Lilly’s amylin-tirzepatide combo and retatrutide set new benchmarks for weight loss

Key points

• The eloralintide-tirzepatide combination achieved up to 23.3% weight loss (54 pounds) in a 48-week Phase 2 trial, outperforming tirzepatide alone (14.8%) and eloralintide alone (12.3%).
• Retatrutide, a triple-agonist targeting GLP-1, GIP, and glucagon, resulted in up to 25% weight loss for patients with obesity and 23% for those with Type 2 diabetes in Phase 3 trials.
• The combination therapy showed higher discontinuation rates due to side effects (10.8% to 27%) compared to tirzepatide alone (2.9%), though Lilly plans to adjust dosing in Phase 3.
• Retatrutide significantly improved cardiometabolic markers, including blood pressure and lipid profiles, and reduced inflammation markers, with 72% of patients achieving an HbA1c below 6.5%.
• Lilly plans to file for retatrutide approval early next year and advance the combination therapy to Phase 3 trials by the end of 2026, including a co-formulation for single-injection administration.

Background

Eli Lilly has been expanding its obesity drug portfolio beyond its existing GLP-1 therapies, such as Zepbound and Mounjaro. Previous coverage highlighted the company's focus on multi-hormone approaches to address patients who do not respond adequately to current treatments. The recent Phase 3 results for retatrutide and Phase 2 data for the amylin-tirzepatide combination build on earlier trials that demonstrated the potential of targeting additional gut hormones like glucagon and amylin to enhance weight loss and metabolic benefits.

How outlets are covering it

CNBC emphasized the combination therapy's potential as an alternative for patients who did not respond to existing GLP-1 products, noting that the amylin-tirzepatide regimen could serve as a 'winning approach' by engaging three hormone systems. The outlet also highlighted concerns about tolerability, with higher discontinuation rates in the combination group compared to tirzepatide alone. NBC News focused on retatrutide's record-breaking weight loss results, particularly for patients with Type 2 diabetes, and noted the drug's potential to rival bariatric surgery in terms of efficacy. The Guardian highlighted retatrutide's broader health benefits, including improvements in blood sugar control, inflammation, and cardiometabolic risk factors, while noting the absence of head-to-head comparisons with existing treatments. Endpoints News, the primary source, focused on the combination therapy's superior weight loss results but did not provide detailed data due to paywall restrictions.

Why it matters

The advancements in obesity drug development by Eli Lilly could significantly impact the treatment landscape for patients with obesity and Type 2 diabetes. The combination therapy and retatrutide offer potential alternatives for individuals who do not respond adequately to existing GLP-1 therapies, addressing a major unmet need in the market. The improved weight loss and metabolic benefits could reduce the burden of obesity-related conditions, such as cardiovascular disease and diabetes, while the development of co-formulations may enhance patient adherence. However, concerns about tolerability and side effects remain, requiring careful monitoring in Phase 3 trials and post-approval studies.

What to watch

Eli Lilly plans to file for retatrutide approval early next year and advance the amylin-tirzepatide combination therapy to Phase 3 trials by the end of 2026. The company will also test a co-formulation of the two drugs for single-injection administration. Regulatory decisions and further clinical data will determine the timeline for market approval and widespread availability of these treatments.