Research pipeline · Not approved
RetatrutideTriple hormone receptor agonist
Retatrutide is an investigational triple hormone receptor agonist being developed by Eli Lilly for obesity. It acts on three receptors, GLP-1, GIP and glucagon, where Mounjaro acts on two and Wegovy on one. In a Phase 3 trial it produced a mean weight reduction of 28.7% at 68 weeks, the highest figure reported in a late-stage obesity trial to date. It is not approved by any regulator and cannot lawfully be prescribed or supplied.
Not available
This compound is investigational. It holds no marketing authorisation from the MHRA, EMA or FDA, so it cannot lawfully be prescribed, sold or supplied for human use in the UK or elsewhere. Products offered online as "research use only" versions of it are unlicensed medicines, of unverified identity and purity, and are outside any clinical oversight.
At a glance
- Developer
- Eli Lilly
- Targets
- GLP-1 · GIP · Glucagon
- Administration
- Once-weekly subcutaneous injection (in trials)
- Stage
- Phase 3 trials
- Reported
- 28.7% · 68 weeks
How Retatrutide differs
The third target is what distinguishes it. Adding glucagon receptor agonism to GLP-1 and GIP is thought to increase energy expenditure, rather than only reducing intake as appetite-led mechanisms do.
That combination is why the reported figures sit above the tirzepatide and semaglutide range. It is also why the safety profile needs the full length of Phase 3 to characterise, glucagon agonism affects glucose handling and heart rate, and those effects take time and numbers to quantify.
Comparisons with licensed treatments should be read carefully: these are separate trials with different populations and endpoints, not head-to-head studies. Retatrutide vs Mounjaro is the comparison most often searched, and no trial has run it: the 28.7% and 20.9% figures come from different studies, so the gap between them is not a measured difference.
Clinical evidence
What the trials showed
Mean weight reduction of 28.7% at 68 weeks
Reported by Eli Lilly as the highest weight reduction seen in a pivotal late-stage obesity trial. Full peer-reviewed publication of the complete dataset is what determines how the result is ultimately interpreted.
Dose-dependent reduction across 48 weeks
The Phase 2 trial published in the New England Journal of Medicine established the dose-response relationship and the tolerability profile that Phase 3 was designed around.
What is known about tolerability
- Gastrointestinal effects, nausea, vomiting, diarrhoea, were the most commonly reported events in trials, consistent with the wider incretin class.
- Increases in heart rate have been observed with glucagon receptor agonism and are among the effects Phase 3 is powered to characterise.
- The complete safety profile is not established. That is precisely what remains to be determined, and it is the reason approval has not been granted.
Availability
Not approved anywhere. Eli Lilly has reported Phase 3 results; regulatory submission and review follow, and neither timing nor outcome can be assumed. Retatrutide cannot be obtained lawfully for human use in the UK.
Retatrutide: Common questions
Can you buy retatrutide in the UK?
No. Retatrutide holds no marketing authorisation from the MHRA, EMA or FDA, so it cannot lawfully be prescribed, sold or supplied for human use. Vials sold online as "research use only" retatrutide are unlicensed medicines of unverified identity, purity and dose, and the MHRA has taken enforcement action against vendors selling them.
Is retatrutide stronger than Mounjaro?
Reported trial figures are higher, 28.7% at 68 weeks against roughly 21% for tirzepatide in SURMOUNT-1, but these are separate trials with different populations, not a head-to-head comparison. Retatrutide is also not approved, so it is not an available option regardless of the numbers.
When will retatrutide be available?
There is no confirmed date. Phase 3 results have been reported, after which a regulator must review a full submission and decide. Neither the timing nor the outcome of that process can be predicted, and any site giving you a launch date is guessing.
Is retatrutide UK availability expected soon?
No date can be assumed. Retatrutide holds no marketing authorisation from the MHRA, EMA or FDA, and Phase 3 has to complete and be reviewed before one is possible. Reporting a trial result is not the same as approval, and the gap between the two is measured in years rather than months. Anything offered as retatrutide UK stock today is unlicensed and of unverified identity.
Sources
- Retatrutide Phase 3 results · Eli Lilly
- Triple–Hormone-Receptor Agonist Retatrutide for Obesity, A Phase 2 Trial · New England Journal of Medicine
Awaiting sign-off by a named clinician.