Pfizer touts Phase 2b data supporting monthly dosing of berobenatide, a potential new GLP-1 option

Pfizer on Saturday presented detailed Phase 2b results for berobenatide (PF’3944), an investigational, monthly GLP-1 receptor agonist (GLP-1 RA) peptide, arguing the data support a Phase 3 dosing approach that includes low, medium and high monthly doses. The company shared the results during a late-breaking experts symposium at the American Diabetes Association’s 86th Scientific Sessions, positioning berobenatide as a potential first-in-class option for weight management and obesity-related comorbidities.

In its Phase 2b program, Pfizer highlighted VESPER-1’s exploratory extension, which followed participants out to 32 weeks on the top weekly berobenatide dose. The company said the extension showed non-placebo-adjusted weight loss of 15.9% for participants who escalated from placebo to 2.4 mg weekly berobenatide, with “no plateau” reported at 32 weeks (week 60 of the overall study). Pfizer also framed VESPER-1 as assessing durability of weight loss and the impact of shifting from weekly dosing to less frequent regimens, including once-monthly administration.

Pfizer said tolerability across its Phase 2b studies was favorable, emphasizing low gastrointestinal adverse events and discontinuations that occurred “despite rapid dose escalation and no allowed step-down.” The company also tied the monthly concept to delivery practicality, saying the treatment could be administered in a very low 0.5 mL injection volume aimed at improving convenience and scalability. Pfizer did not provide granular adverse event rates or arm-by-arm discontinuation counts in the June 6 materials, but it repeatedly characterized discontinuations and GI effects as manageable during the escalation and transition periods it described.

For monthly efficacy support, Pfizer pointed to its previously disclosed Phase 2b VESPER-3 results in adults with obesity or overweight without type 2 diabetes. In the earlier topline release, the company reported statistically significant weight reduction with up to 12.3% mean placebo-adjusted weight loss at week 28, and said the primary endpoint favored berobenatide over placebo across four tested dose regimens (P < 0.001). Pfizer described VESPER-3 as including a titration period with weekly dosing followed by monthly maintenance injections, with the company saying weight loss continued after the planned switch from weekly to monthly dosing.

Pfizer also described Phase 2b findings in participants with obesity or overweight plus type 2 diabetes from VESPER-2, where berobenatide was tested on a weekly schedule. The company said dose-dependent reductions from baseline were observed for both body weight and HbA1c (a measure of average blood glucose). Pfizer added a specific example from VESPER-2: it reported a 2.2% reduction in HbA1c with berobenatide 1.6 mg weekly at week 28 versus a 0.2% reduction with placebo (using an on-treatment efficacy estimand).

Beyond Phase 2, Pfizer reiterated its broader Phase 3 plans. In 2026, it said it intends to advance 10 Phase 3 studies for berobenatide for chronic weight management and obesity-related comorbidities that include knee osteoarthritis and obstructive sleep apnea, as part of a wider program of 20+ obesity trials. Pfizer also said VESPER-6, a pivotal Phase 3 study investigating monthly maintenance dosing of berobenatide, is open for enrollment, and it described SOLIS-1, a Phase 2b study investigating both weekly and monthly dosing of an ultra-long-acting amylin analog (PF’3945) alone and in combination with berobenatide.

Still, the June 6 presentation materials did not disclose several items that investors and clinicians typically look for when evaluating a GLP-1 RA development program, including the exact rates of specific gastrointestinal adverse events across monthly dose arms, full discontinuation counts by study arm for the June 6 set of data, and a complete breakdown of efficacy results for each monthly dose level it plans to carry into Phase 3. Pfizer’s approach appears to rely on multiple Phase 2b datasets (VESPER-1, VESPER-2, and VESPER-3) to justify dose selection, but detailed safety and efficacy summaries are likely to remain the key missing pieces until additional conference slides and full reports are examined.