Record Mounjaro and Eloralintide Weight Loss Study: 23.3%

Last Updated: 2 October 2026

The Mounjaro and eloralintide weight loss study has delivered one of the most talked-about obesity trial results of the year. Presented this week at the European Association for the Study of Diabetes (EASD) annual meeting in Milan, the Phase 2b trial tested an experimental combination of eloralintide — a new amylin-based drug from Eli Lilly — with tirzepatide, the active ingredient in Mounjaro, in 367 adults living with both obesity and type 2 diabetes. The headline figure is striking: participants on the highest dose of the combination, dubbed EloraTZP, lost an average of 23.3% of their body weight over 48 weeks. That is roughly 54 lb, and it far exceeds the 14.8% average seen with tirzepatide alone. But the results come with a significant caveat — side effects and dropouts were notably higher in the combination arms. In this article, we break down exactly what the trial studied, what it found, how it compares with Mounjaro on its own, and what it could mean for people in the UK.

What did the Mounjaro and eloralintide weight loss study find?

The trial found that eloralintide 9 mg combined with tirzepatide 15 mg produced 23.3% average weight loss at 48 weeks in adults with type 2 diabetes and obesity — about 54 lb — versus 14.8% with tirzepatide alone. A1C blood sugar levels fell by 2.9 percentage points, though gastrointestinal side effects caused up to 27% of participants to stop treatment.

What Is Eloralintide?

Definition: Eloralintide is an experimental, once-weekly selective amylin receptor agonist developed by Eli Lilly. Amylin is a hormone released by the pancreas after eating that helps regulate appetite, slow stomach emptying and promote a feeling of fullness. By targeting the amylin receptor specifically, eloralintide aims to reduce hunger through a different hormonal pathway from GLP-1 drugs such as Mounjaro.

The Mounjaro and eloralintide weight loss study is the largest and longest test so far of an amylin drug combined with an incretin medicine, and its findings are reshaping how researchers think about combination obesity treatment.

Until now, most weight loss injections have focused on the incretin hormones — GLP-1 and GIP. Mounjaro (tirzepatide) is a dual GIP and GLP-1 receptor agonist. Eloralintide opens up a third front. Lilly believes that hitting all three pathways at once — GIP, GLP-1 and amylin — can deliver greater appetite suppression and better blood sugar control than any single drug on its own.

Crucially, eloralintide is investigational. It has not been approved by any medicines regulator in the world, including the UK’s MHRA. It cannot be prescribed anywhere, and the only legitimate way to receive it is inside a clinical trial.

How the Mounjaro and Eloralintide Weight Loss Study Was Designed

The Mounjaro and eloralintide weight loss study was a 48-week, double-blind, placebo-controlled Phase 2b trial (registered as NCT06603571) that enrolled 367 adults with overweight or obesity and type 2 diabetes across the United States and Argentina. Participants started with an average body weight of 105.4 kg (232.4 lb) and an average A1C — a measure of blood glucose over two to three months — of 8.1%.

Across ten treatment arms, volunteers were randomised to receive placebo, eloralintide alone, tirzepatide alone, or various combinations of the two, known collectively as EloraTZP. In the trial, the two drugs were given as separate once-weekly injections. Participants in the combination arms started on low doses — eloralintide 1 mg or 3 mg plus tirzepatide 2.5 mg — and escalated every four weeks until reaching their target doses.

The trial’s primary endpoint was percentage change in body weight with EloraTZP versus placebo, while all other comparisons — including the head-to-head-style comparisons with tirzepatide alone — were designated secondary endpoints. Results were calculated using what researchers call the efficacy estimand, which estimates what would have happened if every participant had stayed on treatment for the full 48 weeks. According to HCPLive’s clinical breakdown of the trial, all EloraTZP dose combinations met both the primary and secondary endpoints.

Mounjaro and Eloralintide Weight Loss Study: The Key Results

The results, as reported by BioSpace, were remarkable — particularly because people with type 2 diabetes historically lose less weight on GLP-1-based medicines than people without diabetes. Here is what each arm achieved at 48 weeks:

1. Eloralintide 9 mg + tirzepatide 15 mg: 23.3% average weight loss (about 54.1 lb) and a 2.9 percentage point A1C reduction — the strongest result in the trial.
2. Eloralintide 6 mg + tirzepatide 10 mg: 19.9% weight loss (about 46.2 lb) and a 2.6 point A1C reduction.
3. Eloralintide 6 mg + tirzepatide 5 mg: 19.4% weight loss (about 45.1 lb) and a 2.7 point A1C reduction.
4. Eloralintide 3 mg + tirzepatide 5 mg: 13.2% weight loss (about 30.7 lb) and a 2.2 point A1C reduction.
5. Tirzepatide 15 mg alone (Mounjaro’s active ingredient): 14.8% weight loss (about 34.4 lb) and a 2.4 point A1C reduction.
6. Eloralintide alone: 8.2% to 12.3% weight loss (up to 28.6 lb) and an A1C reduction of 1.1 to 1.4 points.
7. Placebo: 3.0% weight loss and a 0.3 point A1C reduction.

Perhaps the most eye-catching statistic of the Mounjaro and eloralintide weight loss study was that a quarter of participants on the highest combination dose lost at least 30% of their body weight — a benchmark comparable to metabolic (bariatric) surgery. Only 12% of those on tirzepatide alone reached that threshold.

Across every arm, the Mounjaro and eloralintide weight loss study showed a clear dose-response pattern: the more eloralintide added to tirzepatide, the greater the average weight loss — although the very highest eloralintide dose alone performed slightly worse than the dose below it, a quirk researchers will want to understand.

Eloralintide vs Mounjaro Alone: How Big Is the Difference?

At the top dose, adding eloralintide to tirzepatide delivered roughly 8.5 percentage points more weight loss than tirzepatide 15 mg on its own — about 20 additional pounds in this study population. That is a meaningful step up, and it caught the attention of analysts: Citi described the 23.3% figure as comparable to what tirzepatide achieves in people without type 2 diabetes, calling it comfortably above their 17% bar for success.

Treatment (48 weeks)	Average weight loss	Average A1C reduction
Eloralintide 9 mg + tirzepatide 15 mg	23.3% (54.1 lb)	2.9 points
Eloralintide 6 mg + tirzepatide 10 mg	19.9% (46.2 lb)	2.6 points
Eloralintide 6 mg + tirzepatide 5 mg	19.4% (45.1 lb)	2.7 points
Eloralintide 3 mg + tirzepatide 5 mg	13.2% (30.7 lb)	2.2 points
Tirzepatide 15 mg alone	14.8% (34.4 lb)	2.4 points
Eloralintide alone (best dose)	12.3% (28.6 lb)	1.4 points
Placebo	3.0% (7.0 lb)	0.3 points

Lead study author Liana K. Billings, MD, director of clinical and genetics research in diabetes and cardiometabolic disease at Endeavor Health in Illinois, told the EASD meeting: “Tirzepatide at 15 mg is our current very effective GLP-1 therapy for type 2 diabetes and weight management. We have really not seen these degrees of weight loss in people without diabetes in previous studies.” She added that, based on the trends seen at 48 weeks, researchers would “hopefully see continued weight loss” beyond the trial period.

Ken Custer, president of Lilly Cardiometabolic Health, put the rationale plainly: “Patients may not get what they need from a drug like tirzepatide. They may not get what they need from a drug like an eloralintide on its own. The ability to combine them together and provide even greater weight loss — that’s definitely one obvious benefit of the new regimen.”

Side Effects in the Mounjaro and Eloralintide Weight Loss Study: The Tolerability Problem

The Mounjaro and eloralintide weight loss study results were not all good news. The combination caused significantly more gastrointestinal side effects than either drug alone, and those side effects hit hardest during the dose escalation phase. More than four-fifths of participants in the combination arms reported some kind of side effect, with roughly half experiencing nausea.

Treatment discontinuation because of adverse events ranged from 10.8% to 27.0% across the EloraTZP arms, with the highest rate at the top dose. For comparison, only 2.9% of those on tirzepatide alone stopped treatment, 0% to 10.8% stopped eloralintide alone, and 16.7% stopped placebo. The most common adverse events were gastrointestinal and generally described as mild to moderate.

Lilly has acknowledged the problem. At the EASD press conference, Custer said the study design — ramping participants up on two different drugs at the same time — made it “very hard to actually profile final tolerability of an agent.” The company plans to use an optimised dose escalation schedule in Phase 3, which should improve adherence while preserving the impressive efficacy.

Importantly, the Mounjaro and eloralintide weight loss study ramped participants up on both drugs simultaneously — an aggressive approach that likely exaggerated the side effects. With a gentler Phase 3 schedule, real-world tolerability may look quite different from these first results.

It is worth remembering that these were relatively short studies at 48 weeks. Longer-term safety data — including any effects on the thyroid’s calcitonin system, which Lilly’s chief scientific officer Dan Skovronsky has flagged as a key design challenge for amylin drugs — will be essential before regulators anywhere consider approval.

What the Mounjaro and Eloralintide Weight Loss Study Means for the UK

For readers in the UK, the Mounjaro and eloralintide weight loss study is exciting but very much a glimpse of the future rather than a treatment option today. Eloralintide is not licensed by the MHRA, is not available on the NHS, and cannot be obtained privately in the UK. Only tirzepatide — sold as Mounjaro — is authorised here, for type 2 diabetes and for weight management in adults with a BMI of 30 or more, or 27 to 30 with weight-related health problems, alongside a reduced-calorie diet and increased physical activity.

That said, the findings matter for three reasons. First, they suggest that people with type 2 diabetes — who typically respond less well to weight loss medicines — could one day see results matching those in people without diabetes. Second, the study strengthens the case for combination therapy as the next frontier in obesity medicine, much like combination treatments transformed HIV and cancer care. Third, Lilly’s pipeline now gives it a potential answer for patients who do not achieve their goals on Mounjaro alone, a group the company says the combination is specifically designed to serve.

Competition is heating up too. Novo Nordisk’s rival amylin-based combination, CagriSema (cagrilintide plus semaglutide), has shown superiority over semaglutide alone in Phase 3 trials, so the amylin race is now firmly a two-horse contest between the world’s biggest obesity drug makers. UK patients may ultimately benefit from that rivalry through more choice and, potentially, lower prices.

If you are currently considering a weight loss medicine in the UK, speak to your GP or NHS clinician first. Weight loss injections are prescription-only medicines with real risks, and they work best as part of a structured plan that includes diet, activity and behavioural support. Never buy weight loss jabs from unregulated online sellers or social media adverts.

What Happens Next After the Mounjaro and Eloralintide Weight Loss Study: Phase 3 Trials and Beyond

Lilly has confirmed it plans to launch Phase 3 trials of EloraTZP in the fourth quarter of 2026, using a co-formulated single product rather than two separate injections, plus a gentler dose escalation schedule designed to improve tolerability. Phase 3 studies will be larger, longer and more diverse — the real test of whether the headline 23.3% figure holds up in the real world.

Separately, eloralintide is already in Phase 3 development as a single agent for obesity. An earlier Phase 2 study in adults with obesity but without diabetes saw 9 mg of eloralintide alone produce 20.1% average weight loss at 48 weeks — a result analysts at BMO Capital Markets described as a “potentially best in class profile.” The ENLIGHTEN-1 Phase 3 monotherapy trial is expected to complete in March 2028.

Even in the best case, that means several more years of trials, regulatory review and manufacturing scale-up before anything like EloraTZP could reach UK clinics. For now, the Mounjaro and eloralintide weight loss study stands as proof of concept: targeting amylin alongside GLP-1 and GIP can push weight loss into territory once thought achievable only with surgery.

One study investigator, University of Texas diabetes researcher Julio Rosenstock, could not resist a colourful verdict. Having previously nicknamed Mounjaro “King Kong” and Lilly’s triple-hormone drug retatrutide “Godzilla”, he dubbed the new combination the “Incredible Hulk”. Time — and Phase 3 — will tell whether it lives up to the name.

Final Thoughts: A Landmark Result With a Long Road Ahead

The Mounjaro and eloralintide weight loss study has set a new benchmark for what is possible in obesity medicine: 23.3% average weight loss in people with type 2 diabetes, a quarter of top-dose participants losing over 30% of their body weight, and blood sugar improvements to match. The tolerability trade-off is real, but Lilly believes a refined dosing schedule can fix it. If Phase 3 confirms these results, the UK could eventually see a new class of combination weight loss treatment that goes well beyond what Mounjaro can do alone.

Want to stay ahead of the biggest health breakthroughs? Bookmark FamePost’s Health section and check back daily for the latest verified medical news, explained in plain English. And remember: if you are thinking about any weight loss medication, always consult your GP or NHS clinician before making a decision — this article is for information only and is not medical advice.