Maridebart cafraglutide (MariTide): the phase 2 paper and the MARITIME phase 3 trials
Prepared by: Research Desk. Sources are linked for verification.
Published 30 October 2026
At a glance
- What it is: maridebart cafraglutide (MariTide, earlier code AMG 133) is Amgen's investigational antibody–peptide conjugate that blocks the GIP receptor and activates the GLP-1 receptor
- Published efficacy data: one 52-week phase 2 trial in the New England Journal of Medicine with 592 participants (Jastreboff et al., 2025, PubMed)
- Phase 3: more than ten MARITIME trials are registered on ClinicalTrials.gov, including a cardiovascular outcomes trial of about 12,800 people
- Phase 3 results: none found in PubMed as of 30 October 2026
- Status: investigational; not approved in any market we could find
What the molecule is
Most incretin-based investigational compounds are single peptides. Maridebart cafraglutide is built differently. A fully human monoclonal antibody that blocks the glucose-dependent insulinotropic polypeptide receptor (GIPR) is joined, through amino-acid linkers, to two GLP-1 analogue peptides. The antibody part gives the molecule a long half-life, which is why the trials space administrations weeks apart rather than days.
The design rests on a point that is still debated: both activating and blocking the GIP receptor have been linked to lower body weight in animal studies. Amgen's programme takes the antagonist route, while compounds such as tirzepatide and retatrutide activate the GIP receptor. A 2026 review in Antibody Therapeutics discusses the antibody–peptide conjugate format using this molecule as its main example (Yie, 2026, PubMed).
Preclinical and phase 1 data
Amgen scientists described the molecule in Nature Metabolism in February 2024 (Véniant et al., 2024, PubMed). In cell-based systems it acted as a GIPR antagonist and a GLP-1 receptor agonist. It lowered body weight in obese male mice and in cynomolgus monkeys. The same paper reported a randomised, placebo-controlled phase 1 study in people with obesity (NCT04478708). The authors described the safety and tolerability as acceptable and reported weight reduction that was still present up to 150 days after the last administration in the multiple-administration cohorts. Almost all the authors were Amgen employees and stockholders.
The phase 2 trial
The phase 2 results were published online on 23 June 2025 and in print in September 2025 (Jastreboff et al., 2025, NCT05669599). It was a double-blind, placebo-controlled trial with 11 groups in two cohorts, comparing several strengths and schedules, some with a gradual start and some without. The main measure was the percent change in body weight after 52 weeks.
- Obesity cohort (465 participants, mean BMI 37.9): mean weight change ranged from −12.3% to −16.2% across the active groups, against −2.5% with placebo, using the treatment-policy estimand, which counts everyone randomised.
- Obesity with type 2 diabetes cohort (127 participants, mean BMI 36.5): mean weight change ranged from −8.4% to −12.3%, against −1.7% with placebo. HbA1c changed by −1.2 to −1.6 percentage points, against +0.1 with placebo.
- Tolerability: gastrointestinal adverse events were common. The authors reported they were less frequent when the trial used a gradual start and a lower first strength. No unexpected safety signals were reported.
The trial was funded by Amgen. In December 2025 the journal printed letters about the paper, with a reply from the authors (Liu, 2025; Muskiet, 2025; Jastreboff et al., reply, 2025).
The MARITIME phase 3 programme
A ClinicalTrials.gov search on 30 October 2026 returned the following phase 3 records sponsored by Amgen. Sizes are the enrolment figures on each record, which can change.
- MARITIME-1 (NCT06858839): obesity or overweight without diabetes, about 3,850 participants, listed as active and not recruiting.
- MARITIME-2 (NCT06858878): obesity or overweight with type 2 diabetes, about 1,100 participants.
- MARITIME-CV (NCT07037433): cardiovascular outcomes, about 12,800 participants.
- MARITIME-HF (NCT07037459): heart failure with obesity, about 5,050 participants, recruiting.
- MARITIME-OSA-1 and OSA-2 (NCT07225686, NCT07226765): obstructive sleep apnoea, about 250 participants each.
- MARITIME-3-J (NCT06987695): a study in Japan, about 280 participants.
- MARITIME-T2D-3 (NCT07866066): a head-to-head comparison with semaglutide in type 2 diabetes, about 1,300 participants, not yet recruiting, with a listed start date of 2 November 2026.
- Other records: a study of a pen device (NCT07871409), two extension studies (NCT07684144, NCT07684235) and a switching study (NCT07575399).
Separate phase 2 records cover type 2 diabetes (NCT06660173, about 410 participants) and liver fat (NCT07441252).
What has not been reported
We found no peer-reviewed phase 3 results in PubMed as of 30 October 2026. Company press statements and conference abstracts are not covered on this page; a signal is recorded here when a paper or a regulatory record exists.
Limitations
- One efficacy trial: the published human efficacy data come from a single phase 2 trial with small groups per arm.
- Sponsor: the preclinical, phase 1 and phase 2 work was funded and largely written by Amgen.
- Registry data: trial sizes, statuses and dates come from ClinicalTrials.gov records, which sponsors update over time.
- Comparisons: results from different trials of different compounds are not directly comparable because populations and designs differ.
Key terms
- GIPR antagonist: a molecule that blocks the receptor for glucose-dependent insulinotropic polypeptide
- Antibody–peptide conjugate: an antibody chemically joined to one or more peptides, combining the antibody's long half-life with the peptide's activity
- Treatment-policy estimand: an analysis that includes every randomised participant regardless of whether they stopped the study drug
- HbA1c: glycated haemoglobin, a lab measure of average blood glucose over roughly three months
Supplier
Purita is a store that sells peptides for laboratory research use only. It does not list maridebart cafraglutide, which is an investigational antibody–peptide conjugate; the link below goes to the store's homepage.
Affiliate disclosure: this is a paid link. KlowSignal earns a commission if a purchase is made through it, at no extra cost to the buyer. A listing is not an endorsement or a statement about product quality. See the affiliate disclosure.
Related pages
- Research peptide signals: studies and regulatory updates
- About KlowSignal
- How to read a research or regulatory signal
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- Eloralintide: the amylin agonist's phase 2 data and phase 3 trials
- Retatrutide phase 3: TRIUMPH-1 and TRIUMPH-2 results published
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