Subtotal $0.00
Shop Now
MariTide (maridebart cafraglutide) is an investigational obesity medicine from Amgen that is given as an injection once a month or even less often. It is not FDA-approved and cannot be bought anywhere; it is available only to volunteers in clinical trials. MariTide combines an antibody that blocks the GIP receptor with two GLP-1-like peptides that activate the GLP-1 receptor. In a 52-week phase 2 trial published in the New England Journal of Medicine in 2025, average weight loss ranged from 12.3% to 16.2% in people with obesity, compared with 2.5% on placebo. Digestive side effects were common. A large phase 3 program called MARITIME is under way; its first weight-loss trials are scheduled to finish collecting their main data in early 2027.
Peptide Labs does not sell MariTide, any version of maridebart cafraglutide or any prescription drug. Nothing sold online as “MariTide” or as a “research” version of it is the investigational medicine. This article summarizes published trial results, company announcements and ClinicalTrials.gov records. For background on the drug class, see our explainer on how GLP-1 medicines work.
Key Takeaways
- MariTide is an investigational Amgen drug, not FDA-approved and not available outside clinical trials.
- It joins an antibody that blocks the GIP receptor to two peptides that activate the GLP-1 receptor.
- Phase 2 trial: average weight loss of 12.3% to 16.2% at 52 weeks in people with obesity, versus 2.5% on placebo.
- In people with obesity and type 2 diabetes, weight fell 8.4% to 12.3%, versus 1.7% on placebo.
- Nausea, vomiting and constipation were the most common side effects; starting low and stepping up helped.
- The MARITIME phase 3 program includes weight, heart, heart failure and sleep apnea trials.
What is MariTide?
MariTide is Amgen’s name for maridebart cafraglutide, a molecule first studied under the code AMG 133. It is an antibody-peptide conjugate: a fully human monoclonal antibody that blocks the receptor for GIP (glucose-dependent insulinotropic polypeptide), with two GLP-1 analogue peptides attached by short linkers. The GLP-1 part works like the active ingredient in approved medicines such as Wegovy, reducing appetite and slowing digestion. The antibody part does the opposite of what tirzepatide does at the GIP receptor: it blocks the receptor instead of activating it.
Antibodies stay in the body far longer than typical peptides. That is why Amgen is testing MariTide at intervals of every four weeks or longer, rather than the weekly schedule of today’s approved GLP-1 injections. In the phase 1 study, published in Nature Metabolism in 2024, weight loss in some groups was maintained for up to 150 days after the last injection.
How MariTide compares with approved GLP-1 medicines
The table compares MariTide with two approved medicines. No trial has compared them directly, so the table describes how the drugs are designed, not which works better.
| Feature | MariTide (maridebart cafraglutide) | Zepbound (tirzepatide) | Wegovy (semaglutide) |
|---|---|---|---|
| Company | Amgen | Eli Lilly | Novo Nordisk |
| Molecule type | Antibody joined to two GLP-1 peptides | Single peptide | Single peptide |
| Action at the GLP-1 receptor | Activates | Activates | Activates |
| Action at the GIP receptor | Blocks | Activates | None |
| How often it is given | Every 4 weeks or less often in trials | Weekly injection | Weekly injection or daily tablet |
| FDA status for weight management | Investigational, not approved | Approved | Approved |
Why blocking and activating the same receptor can both go along with weight loss is still debated among researchers, and review articles describe it as a paradox. Our comparison of semaglutide and tirzepatide explains the two approved options in more detail.
MariTide phase 2 trial results
The phase 2 trial, led by Yale endocrinologist Ania Jastreboff and funded by Amgen, enrolled 592 adults in two groups. It was randomized, double-blind and placebo-controlled, and tested several strengths given every four or eight weeks, some started at full strength and some stepped up gradually. The main measure was the change in body weight after 52 weeks.
| Group | Who took part | Average weight change at 52 weeks | Placebo |
|---|---|---|---|
| Obesity without diabetes | 465 adults, 63% women, average age 47.9 | Down 12.3% to 16.2% | Down 2.5% |
| Obesity with type 2 diabetes | 127 adults, 42% women, average age 55.1 | Down 8.4% to 12.3% | Down 1.7% |
These figures count everyone who was randomized, including people who stopped early. Amgen’s headline figure of about 20% weight loss comes from a different analysis that estimates the effect in people who stayed on the drug as planned, so it is higher. In the diabetes group, HbA1c (a three-month blood sugar average) fell by 1.2 to 1.6 percentage points, versus a rise of 0.1 on placebo. Amgen also reported that weight loss had not leveled off by week 52. For context on how much weight people lose on approved drugs, see results from the main GLP-1 trials.
Side effects reported in the MariTide trials
Because MariTide has no FDA label, everything known about its safety comes from trials. The NEJM paper reported that digestive side effects were common, and less frequent when people started on a lower strength and stepped up gradually. No unexpected safety signals emerged. Amgen’s announcements add these details:
- The most common side effects were nausea, vomiting and constipation, mostly mild to moderate and short-lived.
- In the groups that stepped up gradually, about 11% stopped because of any side effect and fewer than 8% because of digestive side effects.
- In groups that started at full strength, up to 7.8% stopped because of digestive side effects.
- Amgen reported no association between MariTide and changes in bone mineral density.
Phase 2 trials are too small and too short to find rare problems. Approved GLP-1 medicines carry warnings about pancreatitis, gallbladder disease and other risks, summarized in our guide to side effects across the GLP-1 class. Whether MariTide shares them will only be clear after phase 3. Another investigational drug, Lilly’s retatrutide, shows how trial-only safety data are reported; see what the retatrutide trials have reported.
The MARITIME phase 3 program for the Amgen weight loss drug
Amgen named its phase 3 program for the weight loss drug MARITIME. ClinicalTrials.gov lists these studies, among others:
- MARITIME-1: about 3,850 adults with obesity or overweight without type 2 diabetes, started March 2025; main data collection is scheduled to finish in January 2027.
- MARITIME-2: about 1,100 adults with obesity or overweight and type 2 diabetes, started March 2025.
- MARITIME-CV: about 12,800 people with heart and blood vessel disease, testing whether MariTide reduces heart attacks, strokes and related events.
- MARITIME-HF: about 5,000 people with obesity and a common type of heart failure.
- MARITIME-OSA-1 and OSA-2: obstructive sleep apnea, in people who do and do not use a breathing machine at night.
- MARITIME-SWITCH: about 300 people switching from a weekly GLP-1 injection, started May 2026, plus long-term extension studies that began in July 2026.
When could MariTide be approved?
Nobody can say yet. Approval would require positive phase 3 results, a marketing application and an FDA review, and none of those had happened as of October 2026. Until then, the only legitimate way to receive maridebart cafraglutide is by enrolling in a trial listed on ClinicalTrials.gov, with a study doctor overseeing your care.
Be wary of websites, social media accounts or clinics offering MariTide, “maridebart” vials or similar products. They cannot be the investigational medicine, which is made only for Amgen’s trials, and products sold as research chemicals are not checked by the FDA for identity, purity or sterility. Our article on the legal status of peptides explains the rules.
Frequently Asked Questions
Is MariTide FDA-approved?
No. MariTide is investigational. As of October 2026 it is being tested in phase 3 trials and is available only to people enrolled in those studies.
What is maridebart cafraglutide?
It is the generic name of MariTide: an antibody that blocks the GIP receptor, joined to two peptides that activate the GLP-1 receptor, designed to be given once a month or less often.
How much weight did people lose on MariTide?
In the phase 2 trial, average weight loss at 52 weeks was 12.3% to 16.2% in people with obesity and 8.4% to 12.3% in people who also had type 2 diabetes, versus 2.5% and 1.7% on placebo.
What are the side effects of MariTide?
Nausea, vomiting and constipation were most common, mostly mild to moderate. They were less frequent when people started on a lower strength and stepped up gradually.
How is MariTide different from Zepbound?
Both activate the GLP-1 receptor, but MariTide blocks the GIP receptor while tirzepatide activates it. MariTide is also being tested monthly or less often, not weekly.
Can I get MariTide now?
Only by joining a clinical trial. It is not sold by pharmacies, and anything offered online under that name is not the investigational medicine.
Peptide Labs does not sell GLP-1 medicines or any prescription drug. This article is general information, not medical advice. Read the Medication Guide that comes with a prescription, and ask a pharmacist or prescriber how this information applies to you.
Last reviewed October 2026.
Related guides: Semaglutide vs Tirzepatide: How the Two Drugs Compare, Retatrutide Side Effects: What the Trials Have Reported, GLP-1 for Weight Loss: What the Trials Actually Showed.