MariTide: What to Know About the Monthly Weight-Loss Shot

Everything approved in the GLP-1 class today is either a daily pill or a weekly shot. MariTide is the most advanced attempt to change that. Amgen says its long-acting design supports starting at monthly dosing and staying on it with “as few as 4 or 6 doses per year” [1].

If that holds up in Phase 3, it is a different kind of product: four injections a year instead of fifty-two, with all the knock-on effects that would have on adherence, cost and how people think about staying on treatment long-term.

This page tracks what is known, what is still being tested, and how to get into one of the trials.

None of this is medical advice. MariTide is investigational and not available by prescription.

What exactly is MariTide?

MariTide’s generic name is maridebart cafraglutide, and its development code was AMG 133 [1].

It is an antibody-peptide conjugate: a monoclonal antibody with peptides chemically attached to it. The antibody portion is what gives it a very long half-life, the same engineering trick that lets other antibody drugs be dosed every few weeks or months.

The pharmacology is where it gets interesting [1]:

• The peptide portion activates the GLP-1 receptor, the same target as semaglutide.
• The antibody portion blocks the GIP receptor.

That is the opposite of tirzepatide, which activates GIP. Both drugs cause substantial weight loss in humans. Nobody has fully resolved why blocking and activating the same receptor can both work, and it is one of the most-discussed open questions in the field.

What have the trials shown so far?

Phase 2 (NCT05669599, 592 participants) reported results at 52 weeks that are worth stating carefully, because the headline range gets garbled constantly [1]:

Group	Efficacy estimand	Treatment-policy estimand
Obesity, no type 2 diabetes	16.3% to 19.9% across doses	12.3% to 16.2%
Placebo (same cohort)	2.6%	2.5%
Obesity with type 2 diabetes	up to about 17%	8.4% to 12.3%

The two columns are two ways of analyzing the same trial, not two doses. The efficacy estimand asks what happens to people who stay on treatment as directed; the treatment-policy estimand counts everyone who was randomized. Coverage that reports “12% to 20%” is splicing the bottom of one column to the top of the other. Weight loss had not plateaued by 52 weeks. The data were presented at the American Diabetes Association Scientific Sessions in June 2025.

Two things about that readout shaped everything since:

1. The lack of a plateau. Most obesity drugs flatten out somewhere between 40 and 60 weeks. MariTide participants were still losing at 52 weeks, which is part of why Amgen designed Phase 3 with a long duration and long-term extensions.
2. Nausea and vomiting during escalation. Amgen responded by changing the Phase 3 design to start lower and titrate more slowly. That is a normal and sensible response, but it also means Phase 2 weight-loss numbers may not transfer directly to Phase 3.

The MARITIME program: every trial, in plain English

Amgen listed the full program in its second-quarter 2026 report [1]. Here is what each study is doing and whether you can join.

Trial	Who it studies	Size	Primary completion	Recruiting?
MARITIME-1 (NCT06858839)	Obesity or overweight, no type 2 diabetes	3,853	2027-01-21	No
MARITIME-2 (NCT06858878)	Obesity or overweight with type 2 diabetes	1,105	2027-01-21	No
MARITIME-CV (NCT07037433)	Established heart disease plus obesity or overweight	12,800	2028-06-30	Yes
MARITIME-HF (NCT07037459)	Heart failure with preserved or mildly reduced ejection fraction plus obesity	5,056	2028-06-30	Yes
MARITIME-OSA-1 (NCT07225686)	Sleep apnea, on PAP therapy	250	2027-09-29	Yes
MARITIME-OSA-2 (NCT07226765)	Sleep apnea, not on PAP therapy	250	2027-09-29	Yes
MARITIME-SWITCH (NCT07575399)	People already on weekly tirzepatide or semaglutide	300	2028-01-03	Yes
MARITIME-1 EXTENSION (NCT07684235)	MARITIME-1 completers, maintenance dosing	3,200	—	Completers only
MARITIME-2 EXTENSION (NCT07684144)	MARITIME-2 completers, maintenance dosing	950	—	Completers only
Phase 2b liver fat (NCT07441252)	Obesity or overweight with elevated liver fat	180	2027-09-29	Yes

Amgen also said three additional Phase 3 studies in people with type 2 diabetes would be initiated during 2026 [1].

The two trials most worth watching

MARITIME-1 and MARITIME-2 are the ones that decide whether MariTide gets approved. Both have a primary completion date of January 21, 2027 [2][3]. Primary completion is when the last participant finishes the main measurement, not when results are published. Expect a topline announcement weeks to a few months after that, which puts a MariTide weight-loss headline somewhere in the first half of 2027.

MARITIME-SWITCH is the one most relevant to people already taking a GLP-1. It moves adults who are on weekly tirzepatide or weekly semaglutide onto MariTide on an every-eight-week or quarterly schedule [4]. If people hold their weight loss on four to six injections a year after getting there on a weekly drug, that is a genuinely new option, especially for anyone who dislikes injections or struggles with weekly adherence.

When could MariTide be approved?

Amgen has not published launch guidance. Working from the registry dates:

• Phase 3 primary completion: January 2027
• Topline data: first half of 2027 (estimate)
• Regulatory filing: 2027 (estimate)
• FDA decision: the agency says it has “6 to 10 months” once it accepts a complete application
• Earliest realistic US availability: 2028 (estimate)

Secondary analyst models have clustered around 2028 as well. Treat all of that as an estimate. MariTide has not been filed and could be delayed by the data, by manufacturing, or by the agency.

Why monthly dosing might matter more than peak weight loss

It is tempting to score pipeline drugs purely on the biggest weight-loss percentage. MariTide’s commercial case is different.

Adherence is the quiet crisis in this class. A large share of people who start a weekly GLP-1 are no longer on it a year later. Some of that is side effects, some is cost, some is the simple friction of a weekly injection and a monthly pharmacy trip. Cutting injections from 52 a year to 4 to 12 removes a real barrier.

Cold chain and supply get easier. Fewer doses per patient per year means less manufacturing volume and fewer pens moving through the supply chain for the same number of people treated.

Missed doses hurt less. With a weekly drug, a missed week is a meaningful gap. With a quarterly drug, the concentration curve is much flatter.

The trade-off is the other direction: if you have a bad reaction to a monthly drug, you cannot simply skip next week’s dose. The drug is in you for a long time. That is a real consideration and one reason the slow Phase 3 titration matters.

Amgen is not alone here. Pfizer, which acquired Metsera, is running Phase 3 trials of berobenatide in both monthly and weekly regimens, and has a monthly amylin analog in Phase 2 alongside it. Viking Therapeutics has a maintenance study testing monthly and every-other-week dosing of VK2735. Long-interval dosing is becoming its own competitive lane.

How to join a MariTide trial

MariTide has more open US Phase 3 capacity than almost any other pipeline obesity drug, mostly because MARITIME-CV alone is enrolling 12,800 people [5].

Practical steps:

1. Go to clinicaltrials.gov and search maridebart cafraglutide.
2. Filter to Recruiting and set a distance from your ZIP code.
3. Read the eligibility criteria. The cardiovascular and heart failure trials require an existing diagnosis; the sleep apnea trials require a sleep apnea diagnosis and specify whether you must be on PAP therapy.
4. Use the Contacts and Locations tab to call or email the coordinator at your nearest site.
5. Amgen also runs a study finder at amgentrials.com.

Questions worth asking before you enroll: what is the chance of being randomized to placebo, is there an extension that lets placebo participants receive active drug, how many visits are required, and what happens to your treatment when the study ends.

A clinical trial is research, not treatment. You may receive placebo, and some trials require you to stop your current weight-loss medicine. Talk with your own healthcare provider first.

MariTide at a glance

Item	Status as of 2026-09-14
Sponsor	Amgen
Generic name	Maridebart cafraglutide (formerly AMG 133)
Mechanism	GLP-1 receptor agonist joined to a GIP receptor antagonist
Route	Subcutaneous injection
Dosing	Monthly to start; as few as 4 to 6 doses per year for maintenance
Phase	3
Phase 2 result	Up to about 20% at 52 weeks (efficacy estimand); 12.3% to 16.2% on the treatment-policy estimand. No plateau
Phase 3 data expected	2027 (MARITIME-1 and -2 primary completion January 21, 2027)
Earliest US availability	2028 (estimate)
Trials recruiting	Yes, including two very large outcomes trials

Sources

1. Amgen, “Amgen Reports Second Quarter 2026 Financial Results,” August 4, 2026 — https://www.amgen.com/newsroom/press-releases/2026/08/amgen-reports-second-quarter-2026-financial-results
2. ClinicalTrials.gov, NCT06858839 (MARITIME-1) — https://clinicaltrials.gov/study/NCT06858839
3. ClinicalTrials.gov, NCT06858878 (MARITIME-2) — https://clinicaltrials.gov/study/NCT06858878
4. ClinicalTrials.gov, NCT07575399 (MARITIME-SWITCH) — https://clinicaltrials.gov/study/NCT07575399
5. ClinicalTrials.gov, NCT07037433 (MARITIME-CV) — https://clinicaltrials.gov/study/NCT07037433
6. ClinicalTrials.gov, NCT07037459 (MARITIME-HF) — https://clinicaltrials.gov/study/NCT07037459
7. ClinicalTrials.gov, NCT07225686 (MARITIME-OSA-1) — https://clinicaltrials.gov/study/NCT07225686
8. Amgen clinical trial finder — https://www.amgentrials.com/
9. PR Newswire mirror of Amgen’s Q2 2026 results — https://www.prnewswire.com/news-releases/amgen-reports-second-quarter-2026-financial-results-302842890.html