Reviewed & approved by Dr. Nova Reyes · Last checked 2026-10-25. ← Back to Evidence Library

MariTide (maridebart cafraglutide): what the evidence says

Legend: HUMAN data · ANIMAL / LAB data · UNKNOWN · UNVERIFIED: not yet confirmed against a primary source

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What is it?

Maridebart cafraglutide (also called MariTide or AMG 133) is a fully human antibody against the GIP receptor, linked to two copies of a GLP-1-like peptide. ^{R2, R3} GLP-1 action lowers appetite and blood sugar. GIP is another gut hormone; tirzepatide activates its receptor, while MariTide blocks it. Both approaches have produced weight loss in trials, and scientists still debate why. ^R2 Unknown Whether blocking GIP is better or worse than activating it has not been tested head-to-head in people.

The antibody part makes MariTide last much longer in the body than typical GLP-1 drugs; in phase 1, weight loss persisted long after the last shot (see Study details). ^R2 This also means side effects may take longer to wear off. Unknown

Does it help weight loss?

All results below are from trials funded by Amgen. "Treatment-policy" results count everyone, whether or not they kept taking the drug, which gives a more realistic picture.

• Human Phase 2, obesity without diabetes: in 465 adults, average weight change ranged from −12.3% to −16.2% across MariTide arms vs −2.5% on placebo (treatment-policy). ^R1
• Human Phase 2, obesity with type 2 diabetes: in 127 adults, weight change ranged from −8.4% to −12.3% vs −1.7% on placebo. People with diabetes usually lose less weight on these drugs. ^R1
• Human Phase 1: weight loss depended on the amount given and lasted long after the final shot. ^R2
• Caution Company figures can look bigger. Press releases often quote the "efficacy estimand," which assumes everyone kept taking treatment. We report the more cautious treatment-policy numbers.
• Unknown How MariTide compares head-to-head with semaglutide or tirzepatide in people.

Does it help type 2 diabetes?

• Human Phase 2 diabetes cohort: HbA1c (average blood sugar) fell 1.2 to 1.6 points on MariTide vs a rise of 0.1 on placebo (treatment-policy). This was not the trial's main goal. ^R1
• Human Dedicated phase 2 diabetes trial: Amgen says HbA1c and weight fell meaningfully, but had not released the numbers in the sources we found. ^R4 [UNVERIFIED: company statement as reported in trade press.]
• Unknown Phase 3 diabetes trials are running or planned. ^R5

Is it safe?

What the trials reported:

• Caution Stomach side effects were common, and were less frequent when people started on a lower amount and increased it gradually. No unexpected safety signals were reported. ^R1 Unknown The abstract we reviewed does not give per-arm rates.
• Caution Phase 1: safety and tolerability were described as acceptable. ^R2
• Caution GLP-1 class risks: MariTide acts on the GLP-1 receptor, so the risks known for that drug class (pancreatitis, gallbladder disease, rodent thyroid tumors, low blood sugar with insulin or sulfonylureas, older blood-sugar-lowering pills) are reasonable to expect; see the semaglutide page. Unknown The abstracts we reviewed do not report rates of these events.
• Caution Long-acting drug: if side effects occur, stopping may not end them quickly, because the drug stays in the body for a long time. ^R2 Unknown How long this lasts in practice.
• Unknown Heart safety: the heart-outcome trial (MARITIME-CV) is recruiting. ^R5
• Unknown Long-term safety of blocking the GIP receptor, and rare harms, are unknown.

Compounded and gray-market MariTide: extra risks

• Caution Unregulated "research" vials and antibody complexity. MariTide is an ~150 kDa monoclonal antibody–peptide conjugate (a full human antibody linked to two GLP-1 peptides), which requires biologic manufacturing and cannot be made by routine peptide synthesis; a gray-market product claiming to be MariTide is very unlikely to match the real drug. Only independent analytical testing (such as LC-MS/MS mass spectrometry combined with SDS-PAGE and SEC-HPLC size-exclusion chromatography for an ~150 kDa mAb-peptide conjugate) could confirm what is actually in a vial.
• Caution Don't stack with other GLP-1 drugs. Taking MariTide with semaglutide, tirzepatide, retatrutide or similar drugs means two drugs acting on the same receptor, which no trial on this page tested. Unknown
• Caution Measuring mistakes. FDA has reported people hospitalized after drawing up too much from multi-injection GLP-1 vials. The same syringe-marking problem applies here. See the section on measuring mistakes on our semaglutide page.

What we don't know

• Unknown What is actually in a given gray-market vial
• Unknown Phase 3 results; the first large trials are due to finish in 2027 ^R5
• Unknown Whether MariTide is safe for the heart, or lowers heart attacks and strokes ^R5
• Unknown Whether blocking GIP has long-term effects on bone, fat tissue or other organs
• Unknown Whether and when Amgen will file for approval

Is it legal?

Not FDA-approved; no Drugs@FDA record was found (openFDA search, Oct 24, 2026). We found no announced filing for approval in any country. EU, Japan, China: UNVERIFIED not checked against EMA, PMDA or NMPA. WADA: not named on the 2026 Prohibited List; S0 bans at all times any unapproved substance in development that no other section covers, which describes MariTide ^R6. WADA has not ruled on MariTide by name. As of Oct 24, 2026.

What's in the vial?

Real MariTide is only available inside clinical trials. Because it is an ~150 kDa mAb-peptide conjugate rather than a short synthetic peptide, standard small-peptide HPLC alone cannot verify it; only independent testing (such as LC-MS/MS and SDS-PAGE/SEC-HPLC for an ~150 kDa mAb-peptide conjugate) could confirm what is actually in a vial. We have not found published lab tests of gray-market MariTide. Under the Open Peptide Standard, a GLP-1 vial overfilled by more than 20% is a critical fail (draft threshold). See results at /tests/. A passing test covers one batch, tested on one date. It does not mean the compound itself is safe.

What do users report?

Self-report, not evidence.

Unknown TBD. We'll only list this once we can cite a public source.

Study details

These are doses researchers used, not recommendations. All trials funded by Amgen. All injections subcutaneous.

R1, R2 Human: Weight and diabetes trials

Study	People	Route	Dose used	Follow-up	Reported	Side effects / dropouts	Citation
Phase 2 (Jastreboff 2025), obesity cohort, NCT05669599	465	Subcutaneous	140, 280 or 420 mg every 4 weeks (no escalation); 420 mg every 8 weeks; 420 mg every 4 weeks with 4- or 12-week escalation; vs placebo	52 wk	−12.3% to −16.2% vs −2.5% (treatment-policy)	GI events common, less frequent with escalation and lower starting dose	PMID 40549887
Same trial, obesity + T2D cohort	127	Subcutaneous	140, 280 or 420 mg every 4 weeks vs placebo	52 wk	−8.4% to −12.3% vs −1.7%; HbA1c −1.2 to −1.6 vs +0.1	As above	PMID 40549887
Phase 1 (Véniant 2024), obesity, NCT04478708	Not stated in abstract	Subcutaneous	Single and multiple ascending doses vs placebo	Weight loss maintained up to 150 days after last dose (MAD cohorts)	Dose-dependent weight loss, maintained after dosing ended	Acceptable safety and tolerability	PMID 38316982

R3 Background

Wu 2026, discovery and design of AMG 133 (anti-GIPR antibody/GLP-1 peptide conjugate). PMID 41941715

R4, R5 Company statements and ongoing trials (as of Oct 24, 2026)

• R4 Trade press on Amgen at JPM 2026, Pharmaceutical Technology: dedicated phase 2 T2D trial (NCT06660173) reported meaningful HbA1c and weight reductions, numbers not released. UNVERIFIED Secondary source.
• R5 ClinicalTrials.gov: MARITIME-1, obesity NCT06858839 (3,853 enrolled, active, primary completion est. Jan 2027); MARITIME-2, obesity + T2D NCT06858878 (1,105, active); MARITIME-CV NCT07037433 (recruiting); MARITIME-HF NCT07037459 (recruiting); sleep apnea NCT07225686, NCT07226765; liver fat NCT07441252; Japan NCT06987695. No phase 3 results posted.
• FDA: no Drugs@FDA record (openFDA query, Oct 24, 2026). EMA, PMDA, NMPA: UNVERIFIED not checked.

Full reference list (all PMIDs verified on PubMed, Oct 24, 2026)

1. Jastreboff AM, et al. N Engl J Med. 2025;393(9):843-857. doi:10.1056/NEJMoa2504214. PMID 40549887
2. Véniant MM, et al. Nat Metab. 2024;6(2):290-303. doi:10.1038/s42255-023-00966-w. PMID 38316982
3. Wu B, et al. J Med Chem. 2026;69(8):9348-9362. doi:10.1021/acs.jmedchem.6c00032. PMID 41941715
4. Pharmaceutical Technology. JPM26: Amgen touts MariTide's weight loss, T2D potential off Phase II data. January 2026. https://www.pharmaceutical-technology.com/news/jpm26-amgen-maritide-obesity-t2d-phase-ii/
5. ClinicalTrials.gov. NCT06858839, NCT06858878, NCT07037433, NCT07037459, NCT07225686, NCT07226765, NCT07441252, NCT06987695, NCT06660173.
6. WADA. World Anti-Doping Code International Standard: Prohibited List 2026 (in force Jan 1, 2026). https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf (text read Oct 24, 2026)

Disclaimer

This page is for education and harm reduction. It is not medical advice and not a recommendation to use MariTide. Please talk to a clinician you trust before making medical decisions, seek care right away for severe stomach pain or repeated vomiting, and report problems to FDA MedWatch (https://www.fda.gov/safety/medwatch).

Approved for Adam Greene by Dr. Nova Reyes, 2026-10-25.