Eli Lilly’s Retatrutide Delivers 28% Weight Loss Yet Faces 11.3% Dropout Rate
Retatrutide delivered 28% bodyweight reduction at 80 weeks in TRIUMPH-1, surpassing high-dose Wegovy’s 20.7% at 72 weeks and Zepbound’s 22.5%, despite an 11.3% discontinuation rate versus 5.4–6.2% for competitors. Observational data showed GLP-1 therapies halved lung cancer progression and achieved 95% five-year survival in 137,000 breast cancer patients.
1. Retatrutide Phase III Results
Eli Lilly’s triple agonist retatrutide achieved a 28% mean bodyweight reduction after 80 weeks in the TRIUMPH-1 pivotal trial, matching the 28.7% loss seen in the TRIUMPH-4 study at 68 weeks and exceeding high-dose Wegovy’s 20.7% at 72 weeks and Zepbound’s 22.5% in similar cohorts.
2. Safety and Discontinuation
The 11.3% discontinuation rate for retatrutide due to adverse events outpaced competitors’ rates of 5.4% for Wegovy, 6.2% for Zepbound and 5.9% for CagriSema, with gastrointestinal side effects and diarrhoea slightly more common and dysaesthesia reported in 12.5% of retatrutide patients.
3. Cancer Observational Findings
Observational analyses of over 10,000 early-stage cancer patients indicated GLP-1 therapies halved lung cancer progression, while a retrospective review of 137,000 breast cancer cases showed a 95% five-year survival rate among GLP-1 users versus 89.5% for nonusers, suggesting potential oncology benefits.
4. Market Implications and Outlook
These efficacy and safety data position retatrutide as a powerful challenger to Novo Nordisk’s dominant GLP-1 portfolio, and combined with emerging cancer benefit research, could expand Eli Lilly’s obesity and metabolic franchise pending detailed data presentation at the June ADA conference.