8%, vomiting 8% to 13% vs 2%, constipation 11% to 17% vs 5% (Zepbound label, weight trials)	Headache, fatigue, dizziness, diarrhoea, flatulence, nausea and increased appetite in early studies, with few details published (US FDA). More stomach and gut effects at the highest oral dose tested
Stopped because of side effects	4.3%, 7.1%, 6.2% of the three dose groups vs 2.6% placebo (SURMOUNT-1)	The 2013 summary reports no withdrawal judged related to AOD9604
Serious warnings	Boxed warning: thyroid C-cell tumors in rats, unknown in humans. Not for people with a personal or family history of medullary thyroid carcinoma or MEN 2. Label also lists pancreatitis, gallbladder disease, acute kidney injury from dehydration and serious allergic reactions	Five participants on AOD9604 in the 12-week trial had cancers or growths reported. The principal investigator judged none related to the drug (2013 summary by authors linked to the developer)
Animal findings	Thyroid C-cell tumors in rats (Zepbound label)	Possible bone effects in rats, possible liver toxicity signals in monkeys, and equivocal mutagenic signals (US FDA, 2024)
Routes studied in people	Injection under the skin	By mouth and into a vein only. No human studies by injection under the skin or through the skin
Regulator view	Approved with label warnings	The US FDA "lacks sufficient information to know whether the drug would cause harm when administered to humans"

Product quality. The US FDA considers AOD-9604 "not physically and chemically well characterized", and the certificate of analysis sent with its nomination did not test for impurities or bacterial endotoxins. A 2026 Sports Medicine review says that for unapproved peptides including AOD-9604, "rigorous human safety data are scarce, and there is potential for serious harm to patients."

Unregistered tirzepatide products. FDA Philippines has warned the public against several unregistered tirzepatide products. It says the public has no assurance of their quality, safety and efficacy. See PH status compared below.

Sport and anti-doping

The two are treated differently on the WADA list.

	Tirzepatide	AOD-9604
WADA status	Not prohibited. USADA says tirzepatide is in the WADA 2027 Monitoring Program, which means labs test for it	Prohibited at all times. Named in class S2.2.3 on the 2026 and 2027 lists: "growth hormone fragments, e.g. AOD-9604 and hGH 176-191"

Athletes should check any substance with their national anti-doping organisation.

PH status compared

Tirzepatide is listed as registered in the FDA Philippines Verification Portal as Mounjaro KwikPen and Mounjaro (checked October 7, 2026). The Philippine status of AOD-9604 is unverified.

	Tirzepatide	AOD-9604
Registration	Mounjaro KwikPen (6 records, 0.6 mL) and Mounjaro (6 records, 0.5 mL), solution for injection under the skin, listed as registered in the FDA Philippines Verification Portal (checked October 7, 2026)	Unverified. No record found in Verification Portal searches for "AOD9604" and "AOD-9604" on October 7, 2026
Prescription	Classified as a prescription drug (Rx) in the portal records	No Philippine source found on prescription status
Zepbound	No record found in a portal search on October 7, 2026	Not applicable
FDA Philippines advisories	Several advisories on unregistered tirzepatide products (below)	None found. FDA Philippines website searches for "AOD-9604", "AOD9604" and related terms returned no results on October 7, 2026
Basis	FDA Philippines Verification Portal records	A portal search with no record, which is not an official FDA Philippines statement

FDA Philippines advisories on unregistered tirzepatide products (examples):

Advisory	Date	Product described
FDA Advisory No.2026-0814	July 30, 2026	A tirzepatide product with no Certificate of Product Registration
FDA Advisory No.2026-1283	September 16, 2026	A tirzepatide lyophilized powder for injection, sold with bacteriostatic water
FDA Advisory No.2026-1309	September 17, 2026	A tirzepatide product labelled "For research only"

These advisories cover specific unregistered products, not Mounjaro or Mounjaro KwikPen. To check any product, search the FDA Philippines verification portal at verification.fda.gov.ph. For more on Philippine rules, see are peptides legal in the Philippines.

How the two can and cannot be compared

The facts sit side by side, but they do not come from the same kind of evidence.

What can be compared.

Development stage. Tirzepatide finished phase 3 trials and is approved in the US and the EU. AOD-9604 stopped after phase 2b for obesity.
Trial outcomes as reported. Tirzepatide groups lost more weight than placebo in published phase 3 trials. In AOD-9604's largest trial, the US FDA reports no significant difference from placebo.
Regulatory status. Tirzepatide is registered in the Philippines as Mounjaro and Mounjaro KwikPen. AOD-9604 has no record in the portal search and is prohibited in sport.

What cannot be compared directly.

No head-to-head trial. No trial gave people AOD-9604 or tirzepatide and compared them.
Different lengths and designs. The tirzepatide trials ran 72 weeks. The two AOD-9604 phase 2b trials ran 12 or 24 weeks and gave it by mouth, and the 24-week trial added a diet and exercise program.
Different reporting. Tirzepatide results come from peer-reviewed journals and a US label. AOD-9604 results come from company disclosures and a meeting abstract, as summarised by the US FDA.

Trial averages do not predict how any one person will respond. Whether any medicine suits you is a decision for a licensed doctor.

Frequently asked questions

What is the difference between AOD-9604 and tirzepatide?

Tirzepatide is an approved medicine that activates the GIP and GLP-1 receptors and is sold as Mounjaro and Zepbound. AOD-9604 is a fragment of human growth hormone that was developed as an obesity pill, but its development for obesity stopped in 2007 and the US FDA says no approved drug contains it.

Does AOD-9604 cause as much weight loss as tirzepatide?

No trial has compared them directly. In AOD-9604's largest trial, the US FDA reports no significant difference in weight loss between AOD-9604 and placebo. In SURMOUNT-1, mean weight change was -15.0% to -20.9% across the tirzepatide groups versus -3.1% with placebo over 72 weeks.

Is AOD-9604 approved anywhere?

No approval was found. The US FDA says there are no FDA-approved drug products containing AOD-9604. Australia lists it as a Schedule 4 prescription-only substance, but whether any product is on the Australian Register of Therapeutic Goods was not checked.

Is tirzepatide registered in the Philippines?

Yes. The FDA Philippines Verification Portal (checked October 7, 2026) lists Mounjaro KwikPen and Mounjaro, both tirzepatide solution for injection under the skin, as registered prescription drugs. A search for Zepbound found no record.

Is AOD-9604 legal in the Philippines?

Its status is unverified. No record was found in an FDA Philippines Verification Portal search on October 7, 2026, and no Philippine source on a prescription route was found. A search with no record is not an official FDA Philippines statement.

How does each one work?

The US Zepbound label says tirzepatide activates the GIP and GLP-1 receptors, lowers calorie intake, likely by affecting appetite, and raises insulin sensitivity. AOD-9604 was proposed, from animal studies, to increase fat breakdown without acting on the growth hormone receptor.

Are AOD-9604 and tirzepatide banned in sport?

AOD-9604 is. WADA names it in class S2.2.3 as a growth hormone fragment, prohibited at all times. USADA says tirzepatide is in the WADA 2027 Monitoring Program, which means it is not prohibited but labs test for it.

What are the side effects of each?

For tirzepatide, the US label lists nausea, diarrhea, vomiting and constipation as the most common side effects, plus a boxed warning about thyroid C-cell tumors seen in rats. For AOD-9604, early studies reported headache, fatigue, nausea and other effects, and the US FDA says it has too little information to know whether it would cause harm in humans.

Can I switch from tirzepatide to AOD-9604?

No source on switching between them was found. The US FDA says no approved drug contains AOD-9604 and that it has too little safety information to judge harm in humans. Decisions about your treatment are for a licensed doctor.

Sources

This content is for education only and is not medical advice. Talk to a licensed doctor before starting any treatment.