Eli Lilly announced that its experimental combination regimen achieved greater weight loss than a high dose of tirzepatide alone in a 48-week Phase 2 trial. The study involved patients with obesity and Type 2 diabetes. These findings were presented at the European Association for the Study of Diabetes in Milan, Italy. They offer new hope for patients who struggle to achieve target results on existing single- or dual-hormone therapies.
Targeting Three Hormone Pathways
The experimental treatment pairs Lilly’s amylin-targeting drug, eloralintide, with a low dose of tirzepatide. Tirzepatide is the active ingredient in the company’s popular obesity and diabetes medications Zepbound and Mounjaro. While tirzepatide targets two crucial gut hormones-GLP-1 and GIP-eloralintide introduces a third pathway. It focuses on amylin, a hormone produced in the pancreas that plays a key role in appetite regulation and satiety.
By hitting all three hormone pathways simultaneously, the therapy is designed to curb appetite more aggressively and enhance overall metabolic response. According to Ken Custer, president of Lilly Cardiometabolic Health, this physiological approach gently engages three natural nutrient-stimulated hormone systems rather than overstimulating any single pathway.
Phase 2 Trial Results and Weight Loss Data
In the mid-stage study, patients receiving the highest dose of the combination regimen lost an average of 23.3% of their body weight. This translates to roughly 54 pounds. For a patient population with Type 2 diabetes-which historically experiences more modest weight loss outcomes compared to non-diabetic individuals-these results mark a significant step forward.
For comparison, other cohorts within the study yielded distinct metrics:
- Patients receiving 15 milligrams of tirzepatide alone lost an average of 14.8%, or about 34.4 pounds.
- Patients receiving eloralintide alone dropped an average of 12.3%, or about 28.6 pounds.
- The combination treatment also reduced a key marker of blood sugar levels, A1C, by up to 2.9% on average.
Higher-dose tirzepatide alone reduced A1C by up to 2.4%, while the amylin drug alone lowered it by up to 1.4%.
Tolerability and Discontinuation Rates
While the efficacy data proved robust, the study also highlighted important questions regarding tolerability and treatment persistence. More patients on the combination regimen discontinued treatment due to adverse side effects. This ranged from 10.8% to 27% depending on the specific dosing group, compared to 2.9% of participants on tirzepatide alone.
The most commonly reported side effects were gastrointestinal-related. They were generally mild to moderate in severity and tended to manifest primarily when patients escalated their dosages during the trial. Custer noted that elevated discontinuation rates are common during Phase 2 optimization studies. He expressed confidence that adjusting dosing schedules in upcoming trials will achieve a more favorable balance between efficacy and tolerability.
Next Steps and Future Development
Building on these mid-stage findings, Eli Lilly announced plans to advance the combination regimen into Phase 3 trials by the end of the year. The company is also evaluating a co-formulation of the two molecules. This would allow patients to administer both tirzepatide and eloralintide through a single, combined injection.
As the pharmaceutical landscape shifts toward multi-agonist therapies-including Lilly’s separate triple-agonist candidate retatrutide-experts suggest that these next-generation treatments could soon expand options for millions of patients seeking alternatives to current blockbuster therapies.
