Short answer: MariTide (maridebart cafraglutide, code AMG 133) is Amgen’s investigational obesity drug — a peptide–antibody conjugate that agonises the GLP-1 receptor and antagonises the GIP receptor, with a ~21-day half-life supporting once-monthly subcutaneous dosing. Phase 2 (NEJM, 2025) reported mean weight loss of up to ~20% at 52 weeks in obesity without diabetes, with no plateau. It is in the Phase 3 MARITIME programme and has no marketing authorisation anywhere in the world. MariTide is a proprietary conjugate, not a reference peptide — New-U does not sell it. Part of our next obesity-research wave overview.
Plain-English summary. MariTide is an unapproved investigational drug. The FDA, MHRA and EMA have not authorised it. It is also structurally a biologic (an antibody conjugate), not a simple peptide that research-compound suppliers stock. This page is general information, not legal or medical advice; do not use unapproved compounds on people.
Most obesity drugs are peptides. MariTide is not — it is a peptide–antibody conjugate: a monoclonal-antibody scaffold with GLP-1 analogue peptides chemically attached. That architecture is the whole point. Antibodies circulate for weeks, so bolting the active peptides onto an antibody backbone stretches the half-life to roughly 21 days — about three times semaglutide’s ~7 days — which is what makes once-monthly (and potentially less-frequent) dosing realistic.
Its developmental code was AMG 133; the generic name is maridebart cafraglutide. The molecular and pharmacology detail is indexed under PubMed: maridebart cafraglutide.
Here is the genuinely counter-intuitive part. Tirzepatide, the most successful incretin drug to date, activates the GIP receptor. MariTide does the opposite — it blocks it — while still agonising GLP-1. And yet both produce major weight loss. How can activating and blocking the same receptor both work?
For the contrasting GIP-agonist design, see our tirzepatide research guide.
The Phase 2 trial was published in the New England Journal of Medicine in 2025 and presented at the American Diabetes Association’s 85th Scientific Sessions. Headline findings over 52 weeks:
| Population | Mean weight change at 52 weeks | Notable |
|---|---|---|
| Obesity, without type-2 diabetes | up to ~−20% | No plateau by week 52 |
| Obesity, with type-2 diabetes | up to ~−17% | HbA1c reduced up to ~2.2% |
Beyond weight, the trial reported improvements across pre-specified cardiometabolic measures — waist circumference, blood pressure, high-sensitivity C-reactive protein (hs-CRP) and selected lipids. The fact that the weight curve had not flattened at 52 weeks is one reason the Phase 3 readouts are closely watched.
MariTide has advanced into the MARITIME Phase 3 programme — 72-week studies evaluating efficacy, safety and tolerability in people with obesity or overweight, with and without type-2 diabetes. Topline timing and any regulatory submission schedule are subject to change; refer to Amgen investor disclosures for the current position. Registered studies are listed on ClinicalTrials.gov.
| Compound | Receptor profile | Format | Cadence | Status |
|---|---|---|---|---|
| MariTide | GLP-1 agonist + GIP antagonist | Peptide–antibody conjugate | ~Monthly | Phase 3, no approval |
| Tirzepatide | GLP-1 + GIP agonist | Peptide | Weekly | Approved |
| Retatrutide | GLP-1 + GIP + glucagon agonist | Peptide | Weekly | Phase 3, no approval |
| Semaglutide | GLP-1 agonist | Peptide | Weekly | Approved |
MariTide’s distinctive selling points are the monthly cadence and the GIP-antagonist mechanism — both unusual in a field otherwise converging on weekly GIP agonists.
Because MariTide is an antibody conjugate rather than a short synthetic peptide, it sits outside what research-compound suppliers can characterise and verify by HPLC and mass spec. New-U does not sell MariTide, and any listing claiming to is selling something it cannot authenticate. The lawful, verifiable research references in the same therapeutic area are the established GLP-1-class peptides:
Each ships as a sealed, lyophilised reference peptide with a per-batch Certificate of Analysis, verified to >99% HPLC purity, research use only, not for human consumption.
Because there is no licensed MariTide product anywhere, treat any “buy MariTide” listing with maximum caution. Walk away if it:
What is MariTide?
Amgen’s investigational obesity drug maridebart cafraglutide (AMG 133) — a peptide–antibody conjugate that agonises GLP-1 and antagonises GIP, dosed about once a month.
Is MariTide approved?
No. As of mid-2026 it has no marketing authorisation anywhere; it is in the Phase 3 MARITIME programme.
How much weight loss did it show?
Up to ~20% mean over 52 weeks in obesity without diabetes (Phase 2, NEJM 2025), without a plateau.
Why block GIP when tirzepatide activates it?
An open question — likely receptor desensitisation and central-vs-peripheral GIP signalling. Both designs produce weight loss; the mechanism is unsettled.
Can I buy MariTide as a research compound?
No — it is a proprietary antibody conjugate, not a verifiable reference peptide. New-U catalogues the established GLP-1-class references instead. Research use only.
External links are provided for research reference only; New-U is not affiliated with the cited organisations and links carry no endorsement either way.
New-U Research Compounds catalogues semaglutide, tirzepatide and retatrutide as sealed 10-vial packs of lyophilised reference peptide, independently verified by Janoshik and Freedom Diagnostics for >99% HPLC purity, with a per-batch Certificate of Analysis. Research use only — not for human consumption.
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