Berobenatide: Pfizer's Monthly GLP-1 Peptide Is Now in Eleven Phase 3 Trials
Published: November 4, 2026 · 3 min read · By Grey Peptides News Desk · ✓ Sourced
Berobenatide is the new name for PF-08653944, the long-acting GLP-1 peptide developed first by Metsera as MET-097i and now by Pfizer. Pfizer's November 3 pipeline update lists it in phase 3 for weight management, and eleven phase 3 trials are now registered, the newest posted on November 4. The aim is a GLP-1 injection taken once a month rather than once a week. There are no phase 3 results yet, and it is not approved anywhere.
What berobenatide is
Berobenatide acts on the GLP-1 receptor, the same target as semaglutide. Metsera, which developed it as MET-097i, called it its foundational peptide, and said its platform aims for a half-life close to that of albumin, the main protein in blood. Pfizer describes it as a fully biased agonist, a design meant to favour one of the receptor's signalling routes over others; no trial has yet shown whether that changes what patients experience. The point of the long half-life is dosing: people start weekly and then move to one injection a month.
The phase 3 trials
- VESPER-4 (NCT07311850): weekly injections against placebo in 3,578 adults with overweight or obesity, weight change at week 64. Enrolment is complete, and it is the first due to finish, in September 2027 by the registry's estimate.
- VESPER-5 (NCT07400653): the same question in 1,078 adults who also have type 2 diabetes.
- VESPER-6 (NCT07595549): monthly dosing against placebo, about 954 adults, weight change at week 72.
- Japan and China: four trials, weekly and monthly, in local populations (NCT07794761, NCT07794774, NCT07792954, NCT07874633).
- Sleep apnoea: VESPER-OSA 1 and 2 (NCT07823608, NCT07881757) measure breathing interruptions at week 52, with and without a CPAP machine.
- Switching: VESPER-SWITCH (NCT07845500) moves about 660 people from weekly semaglutide or tirzepatide to monthly berobenatide and asks whether their weight holds.
- Knee osteoarthritis: VESPER-OA 2 (NCT07915609), posted on November 4, measures knee pain at week 52 in about 756 adults with overweight or obesity.
What earlier trials showed
The efficacy figures so far are the companies' own. Metsera reported that in VESPER-1, a 28-week phase 2b trial in 239 adults without diabetes, weekly doses gave 8.1% to 14.1% more weight loss than placebo. Pfizer reported that in VESPER-3, where people switched from weekly to monthly injections, weight fell up to 12.3% more than on placebo at 28 weeks among those who stayed on treatment, or 10.5% counting everyone randomised, and was still falling. Side effects were mostly digestive and mild to moderate. Neither trial is in a journal, and PubMed holds no paper on the drug.
What else changed
The same pipeline update lists a combination of berobenatide with PF-08653945, an amylin analogue, in phase 2, and shows a phase 1 combination with a GIP receptor agonist as discontinued since August. Berobenatide now has its own row in our pipeline tracker, with each trial linked to its registry record.
Related on Grey Peptides
Berobenatide's row, its trials and the next readout. Semaglutide encyclopedia entry
The weekly GLP-1 that VESPER-SWITCH moves people from. Tirzepatide encyclopedia entry
The other weekly drug in the switch study.
ClinicalTrials.gov - VESPER-4, phase 3 trial of PF-08653944 (berobenatide) (NCT07311850)
The eleven phase 3 registrations were read on ClinicalTrials.gov on November 4, 2026, the day the newest (NCT07915609) was posted. The phase listing is from Pfizer's own pipeline update of November 3, 2026, and the phase 2b figures are Pfizer's and Metsera's own releases, read the same day; none of the berobenatide trials has been published in a journal.