How effective will MariTide be for weight loss?
The investigational weight loss drug MariTide (maridebart cafraglutide) achieved 12%–16% mean weight loss (intent-to-treat) in obese patients without diabetes, and up to 20% when excluding dropouts after 52 weeks in phase 2 trials, compared to about 2% with placebo. Notably, weight loss was still ongoing at one year, indicating further potential.
MariTide Phase 2 Clinical Trial Results
Phase 2 studies of MariTide included two groups: adults with obesity, and adults with obesity and type 2 diabetes. The primary end point of the studies was the percent change in body weight from baseline over 52 weeks.
In adults with obesity but no diabetes:
- Mean weight loss: –12.3% to –16.2% (intent-to-treat); –16.3% to –19.9% (efficacy estimand) at 52 weeks.
- Placebo group: –2.5% to -2.6% weight loss.
In adults with obesity and type 2 diabetes:
- Mean weight loss: –8.4% to –12.3% (intent-to-treat); –12.1% to –17.0% (efficacy estimand).
- Placebo group: -1.4% to –1.7% weight loss.
Weight loss curves had not plateaued by Week 52, suggesting further loss is possible with continued treatment.
Who Lost How Much?
Proportion of MariTide users achieving weight loss milestones (obesity cohort, highest dose):
- ≥ 5% loss: 85% (vs 26% with placebo)
- ≥ 10% loss: 72% (vs 12% with placebo)
- ≥ 15% loss: 54% (vs 3% with placebo)
Proportion of MariTide users achieving weight loss milestones (obesity and type 2 diabetes cohort, highest dose):
- ≥ 5% loss: 78% (vs. 16% with placebo)
- ≥ 10% loss: 63% (vs 1% with placebo)
- ≥ 15% loss: 47% (vs 0% with placebo)
Durability and Trajectory
Weight loss was steady and progressive throughout the 52 weeks of the phase 2 studies, with no plateau reached. Extension studies are needed to test whether monthly or less frequent dosing can maintain or enhance this effect over longer periods. Dose escalation strategies (starting at a lower dose and gradually increasing) have improved tolerability and reduced dropouts due to gastrointestinal (GI) side effects without sacrificing efficacy.
Diabetes vs Non-Diabetes Results
Absolute weight loss was smaller in participants with type 2 diabetes, but they still achieved substantial reductions. In those with type 2 diabetes, HbA1c (blood sugar marker) fell by 1.2%–1.6%, and most met American Diabetes Association (ADA) weight targets. Cardiometabolic improvements (blood pressure, cholesterol, inflammation) were also observed.
How Does MariTide Compare to Today’s Leaders?
Based on phase 2 trials, MariTide’s efficacy is between Wegovy and Zepbound for adults identified as obese, but with only monthly injections, potentially improving convenience and adherence.
| Drug & Dose | Mean % Loss | Duration | Frequency | Study |
| MariTide 420 mg | 16–20% | 52 weeks | Monthly | NEJM 2025 |
| Semaglutide (Wegovy) 2.4 mg | 15% | 68 weeks | Weekly | STEP 1 |
| Tirzepatide (Zepbound) 15 mg | 21% | 72 weeks | Weekly | SURMOUNT 1 |
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What Phase 3 Trials Will Confirm
Phase 3 trials are the critical next step in determining whether MariTide’s promising phase 2 results will hold up in a much larger and more diverse population. These studies are designed to rigorously evaluate the drug’s long-term safety, efficacy, and tolerability over 72 weeks, using optimized dosing strategies and enrolling thousands of participants with obesity, both with and without type 2 diabetes. The outcomes will provide the definitive evidence needed for regulatory approval and to guide future clinical use.
- Ongoing phase 3 MARITIME trials (72 weeks) will test optimized dose escalation (21→35→70 mg), aiming to maintain weight loss with fewer GI side effects.
- Primary endpoint: Percent weight change at Week 72
- Key secondary endpoints: Include change in waist circumference, proportion achieving ≥5%, ≥10%, and ≥15% weight loss, change in systolic blood pressure, change in triglycerides, change in HbA1c
Factors That Influence Individual Response
Individual responses to MariTide can vary widely, with some people experiencing dramatic weight loss while others see more modest results. Several factors influence how much weight a person is likely to lose, how well they tolerate the medication, and whether they can maintain their progress over time.
- Baseline BMI: Higher BMI may predict greater absolute weight loss.
- Dose-escalation schedule: Slower escalation reduces GI side effects (nausea, vomiting), which are the main reason for discontinuation.
- Lifestyle add-ons: Diet and activity programs, identical to those used in other GLP-1 trials, improve the odds of achieving ≥15% weight loss.
- Adherence: Those who complete the full treatment period see the greatest benefit.
References
- American Diabetes Association Professional Practice Committee. (2023, December 11). 8. Obesity and Weight Management for the Prevention and Treatment of Type 2 Diabetes: Standards of Care in Diabetes–2024. Diabetes Care, 47(Supplement 1), S145. https://diabetesjournals.org/care/article/47/Supplement_1/S145/153942/8-Obesity-and-Weight-Management-for-the-Prevention
- Amgen. (2024, November 26). AMGEN ANNOUNCES ROBUST WEIGHT LOSS WITH MARITIDE IN PEOPLE LIVING WITH OBESITY OR OVERWEIGHT AT 52 WEEKS IN A PHASE 2 STUDY. Amgen. https://www.amgen.com/newsroom/press-releases/2024/11/amgen-announces-robust-weight-loss-with-maritide-in-people-living-with-obesity-or-overweight-at-52-weeks-in-a-phase-2-study
- Jastreboff, A. M., Ryan, D. H., Bays, H. E., Ebeling, P. R., Mackowski, M. G., Philipose, N., Ross, L., Liu, Y., Burns, C. E., Abbasi, S. A., Pannacciulli, N., & MariTide Phase 2 Obesity Trial Investigators (2025). Once-Monthly Maridebart Cafraglutide for the Treatment of Obesity - A Phase 2 Trial. The New England journal of medicine, 10.1056/NEJMoa2504214. Advance online publication. https://doi.org/10.1056/NEJMoa2504214
- Jastreboff, A. M., Aronne, L. J., Ahmad, N. N., Wharton, S., Connery, L., Alves, B., Kiyosue, A., Zhang, S., Liu, B., Bunck, M. C., Stefanski, A., & SURMOUNT-1 Investigators (2022). Tirzepatide Once Weekly for the Treatment of Obesity. The New England journal of medicine, 387(3), 205–216. https://doi.org/10.1056/NEJMoa2206038
- Javor, E., Lucijanić, M., & Skelin, M. (2021). Once-Weekly Semaglutide in Adults with Overweight or Obesity. The New England journal of medicine, 385(1), e4. https://doi.org/10.1056/NEJMc2106918
- MariTime. About the MARITIME-1 study. Accessed on June 29, 2025 at https://www.maritimestudy.com/en-us/maritime-1
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