This treatment is in clinical trials and has not been approved by the FDA or any regulatory authority. It is not available for prescription. Current stage: Phase 3 initiated (72-week studies enrolling). Estimated approval: 2027+ (estimated — not confirmed) — subject to change.
MariTide
Amgen · Code: AMG 133
MariTide takes a completely different approach to other weight loss drugs. While tirzepatide activates the GIP receptor, MariTide blocks it — using the opposite strategy — while also activating GLP-1. This antibody-peptide conjugate (a different drug class entirely from small molecules or peptide injections) only needs to be injected once a month or less, which could be transformative for adherence.
Quick read · 4 min
MariTide is an investigational drug currently in Phase 3 initiated (72-week studies enrolling). Best trial result so far: up to 20% average weight loss. Estimated approval: 2027+ (estimated — not confirmed) — this is not confirmed and timelines can shift.
Why this matters:
Most GIP drugs (tirzepatide, retatrutide) activate the GIP receptor. MariTide blocks it instead — proving that GIP can be targeted in opposite directions. Monthly dosing could be transformative for adherence. These treatments are still under investigation, and results in larger trials may differ from early data.
Development stage and timeline
Current stage:
Phase 2 complete. Phase 3 initiated — 72-week chronic weight management studies enrolling with three target dose arms (starting at 21mg, titrating to 35mg then 70mg).
Next milestone:
Phase 3 data expected 2027. Estimated approval: 2027+ (preliminary; not confirmed).
How it works
MariTide is an antibody-peptide conjugate that simultaneously blocks GIP receptors (antagonist) and activates GLP-1 receptors (agonist). This is the opposite of tirzepatide, which activates GIP. Both approaches produce significant weight loss — suggesting GIP plays a complex role in appetite regulation that can be targeted in different ways. The monthly dosing is made possible by the antibody component, which has a much longer half-life than peptide drugs.
Phase 2 trial data by dose
In the Phase 2 trial (where people were randomly assigned to different doses or a dummy pill), participants on different doses lost the following amounts of weight. Phase 3 data is pending.
| Dose | At 24 weeks | At 48 weeks |
|---|---|---|
| –% | –% | |
| –% | –% |
Side effects (early-stage data)
Frequencies from Phase 2 trial data. Final Phase 3 safety profile may differ.
Notable findings
- ✓Monthly (or less frequent) dosing — potentially much better adherence than weekly injections
- ✓Works differently from all current approved drugs — a new mechanism class
- ✓~17% weight loss in participants with type 2 diabetes (Phase 2, 52 weeks)
- ✓Weight had not plateaued by 52 weeks in Phase 2 — suggesting potential for greater loss with longer treatment
What this tends to offer vs. what it involves
What this tends to offer
- ✓Up to ~20% weight loss in Phase 2 — comparable to tirzepatide
- ✓Once-monthly injection — potentially transformative for adherence
- ✓Antibody-based design offers different pharmacological profile
- ✓Weight not plateauing in Phase 2 suggests potential for longer-term benefit
What this involves
- ◆Phase 3 still ongoing — not yet completed
- ◆Antibody-peptide format is more complex than small molecules
- ◆Long-term safety and cardiovascular outcomes not yet studied
- ◆Approval 2027+ estimated — several years away
How it differs from approved drugs
MariTide's defining difference is twofold: it's given monthly (not weekly), and it blocks the GIP receptor rather than activating it. All other approved and pipeline drugs that work on GIP (tirzepatide, retatrutide) activate GIP — MariTide blocks it. The fact that both approaches produce significant weight loss is scientifically surprising and suggests GIP is more complex than originally thought.
Community insights
These are personal experiences shared in public online communities — not medical advice.
“The monthly injection is the defining feature — people on Wegovy or Zepbound report weekly dosing becomes routine, but monthly would be even more adherence-friendly.”
“GIP antagonism intrigues pharmacologically-minded followers, but clinical significance vs. GIP agonists remains uncertain.”
Sources & references
- [1]Phase 2 randomised dose-finding studyAdults with obesity (with and without type 2 diabetes) · 52 weeksUp to ~20% weight loss (non-diabetic cohort) and ~17% (type 2 diabetes cohort) at 52 weeks. No weight plateau observed. Monthly dosing confirmed feasible.Nature Medicine / Amgen press release (2024) ↗