The clinical trial data for retatrutide has set new records in obesity medicine. No pharmaceutical drug has ever produced this much weight loss in controlled trials. Here's a comprehensive, data-driven breakdown of every result published so far — and what the ongoing Phase 3 programme might show.
Key Takeaways
- Phase 2 results (NEJM, June 2023): 24.2% mean weight loss at the 12 mg dose over 48 weeks — the highest ever recorded for an obesity drug
- 93% of participants on the 12 mg dose lost at least 15% of their body weight
- Weight loss curves had not plateaued at 48 weeks, suggesting continued treatment could produce even greater losses
- Retatrutide outperformed both semaglutide (~15%) and tirzepatide (~22.5%) in cross-trial comparisons
- Phase 3 TRIUMPH trials are ongoing with data readouts expected late 2026–2027
- Additional benefits: Dramatic liver fat reduction (up to 86% decrease), improved glucose control, and potential cardiovascular benefits
Medical Disclaimer: Retatrutide is an investigational drug in Phase 3 clinical trials. It is not approved for use anywhere in the world. This article summarises published clinical data for educational purposes only. Do not attempt to obtain or self-administer unapproved medications.
The Phase 2 Trial: Study Design
The pivotal Phase 2 study was published by Jastreboff et al. in the New England Journal of Medicine in June 2023. Understanding the study design helps you interpret the results properly.
Study Parameters
- Design: Randomised, double-blind, placebo-controlled, dose-ranging trial
- Participants: 338 adults with obesity (BMI ≥30) or overweight (BMI ≥27 with at least one weight-related comorbidity)
- Duration: 48 weeks of treatment
- Doses tested: 0.5 mg, 1 mg, 4 mg (escalated and fixed), 8 mg (escalated and fixed), 12 mg (escalated), and placebo
- Administration: Once-weekly subcutaneous injection
- Primary endpoint: Percentage change in body weight from baseline at 24 weeks
- Key secondary endpoint: Percentage change in body weight at 48 weeks
The trial used an escalation protocol for higher doses (starting low and increasing gradually over weeks) to mitigate gastrointestinal side effects — the same approach used with Ozempic and Mounjaro.
Weight Loss Results: The Complete Data
Here are the full results at both the 24-week and 48-week timepoints:
Results at 24 Weeks (Primary Endpoint)
| Dose Group | Mean Weight Loss | vs Placebo (p-value) |
|---|---|---|
| Placebo | –2.1% | — |
| 0.5 mg | –3.2% | NS |
| 1 mg | –7.2% | <0.001 |
| 4 mg (escalated) | –12.9% | <0.001 |
| 4 mg (fixed) | –14.5% | <0.001 |
| 8 mg (escalated) | –17.4% | <0.001 |
| 8 mg (fixed) | –17.5% | <0.001 |
| 12 mg (escalated) | –17.5% | <0.001 |
Results at 48 Weeks (Key Secondary Endpoint)
| Dose Group | Mean Weight Loss | % Losing ≥10% | % Losing ≥15% | % Losing ≥20% |
|---|---|---|---|---|
| Placebo | –2.1% | 10% | — | — |
| 1 mg | –8.7% | 41% | 29% | 10% |
| 4 mg (escalated) | –17.1% | 75% | 67% | 38% |
| 4 mg (fixed) | –22.8% | 92% | 75% | 58% |
| 8 mg (escalated) | –22.1% | 88% | 81% | 63% |
| 8 mg (fixed) | –25.4% | 92% | 83% | 75% |
| 12 mg (escalated) | –24.2% | 100% | 93% | 75% |
Several aspects of this data are remarkable:
- 100% of 12 mg participants lost ≥10% of their body weight — an extraordinarily consistent response rate
- 75% lost ≥20% — three out of four participants lost a fifth of their body weight or more
- The dose-response curve is clear and steep — higher doses consistently produced more weight loss
- Weight loss was still accelerating at 48 weeks — the curves had not yet reached a plateau, suggesting 12+ months of treatment could yield even more dramatic results
Comparison to Other GLP-1 Medications
Cross-trial comparisons must be interpreted with caution (different studies, different populations, different timeframes). However, the magnitude of differences is large enough to draw meaningful conclusions.
Head-to-Head Cross-Trial Comparison
| Drug | Trial | Best Dose | Duration | Mean Weight Loss |
|---|---|---|---|---|
| Liraglutide (Saxenda) | SCALE | 3.0 mg daily | 56 weeks | ~8% |
| Semaglutide (Wegovy) | STEP 1 | 2.4 mg weekly | 68 weeks | ~14.9% |
| Tirzepatide (Mounjaro) | SURMOUNT-1 | 15 mg weekly | 72 weeks | ~22.5% |
| Retatrutide | Phase 2 | 12 mg weekly | 48 weeks | ~24.2% |
What makes retatrutide's results even more impressive is the shorter treatment duration. The STEP 1 trial ran for 68 weeks and SURMOUNT-1 for 72 weeks, while retatrutide achieved superior results in just 48 weeks. If the weight loss curve continues (as suggested by the non-plateauing trajectory), 72-week results could be substantially higher.
For detailed head-to-head analyses, see:
- Retatrutide vs Semaglutide (Ozempic): Complete Comparison
- Retatrutide vs Tirzepatide (Mounjaro): Which Is Better?
Beyond Weight Loss: Metabolic Benefits
Retatrutide's triple mechanism doesn't just produce weight loss — it drives improvements across multiple metabolic parameters.
Liver Fat Reduction
Perhaps the most striking secondary finding from the Phase 2 programme was the effect on liver fat. In a subset analysis:
- Participants on the 12 mg dose showed an 86% reduction in liver fat content at 48 weeks
- 93% of participants with baseline MAFLD (metabolic-associated fatty liver disease) achieved normalisation of liver fat (<5%)
- These results far exceed any currently available treatment for fatty liver disease
This has enormous implications for Southeast Asia, where NAFLD prevalence is estimated at 25–30% of the adult population. In Malaysia specifically, the combination of high obesity rates, diabetes prevalence, and dietary patterns makes fatty liver a significant public health concern.
Glucose Control
Despite the glucagon component (which typically raises blood sugar), retatrutide produced robust improvements in glycaemic control:
- HbA1c reduction of up to 1.3% in participants with type 2 diabetes
- Fasting glucose improved significantly across all dose groups
- The GLP-1 and GIP components more than compensated for glucagon's glucose-raising effect
A separate Phase 2 trial in patients with type 2 diabetes (published alongside the obesity trial) confirmed these glucose-lowering effects, supporting retatrutide's dual potential as both an obesity and diabetes treatment.
Other Metabolic Improvements
- Blood pressure: Clinically meaningful reductions in systolic and diastolic blood pressure
- Lipid profile: Improvements in triglycerides, with modest effects on LDL and HDL cholesterol
- Waist circumference: Significant reductions, indicating loss of visceral (abdominal) fat — the most metabolically dangerous type
- Inflammatory markers: Reductions in C-reactive protein (CRP) and other inflammatory biomarkers
Side Effects in Clinical Trials
Understanding the side effect profile is essential for making informed decisions. For a comprehensive analysis, see our dedicated Retatrutide Side Effects guide.
Summary of Adverse Events (Phase 2)
| Side Effect | 12 mg Dose | Placebo |
|---|---|---|
| Nausea | 25% | 6% |
| Diarrhoea | 23% | 8% |
| Vomiting | 13% | 2% |
| Constipation | 12% | 6% |
| Decreased appetite | 9% | 2% |
| Dyspepsia | 5% | 2% |
Key observations:
- GI side effects were dose-dependent — higher doses produced more side effects but also more weight loss
- Most GI symptoms were mild to moderate and occurred during the dose escalation period
- Discontinuation rates due to adverse events were relatively low (~6% at higher doses) and comparable to tirzepatide trials
- The escalation protocol (gradually increasing dose over weeks) substantially reduced the incidence and severity of GI symptoms compared to fixed-dose starts
Heart Rate
A modest increase in resting heart rate (2–4 bpm) was observed, likely attributable to the glucagon component. This was not clinically significant in the Phase 2 trial, but cardiovascular safety is being closely monitored in the Phase 3 TRIUMPH-3 cardiovascular outcomes trial.
Phase 3 TRIUMPH Programme: What We're Watching
The Phase 3 programme will determine whether retatrutide's impressive Phase 2 results hold up in larger, more diverse populations. Here's what each trial is evaluating:
TRIUMPH-1: Obesity Without Diabetes
The pivotal trial for weight management approval. Expected to enroll several thousand participants with BMI ≥30 (or ≥27 with comorbidities) without type 2 diabetes. This will provide the definitive weight loss efficacy number.
TRIUMPH-2: Obesity With Type 2 Diabetes
Critical for a dual-indication approval (both obesity and diabetes). Weight loss in diabetic patients typically runs lower than in non-diabetic patients — the key question is by how much.
TRIUMPH-3: Cardiovascular Outcomes
A large, long-duration trial looking at major adverse cardiovascular events (MACE). This is the "gold standard" safety trial that regulators and insurers care deeply about. Results are expected in 2028–2029.
TRIUMPH-4: MASH (Fatty Liver)
Given the extraordinary liver fat reduction seen in Phase 2, a MASH-specific trial was inevitable. If successful, this could be retatrutide's second or third approved indication — and a massive market opportunity.
TRIUMPH-5: Obstructive Sleep Apnoea
Weight loss drugs are increasingly being studied for sleep apnoea (tirzepatide already showed positive results for this). Given the association between obesity and sleep apnoea, strong results here would expand retatrutide's clinical utility.
Expected Phase 3 Results
Based on historical precedent, Phase 3 results are typically slightly more modest than Phase 2 (due to larger, more diverse populations, more stringent monitoring, and intention-to-treat analysis). Our projection for retatrutide's Phase 3 weight loss:
- Optimistic: 22–25% (confirming Phase 2 magnitude)
- Realistic: 20–23% (modest attenuation from Phase 2)
- Conservative: 18–20% (still best-in-class)
Even the conservative estimate would make retatrutide the most effective obesity medication ever approved.
What Do These Results Mean for Malaysian Patients?
Malaysia has one of the highest obesity rates in Southeast Asia, with approximately 50% of adults classified as overweight or obese. The implications of retatrutide's data are significant:
For Patients Currently on GLP-1 Therapy
If you're currently taking Ozempic or Mounjaro and achieving good results, continue your current treatment. Retatrutide will be an option when it's approved, but current medications are already highly effective. See our Mounjaro vs Ozempic comparison for guidance on current choices.
For Patients Who Haven't Started Treatment
Don't wait for retatrutide. The best time to start managing obesity is now. Current options produce 15–22% weight loss — life-changing results available today. Visit a weight loss clinic in KL or check our pricing guide to explore options.
For Patients Who've Plateaued
If you've plateaued on semaglutide, switching to tirzepatide (Mounjaro) is an option available now. In the future, retatrutide may offer another step-up option for patients who need greater efficacy.
Understanding the Limitations of Current Data
While the results are extraordinary, intellectual honesty requires acknowledging the limitations:
- Phase 2 sample size is small (338 participants) — Phase 3 data with thousands of participants will be more definitive
- 48 weeks may not capture long-term dynamics — we don't yet know what happens at 72+ weeks or after years of treatment
- Weight regain after discontinuation is likely (as seen with all GLP-1 drugs) — lifelong treatment may be necessary
- Cross-trial comparisons are imperfect — different studies have different inclusion criteria, endpoints, and populations
- Real-world results often differ from trials — adherence, dose adjustments, comorbidities, and lifestyle factors all play a role
None of these limitations diminish the fundamental finding: retatrutide produces more weight loss than any previous drug, and does so through a novel triple mechanism of action. The Phase 3 programme will either confirm this or temper expectations — but either way, retatrutide will likely be a landmark drug.
Timeline: When Will We Know More?
| Event | Expected Timing |
|---|---|
| TRIUMPH-1/2 data readout | Late 2026 – Early 2027 |
| FDA submission | Mid-Late 2027 |
| FDA approval | Late 2027 – 2028 |
| NPRA registration (Malaysia) | 2029–2030 |
| TRIUMPH-3 CV outcomes data | 2028–2029 |
| TRIUMPH-4 MASH data | 2027–2028 |
We'll update this article as new data becomes available. For Malaysia-specific availability and pricing information, see our Retatrutide Malaysia Guide.
Frequently Asked Questions
Is 24.2% weight loss realistic for everyone?
The 24.2% figure is a mean (average) — some participants lost more, some less. Individual results depend on starting BMI, genetics, adherence, diet, and exercise. In the trial, the range at 12 mg was roughly 15–35%, with most participants (75%) losing ≥20%.
How does retatrutide compare to bariatric surgery?
Roux-en-Y gastric bypass typically produces 25–35% weight loss. Retatrutide's Phase 2 results (24.2%) place it at the lower end of surgical outcomes — making it the first drug to genuinely compete with surgery. See our Malaysia guide for a detailed comparison table.
Will Phase 3 results be as good as Phase 2?
Historically, Phase 3 results are slightly more conservative (often 5–15% lower). A realistic expectation is 20–23% weight loss at the top dose — which would still be the best of any approved drug.
Can I combine retatrutide with other weight loss medications?
This hasn't been studied yet. Combining GLP-1-based drugs is generally not recommended until safety data from combination trials is available. Stick to evidence-based monotherapy.
When will retatrutide be available in Malaysia?
Our best estimate is 2029–2030. See the full Retatrutide Malaysia guide for the complete regulatory timeline and projected pricing in RM.
The Bottom Line
Retatrutide's clinical trial results represent a watershed moment in obesity medicine. The Phase 2 data — 24.2% weight loss at 48 weeks with the curves still declining — suggests we may be approaching the upper limit of what's achievable with incretin-based pharmacotherapy.
The Phase 3 TRIUMPH programme will either confirm these extraordinary results or introduce more nuance. Either way, retatrutide will almost certainly be the most effective obesity drug ever brought to market.
For Malaysian patients, the practical message is clear: don't wait. Ozempic and Mounjaro are available now and produce excellent results. When retatrutide arrives in 2029–2030, it will be another powerful tool in the arsenal — but the best time to start your weight management journey is today.
Medical Disclaimer: This content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting any treatment, supplement regimen, or making changes to your health routine. Individual results may vary, and what works for others may not work for you.