Retatrutide: Mechanism, Trials & SA Status

Retatrutide is the furthest from market of the three compounds covered here: it has no regulatory approval anywhere in the world, in any country, for any use. Everything about it — including anything sold under that name online — is investigational.

How it works

Retatrutide (developed by Eli Lilly under the code LY3437943) activates three receptors at once: GIP, GLP-1, and the glucagon receptor. The added glucagon-receptor activity is the mechanistic difference from tirzepatide — it's theorized to increase energy expenditure and fat metabolism on top of the appetite-suppressing, insulin-modulating effects shared with the other two compounds. That's the basis for it being studied as a potentially more potent weight-loss agent than dual or single-receptor drugs.

What the trial data actually shows

The Phase 2 trial (registered as NCT04881760) enrolled adults with obesity or overweight without diabetes and tested four doses (1mg, 4mg, 8mg, 12mg) against placebo. At 24 weeks, the trial's primary endpoint showed mean weight reduction of up to 17.5% (about 18.7 kg) on the highest dose. A secondary endpoint at 48 weeks reported mean weight reduction of up to 24.2% (about 26.2 kg). The manufacturer describes retatrutide's safety profile in this trial as broadly similar to other incretin-based therapies, with gastrointestinal effects as the most common side effects.

Source: "Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial," The New England Journal of Medicine.

Eli Lilly has since moved retatrutide into Phase 3 trials, still investigating both obesity and type 2 diabetes indications. Phase 3 is the stage that, if successful, precedes a regulatory approval filing — it is not itself an approval, and results at this stage aren't final.

South Africa status: retatrutide isn't a case of "approved elsewhere, not yet registered in South Africa" — it isn't approved anywhere, for anyone, at any dose. Any vial sold as "retatrutide" today, in South Africa or elsewhere, is being sold outside of any completed regulatory review. SAHPRA's public warnings about unregistered peptide products apply here with the least ambiguity of the three compounds on this site. See how we rate for our full regulatory framing.

See our vendor comparison for how vendors selling compounds like this document their own testing and sourcing claims.

This page is educational information about a molecule and its trial history. It is not medical advice, not a recommendation to use retatrutide, and not an endorsement of any vendor.