Quick answer: what is Maridebart Cafraglutide?
Maridebart cafraglutide (MariTide, AMG 133) is Amgen's investigational obesity therapy — a peptide-antibody conjugate.
New to peptides? Start with what are peptides? and how do peptides work?
Quick facts
- Class
- Peptide-antibody conjugate (GLP-1 agonist + GIP receptor antagonist)
- Maker
- Amgen
- Studied for
- Chronic weight management; type 2 diabetes
- Dosing
- Monthly or less frequent (investigational)
- Status
- Phase 3 (MARITIME program, from 2026); not approved
- Maker
- Amgen
- Mechanism
- GLP-1 agonist + GIP receptor antagonist (conjugate)
- Status
- Phase 3 (MARITIME); monthly dosing
Key takeaways
- It activates the GLP-1 receptor while blocking the GIP receptor, a distinct dual mechanism.
- Its standout feature is dosing as infrequently as once a month; Phase 2 showed up to about 20% weight loss.
- It is in Phase 3 (the MARITIME program) and is not approved.
Overview
Maridebart cafraglutide, known by the code MariTide (AMG 133), is one of the more unusual entries in obesity medicine: a peptide-antibody conjugate. It links two GLP-1 analog peptides to a monoclonal antibody that blocks the GIP receptor, combining a peptide drug with an antibody in one molecule.[2]
Its standout feature is dosing frequency — as infrequently as once a month, versus weekly for most incretin drugs. Developed by Amgen, it is in Phase 3 (the MARITIME program) and is not approved.
How it works
MariTide does two things at once. The GLP-1 peptide portion activates the GLP-1 receptor, curbing appetite as other incretin drugs do. The antibody portion blocks the GIP receptor — the opposite of what tirzepatide does at GIP.[2] That GLP-1-agonist / GIP-antagonist combination is a distinct and somewhat counterintuitive strategy, and the antibody backbone is what gives the molecule its very long duration and monthly dosing.
Clinical evidence
In a Phase 2 trial published in 2025, once-monthly maridebart cafraglutide produced up to roughly 20% weight loss at about a year, with the effect not clearly plateauing by the end of the study.[1] Earlier preclinical and Phase 1 work established the conjugate approach and the GIP-antagonist mechanism.[2]
Amgen has moved the drug into a large Phase 3 program covering obesity, type 2 diabetes, and cardiovascular and sleep-apnea outcomes. As an investigational agent, its full benefit-risk profile is not yet established.
Safety & status
Reported side effects are predominantly gastrointestinal, consistent with GLP-1-based therapies. Comprehensive long-term safety awaits the Phase 3 readouts. Maridebart cafraglutide is not FDA-approved and is not available outside clinical trials. See the weight-loss peptides category for context, and tirzepatide for the contrasting GIP-agonist approach.
Frequently asked questions
What is maridebart cafraglutide (MariTide)?
Maridebart cafraglutide, coded MariTide (AMG 133), is Amgen's investigational obesity drug. It is a peptide-antibody conjugate that activates the GLP-1 receptor and blocks the GIP receptor, and can be dosed as infrequently as once a month.
How is MariTide different from tirzepatide?
Both act on GLP-1 and GIP, but in opposite ways at GIP: tirzepatide activates the GIP receptor, while MariTide blocks it. MariTide is also a peptide-antibody conjugate dosed monthly, versus weekly for tirzepatide.
Is MariTide approved?
No. Maridebart cafraglutide is investigational and in Phase 3 (the MARITIME program). It is not FDA-approved and is available only through clinical trials.
References
Each source links to its original record — peer-reviewed studies, regulator pages, or reference texts, labelled by type. We summarize findings neutrally; a citation is a reference, not an endorsement, and not a claim that its authors reviewed this page.
- Jastreboff AM, Ryan DH, Bays HE, et al. Once-Monthly Maridebart Cafraglutide for the Treatment of Obesity - A Phase 2 Trial. N Engl J Med. 2025. Peer-reviewed study
- Véniant MM, Lu SC, Atangan L, et al. A GIPR antagonist conjugated to GLP-1 analogues promotes weight loss with improved metabolic parameters in preclinical and phase 1 settings. Nat Metab. 2024. Peer-reviewed study