Pfizer details monthly berobenatide data and plans 10 Phase 3 trials in 2026
Berobenatide is not approved, but Pfizer's new Phase 2b results point toward a GLP-1 injection taken once a month instead of once a week.
Pfizer said its investigational weight-loss drug berobenatide delivered continuous weight loss as patients moved from weekly to monthly dosing, and outlined plans for 10 Phase 3 trials of the drug in 2026 [1].
The results were presented June 6 at the American Diabetes Association Scientific Sessions in New Orleans [1][2]. Berobenatide, also coded PF'3944 and previously known as MET-097i, is an injectable GLP-1 receptor agonist peptide that Pfizer is developing for once-monthly use [1][2]. Pfizer picked up the drug through its $10 billion acquisition of the obesity biotech Metsera [2]. No GLP-1 medication is currently approved for monthly dosing.
The Phase 2b numbers
In a 32-week exploratory extension of the Phase 2b VESPER-1 study, adults with obesity or overweight who escalated from placebo to 2.4 milligrams of berobenatide weekly lost 15.9% of their body weight, a figure not adjusted for placebo, with no plateau observed at 32 weeks, which was week 60 of the overall study [1]. Pfizer said this is the first time clinical experience with the top weekly dose has been presented [1][2].
In VESPER-2, which tested weekly berobenatide in adults with obesity or overweight who also have type 2 diabetes, the 1.6 mg weekly dose produced a 2.2% reduction in HbA1c, a measure of average blood sugar, at week 28, compared with a 0.2% reduction on placebo, using an on-treatment efficacy measure [1][2]. Pfizer said dose-dependent reductions from baseline were seen for both body weight and HbA1c [1][2].
VESPER-3 tested monthly maintenance dosing in about 250 adults with obesity or overweight without type 2 diabetes. Pfizer previously reported placebo-adjusted weight loss of 10% and 12.3% at week 28 on the low and medium monthly doses the company is taking into Phase 3 [2].
Pfizer described tolerability as favorable, with low rates of gastrointestinal adverse events and discontinuations even though the studies used rapid dose escalation and did not allow step-down dosing [1]. The company also highlighted a 0.5 milliliter injection volume [1].
"In Phase 2b studies, berobenatide delivered continuous, uninterrupted weight loss at all doses selected for Phase 3, while preserving a tolerable profile as people transitioned from a weekly to a monthly maintenance dose," said Jim List, Pfizer's chief internal medicine officer [1].
John B. Buse of the University of North Carolina School of Medicine said the evidence shows "meaningful weight loss with a well-tolerated profile following a switch from weekly to monthly dosing," adding that "if approved, berobenatide has the potential to not only be effective, but practical and sustainable in real life" [1].
Direct comparisons are difficult at this stage. Fierce Biotech noted that Eli Lilly's approved Zepbound (tirzepatide) showed 20.9% weight loss after 72 weeks in a late-stage trial, while Novo Nordisk reported 18.7% for the high dose of Wegovy (semaglutide) after the same period [2]. Cross-trial comparisons carry inherent flaws, and berobenatide's effect over a longer timeframe has not yet been reported [2].
Why it matters for patients
Weekly injections are the standard for the GLP-1 obesity drugs on the market, including Wegovy, Zepbound and their lower-dose versions used for diabetes. A monthly shot could reduce how often patients have to plan around a dose, though Pfizer has not reported data showing that monthly dosing improves real-world adherence.
Weight loss goals, side effects and cost are the factors patients weigh now, and berobenatide's full profile across larger and longer trials is not yet known. Nothing presented at the conference is adjusted for placebo at 32 weeks on the 2.4 mg weekly dose, and the Phase 3 program will test whether the results hold up [1][2].
Berobenatide has not been approved by the Food and Drug Administration. Pfizer has not disclosed pricing, insurance coverage or a filing timeline for the drug.
What happens next
Pfizer said it plans to advance 10 Phase 3 berobenatide trials in 2026, covering chronic weight management and obesity-related conditions including knee osteoarthritis and obstructive sleep apnea, as part of more than 20 obesity trials planned this year [1]. VESPER-4 is testing weekly berobenatide in adults with obesity or overweight without type 2 diabetes, and VESPER-5 is testing it in people who also have diabetes and is evaluating the higher 2.4 mg weekly dose in Phase 3 [1][2].
VESPER-6, which tests monthly berobenatide, is now open for enrollment [1][2]. A Phase 2b study called SOLIS-1 is also enrolling to test weekly and monthly dosing of an ultra-long-acting amylin analog, PF'3945, both alone and combined with berobenatide [1].
Sources
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