Amgen's obesity drug: what you need to know about MariTide

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Several new weight loss treatments are in development, including Amgen's MariTide. Get the key facts about this US-made injectable medication.

If you're considering losing weight, you've probably heard of the two main weight loss medications available in the UK.

First, there's Wegovy (semaglutide) – sometimes incorrectly called 'Ozempic'. When taken alongside a healthy diet and regular exercise, this weekly injectable medication yields an average weight loss of around 15%.¹

Then there's Mounjaro (tirzepatide), which – like Wegovy – is taken weekly as an injection. On average, Mounjaro users lose around 21% of their starting body weight.²

Wegovy and Mounjaro have been hitting headlines in recent years. But they're not the only treatments of their kind. Behind the scenes, researchers are studying several new injectable medications that work in similar ways.

One of these new treatments is MariTide, from the American drug company Amgen.

Could MariTide be a viable alternative to Mounjaro and Wegovy? Let's learn more about this new weight loss medication and see what the research says.

What is MariTide?

MariTide is Amgen's name for a drug called 'maridebart cafraglutide'. Like Wegovy and Mounjaro, it's an injectable medication that works by acting on natural hormones involved in digestion and appetite.

Right now, researchers are studying MariTide in phase 3 clinical trials. Phase 3 trials are the final and most in-depth study phase before a drug is approved for treatment.

What's different about MariTide?

MariTide has two main differences compared to Wegovy and Mounjaro: the way it works and how often you take it.

How it works

Wegovy, Mounjaro and MariTide are part of the same broad family of medications. They all work by acting on natural hormones in the body. However, MariTide works on different hormones in different ways:

Wegovy is a single agonist. It activates the body's receptors for a single hormone called 'GLP-1'. This hormone is involved in managing blood sugar and regulating appetite.
Mounjaro is a dual agonist. It activates GLP-1 and GIP receptors. When you take Mounjaro, GIP works together with GLP-1 to boost appetite suppression, as well as promote healthy fat storage. This dual action is likely why Mounjaro tends to yield better results than Wegovy.
MariTide is both a hormone agonist and an antagonist. It combines drugs that activate GLP-1 receptors and block GIP receptors. This is based on research that showed beneficial effects in animals treated with a similar combination of drugs.³

How often you take it

Another big difference with MariTide is its dosing schedule (how often it's taken).

Wegovy and Mounjaro are taken once weekly. However, Amgen is proposing that MariTide only needs to be taken once per month – or perhaps even less frequently than that.⁴

Picture of a person using an injection pen.

Once-monthly dosing could prove easier to manage for people who struggle with Wegovy and Mounjaro's more frequent dosing schedule. But the question remains: how well does it actually work?

Is MariTide effective for weight loss?

Early results from MariTide studies were very positive.

In November 2023, Amgen announced initial findings from its MariTide phase 2 trial. The new medication, they claimed, yielded an average of up to 20% weight loss after 52 weeks.⁴

This result suggested that MariTide was more effective than Wegovy (15% average weight loss¹) and only slightly less effective than Mounjaro (21%²).

What's more, the weight loss didn't significantly slow down even as the trial drew to a close. That suggested that patients could lose even more weight if they kept taking the drug.⁴

Unfortunately for Amgen, more recent results have been less impressive.

In June 2025, Amgen unveiled the full data from its phase 2 trial. The company now claimed that MariTide only resulted in up to 16% average weight loss among study participants, not 20% as previously claimed.⁵

The discrepancy is down to how the results were calculated. The 20% figure, it turns out, only factored in participants who completed the study – not those who discontinued treatment because of side effects.

What's next for MariTide?

Despite these mixed results, Amgen is pushing forward with phase 3 trials for MariTide.⁶

You might wonder why, considering that the full phase 2 trial data only showed a mild improvement on Wegovy's average weight loss. But the company hopes to differentiate MariTide by marketing it as an option for long-term weight maintenance.

'Maritide is a true differentiation compared to what's available in the market', said Amgen's Murdo Gordon. 'We hope to go into this market not just to reduce the weight of patients who struggle with obesity, but also to help deliver on the medical benefit of managing that weight.'⁶

For Amgen, everything now hinges on the results of those phase 3 trials. We'll be sure to keep you posted when we know more.

Do you want to lose weight using clinically proven injectable treatments like Wegovy or Mounjaro? At SemaPen, we do so much more than provide the medication. Our weight loss programmes are built by UK obesity experts and include wraparound support to give you the best chance of success. Why not learn more about our programmes, or get started by downloading the SemaPen app and taking our simple digital consultation?

Sources

1. Wilding, J.P.H. et al. (2021) "Once-Weekly Semaglutide in Adults with Overweight or Obesity" The New England Journal of Medicine, 384(11) https://doi.org/10.1056/NEJMoa2032183

2. Jastreboff, A.M. et al. (2022) "Tirzepatide Once Weekly for the Treatment of Obesity" The New England Journal of Medicine, 387(3) https://doi.org/10.1056/NEJMoa2206038

3. Véniant, M.M. et al. (2024) "A GIPR antagonist conjugated to GLP-1 analogues promotes weight loss with improved metabolic parameters in preclinical and phase 1 settings" Nature Metabolism, 6:290–303 https://doi.org/10.1038/s42255-023-00966-w

4. Amgen (2024) AMGEN ANNOUNCES ROBUST WEIGHT LOSS WITH MARITIDE IN PEOPLE LIVING WITH OBESITY OR OVERWEIGHT AT 52 WEEKS IN A PHASE 2 STUDY [press release]. Retrieved from https://www.amgen.com/newsroom/press-releases/2024/11/amgen-announces-robust-weight-loss-with-maritide-in-people-living-with-obesity-or-overweight-at-52-weeks-in-a-phase-2-study

5. Amgen (2025) RESULTS FROM AMGEN'S PHASE 2 OBESITY STUDY OF MONTHLY MARITIDE PRESENTED AT THE AMERICAN DIABETES ASSOCIATION 85TH SCIENTIFIC SESSIONS [press release]. Retrieved from https://www.amgen.com/newsroom/press-releases/2025/06/results-from-amgens-phase-2-obesity-study-of-monthly-maritide-presented-at-the-american-diabetes-association-85th-scientific-sessions

6. Manalac, T. (2025) Amid Obesity Bidding War, Amgen Believes It Can Stand Out in Crowded Space. BioSpace. Retrieved from https://www.biospace.com/business/amid-obesity-bidding-war-amgen-believes-it-can-stand-out-in-crowded-space

This article was reviewed and approved by Sarah Abdula, Specialist Dietitian, on 28 January 2026.

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