MariTide
MariTide (Maridebart Cafraglutide)
Also called MariTide, maridebart cafraglutide, AMG 133
The monthly incretin
MariTide is Amgen's attempt at a once-a-month weight-loss injection instead of a weekly one. It is an antibody with two GLP-1 peptides stuck to it, which is why it lasts so long. In its Phase 2 trial people lost around 20% of their body weight. Not approved yet.
MariTide is Amgen's attempt at a monthly rather than weekly weight-loss injection. To manage that, it is not really a peptide at all but an antibody with two small peptides attached, which is a much bigger, slower molecule that your body takes weeks to clear. In its Phase 2 trial people lost around 20% of their body weight on twelve injections a year. It is still in testing.
- Half-life
- Weeks rather than days
- Route studied
- Subcutaneous injection (trials)
- Status
- Investigational; not approved
Human trials published, with more underway
What MariTide has been studied for
The reasons people look it up, roughly in order of how often, and what research exists for each. Interest in a use is not evidence that it works; the evidence is stated under each one.
- Weight loss (investigational)
- Studied as a once-monthly injection in a phase 2 trial (New England Journal of Medicine, 2025), where participants lost around 20% of body weight. The phase 3 MARITIME programme is running.
- Weight regain after stopping
- Because it clears so slowly, weight regain after the last dose looked slower than usual in the phase 2 trial. A phase 2 observation rather than a settled finding.
Mechanism of Action
How MariTide works
The interesting thing here is the delivery, not the destination.
- What it does. The business end is the same as Wegovy: it copies GLP-1 to turn appetite down.
- Why it lasts a month. Those peptides are bolted onto an antibody, the same kind of large protein your immune system uses. Antibodies are built to hang around for weeks, so the appetite signal keeps running long after a normal injection would have washed out.
- The other half of the design. It also blocks a receptor called GIP rather than activating it, which is the opposite of what tirzepatide does. Two drugs doing opposite things to the same receptor and both producing weight loss is one of the genuinely odd puzzles in this field, and nobody has fully explained it.
- What that means. One injection lasts about a month, and so does any side effect: clearing it takes weeks rather than days.
MariTide side effects: what studies reported
Mostly stomach-related, shaped by the monthly schedule: in phase 2, nausea and vomiting were concentrated in the days after each injection.
Most commonly reported
- Nausea concentrated in the days right after an injection
- Vomiting
- Reduced appetite
Worth keeping an eye on
- Side effects can be heavier early on than with weekly drugs
- The drug clears slowly, so side effects can take weeks to fade
Dose-related findings. In phase 2, groups that started at the full dose reported more gastrointestinal side effects, and later trial arms used a gradual step-up.
Source: Phase 2 trial, New England Journal of Medicine, 2025. This is a summary of published findings, not a complete safety profile and not medical advice. Questions about MariTide belong with a licensed clinician who knows your history.
Your Genetics & MariTide
The genes involved in how MariTide works
MariTide works through the receptors these genes build, and the genes vary from person to person. Researchers have linked some of that variation to differences in how people respond. A DNA report tells you which versions you carry.
GIPR · ••
The Glu354Gln (E354Q) variant reduces GIP receptor function and has been associated with lower body mass index in population studies. No human study has shown that carriers respond differently to a GIP-blocking drug such as MariTide; any link is a hypothesis, not a prediction.
GIPR · ••
A second GIPR variant associated with reduced receptor function and body weight in population studies. No study has tested it with MariTide.
FTO · ••
FTO risk alleles are associated with higher body weight and appetite in population studies. No study has tested whether FTO genotype changes response to MariTide.
GLP1R · ••
Builds the receptor MariTide's GLP-1 half acts on. Some human studies have associated the Gly168Ser variant with differences in response to other GLP-1 drugs. It has not been studied with MariTide.
The dots after each gene are where your own result goes. Your report fills them in with the two letters you carry at that position.
Which of these variants do you carry?
Your report reads the DNA file you already have against this research.
Access
Access and legal status
MariTide: Investigational; not approved. Decisions about any prescription medicine belong to a prescriber. We don't link to any seller, and nothing on this page is a recommendation to obtain or use it.
Your DNA and MariTide: see which of the variants studied alongside it you carry, and what that research does and does not show. Read my DNA, $99 →
Educational information only, not medical advice. Most peptides are not FDA-approved. Do not start, stop or change any medication or peptide because of this page; talk to a licensed clinician.
Worth knowing about MariTide
Interactions and situations where there is a specific reason to be careful. Where the honest answer is that nobody has studied something, it says so and says what that leaves open.
- Not available
- Phase 2 done, larger trials running. No prescription route exists.
- A monthly dose is hard to take back
- The convenience cuts both ways. With a weekly drug a bad reaction fades in days; here a reaction can last for weeks.
Last updated
Frequently Asked Questions
What is MariTide?
MariTide (maridebart cafraglutide) is an investigational weight-loss drug from Amgen, studied as a once-monthly injection. It combines GLP-1 receptor activation with GIP receptor blocking in an antibody-peptide conjugate.
Why does MariTide block GIP when tirzepatide activates it?
It is one of the genuine open questions in obesity pharmacology: both activating and blocking the GIP receptor appear to support weight loss, through different mechanisms. MariTide blocks it; tirzepatide activates it. The phase 3 data will help explain why.
Is MariTide approved?
No. As of 2026 MariTide is investigational, in the Phase 3 MARITIME programme. It is not an available prescription.
Watch
What clinicians and researchers say about MariTide
Your DNA and MariTide
What the research says about your variants.
The report
Which MariTide variants do you carry?
Your report reads the DNA file you already have against the published research on 31 peptides, marker by marker, and says what that research does and does not show.
Read my DNA, $99