VESPER: What Is Actually Registered for Berobenatide

What the registry actually contains

Searching the registry by intervention returns a coherent programme, and it is worth setting out because company communications and registry records use different names for the same studies. VESPER-1 (NCT06712836) is a Phase 2 trial of 239 participants, completed, with primary completion 3 July 2025. VESPER-2 (NCT06897202) is Phase 2, 133 participants, completed, primary completion 29 December 2025. VESPER-3 (NCT06973720) is Phase 2, 268 participants, primary completion 16 December 2025, and is registered as a study of once-weekly switching to once-monthly dosing. VESPER-4 (NCT07311850) is Phase 3 with an estimated 3,578 participants and primary completion 21 September 2027.

The two Phase 3 trials whose acronyms are not registered

Two more Phase 3 records exist and neither carries a registered acronym, which is a small thing that causes real confusion. NCT07400653 has an official title ending '(VESPER-5)' - the name is present in the free-text title but the structured acronym field is empty, so the trial does not surface when you search the registry by that name. It is a Phase 3 trial of 1,044 participants in people with overweight or obesity and type 2 diabetes, with primary completion 12 October 2027. NCT07595549 is a Phase 3 trial of 954 participants that began recruiting on 10 June 2026 with primary completion 4 May 2028; press coverage calls it VESPER-6, and the registry record carries that name in neither the acronym field nor the title. If you are trying to verify a claim about 'VESPER-6', that is why you cannot find it.

Why the trial sizes tell you where the programme is

The step from Phase 2b to Phase 3 here is a factor of thirteen: 268 participants in VESPER-3, 3,578 in VESPER-4. That is not unusual for obesity, where the safety database has to be large enough to characterise uncommon events and regulators expect a substantial exposure population. It does mean the informative efficacy data available today comes from studies of a few hundred people, and the pivotal evidence does not exist yet. Primary completion for the first Phase 3 is September 2027.

What the programme is testing that others are not

The distinguishing design feature is the dosing schedule. VESPER-3's registered title describes weekly dosing switching to monthly: four regimens of twelve weekly doses of MET097, with or without titration, followed by multiple monthly doses, against a placebo arm on the same schedule. The primary endpoint is percent change in body weight at week 28. No approved GLP-1 receptor agonist is dosed monthly, so the question the programme exists to answer is whether the weight reduction achieved on a weekly schedule holds when the interval is stretched fourfold.

What has been reported so far

Pfizer reported VESPER-3 topline on 3 February 2026: placebo-adjusted weight loss at week 28 of up to 12.3% on the efficacy estimand with a 4.8 mg monthly dose, and 10.5% on the treatment-policy estimand for that arm. A separate arm reported 10% and 8.4% on the same pair of estimands. From VESPER-1's Part B extension, 15.9% non-placebo-adjusted mean weight loss at 32 weeks on the top weekly dose. From VESPER-2, HbA1c fell 2.2 percentage points on the 1.6 mg weekly dose against 0.2 on placebo. Every one of those numbers comes from a Phase 2b study of a few hundred people, and none of them is pivotal evidence.

What this means for anyone reading about it

Berobenatide is not licensed anywhere, for anything. It is an investigational compound in Phase 3 development with first approvals discussed for 2028 at the earliest. It is not supplied here in any form and there is no research material corresponding to it on this site. It is covered because the monthly-dosing question is the most interesting open engineering problem in the class, and because a reader trying to check a claim about it should be able to find the registry numbers in one place.

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