Berobenatide
Berobenatide (MET-097i, PF-08653944)
Also known as: MET-097i, PF-08653944, PF'3944
An ultra-long-acting GLP-1 agonist with a roughly 15-day half-life built for once-monthly injection, the centerpiece of Pfizer's Metsera acquisition and now heading into ten Phase 3 trials.
Overview
Berobenatide uses an albumin-binding 'halo-lipidation' design that stretches the half-life of a fully biased GLP-1 receptor agonist to about 360 hours. Weekly dosing produced up to 14.1% placebo-adjusted weight loss at 28 weeks (VESPER-1), and in VESPER-3 participants switched to monthly maintenance kept losing weight, reaching 10% to 12.3% placebo-adjusted loss at week 28 with no plateau. Pfizer completed its purchase of Metsera in late 2025 and planned a broad Phase 3 program for 2026.
Mechanism of action
Long-acting GLP-1 receptor agonism (appetite suppression, slowed gastric emptying) with an engineered half-life that allows weekly induction followed by monthly dosing.
Key studies & citations
- Human2026
VESPER-3: monthly maintenance dosing of MET-097i
10.0% and 12.3% placebo-adjusted loss at week 28 after switching to monthly dosing.
ClinicalTrials.gov NCT06973720 - Human2026
Pfizer's ultra-long-acting injectable GLP-1 RA shows robust weight loss
Monthly regimen continued to reduce weight with no plateau at 28 weeks.
Pfizer press release - Human2025
Metsera reports positive Phase 2b results for MET-097i
Up to 14.1% placebo-adjusted weight loss at 28 weeks on weekly dosing.
Metsera press release
Frequently asked questions
Why does a monthly GLP-1 matter?
Fewer injections and steadier drug levels could improve adherence, and a monthly maintenance schedule is being tested as a way to hold weight after the initial loss.
Is berobenatide the same as semaglutide?
No. Both activate the GLP-1 receptor, but berobenatide is a different molecule with a half-life roughly two times longer, designed for monthly dosing.