Pfizer Rationalizes Obesity Pipeline: Discontinues Oral Metsera Asset and Backs Monthly Injectable Berobenatide
Following its blockbuster acquisition of biotech darling Metsera in late 2025, Pfizer has executed a strategic cleanup of its clinical-stage obesity pipeline to consolidate its bets. The pharma giant discontinued several early-stage and redundant assets—including the ex-Metsera oral GLP-1 asset MET-224o and the GIPR antagonist PF-07976016—to focus its resources on its crown jewel: berobenatide (PF-08653944, formerly MET-097i), an investigational, potential first-in-class, ultra-long-acting monthly injectable GLP-1 receptor agonist (RA) peptide.
By mid-2026, Pfizer officially transitioned berobenatide into pivotal Phase 3 development, positioning itself to challenge the Eli Lilly and Novo Nordisk duopoly with a highly convenient monthly dosing regimen.
Entering Phase 3: The VESPER Program
Pfizer's Phase 3 program for berobenatide is highly aggressive, with plans to advance 10 Phase 3 trials in 2026 covering chronic weight management and obesity-related comorbidities (such as knee osteoarthritis and obstructive sleep apnea).
Key Phase 3 trials currently underway include:
- VESPER-6 (NCT07595549): A pivotal Phase 3 randomized, double-blind, placebo-controlled study investigating once-monthly berobenatide in adults with overweight or obesity. The trial is officially open and actively recruiting patients.
- VESPER-4: An ongoing Phase 3 pivotal study investigating once-weekly berobenatide in adults with obesity or overweight without type 2 diabetes.
- VESPER-5: A planned Phase 3 study investigating once-weekly berobenatide in adults with obesity or overweight with type 2 diabetes.
"These data highlight the potential for berobenatide to be the first approved monthly GLP-1 RA peptide and support our extensive Phase 3 program that includes 10 studies for chronic weight management and obesity-related comorbidities." — Jim List, M.D., Ph.D., Chief Internal Medicine Officer, Pfizer, Pfizer Press Release, June 5, 2026
Clinical Background and Efficacy
Pfizer's decision to back berobenatide is supported by strong Phase 2b data presented at the American Diabetes Association (ADA) 2026 Scientific Sessions. The VESPER trials demonstrated robust, continuous, and uninterrupted weight loss:
- VESPER-1 (Part B extension): Achieved a non-placebo-adjusted weight loss of 15.9% at 32 weeks on a 2.4 mg weekly dose, with no plateau observed.
- VESPER-3: Demonstrated that patients could successfully transition from weekly induction dosing to monthly maintenance dosing (up to a 9.6 mg monthly dose selected for Phase 3) while maintaining a favorable tolerability profile and low gastrointestinal side effects.
Strategic Impact for Investors
Pfizer’s $10 billion acquisition of Metsera in late 2025 was designed to pivot the company away from its previous oral GLP-1 setbacks (such as the discontinuation of danuglipron due to tolerability and liver enzyme issues) and establish a broad, competitive obesity platform. By discontinuing redundant assets like MET-224o, Pfizer is fully committing to a monthly injectable strategy. If berobenatide's Phase 3 VESPER program succeeds, Pfizer could capture a highly lucrative share of the obesity market by offering patients a monthly alternative to Lilly's weekly Zepbound and Novo's weekly Wegovy.