Berobenatide
Medium EvidenceA once-monthly injectable GLP-1 receptor agonist developed by Pfizer (acquired from Metsera), showing 12.3% placebo-adjusted weight loss in Phase 2b trials with a tolerability profile comparable to weekly semaglutide.
What It Is
Berobenatide is an investigational long-acting injectable glucagon-like peptide-1 receptor agonist (GLP-1 RA) originally developed by Metsera and acquired by Pfizer in November 2025 for approximately $7 billion. Its key differentiator is dosing interval: berobenatide is designed for once-monthly subcutaneous injection, compared with the once-weekly standard for semaglutide (Wegovy) and tirzepatide (Zepbound). The extended half-life is achieved through Metsera's proprietary fatty acid conjugation and half-life extension technology. Phase 2b VESPER-3 trial data presented at ADA 2026 (June 5-8, New Orleans) showed placebo-adjusted weight loss of up to 12.3% at 28 weeks with the 4.8 mg monthly dose in adults with obesity without type 2 diabetes, with no evidence of weight loss plateau at week 28. In a 32-week exploratory extension, participants who escalated from placebo to 2.4 mg weekly berobenatide achieved a non-placebo-adjusted weight loss of 15.9%, suggesting further efficacy at longer durations. For type 2 diabetes, Phase 2b VESPER-1 data presented at ADA 2026 showed up to 10.2% weight loss alongside a 2.2 percentage-point reduction in blood glucose at 28 weeks in adults with obesity and T2D. The gastrointestinal tolerability profile was comparable to weekly Wegovy: 83% of treated participants reported no or only mild key gastrointestinal adverse events, with GI events largely clustered near dose administration and decreasing over time. Pfizer announced plans to initiate 10 Phase 3 studies for berobenatide in 2026, targeting chronic weight management and obesity-related comorbidities including knee osteoarthritis and obstructive sleep apnea.
Regulatory Status
Phase 2b data presented at ADA 2026 (June 2026). Pfizer plans to initiate 10 Phase 3 trials in 2026 for weight management and obesity comorbidities. No FDA submission yet.
Effective: June 2026
View FDA SourceWhy Researchers Study It
Berobenatide is the most advanced once-monthly GLP-1 RA in clinical development. Monthly dosing could significantly expand patient adherence compared with weekly injectables, particularly in populations where weekly injection burden drives discontinuation. If Phase 3 results confirm Phase 2b efficacy and tolerability, berobenatide would be the first monthly GLP-1 RA on the market — potentially reshaping the obesity drug landscape.
Proposed Mechanisms
- GLP-1 receptor agonism reduces appetite and food intake via hypothalamic signaling
- Slows gastric emptying to prolong post-meal satiety
- Stimulates glucose-dependent insulin secretion from pancreatic beta cells
- Fatty acid conjugation extends half-life to enable monthly dosing without loss of receptor engagement
- Sustained receptor activation from once-monthly injection may reduce peak-trough GI side effect cycles
Evidence Snapshot
| Study Type | Model | Outcome | Link |
|---|---|---|---|
| Human (Phase 2b, VESPER-3) | Adults with obesity without T2D, monthly dosing arms, 28 weeks | 12.3% placebo-adjusted weight loss at 4.8 mg monthly dose; no plateau at week 28 | Source |
| Human (Phase 2b, VESPER-3 extension) | Participants escalated from placebo to 2.4 mg weekly, 32 weeks | 15.9% non-placebo-adjusted weight loss at 32 weeks; weight loss continuing without plateau | Source |
| Human (Phase 2b, VESPER-1) | Adults with obesity and type 2 diabetes, 28 weeks | 10.2% weight loss + 2.2 percentage-point blood glucose reduction; consistent GLP-1 RA safety profile | Source |
Commonly Discussed Benefits
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Safety & Cautions
- Phase 3 trials not yet initiated as of June 2026
- Weight loss at 12.3% is lower than leading weekly injectables (semaglutide 2.4 mg: ~15%, tirzepatide 15 mg: ~22%) — though longer duration and higher doses may close the gap
- Monthly dosing means missed injections could lead to longer gaps in drug coverage than with weekly agents
- Long-term safety data beyond 32 weeks is not yet available
- Not FDA-approved for any indication
Comparisons
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Citations
- [1] Pfizer — Robust Phase 2b Efficacy and Favorable Tolerability Support Monthly Dosing for Berobenatide (ADA 2026) PubMed
- [2] STAT News — Detailed data show Pfizer's monthly obesity drug continues to show potential (June 2026) PubMed
- [3] Fierce Biotech — ADA: Pfizer pads case for berobenatide in obesity, adding validation to Metsera buy PubMed
- [4] Endpoints News — ADA26: Pfizer monthly shot shows effect on obesity, diabetes PubMed
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