June 5, 2026 · Last updated: June 5, 2026
What Is MariTide? Amgen’s Once-Monthly GLP-1/GIP Drug Heads Into a Six-Study Phase 3 Program
A peptide-antibody conjugate that activates GLP-1 while blocking GIP — the mirror image of tirzepatide — MariTide is now in an expanding Phase 3 program, including a trial switching patients off weekly GLP-1s.
MariTide (maridebart cafraglutide, formerly AMG 133) is Amgen’s entry into the obesity-drug race, and it’s built differently from the Wegovy/Zepbound class. It’s a long-acting peptide-antibody conjugate — two GLP-1 peptide analogs attached to a monoclonal antibody — given subcutaneously once monthly or less frequently, versus the weekly injections of semaglutide and tirzepatide.
The mechanistic twist is the headline. MariTide activates the GLP-1 receptor (like the existing drugs) but antagonizes the GIP receptor — the opposite of tirzepatide, which activates GIP. Two opposing approaches to the same receptor, both producing weight loss, which is part of why the drug has drawn scientific attention.
In its Phase 2 trial (NCT05669599, published in the New England Journal of Medicine), MariTide produced mean weight reductions of up to roughly 20% in participants with obesity without type 2 diabetes, and up to about 17% in those with both obesity and diabetes, over 52 weeks — and notably, the curve had not plateaued by the end of the study.
The news peg: on its April 30, 2026 earnings call, Amgen detailed an expanding Phase 3 program. The company has initiated six global Phase 3 studies spanning four areas — chronic weight management, cardiovascular outcomes, heart failure, and obstructive sleep apnea — and added a study evaluating patients switching from weekly GLP-1 therapies, a direct competitive move against the established players.
MariTide is not FDA-approved; it remains investigational, with access limited to its trials. But between the monthly dosing, the distinct GIP-antagonist mechanism, and a Phase 3 footprint reaching well beyond weight loss, it’s one of the more closely watched peptide-based assets in the pipeline.
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This article is for informational and educational purposes only and does not constitute medical advice. MariTide (maridebart cafraglutide) remains an investigational compound under active Phase 3 evaluation and is not FDA-approved for any indication. All research compounds referenced are for laboratory use only.
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