Metabolic / Published Sep 8, 2026 / Reviewed Sep 27, 2026 / 9 min read
MariTide (Maridebart Cafraglutide): The Once-Monthly GLP-1 Agonist and GIP Blocker, Explained
Written by Aaron CuhaReviewed Sep 27, 2026
How Amgen's once-a-month weight-loss shot works, why it blocks GIP when tirzepatide switches it on, how much weight 592 people lost in a year, what happened in the second year, the big studies now running, why people quit and how the dosing changed, and where Pfizer's berobenatide fits as the other monthly shot. Plain English, every study linked.
Key takeaways
- MariTide is still being tested. It is in large final-stage studies (called MARITIME) and is not approved anywhere. Nothing sold under the name is the Amgen drug.
- It is an antibody that blocks the GIP hormone signal, with two GLP-1 copies attached. It lasts long enough in the body to be given as one shot a month or less often. Tirzepatide switches GIP on, MariTide blocks it, and both take weight off.
- In a year-long study of 592 people, those without diabetes lost 12.3% to 16.2% of body weight, counting everyone who started. People who kept taking it lost up to 19.9%. People on a dummy shot lost 2.5%. Weight was still coming off at a year.
- About 11% of people who started on a slowly rising dose quit because of side effects. Nausea and vomiting came mostly around the first shot. The big studies now use a slower ramp, from 21 mg to 35 mg to 70 mg over eight weeks.
- Pfizer's berobenatide is the other monthly GLP-1 shot. It is a long-lasting peptide, not an antibody. On monthly shots, people lost 12.3% more than on a dummy shot at 28 weeks (VESPER-3, February 2026). Ten big studies of it are starting.
What is MariTide and is it approved?
Direct answer
MariTide (maridebart cafraglutide, once called AMG 133) is Amgen's weight-loss drug still being tested. It is an antibody that blocks the GIP hormone signal, joined to two copies of a GLP-1 drug. It is given as a shot once a month. As of September 2026, it is in large final-stage studies (MARITIME) and not approved by the FDA or anyone else.
Every other shot in this group is a peptide given weekly. MariTide is a different kind of molecule. It is an antibody with peptides attached, and the antibody does two jobs: it makes the drug last and it blocks GIP. In Amgen's first small study in people, weight loss grew with the dose, and weight stayed below the starting point for up to 150 days after the last shot. That is what made a monthly shot look possible (Nature Metabolism, 2024). Profile: MariTide. Side by side with the approved drug: MariTide versus tirzepatide.
How can blocking GIP and activating GIP both cause weight loss?
Direct answer
This is the GIP puzzle. Tirzepatide switches the GIP signal on, along with GLP-1. In 2,539 people it took off 20.9% of body weight at 72 weeks. MariTide blocks the GIP signal, along with GLP-1. It took off up to 19.9% at 52 weeks in 592 people. Both work in people. One idea is that switching GIP on for a long time wears the signal out, which acts like blocking it.
GIP is the gut hormone that fat cells respond to most. For years, animal studies pointed both ways. In Amgen's animal work, blocking GIP took weight off. Yet drugs that switch GIP on also take weight off when paired with GLP-1. Amgen bet on blocking. It built a human antibody against the GIP signal and attached GLP-1 copies to it, so both effects arrive at once. Tirzepatide bet on switching it on (NEJM, SURMOUNT-1, 2022). Both bets paid off in people. That means nobody really understands what GIP does in people yet. Be wary of anyone selling a confident story about it.
What happened to people in the year-long study?
Direct answer
In a 52-week study (NEJM, June 2025) of 465 adults with obesity and 127 with obesity and diabetes, monthly MariTide took off 12.3% to 16.2% without diabetes and 8.4% to 12.3% with diabetes, counting everyone who started. People on a dummy shot lost 2.5% and 1.7%. People who kept taking it lost up to 19.9% and 17.0%. Weight was still coming off.
| Who | Doses tested | Weight lost, everyone who started | Weight lost, people who kept taking it | Dummy shot | Also | Size of the evidence |
|---|---|---|---|---|---|---|
| 465 people with obesity, no diabetes | 140, 280 or 420 mg every 4 weeks at full dose from the start; 420 mg every 8 weeks; 420 mg every 4 weeks, built up over 4 or 12 weeks | 12.3% to 16.2% | 16.3% to 19.9% | 2.5% | Still losing at 52 weeks | Mid-sized study in people |
| 127 people with obesity and type 2 diabetes | Same doses | 8.4% to 12.3% | 12.1% to 17.0% | 1.7% | Long-term blood sugar (HbA1c) fell up to 2.2 points | Mid-sized study in people |
The two numbers mean different things. 'Everyone who started' includes people who quit. 'People who kept taking it' is what those who stayed on it got. Amgen led with the roughly 20% number in November 2024, and the journal led with the lower one in June 2025. Both are true readings of the same study (NEJM, 2025). The gap between them is mostly about people quitting, covered below. On the comparison table, MariTide's 52-week result sits close to tirzepatide's 72-week result, with half as many shots.
What happened in the second year?
Direct answer
People who had lost at least 15% by week 52 could keep going, and more than 90% of them did. They were put on a dummy shot, 70, 140 or 420 mg monthly, or 420 mg every 12 weeks. On January 14, 2026, Amgen said most kept their weight off for another 52 weeks on lower monthly or every-three-month doses.
The second year was built for the question insurers ask. Once the weight is off, can a monthly shot become a shot every three months? At the J.P. Morgan conference, Amgen said yes in principle. It said the drug worked 'on a monthly dosing schedule' and showed 'potential when administered quarterly' (Clinical Trials Arena, January 2026). The full second-year numbers, including how much weight came back for people switched to the dummy shot, were not in a journal as of September 2026. So this rests on what the company said.
What are the big MARITIME studies?
Direct answer
As of Amgen's early 2026 report, MARITIME-1 (obesity without diabetes) and MARITIME-2 (with diabetes) are signing people up. Others test heart problems (MARITIME-CV), heart failure (MARITIME-HF) and sleep apnea (MARITIME-OSA-1 and OSA-2). MARITIME-SWITCH moves people from weekly tirzepatide or semaglutide to MariTide every eight weeks or every three months. Follow-on studies test how to keep weight off.
- MARITIME-1 and MARITIME-2: the main long-term weight studies. People who finish can move on to monthly, every-eight-week or every-three-month shots, to see which keeps the weight off.
- MARITIME-CV and MARITIME-HF: studies in people with obesity plus clogged arteries or heart failure. These are the studies that would let the label claim heart benefits.
- MARITIME-OSA-1 and MARITIME-OSA-2: two studies in adults with obstructive sleep apnea, where breathing stops again and again during sleep. OSA-1 (NCT07225686) is in people who already use a CPAP breathing machine at night. It has finished signing people up. OSA-2 (NCT07226765) is in people who do not use one, and it is still signing people up. Both compare MariTide with a dummy shot. Neither had reported results as of 27 September 2026.
- MARITIME-SWITCH: the first big study built around switching from an approved weekly drug to a less frequent shot. It tests whether the convenience idea holds up.
- Three more type 2 diabetes studies due to start in 2026, plus a mid-sized study on liver fat.
None of the big studies had reported results as of September 2026 (Amgen first quarter 2026 results). Six big studies around the world running at once shows how much Amgen is betting on a monthly shot.
Why did so many people stop, and what changed for the big studies?
Direct answer
In the year-long study, about 11% of people who started on a slowly rising dose quit because of side effects, and under 8% because of stomach problems. People who started at full dose did worse. Nausea lasted a typical 6 days, and vomiting 1 to 2 days. The big studies now climb from 21 mg to 35 mg to 70 mg over eight weeks.
The year-long study had groups that went straight to 280 or 420 mg a month with no build-up, and those groups felt the worst. Every GLP-1 drug has taught the same lesson. The first dose drives the nausea, and a slower climb helps. In June 2025, Amgen set the new build-up at 21, 35 and 70 mg 'over a further optimized eight-week dose escalation period' (Amgen, June 2025). Note that 70 mg is far below the 140 to 420 mg used before. Whether the lower dose takes off less weight is one thing MARITIME-1 will show. A monthly shot also can't be 'paused' like a weekly one. Once it is in, the antibody stays for weeks, so if you feel sick, you can't just skip a dose.
Where does berobenatide, the other monthly, fit?
Direct answer
Berobenatide (once called MET-097i) is Pfizer's very long-lasting GLP-1 peptide, from its purchase of Metsera. It is not an antibody and does nothing to GIP. In VESPER-3, about 54 people per group moved from weekly to monthly shots. At 28 weeks they had lost 10% and 12.3% more than people on a dummy shot (February 3, 2026). Pfizer plans ten big studies in 2026.
| [MariTide](/compounds/maritide) | [Berobenatide](/compounds/berobenatide) | |
|---|---|---|
| Company | Amgen | Pfizer (via Metsera) |
| What it is | An antibody that blocks GIP, with two GLP-1 peptides attached | A long-lasting GLP-1 peptide |
| GIP | Blocks it | Does nothing to it |
| Best weight result | Up to 19.9% at 52 weeks for people who kept taking it (592 people) | 15.9% at 32 weeks on 2.4 mg weekly, still losing (VESPER-1); 12.3% more than a dummy shot at 28 weeks on monthly shots (VESPER-3) |
| Where it stands | Large final-stage studies (MARITIME) | Large final-stage studies starting 2026 (VESPER-4, 5, 6 and others) |
| Size of the evidence | Mid-sized study in people, published in a journal | Mid-sized study in people, reported by the company |
Berobenatide's results are newer and shorter: 28 weeks of monthly shots, against MariTide's 52 weeks of monthly shots plus a second year (Pfizer, February 2026; Pfizer, June 2026). Pfizer's pitch is that people feel less sick, with 'low gastrointestinal adverse events and discontinuations despite rapid dose escalation'. Whether a GLP-1 alone can take off as much as MariTide or tirzepatide is still unknown.
The bottom line
MariTide is the first drug to show, in a big study, that blocking GIP instead of switching it on works for weight loss. It is also the first to show a year of monthly shots with weight still coming off. The published evidence is one year-long study in 592 people. The second-year results and the gentler dosing come only from the company so far. MARITIME-1 had not reported as of September 2026, and nothing sold as MariTide or 'AMG 133' today is the Amgen drug. Related: the 2026 GLP-1 field guide and GLP-1 pills.
Frequently asked questions
How often is MariTide injected?
Once a month in the year-long study, with some groups testing every eight weeks. In the second year, some people went to every 12 weeks. The big studies now running test monthly, every eight weeks and every three months.
Is MariTide better than tirzepatide?
Nobody has tested them against each other. MariTide's best result, up to 19.9% at 52 weeks for people who kept taking it, is close to tirzepatide's 20.9% at 72 weeks in SURMOUNT-1, with a quarter of the shots. But they were different studies of different lengths.
When will MariTide be available?
It is in large final-stage studies with no results reported as of September 2026. Approval needs those results plus an FDA review, so 2027 at the earliest.
What is MARITIME-OSA-1?
It is Amgen's study of MariTide in adults with obstructive sleep apnea who already use a CPAP breathing machine, compared with a dummy shot (NCT07225686). It has finished signing people up and had not reported results as of 27 September 2026. Its sister study, MARITIME-OSA-2 (NCT07226765), tests people who do not use CPAP and is still signing people up. Tirzepatide is the drug already approved for sleep apnea in people with obesity.
Can you buy MariTide or AMG 133?
No. It is an antibody drug made only by Amgen for its studies. Anything sold under either name online is not the drug.
Compound profiles mentioned
- MariTideLimited. People have taken it in a published study, but fewer than 100 of them. 1 completed trial, none stating how many people.Metabolic
- TirzepatideStrong. At least two finished studies in people, and at least 1,000 people who took it. 9 completed trials, 22,802 people given it.Metabolic
- BerobenatideLimited. People have taken it in a published study, but fewer than 100 of them. 3 completed trials, none stating how many people.Metabolic
- SemaglutideStrong. At least two finished studies in people, and at least 1,000 people who took it. 12 completed trials, 42,363 people given it.Metabolic
- RetatrutideStrong. At least two finished studies in people, and at least 1,000 people who took it. 5 completed trials, 1,345 people given it.Metabolic
- AmycretinModerate. At least one finished study in people, and at least 100 people who took it. 1 completed trial, 125 people given it.Metabolic
- CagriSemaStrong. At least two finished studies in people, and at least 1,000 people who took it. 3 completed trials, 4,954 people given it.Metabolic
Sources
- Study in people2025
Maridebart Cafraglutide Versus Placebo in Adult Participants With Obstructive Sleep Apnea on Positive Airway Pressure Therapy (MARITIME-OSA-1)
Registered study of MariTide against a dummy shot in adults with obstructive sleep apnea who use CPAP. Status on 27 September 2026: no longer signing people up, no results posted.
ClinicalTrials.gov NCT07225686 - Study in people2025
Maridebart Cafraglutide Versus Placebo in Adult Participants With Obstructive Sleep Apnea Not on Positive Airway Pressure (PAP) Therapy (MARITIME-OSA-2)
Registered study of MariTide against a dummy shot in adults with obstructive sleep apnea who do not use CPAP. Status on 27 September 2026: signing people up, no results.
ClinicalTrials.gov NCT07226765 - Study in people2022
Tirzepatide once weekly for the treatment of obesity (SURMOUNT-1)
2,539 people: 20.9% weight loss at 72 weeks on 15 mg, against 3.1% on a dummy shot.
New England Journal of Medicine - Study in people2025
Once-monthly maridebart cafraglutide for the treatment of obesity: a Phase 2 trial
592 people: 12.3% to 16.2% weight loss at 52 weeks counting everyone who started, against 2.5% on a dummy shot. Fewer stomach problems when the dose was built up slowly.
New England Journal of Medicine - Study in people2024
Amgen announces robust weight loss with MariTide in people living with obesity or overweight at 52 weeks in a Phase 2 study
Up to about 20% weight loss. About 11% quit because of side effects in the slow build-up groups. Nausea lasted a typical 6 days.
Amgen press release - Study in people2026
JPM26: Amgen touts MariTide's weight loss, T2D potential off Phase II data
Second year: weight kept off on monthly and every-three-month shots. Six big studies running around the world.
Clinical Trials Arena - Study in people2025
Results from Amgen's Phase 2 obesity study of monthly MariTide presented at the American Diabetes Association 85th Scientific Sessions
New build-up for the big studies: 21, 35 and 70 mg over eight weeks. MARITIME studies signing people up.
Amgen press release - Study in people2026
Amgen reports first quarter 2026 financial results
Lists MARITIME-1, -2, -CV, -HF, -OSA-1, -OSA-2, -SWITCH and the follow-on studies on keeping weight off.
Amgen (SEC filing) - Study in people2026
Robust Phase 2b efficacy and favorable tolerability support monthly dosing for Pfizer's GLP-1 RA berobenatide
VESPER-1: 15.9% weight loss at 32 weeks on 2.4 mg weekly. Ten big studies planned for 2026.
Pfizer press release - Study in people2026
Pfizer's ultra-long-acting injectable GLP-1 RA shows robust and continued weight loss with monthly dosing in Phase 2b trial (VESPER-3)
10% and 12.3% more weight loss than a dummy shot at 28 weeks on monthly shots, still losing.
Pfizer press release - Study in people2024
A GIPR antagonist conjugated to GLP-1 analogues promotes weight loss with improved metabolic parameters in preclinical and phase 1 settings
First small study in people: more weight loss at higher doses, and weight stayed down for up to 150 days after the last shot.
Nature Metabolism
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