Eli Lilly announced promising results from a mid-stage clinical trial testing a combination obesity regimen in patients with obesity and Type 2 diabetes. The experimental therapy combined Lilly’s amylin-targeting drug eloralintide with a low dose of tirzepatide, the key component in its established drugs Zepbound and Mounjaro. Over 48 weeks, patients on the highest doses of the combo lost an average of 23.3% of their body weight, significantly outperforming those taking tirzepatide alone, who lost 14.8%, or eloralintide alone, which showed 12.3% weight loss.

The combination approach targets three hormonal pathways—GLP-1, GIP, and amylin—that regulate appetite and satiety, which Lilly believes can provide an enhanced weight loss effect. The study also showed favorable improvements in blood sugar control, with the combo reducing A1C levels by up to 2.9%, compared to 2.4% with tirzepatide alone. Lilly plans to initiate Phase 3 trials for the combo regimen by the end of 2026 and intends to develop a co-formulated injection for easier administration.

Despite the encouraging results, the combo treatment was associated with a higher rate of discontinuation due to side effects, primarily mild to moderate gastrointestinal issues, compared to tirzepatide alone. Lilly executives acknowledge these tolerability challenges but emphasize that dosing adjustments in upcoming Phase 3 studies are expected to improve the balance between effectiveness and side effects. Historical data from earlier trials with high-dose tirzepatide help contextualize the discontinuations as part of early drug development.

Analysts consider Lilly’s combination regimen a potential “winning approach,” given it targets multiple appetite-regulating hormones simultaneously, which might benefit patients who do not get adequate results from current GLP-1 therapies. The strategy positions Lilly competitively against Novo Nordisk’s similar amylin-GLP-1 combination candidate. With millions of patients needing better treatment options, Lilly’s phase advancement underscores the significant market potential for this next-generation obesity therapy.