The Short Answer
Eloralintide and retatrutide are both investigational once-weekly injections from Eli Lilly, and neither is FDA-approved. They work in different ways:
- Eloralintide is a selective amylin receptor agonist. Lilly says its effect is likely driven by satiety (feeling full).
- Retatrutide is a triple agonist of the GIP, GLP-1 and glucagon receptors.
Retatrutide is further along: it has Phase 3 results (TRIUMPH-1). Eloralintide has Phase 2 results, and its Phase 3 program (ENLIGHTEN) is now recruiting. That means their weight-loss numbers come from different trial stages, lengths and populations, so they can't be compared head to head.
This is an educational comparison, not a dosing guide. The doses below are the doses studied in trials, not recommendations.
Side-by-Side
| Eloralintide | Retatrutide | |
|---|---|---|
| Developer | Eli Lilly | Eli Lilly |
| Target | Amylin receptor (selective) | GIP + GLP-1 + glucagon receptors |
| Former code | LY3841136 | LY3437943 |
| Dosing frequency studied | Once weekly | Once weekly |
| Latest stage with results | Phase 2 (48 weeks, 263 adults) | Phase 3 TRIUMPH-1 (80 weeks, 2,339 adults) |
| Top mean weight loss reported* | 20.1% at 9 mg vs 0.4% placebo | 28.3% at 12 mg vs 2.2% placebo |
| Most common side effects | Mild-to-moderate GI symptoms and fatigue | Nausea, diarrhea, constipation, vomiting; dysesthesia |
| FDA status | Investigational | Investigational |
*Efficacy estimand, per Lilly. Different trial lengths and populations, so this isn't a fair head-to-head comparison.
Eloralintide: What the Phase 2 Trial Showed
Lilly's Phase 2 trial (NCT06230523), published in The Lancet in November 2025, randomized 263 adults with obesity or overweight and no type 2 diabetes. At 48 weeks, Lilly reported mean weight loss of:
| Eloralintide arm | Mean weight change |
|---|---|
| 1 mg | -9.5% |
| 3 mg | -12.4% |
| 6 mg | -17.6% |
| 9 mg | -20.1% |
| 6/9 mg escalation | -19.9% |
| 3/6/9 mg escalation | -16.4% |
| Placebo | -0.4% |
Lilly said the most common adverse events were mild to moderate GI symptoms and fatigue, more frequent at higher doses, lower with slower escalation, and similar to placebo at 1 mg and 3 mg. Lilly is pitching it as a possible alternative to incretin drugs for people who don't tolerate them, and as a possible add-on.
Phase 3 is underway. ENLIGHTEN-1 (NCT07321886) is a Phase 3 trial in obesity without type 2 diabetes and is recruiting. Lilly has also completed a Phase 2 study of eloralintide with tirzepatide in adults with type 2 diabetes (NCT06603571).
More: eloralintide weight loss results, eloralintide side effects and eloralintide vs cagrilintide.
Retatrutide: What TRIUMPH-1 Showed
TRIUMPH-1 (NCT05929066) randomized 2,339 adults with obesity or overweight and no diabetes for 80 weeks. Lilly reported (May 21, 2026):
| Retatrutide arm | Mean weight change at 80 weeks |
|---|---|
| 4 mg | -19.0% |
| 9 mg | -25.9% |
| 12 mg | -28.3% |
| Placebo | -2.2% |
45.3% of people on 12 mg lost at least 30% of their body weight. The most common side effects were nausea (28.6% to 42.4% vs 14.8% on placebo), diarrhea, constipation and vomiting. Dysesthesia (skin burning or tingling) was reported in 5.1% to 12.5% vs 0.9% on placebo. Discontinuation due to side effects was 4.1% to 11.3% vs 4.9% on placebo.
More: retatrutide side effects and the TRIUMPH-1 tracking guide.