Clinical Significance
Maritide (maridebart cafraglutide) represents a paradigm shift in obesity pharmacotherapy: the first monthly injectable GLP-1-based medication. Phase 2 data demonstrates up to 20% weight loss at 52 weeks with no plateau observed, suggesting continued efficacy beyond one year.[1]
For patients: Maritide offers 12 fewer injections per year compared to weekly GLP-1 medications, potentially improving adherence while maintaining competitive efficacy (20% vs 21% for tirzepatide, 15% for semaglutide). The unique GLP-1 agonist + GIP antagonist mechanism—opposite of tirzepatide's dual agonism—provides an alternative approach for patients who may not respond optimally to existing therapies. Over 90% of participants chose to continue treatment beyond 52 weeks, suggesting high patient satisfaction.
For clinicians: The dose escalation strategy substantially reduces GI discontinuation rates from 12-27% (fixed dosing) to under 8% (escalation). The 21-day half-life enables sustained weight loss up to 150 days post-treatment, offering potential for intermittent dosing strategies. Phase 3 MARITIME program includes cardiovascular and heart failure trials, positioning maritide for potential label expansion beyond obesity.
Key differentiator: Monthly dosing convenience with weight loss durability—maximum weight loss maintained for 2 months after the last dose in Phase 1 studies.[2]
What Research Questions Are Being Answered?
The maritide clinical trial program investigates monthly GLP-1 agonist + GIP antagonist therapy for obesity, diabetes, and cardiometabolic conditions
Can monthly dosing achieve weight loss comparable to weekly GLP-1 medications?
Does maritide's extended half-life provide sustained weight loss after dosing stops?
Will Phase 3 confirm monthly maritide's efficacy and safety in larger populations?
Development Timeline
Maritide's path from first-in-human Phase 1 studies to Phase 3 MARITIME program
- 14.5% body weight loss at day 85 (highest dose) vs 1.5% placebo
- Weight maintained up to 150 days following last dose
- Maximum weight loss sustained for 2 months post-treatment
- Acceptable safety and tolerability profile
- 21-day half-life enabling monthly dosing
First demonstration that monthly GLP-1-based dosing can achieve meaningful weight loss with sustained effects weeks after treatment cessation.
Phase 1 data informed Phase 2 dose selection and validated monthly dosing feasibility, leading to Phase 2 initiation.
- BMI ≥30 kg/m²
- Age 18-65 years
- Stable weight for 3 months
- No diabetes (HbA1c <6.5%)
- Prior GLP-1 agonist use
- Cardiovascular disease
- History of pancreatitis
- Weight loss surgery
Phase 1 validated maritide's unique value proposition: monthly dosing enabled by antibody-peptide conjugate structure with sustained weight loss extending months beyond treatment. This durability distinguishes maritide from weekly GLP-1 medications and suggests potential for intermittent dosing strategies.
- Up to 20% weight loss in obesity cohort at 52 weeks
- Mean weight loss: 12.3-16.2% (obesity) vs 2.5% placebo
- No weight plateau observed at 52 weeks
- Over 90% of participants chose to continue beyond 52 weeks
- Dose escalation reduced GI discontinuation to <8%
- HbA1c reduction up to 2.2% in diabetes cohort
First monthly obesity medication to achieve weight loss comparable to weekly GLP-1 therapies. Validated that fewer injections can maintain efficacy while reducing patient burden.
Results supported Phase 3 MARITIME program initiation with optimized 8-week dose escalation (21→35→70 mg).
- Obesity cohort: BMI ≥30 (or ≥27 with comorbidity)
- Diabetes cohort: BMI ≥30 + type 2 diabetes
- Age 18-75 years
- HbA1c 7-10% (diabetes cohort)
- Recent GLP-1 agonist use
- Cardiovascular events within 6 months
- History of pancreatitis
- Uncontrolled hypertension
Phase 2 established maritide as a viable monthly obesity medication with efficacy rivaling weekly alternatives. The lack of weight plateau at 52 weeks suggests continued benefit with extended treatment. Critically, dose escalation reduced GI discontinuation from 12-27% to under 8%, solving the primary tolerability challenge. The >90% continuation rate indicates strong patient acceptance of monthly dosing.
- BMI ≥30 kg/m² or BMI ≥27 kg/m² with comorbidity
- Age 18-75 years
- Stable weight (±5%) for 3 months
- No diabetes (HbA1c <6.5%)
- Type 2 diabetes
- Recent cardiovascular events
- History of pancreatitis or medullary thyroid carcinoma
- Prior bariatric surgery
MARITIME-1 will validate Phase 2 findings in a larger, more diverse population. The optimized 8-week dose escalation (refined from Phase 2's 4-12 week escalations) aims to maximize tolerability while achieving rapid therapeutic dosing. Success would position maritide as a differentiated option for patients prioritizing injection frequency reduction.
- BMI ≥30 kg/m² (or ≥27 kg/m² with diabetes)
- Type 2 diabetes with HbA1c 7-10%
- Age 18-75 years
- On stable diabetes medications
- Type 1 diabetes
- Recent cardiovascular events
- Severe diabetic complications (retinopathy, neuropathy)
- History of pancreatitis
MARITIME-2 addresses the dual challenge of obesity + diabetes management with monthly dosing. Phase 2 showed up to 2.2% HbA1c reduction alongside 8.4-12.3% weight loss in this population. Success could position maritide as preferred option for patients requiring both glycemic control and weight management with minimal injection burden.
Safety & Tolerability
Adverse Events
| Adverse Event | Maritide (%) | Placebo (%) | Severity / Notes |
|---|---|---|---|
| Nausea | ~80-90 | ~20 | Mild-moderate; primarily first dose; median resolution 6 days |
| Vomiting | ~40-60 | ~10 | Mild-moderate; transient; median resolution 1-2 days |
| Constipation | ~30-40 | ~10 | Mild; managed with standard interventions |
| Diarrhea | ~25-35 | ~15 | Mild-moderate; self-limited |
| Abdominal pain | ~20-30 | ~10 | Mild; typically early in treatment |
| Decreased appetite | ~40-50 | ~5 | Expected mechanism; mild to moderate |
Discontinuation Due to Adverse Events
Access & Trial Participation
Current Development Status
- Phase 3 MARITIME trials: Enrollment complete (4,500+ participants), not recruiting
- Primary readouts expected: Q1 2027 (MARITIME-1 and MARITIME-2)
- FDA submission anticipated: 2027-2028 if trials meet endpoints
- U.S. FDA approval projected: 2029-2030
- Additional Phase 3 trials planned: Cardiovascular disease, heart failure, kidney disease, obstructive sleep apnea
Clinical Trial Information
MARITIME-1 and MARITIME-2 enrollment is complete and no longer recruiting. Additional Phase 3 trials may open in 2025-2026. To monitor for future opportunities:
- Visit ClinicalTrials.gov
- Search "maritide" OR "maridebart cafraglutide" OR "AMG 133"
- Filter for "Recruiting" or "Not yet recruiting" status
- Check maritimestudy.com for official trial information
- Consult your healthcare provider about eligibility and enrollment
- Sign up for trial alerts to be notified when new studies open
Frequently Asked Questions
Timeline estimate:
- Phase 3 readouts: Q1 2027 (MARITIME-1 and MARITIME-2)
- NDA submission: 2027-2028 (if trials positive)
- FDA approval: Projected 2029-2030
- Commercial availability: 2030 (estimated)
Maritide is currently not accessible outside clinical trials. MARITIME trials are closed to enrollment.
Efficacy: Maritide achieves up to 20% weight loss, comparable to Zepbound 15mg (21%) and superior to Wegovy (15.1%).
Dosing: Maritide is dosed monthly (every 4 weeks) vs weekly for Wegovy/Zepbound—resulting in 12 fewer injections per year.
Mechanism: Maritide is a GLP-1 agonist + GIP antagonist (blocks GIP), opposite of Zepbound's dual agonism. This unique mechanism may benefit patients who don't respond optimally to dual agonists.
Tolerability: With dose escalation, maritide achieves <8% GI discontinuation, comparable to Wegovy (4-7%) and Zepbound (4-7%). Fixed dosing without escalation showed higher discontinuation (12-27%).
Durability: Maritide's 21-day half-life provides sustained weight loss up to 150 days post-treatment—unique among GLP-1 therapies.
Maritide is an antibody-peptide conjugate: a GLP-1 peptide attached to a long-acting antibody scaffold. This structure provides a ~21-day half-life (vs 7 days for semaglutide), enabling monthly administration.
Patient benefits:
- 12 fewer injections per year (12 vs 52 annually)
- Improved adherence potential (fewer doses to remember)
- Reduced injection-site burden
- Sustained drug levels with less peak-trough variation
Weight loss durability: Phase 1 showed maximum weight loss maintained for 2 months after last dose, suggesting potential for intermittent dosing strategies.
Tirzepatide (Zepbound/Mounjaro): GLP-1 agonist + GIP agonist—activates both receptors
Maritide: GLP-1 agonist + GIP antagonist—activates GLP-1, blocks GIP
Why block GIP? Research suggests GIP receptor blockade may enhance satiety by removing GIP's inhibitory effects on appetite suppression. The antagonism may also provide metabolic benefits through different pathways than dual agonism.
Clinical implication: Maritide offers an alternative mechanism for patients who may not achieve optimal results with tirzepatide's dual agonism. Head-to-head trials comparing mechanisms are needed.
Overall safety: Phase 1 and Phase 2 trials showed acceptable safety profiles with no unexpected signals. Most common AEs were GI-related (nausea, vomiting), similar to GLP-1 class.[1]
Bone mineral density (BMD) concerns: In November 2024, analyst reports highlighted Phase 1 data showing ~4% BMD loss with 420mg dose over 12 weeks. Amgen stated it sees "no association between maritide administration and BMD changes" and attributes findings to rapid weight loss (a known effect of all obesity medications in the first 1-3 months).[4]
What's being done: Phase 3 MARITIME trials include BMD monitoring as a secondary endpoint. Fracture risk and long-term BMD data will be available in 2027.
Context: BMD changes are expected with significant weight loss across all obesity medications. Long-term studies show BMD typically stabilizes or recovers after weight stabilization.
Coverage outlook (post-FDA approval, projected 2029-2030):
Likely covered scenarios:
- Obesity (BMI ≥30) or overweight (BMI ≥27) with comorbidities—if FDA label matches current GLP-1 indications
- Type 2 diabetes with obesity (if diabetes indication approved)—diabetes coverage typically broader
- Patients intolerant to weekly GLP-1 medications—monthly dosing may be preferred alternative
Uncertain coverage:
- Cosmetic weight loss without medical necessity—unlikely
- Coverage parity with Wegovy/Zepbound will depend on pricing and formulary placement
Key factor: Monthly dosing may improve adherence, potentially making maritide cost-effective vs weekly options despite likely similar pricing. Prior authorization will almost certainly be required.
References
- [1]Aronne LJ, et al. Once-Monthly Maridebart Cafraglutide for the Treatment of Obesity—A Phase 2 Trial. N Engl J Med. 2025;392(25):2370-2383. doi:10.1056/NEJMoa2504214View source →
- [2]Coskun T, et al. A GIPR antagonist conjugated to GLP-1 analogues promotes weight loss with improved metabolic parameters in preclinical and phase 1 settings. Nat Metab. 2024;6(2):290-303. doi:10.1038/s42255-023-00966-wView source →
- [3]Amgen. Inside Amgen's Phase 3 MARITIME Program: Advancing the Future of Obesity Care. June 2025.View source →
- [4]Amgen. Amgen Provides Statement on MariTide Phase 1 Data. Press Release. November 2024.View source →
- [5]Amgen. Amgen Announces Robust Weight Loss With MariTide in People Living With Obesity or Overweight at 52 Weeks in a Phase 2 Study. Press Release. November 2024.View source →
- [6]Amgen. Results From Amgen's Phase 2 Obesity Study of Monthly MariTide Presented at the American Diabetes Association 85th Scientific Sessions. June 2025.View source →
- [7]ClinicalTrials.gov. A Study to Evaluate AMG 133 in Subjects With Obesity or Overweight. NCT04478708. Updated 2023.View source →
- [8]ClinicalTrials.gov. A Study of Maridebart Cafraglutide in Adult Participants With Obesity or Overweight. NCT05669599. Updated 2025.View source →
- [9]ClinicalTrials.gov. Efficacy and Safety of Maridebart Cafraglutide in Adult Participants With Type 2 Diabetes Mellitus Who Have Obesity or Are Overweight (MARITIME-2). NCT06858878. Updated 2025.View source →
- [10]MARITIME Study. Weight Management and Related Conditions Research. Official trial website.View source →
Last updated October 6, 2026
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