Retatrutide - New breakthrough for losing weight

Retatrutide is an experimental, once-weekly injectable medicine developed by Eli Lilly that is being studied for weight loss and metabolic conditions. The drug has attracted considerable attention because clinical studies have shown very large average weight reductions. However, it is important to emphasize that retatrutide is not (yet) routinely available and is still in clinical development.

What exactly is Retatrutide?

Retatrutide is a so-called “triple agonist”: a single peptide that simultaneously activates three receptors involved in appetite, glucose regulation, and energy expenditure:

·       GLP-1 receptor

·       GIP receptor

·       Glucagon receptor

This combination differs from well-known GLP-1 medications such as semaglutide (Ozempic®, Wegovy®, Rybelsus®) and the dual agonist tirzepatide (Mounjaro®) (GIP/GLP-1), because retatrutide also adds the glucagon pathway.

How does it work (in broad terms)? 

Retatrutide is designed to act through multiple hormonal pathways at the same time to:

·       reduce appetite and increase satiety (e.g., via GLP-1/GIP),

·       improve glucose levels (incretin effect),

·       and potentially influence energy expenditure/metabolism (the glucagon receptor is a relevant link here).

Importantly, what this means in practice for an individual patient—and which dosing/strategy fits—still needs to be further confirmed in phase 3 research.

What do we know from studies so far?

In a large phase 2 obesity study, an average weight loss of around 24% was reported after 48 weeks at the highest dose (with a clear dose-response effect). Retatrutide has also been studied in type 2 diabetes in a phase 2 trial, where both glycemic improvements and substantial weight reductions were observed. More recently, Lilly reported initial positive phase 3 results within the TRIUMPH program (including TRIUMPH-4). Note: press releases provide an initial impression, but full scientific publication and review remain important for definitive conclusions.

Regulatory status: US and EU (current situation)

United States (FDA)

At this time, retatrutide is not FDA-approved for the treatment of obesity or other indications. The FDA has also explicitly warned that retatrutide has not been established as safe and effective and must not be used in compounding under federal rules.

European Union (EMA)

Retatrutide is also not currently an authorized medicine in the EU for routine prescribing. That said, formal regulatory steps are already visible in the development pathway, such as an EMA decision related to a Paediatric Investigation Plan (PIP) (with deferral/waiver), which is consistent with medicines progressing toward later-stage development.

In short: phase 3 is ongoing, but marketing authorization (US/EU) still requires completion of studies, dossier submission, and review by regulatory authorities.

Why are we already receiving so many questions about it at Aevita?

Interest is mainly driven by:

·       Promising efficacy in phase 2 studies and early phase 3 signals.

·       The rapid development of new obesity medicines and the demand for options for people who need greater weight loss.

·       Unfortunately, “research chemical” offers are also circulating online. The FDA emphasizes that retatrutide is not approved for human use; products sold as “retatrutide” outside of clinical trials therefore pose a major risk (unknown quality/purity/dosing).

When will Retatrutide become available?

That depends on the outcomes of the phase 3 TRIUMPH program and the speed of regulatory review. At present, the most accurate answer is: there is no official date yet, and until approval the medicine is only accessible through clinical studies.

Frequently asked question:

Can a doctor already prescribe Retatrutide?

No, not as a routine medicine. Until it is approved, it can only be used within the framework of clinical research.

If you have a BMI of ≥27 with a weight-related condition, or a BMI of ≥30, and you would like to know which medical weight-loss options are already available today, start our intake now.

— Michael Hendriks, CEO Aevita