Pfizer’s VESPER-1 extension data, presented Saturday at the American Diabetes Association Scientific Sessions in New Orleans, put a 15.9% non-placebo-adjusted weight loss number on the weekly top dose of berobenatide, the GLP-1 receptor agonist at the center of its $10 billion Metsera buy.
That figure comes from a 32-week extension in which patients escalated from placebo to the 2.4 mg weekly dose. Pfizer Chief Internal Medicine Officer Jim List called it “continuous, uninterrupted weight loss” while patients transitioned from weekly to monthly dosing. No plateau.
VESPER-2 adds the diabetes data point: berobenatide at 1.6 mg weekly produced a 2.2% HbA1c reduction versus 0.2% on placebo, with dose-dependent signals across both body weight and blood sugar in patients with obesity or overweight who also carry Type 2 diabetes.
The benchmarking gap is real. Lilly’s Zepbound showed 20.9% weight loss after 72 weeks; Novo’s Wegovy hit 18.7% at the same timepoint, both in late-stage trials. Berobenatide’s 15.9% is at 32 weeks with no plateau; the 72-week ceiling is unwritten. Cross-trial comparisons aren’t clean, but closing that gap is Pfizer’s Phase 3 mandate.
Pfizer is planning 10 late-stage programs in 2026 as part of its Metsera acquisition, covering chronic weight management plus knee osteoarthritis and obstructive sleep apnea. VESPER-4 targets weekly dosing without Type 2 diabetes; VESPER-5 adds T2D and the 2.4 mg dose; VESPER-6 tests once-monthly dosing. That’s a Phase 3 footprint that won’t need validating. It’s already enrolling.
VESPER-3 data from February showed 12.3% placebo-adjusted weight loss at 28 weeks on monthly dosing. Pfizer is also running combination studies with amylin asset MET-233i, which could push efficacy beyond what weekly dosing alone shows.
Worth auditing: VESPER-4 through VESPER-6 enrollment timelines, expected in 2026.
Rebecca Lauren