Pfizer (NYSE: PFE) presented detailed Phase IIb data at the American Diabetes Association's 86th Scientific Sessions showing that berobenatide (PF-3944; previously called MET-097i), its investigational GLP-1 receptor agonist. The molecule - acquired through its approximately USD 7 billion acquisition of Metsera in November 2025 - delivered nearly 16% non-placebo-adjusted weight loss at 32 weeks on weekly dosing with no plateau observed, while also demonstrating the feasibility of transitioning patients to a monthly maintenance regimen. The data support a 10-study Phase III program and potentially point the way forward for Pfizer as a credible challenger in the obesity market after the previous failure of its in-house oral GLP-1 agonist danuglipron.
Berobenatide is a fully biased, ultra-long-acting GLP-1 receptor agonist peptide designed to activate the GLP-1 receptor while minimizing downstream signaling pathways associated with gastrointestinal side effects, with a half-life supporting both weekly and monthly subcutaneous administration in a 0.5 mL injection volume.
Trial data
The ADA presentation covered three Phase IIb VESPER studies. In the VESPER-1 32-week exploratory extension (Part B), participants who escalated from placebo to 2.4 mg weekly berobenatide achieved a mean non-placebo-adjusted weight loss of 15.9% at week 60 of the overall study, with no plateau observed — the first clinical data at the top weekly dose to be disclosed publicly. VESPER-3, a 64-week randomized, double-blind, placebo-controlled study in adults with obesity or overweight without type 2 diabetes, previously reported its primary endpoint and presented detailed results at ADA: placebo-adjusted weight loss of up to 12.3% at week 28 with the 4.8 mg monthly maintenance dose following a weekly titration phase, with no weight loss plateau. The VESPER-2 study, in adults with obesity or overweight and type 2 diabetes, showed dose-dependent reductions in both body weight and HbA1c; the 1.6 mg weekly dose achieved a 2.2% reduction in HbA1c at week 28 versus 0.2% for placebo. Across all three studies, gastrointestinal adverse events were predominantly mild or moderate, discontinuation rates were low despite rapid dose escalation and no permitted step-down, and no severe nausea or vomiting was reported in the monthly dosing arms. The data are described as supporting the planned Phase III low, medium, and high dosing strategy.