Pfizer’s monthly GLP-1 shows 15.9% weight loss, pressures Eli Lilly
LLY•Pfizer’s berobenatide achieved a 15.9% body-weight reduction over eight months at its highest weekly dose in Phase 2b VESPER-1 and showed nearly 15% loss after 14 months with monthly dosing in VESPER-3. The once-a-month drug and 20 trial launches in 2026 could challenge Eli Lilly’s weekly Zepbound franchise.
1. Phase 2b Trial Outcomes
In the VESPER-1 study, patients on the highest weekly berobenatide dose saw an average 15.9% reduction in body weight over eight months without plateauing. In VESPER-3, overweight or obese participants without diabetes on the highest four-weekly dose lost nearly 15% after 14 months, demonstrating continuous weight loss with a tolerable safety profile.
2. Impact on Eli Lilly’s Obesity Franchise
Berobenatide’s once-a-month regimen offers a distinct convenience edge over weekly therapies like Zepbound, potentially improving patient adherence and retention. As obesity care shifts toward primary-care physicians, Pfizer’s broad commercial network could intensify competition and squeeze Eli Lilly’s market share and pricing power.
3. Berobenatide’s Development Roadmap
Pfizer plans more than 20 trials in 2026, including 10 Phase 3 studies for berobenatide, targeting comorbidities such as sleep apnea and knee osteoarthritis. Expansion into China and Japan is underway, positioning the drugmaker to become the first to offer a monthly GLP-1 agonist if regulatory approval is secured.
