Berobenatide

In plain English

Berobenatide works on the same target as semaglutide, the GLP-1 receptor. What makes it different is the schedule. Wegovy and Zepbound are weekly shots. Berobenatide was engineered to last long enough in the body to be given once a month.

A start-up called Metsera developed it under the code MET-097i. Pfizer completed its purchase of Metsera on November 13, 2025, at an enterprise value of about $7.0 billion, and now calls the medicine PF-08653944.

Berobenatide at a glance

What the trials found

The key trial for the monthly idea is VESPER-3. About 268 adults with overweight or obesity and without type 2 diabetes were randomized to one of four berobenatide regimens or placebo. The main measure was weight change at week 28.

The trial amounts are what Pfizer tested in research settings. They are not dosing instructions. In VESPER-3, weekly injections rose in steps for 12 weeks, then switched to a larger once-monthly amount of 3.2 mg or 4.8 mg.

Safety so far

Pfizer said stomach and gut side effects, the usual GLP-1 effects, were mostly mild or moderate, with no more than one severe nausea or vomiting case in any group and no severe diarrhea. In the two arms Pfizer reported on, five people stopped because of side effects during the weekly phase and five during the monthly phase. No one on placebo stopped. Full rates for each side effect, and the safety picture over a longer time, are not public.

Why monthly matters

If a monthly medicine works as well as a weekly one, a year of treatment means 12 injections instead of 52. That could make long treatment easier to stick with, and weight often returns after stopping, as the guide on weight regain after stopping explains. Pfizer has a Phase 3 trial, VESPER-SWITCH, built around monthly use for keeping weight off. Whether monthly dosing helps people over years is not something the current trials can answer.

How to read these numbers

Do not line these results up against Wegovy or Zepbound numbers. Those big trials ran 68 to 72 weeks, and berobenatide's headline numbers are from 28 weeks, in different groups of people, reported by the sponsor. No head-to-head trial exists. The fair reading is narrow: monthly dosing did not stop weight loss from continuing, and the long-term answer is pending.

If you see berobenatide for sale

Berobenatide has no approved product. Material sold online under this name has no verified identity, strength or purity, and its structure has not even been published. The only legitimate access today is through Pfizer's trials.

What is still unknown

• The 64-week VESPER-3 result. The registry lists the trial as completed on October 19, 2026, but no results were found.
• Phase 3 results for weekly and monthly use.
• Full side effect and stopping rates, and long-term safety.
• The drug's chemical structure.
• Whether and when regulators will review it.

Quick answers

What is berobenatide?

Berobenatide is Pfizer's investigational GLP-1 injection, built for once-monthly use. It was developed by Metsera as MET-097i and is also coded PF-08653944.

Is berobenatide the same as MET-097i?

Yes. MET-097i is the earlier Metsera code, and PF-08653944 is Pfizer's code for the same medicine.

How much weight loss did berobenatide show?

In the 28-week VESPER-3 trial, up to 12.3% more than placebo. In an extension of VESPER-1, an average of 15.9% at the highest weekly amount, not adjusted for placebo. Both figures are reported by Pfizer.

Is berobenatide given weekly or monthly?

Both are being studied. The trials start with weekly injections and the monthly trials then switch to a monthly amount.

Has berobenatide been tested in people with type 2 diabetes?

Yes. VESPER-2 reported a 2.2 point fall in HbA1c at 1.6 mg weekly by week 28, versus 0.2 on placebo.

Is berobenatide approved?

No. It is in Phase 3 and is not approved anywhere.

How is it different from semaglutide?

It uses the same receptor but is designed for monthly rather than weekly use. It has no head-to-head trial against semaglutide.

Where can I read more?

PeptideBlog has a detailed write-up of the berobenatide VESPER trials, and its berobenatide entry lists the Phase 3 trials.

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