Pfizer Emerges as GLP-1 Heavyweight with Berobenatide (PF'3944) Phase 2b Clinical Data at ADA 2026

Pfizer Emerges as GLP-1 Heavyweight with Berobenatide (PF'3944) Phase 2b Clinical Data at ADA 2026

Pfizer Inc. (NYSE: PFE) has aggressively positioned itself as a major competitor to Eli Lilly and Novo Nordisk in the obesity space. Following its multi-billion dollar acquisition of Metsera in late 2025, Pfizer presented highly competitive Phase 2b clinical data for its monthly injectable peptide, berobenatide (PF'3944, formerly MET-097i), at the 86th Scientific Sessions of the American Diabetes Association (ADA) on June 6, 2026.

The clinical results from the VESPER development program establish berobenatide as a potential first-in-class, ultra-long-acting GLP-1 receptor agonist (RA) capable of delivering competitive weight loss on a monthly maintenance schedule, challenging the weekly injection paradigm currently dominated by Lilly's Zepbound and Novo's Wegovy.

The Metsera Acquisition as Pfizer's GLP-1 Foundation

On November 13, 2025, Pfizer completed the acquisition of Metsera, Inc. for $65.60 per share in cash, representing an enterprise value of approximately $7.0 billion, plus contingent value rights (CVRs) of up to $20.65 per share (pushing the potential total deal value over $10 billion). This transaction brought several high-value clinical-stage assets to Pfizer's pipeline, including:

• MET-097i (now berobenatide or PF'3944): a weekly and monthly injectable GLP-1 RA.
• MET-233i (now PF-08653945 or PF'3945): a monthly amylin analog.
• An oral GLP-1 RA in Phase 1 development.

Phase 2b VESPER Clinical Data Highlights

At the June 2026 ADA Meeting, Pfizer showcased detailed data from its Phase 2b VESPER trials, demonstrating robust weight loss and favorable tolerability:

• VESPER-1 (Extension Part B): In adult participants with obesity or overweight, weekly treatment with 2.4 mg of berobenatide achieved a non-placebo-adjusted weight loss of 15.9% at 32 weeks (Week 60 of the overall study), with no weight-loss plateau observed.
• VESPER-3 (Monthly Maintenance): This 64-week study evaluated a weekly titration phase to week 12, followed by a switch to monthly dosing. At week 28, participants on the low and medium monthly maintenance doses (which are moving to Phase 3) achieved up to 12.3% mean placebo-adjusted weight loss. Efficacy was maintained after transitioning from weekly to monthly dosing, with no plateau observed.
• VESPER-2 (Type 2 Diabetes): Evaluated weekly dosing in adults with obesity and type 2 diabetes. At week 28, weekly treatment with 1.6 mg of berobenatide delivered a 2.2% reduction in HbA1c (efficacy estimand) compared to 0.2% for placebo.

Broad Phase 3 Launch and Combination Strategy

To capitalize on this data, Pfizer is launching a massive Phase 3 program in 2026 consisting of 10 clinical trials. This includes VESPER-4 (weekly dosing in obesity), VESPER-5 (weekly dosing in obesity with type 2 diabetes), and VESPER-6 (monthly maintenance dosing in obesity, currently open for enrollment). In addition, Pfizer is running the SOLIS-1 Phase 2b trial to evaluate the amylin analog PF'3945 both as a monotherapy and in combination with berobenatide, preparing a next-generation dual-acting regimen.

Financially, Pfizer has the capital to fund this aggressive expansion, reporting a trailing twelve-month (TTM) revenue of $63.32 billion and $2.18 billion in quarterly free cash flow as of March 31, 2026.

Quotes

"Results from multiple Phase 2b dose finding studies for berobenatide (PF’3944) highlight a potential first-in-class monthly GLP-1 receptor agonist (GLP-1 RA) peptide, and support the planned Phase 3 low, medium and high dosing strategy" — Pfizer Press Release, June 6, 2026

"VESPER-1 achieved a non-placebo-adjusted weight loss of almost 16% with no plateau observed at 32 weeks on 2.4 mg weekly berobenatide" — Pfizer Press Release, June 6, 2026

"The study demonstrated statistically significant weight reduction with up to 12.3% mean placebo-adjusted weight loss at week 28 (efficacy estimand)... These data show robust and continuous weight loss after switching to monthly dosing¹, with no plateau observed at week 28, suggesting continued weight loss is expected as the study continues through week 64." — Pfizer Press Release, February 3, 2026