Tirzepatide Tops Semaglutide
- New SURMOUNT‑5 trial data show tirzepatide produced larger average weight losses than semaglutide in the head‑to‑head comparison. (x.com) - Reported numbers were about 20.2% weight loss for tirzepatide versus 13.7% for semaglutide in that dataset. (x.com) - Those efficacy gaps are fueling real‑world switching, payer favoritism, and debate over which incretin profiles offer the best tradeoffs. (x.com)
These obesity drugs copy gut hormones that help people feel full and eat less, and in the first published head-to-head trial, tirzepatide produced larger average weight loss than semaglutide. (nejm.org) In the SURMOUNT-5 phase 3b trial, 751 adults with obesity, or overweight plus a weight-related condition, but without diabetes were randomly assigned to weekly tirzepatide or semaglutide for 72 weeks. (acc.org) Average weight loss was 20.2% with tirzepatide and 13.7% with semaglutide, according to Eli Lilly’s December 4, 2024 release and the New England Journal of Medicine paper published July 3, 2025. (lilly.com, nejm.org) The same trial found larger waist-size reductions with tirzepatide, and a Journal Watch summary of the paper said the mean weight drop was about 20% versus 14% at week 72. (acc.org, nejm.org) The comparison landed in a market where both drugs were already cleared in the United States for chronic weight management, but the medicines are not identical. Tirzepatide activates two hormone pathways, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1, while semaglutide targets glucagon-like peptide-1 alone. (fda.gov, fda.gov) Semaglutide also carries an added U.S. label claim that tirzepatide does not: reducing major cardiovascular events in adults with established cardiovascular disease and obesity or overweight, based on the SELECT outcomes trial. (fda.gov, nejm.org) Both drugs have boxed warnings about thyroid C-cell tumors seen in rodents, and both labels list stomach side effects among the main tolerability issues. (fda.gov, fda.gov) That leaves doctors, patients, and insurers comparing a larger average weight-loss effect for tirzepatide against semaglutide’s longer cardiovascular-outcomes record in obesity. The head-to-head data did not settle every question, but it gave the market a direct 72-week comparison instead of cross-trial guesswork. (nejm.org, nejm.org)
