Monthly Obesity Treatment
Pfizer's Berobenatide Phase 2 Results Show Strong Weight Loss for Monthly Dosing
Pfizer used ADA Scientific Sessions to present additional Phase 2 evidence for berobenatide (PF-08653944), an experimental ultra-long-acting GLP-1 receptor agonist it acquired through its Metsera purchase, aiming to shift obesity treatment from weekly injections to a monthly option. In VESPER-3, which studied people with obesity or overweight without type 2 diabetes, the monthly regimen produced up to 12.3% placebo-adjusted weight loss by 28 weeks and showed no plateau after transitioning from weekly to monthly dosing in the trial’s reported updates. In VESPER-1 extension data, patients who escalated from placebo to the top weekly dose achieved non-placebo-adjusted weight loss of 15.9% with no plateau at 32 weeks, supporting the durability case for longer dosing intervals. Pfizer also reported that VESPER-2 showed dose-dependent improvements in both body weight and HbA1c in participants with type 2 diabetes, while emphasizing tolerability with relatively low gastrointestinal side effects and limited discontinuations during rapid escalation. Across the program, Pfizer highlighted features intended to improve real-world usability—such as a very small injection volume and a dosing design meant to make monthly maintenance feasible—while noting adverse events may rise during the weekly-to-monthly transition. The company further outlined plans to advance berobenatide into 10 Phase 3 trials in 2026, including studies of weekly dosing without diabetes and a dedicated monthly-dosing program.
Key Points
John Buse, MD, PhD, said monthly dosing could be a “straightforward convenience gain” for patients—roughly “12 or 13 injections per year versus 52”—arguing it’s easier to manage than current weekly GLP-1 regimens.
In the VESPER-1 open-label extension, Pfizer’s ADA update reported that the program defined a new maximum monthly dose of 9.6 mg for phase 3 advancement, alongside evidence supporting a weekly-to-monthly transition without a significant added tolerability burden.
Pfizer’s expert symposium materials emphasized tolerability “despite rapid dose escalation” and specified that there was “no allowed step-down” during the escalation scheme—an important design detail for interpreting discontinuations and adverse-event rates.
In VESPER-2 (type 2 diabetes), Pfizer highlighted a specific HbA1c differential: a 2.2% blood-sugar reduction with 1.6 mg weekly versus a 0.2% reduction on placebo.
Pfizer provided specific Phase 3 timing and trial structure: VESPER-4 (weekly, no type 2 diabetes) began in late 2025; VESPER-5 (type 2 diabetes) is set to start in March 2026; and VESPER-6 is the dedicated monthly-dosing study.
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