Retatrutide vs Efpeglenatide
Comprehensive side-by-side comparison of mechanisms, dosing, side effects, and research
Also: LY3437943, Triple G
Retatrutide is the heavy hitter of the new weight-loss drugs: a once-weekly injectable peptide that hits three receptors at once - GIP, GLP-1, and glucagon - earning it the nickname triple-G agonist. In phase 2 it produced about 24 percent weight loss at the top dose, and in the phase 3 TRIUMPH-1 trial Lilly reported 28.3 percent at 12 mg over 80 weeks. It is investigational, made by Eli Lilly, and not FDA approved; Lilly plans to file with the FDA in the first quarter of 2027. Because it is not an approved drug, FDA says it cannot be legally compounded.
Also: Eppe, HM11260C
Efpeglenatide is a long-acting, once-weekly GLP-1 agonist from Hanmi Pharmaceutical, made by linking an exendin-4 analog to an antibody fragment so it lasts days instead of hours. Sanofi licensed it for diabetes in 2015 and handed it back in 2020 despite a positive heart outcomes trial. Hanmi relaunched it for obesity, and on 7 October 2026 South Korea approved it as Eppe, the country's first homegrown GLP-1 obesity drug. It is not approved by the FDA or EMA.
Key Comparison Insights
- Both peptides belong to the Weight Loss category, suggesting similar primary applications.
Detailed Comparison
| Attribute | Retatrutide | Efpeglenatide |
|---|---|---|
| Category | Weight Loss | Weight Loss |
| FDA Status | Not FDA Approved | Not FDA Approved |
| Clinical Status | Pre I II III IV FDA | Pre I II III IV FDA |
| Mechanism of Action | Retatrutide combines three hormone signals into one molecule. The GLP-1 component curbs appetite and slows stomach emptying, the GIP component supports insulin response and may improve how fat tissue handles nutrients, and the added glucagon receptor activity is the novel piece: glucagon can increase energy expenditure and fat burning in the liver. The idea is that two arms cut how much you eat while the third raises how much you burn, which is why retatrutide is thought to push weight loss further than GLP-1-only drugs like semaglutide or even the dual GIP/GLP-1 agonist tirzepatide. The exact contribution of each receptor in humans is still being worked out, so consider the glucagon-driven energy-expenditure story a strong hypothesis rather than fully nailed down. | Efpeglenatide activates the GLP-1 receptor, which raises insulin release after meals, lowers glucagon, slows stomach emptying and reduces appetite. The active part is an exendin-4 analog (the same parent peptide as exenatide and lixisenatide) attached through a small linker to a human IgG4 Fc fragment, using Hanmi's LAPSCOVERY platform. The Fc piece makes the molecule big enough to dodge kidney clearance and lets it recycle in the body, which stretches its half-life to weekly dosing. Hanmi argues its lower brain penetration explains the milder GI profile; that is a company argument rather than an independently proven fact. |
| Common Dosing | 4-12 mg weekly Once weekly, same day each week | 10 mg once weekly maintenance (Korean label) Once weekly |
| Administration | Subcutaneous injection weekly | Subcutaneous auto-injector once weekly |
| Typical Duration | Long-term use expected | Long-term (chronic weight management); 40-64 weeks in the Korean phase 3 |
| Best Time to Take | Morning, same day each week | Same day each week |
Possible Side Effects May vary by individual |
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| Research Summary | The first big human evidence was the phase 2 trial by Jastreboff and colleagues (New England Journal of Medicine, 2023), which randomized 338 adults with obesity (without type 2 diabetes) over 48 weeks. Mean weight reduction reached about 24 percent at the 12 mg dose, and weight loss had not clearly plateaued by week 48. In a liver-fat substudy of 98 participants, liver fat dropped by about 81 to 82 percent at the 8 and 12 mg doses by week 24. Phase 3 has since read out: in TRIUMPH-1, Lilly reported mean weight loss of 19.0, 25.9 and 28.3 percent at 4, 9 and 12 mg over 80 weeks versus 2.2 percent on placebo (efficacy estimand, which assumes people stayed on the drug; analyses counting everyone randomized come out a few points lower). TRIUMPH-2 (type 2 diabetes plus obesity) reached about 20.8 percent at 12 mg, and TRIUMPH-3 (severe obesity plus heart disease) about 22.6 percent. Side effects were dominated by dose-dependent gastrointestinal issues like nausea, vomiting, and diarrhea, plus a dysesthesia (skin sensitivity) signal at the top dose. Retatrutide sold outside of trials is not an approved, quality-controlled medicine. | The strongest data come from Sanofi's AMPLITUDE-O trial (NEJM 2021), which enrolled people with type 2 diabetes and cardiovascular or kidney disease. Efpeglenatide 4 or 6 mg weekly cut major cardiovascular events by 27% versus placebo (7.0% vs 9.2%, hazard ratio 0.73) over a median of 1.8 years, and also reduced kidney outcomes. Sanofi still returned the rights in 2020 for business reasons. Hanmi then ran a Korean phase 3 obesity trial in 448 adults without diabetes (average BMI 32): at 40 weeks, weight loss was 9.02% versus 0.89% on placebo, and 75.1% lost at least 5%. That is less weight loss than semaglutide or tirzepatide in their pivotal trials, though trial designs differ, and GI side effects were somewhat lower (diarrhea 17.6%, nausea 16.6%, vomiting 11.6%). Korea's MFDS approved it for chronic weight management on 7 October 2026, with launch planned for late October. Bottom line: a solid, proven drug class member with real outcome data, but modest weight loss and no Western approval. |
Frequently Asked Questions: Retatrutide vs Efpeglenatide
What is the difference between Retatrutide and Efpeglenatide?
Retatrutide is a weight loss peptide that retatrutide is the heavy hitter of the new weight-loss drugs: a once-weekly injectable peptide that hits three receptors at once - gip, glp-1, and glucagon - earning it the nickname triple-g agonist. in phase 2 it produced about 24 percent weight loss at the top dose, and in the phase 3 triumph-1 trial lilly reported 28.3 percent at 12 mg over 80 weeks. it is investigational, made by eli lilly, and not fda approved; lilly plans to file with the fda in the first quarter of 2027. because it is not an approved drug, fda says it cannot be legally compounded. Efpeglenatide is a weight loss peptide that efpeglenatide is a long-acting, once-weekly glp-1 agonist from hanmi pharmaceutical, made by linking an exendin-4 analog to an antibody fragment so it lasts days instead of hours. sanofi licensed it for diabetes in 2015 and handed it back in 2020 despite a positive heart outcomes trial. hanmi relaunched it for obesity, and on 7 october 2026 south korea approved it as eppe, the country's first homegrown glp-1 obesity drug. it is not approved by the fda or ema. The main differences lie in their mechanisms of action and clinical applications.
Which is better, Retatrutide or Efpeglenatide?
Neither is universally "better" - the choice depends on your specific goals. Retatrutide is typically used for weight loss purposes, while Efpeglenatide is used for weight loss. Always consult with a healthcare provider to determine which may be appropriate for your situation.
Can Retatrutide and Efpeglenatide be used together?
Some peptide protocols combine multiple compounds for synergistic effects. However, using Retatrutide and Efpeglenatide together should only be considered under medical supervision, as both compounds have their own side effect profiles and potential interactions. Research on their combined use may be limited.