MariTide / Maridebart cafraglutide (AMG 133)

MariTide is an investigational antibody-peptide conjugate. The antibody portion antagonizes the GIP receptor; the peptide portion agonizes the GLP-1 receptor. The combination is mechanistically distinctive in the GLP-1 / GIP space — opposite in direction from tirzepatide's dual GIP/GLP-1 agonism.

MariTide originated from Amgen's research into the role of GIP receptor signaling in body weight regulation — work that produced the surprising finding that GIP receptor antagonism, rather than agonism, may be what drives part of the additive weight loss seen in dual-receptor strategies. The molecule was developed as a peptibody / antibody-peptide conjugate combining anti-GIPR monoclonal antibody activity with GLP-1 receptor agonism.

Phase 1 first-in-human results published in Nature Metabolism in 2024 established the proof-of-concept; Phase 2 data has supported Phase 3 advancement.

GLP-1 receptor agonism contributes the standard incretin appetite suppression and glycemic control. GIP receptor antagonism — the surprising arm — has been associated in preclinical work with reduced body weight via mechanisms including effects on adipose tissue, central appetite signaling, and possibly nausea modulation. The Amgen team's hypothesis is that GIP antagonism explains a meaningful portion of the additive weight loss attributed to GIP/GLP-1 modulation, and that doing it via antagonism rather than agonism produces a cleaner profile.^[1]

The antibody backbone supports a long half-life and once-monthly subcutaneous administration — a significant differentiation from weekly peptide GLP-1s. Steady state is approached over multiple monthly doses.

The peer-reviewed literature on MariTide is summarized below across two tiers: human research (the highest standard), and preclinical / emerging research (animal models and early-stage human work).

This table summarizes commonly discussed claims and how the published evidence weighs in. The aim is clarity — supported claims, claims that look promising but need more data, and claims that outrun the science.

Phase 2/3 trial protocols use monthly subcutaneous injection. As an investigational drug, MariTide is available only through trial enrollment.

MariTide is one of the most intellectually interesting molecules in late-stage metabolic development. The mechanistic premise — that GIP antagonism rather than agonism is the right way to combine with GLP-1 — is a striking inversion of what the field assumed before tirzepatide was approved. Combined with a monthly dosing format that no other late-stage GLP-1 candidate offers, MariTide represents a credible alternative path to next-generation obesity care.

What to watch: The Phase 3 MARITIDE-1 trial readout (expected 2027) is the gating event — will determine whether the ~21% Phase 2 weight loss replicates at scale and whether the GIP-antagonism hypothesis holds against larger populations. The T2D Phase 3 program (MARITIDE-2) extends the story into diabetes. If MariTide reaches approval at the Phase 2 efficacy level, it would compete with tirzepatide at the dosing-convenience axis (monthly vs weekly) — a substantial market advantage even at comparable efficacy.

For the broader pipeline view, see our MariTide AMG 133 explainer article and the broader emerging-drug coverage in our Best Peptides for Weight Loss 2026 ranking. For comparisons across the modern GLP-1 class (Semaglutide → Tirzepatide → Retatrutide → MariTide → CagriSema), see our 3-way comparison article. The other Phase 3 GLP-1-class candidates worth tracking alongside MariTide are Retatrutide (triple agonist), CagriSema (semaglutide + amylin), Survodutide (GLP-1/glucagon dual), and the emerging HU6 controlled mitochondrial uncoupler that represents a fundamentally different mechanism class.