What Is MariTide? Amgen’s Once-Monthly Weight Loss Injection

MariTide is an investigational weight-loss injection from Amgen with an unusual selling point: you’d take it just once a month, rather than once a week like current GLP-1 drugs. It works through a novel combination, pairing GLP-1 activation with blocking (not activating) the GIP receptor. It’s not FDA approved. In a mid-stage trial it produced up to about 20% average weight loss over a year, and the weight loss hadn’t leveled off by the end. Here’s how a monthly shot could work and where MariTide stands.

The Monthly Dosing Advantage

Current injectable weight-loss drugs are taken weekly, which for many people is manageable but still a frequent commitment. MariTide is designed for once-monthly (or even less frequent) dosing, thanks to a long half-life of about 21 days, roughly three times longer than weekly semaglutide. The potential benefit is straightforward: fewer injections could mean better adherence and, in principle, easier long-term use, which matters a lot for a chronic condition like obesity where people often need ongoing treatment.

MariTide (also called maridebart cafraglutide, formerly AMG 133) is built as a peptide-antibody conjugate, essentially GLP-1 peptides attached to an antibody, which is what gives it that long duration.

An Unusual Mechanism

Here’s where MariTide gets scientifically interesting. Most dual-hormone drugs (like tirzepatide) activate both the GLP-1 and GIP receptors. MariTide activates GLP-1 but blocks GIP. That sounds contradictory, since you might expect activating and blocking the same receptor to have opposite effects, but genetic evidence supports it: people with gene variants that reduce GIP signaling tend to have lower body weight. So MariTide’s approach of antagonizing GIP while stimulating GLP-1 is grounded in human genetics.

What Phase 2 Showed

The results come from a phase 2 trial published in the New England Journal of Medicine in 2025. In people with obesity without diabetes, MariTide produced up to about 20% average weight loss at 52 weeks, compared with roughly 2.6% on placebo, and up to about 17% in people with obesity and type 2 diabetes. Importantly, the weight loss had not plateaued by the end of the study, suggesting more might be possible with longer treatment.

The Tolerability Question

Like other drugs in this space, MariTide’s most common side effects were gastrointestinal (nausea, vomiting, constipation), mostly mild and mostly tied to the first dose. Starting at lower doses and escalating gradually reduced these substantially. Consider a hypothetical patient who struggles to remember a weekly injection. A once-monthly option that still delivers strong weight loss could genuinely change how manageable treatment feels, provided the tolerability holds up in larger trials. Amgen has moved MariTide into phase 3 testing, which will tell us more.

What This Means for You Right Now

MariTide is not available, and TrimRx does not offer it. TrimRx provides medications you can access today, including compounded semaglutide and compounded tirzepatide plus brand options like Ozempic, Wegovy, Mounjaro, and Zepbound. If you’re ready to pursue weight loss now, those are the options to consider, since MariTide is still working through late-stage trials.

A monthly weight-loss shot is a genuinely appealing idea, but for now MariTide is a promising candidate rather than an available treatment.

Frequently Asked Questions

How is MariTide different from Ozempic or Zepbound?

Two main ways: dosing and mechanism. MariTide is designed for once-monthly injection (versus weekly for those drugs), and it blocks the GIP receptor while activating GLP-1, whereas tirzepatide (Zepbound) activates both. In phase 2, MariTide produced up to about 20% weight loss.

Is MariTide FDA approved?

No. MariTide is investigational and not FDA approved. It completed a phase 2 trial and has advanced to phase 3 testing, so it’s only available through clinical trials.

Can I get MariTide from TrimRx?

No. TrimRx offers currently available medications like compounded semaglutide and tirzepatide and brand GLP-1 options. MariTide is not approved or available and is not among them.

To focus on what you can start with today, you can explore the options available to you now with a licensed provider.

This information is for educational purposes and is not medical advice. MariTide is investigational and not FDA approved; details and timelines may change. Consult a healthcare provider before starting any medication. Individual results may vary.