Journal

Retatrutide Phase 3: Why We Will Not Print the Number You Came Here For

The figures circulating for retatrutide's phase 3 results trace overwhelmingly to sources selling peptides. Here is what can actually be said.

What is actually established

Retatrutide, developed by Eli Lilly, adds glucagon receptor agonism to the GLP-1 and GIP mechanisms tirzepatide already combines. The theory is additive: glucagon receptor activation increases energy expenditure and shifts hepatic lipid metabolism, on top of the appetite and glycaemic effects of the other two.

Its phase 2 trial was published in the New England Journal of Medicine in 2023 (DOI 10.1056/NEJMoa2301972). That is a real, citable primary source, and it is the strongest thing we can point to.

The phase 3 programme is TRIUMPH. It is running.

Why we are not printing a phase 3 figure

Searches for retatrutide phase 3 results return specific numbers with confident framing. When we traced them, the sources were overwhelmingly commercial: at least one vendor selling research peptides, and sites carrying provider advertising inside clinical copy.

We could not locate the figure in a peer-reviewed publication or a registry results posting. Under our evidence policy that makes it unverified, and unverified clinical figures do not publish here regardless of how many places repeat them.

This is the same standard applied to everything else on this site — and it is worth stating plainly that the standard costs us traffic on this page specifically. A number would rank better than an explanation.

Why this particular compound attracts a grey market

Three conditions coincide. Enormous search interest. No approved product, so no lawful supply and no price anchor. And a compound available to laboratories as a research chemical.

The result is a market selling an unapproved drug to consumers with "research use only" labelling, which is a complete answer about what it is. There is no prescriber, no licensed pharmacy, no verified testing and no recourse. It is not a cheaper version of compounded medicine — compounding at least happens inside the regulatory system, with a pharmacy licence and an identifiable prescriber.

What would change this page

A TRIUMPH publication in a peer-reviewed journal, or results posted to the trial registry. At that point we capture the design, population, dose, comparator, duration, result, adverse events and discontinuations together, record the identifiers, and publish figures with the estimand stated.

We check the registry on our normal review cycle. This page updates when there is something to update it with.

What to do with a retatrutide number you see elsewhere

1. Ask what the source is, and whether you can open it.
2. Check whether that source sells peptides or carries provider advertising.
3. Check whether the figure names an estimand — trial results are usually published with more than one.
4. Check whether it names the dose and duration. A percentage without them is not a result.

Those four questions dispose of most of what is circulating.

If you are considering treatment now

Approved options exist and have published evidence: tirzepatide at about 20.9% mean reduction in SURMOUNT-1, oral semaglutide at 13.6% to 16.6% in OASIS 4, orforglipron at approximately 11% to 12.4% in ATTAIN-1. Within lawful compounding, published flat-rate programmes run from around $147 a month.

An unapproved compound with unverifiable figures is not a better version of any of those. It is a different category of risk.

What the phase 2 trial actually showed

The 2023 New England Journal of Medicine publication is the citable evidence for this compound. It was a phase 2 trial — designed to establish dose ranging and preliminary efficacy, not to support approval.

Phase 2 results routinely differ from phase 3 in this field, usually downward, because phase 3 enrols broader populations and uses more conservative analyses. Treating a phase 2 figure as a prediction of phase 3 is a recognised error, and treating an unverified phase 3 figure as established is a larger one.

Why "everyone is reporting it" is not evidence

This is the mechanism described on our page about AI and search misinformation, operating in real time. A figure appears in a commercial source. Others repeat it. The repetition becomes the apparent corroboration. An assistant asked the question finds several sources agreeing and reports consensus.

No verification happened at any step. Repetition is what retrieval systems reward, and it is not the same as confirmation.

What a triple agonist would need to demonstrate

Not just greater weight reduction. Glucagon receptor agonism raises energy expenditure, which is the mechanism of interest, and it also has metabolic effects that need characterising over time — hepatic, glycaemic and cardiovascular.

A compound producing more weight loss with a worse tolerability or safety profile is not automatically better than tirzepatide. That is what phase 3 exists to establish, across a larger population and a longer horizon.

Our commitment on this page

When TRIUMPH results publish in a peer-reviewed journal or post to the registry, this page gets the same treatment as every other trial on this site: design, population, sample size, dose, comparator, duration, primary endpoint, result with the estimand named, adverse events, discontinuations and limitations, with identifiers recorded and an evidence ID in the ledger.

Until then it stays as it is. If that costs us the search position, that is the cost of the standard.

Questions readers actually ask