Pfizer opens berobenatide Phase 3 trials, starting with monthly-dose obesity study
Pfizer is testing berobenatide, an unapproved GLP-1 injection given monthly or weekly, in late-stage trials that could eventually give US patients another obesity treatment option.
Pfizer has opened the first of its September 2026 berobenatide Phase 3 trials: a placebo-controlled study of a once-monthly injection in adults with overweight or obesity, listed as recruiting on September 4 [1]. Registrations for three more late-stage berobenatide trials in Japan and China carry start dates in the same period [2].
The U.S. registration, NCT07595549, is titled "A Study to Learn About the Study Medicine Called Berobenatide (PF-08653944) in People With Overweight or Obesity" [1]. Berobenatide, also known as PF-08653944 and MET 097, is a synthetic peptide that acts as a GLP-1 receptor agonist. It is listed at Phase 3, its highest phase, with obesity and type 2 diabetes as its active indications [2].
Two companion studies in Japan give the clearest picture of what is being tested. VESPER-JM (NCT07794774) will test once-monthly berobenatide in about 197 adults with obesity disease, some of whom may also have type 2 diabetes. Participants take part for about 21 months, with roughly 16 visits at the study site and two phone visits. VESPER-JW (NCT07794761) tests a once-weekly version in about 180 adults with obesity disease over about 22 months, with about 15 site visits and two phone visits. Both are randomized, double-blind and placebo-controlled, both list start dates of September 27, 2026, and both are sponsored by Pfizer. In each, the drug or a placebo is injected under the skin of the abdomen, and researchers compare weight loss, safety and other health measures [2]. A third registration, NCT07792954, covers once-weekly PF-08653944 in Chinese adults with overweight or obesity and lists a start date of August 31, 2026; it is listed as not yet recruiting [2]. The registration dates do not match one another — September 27 for the two Japan studies, August 31 for the China study — and study start dates can be updated.
Berobenatide is experimental. It reached Pfizer through the company's $10 billion acquisition of Metsera, and its originator is listed as D&D Pharmatech [2]. On August 4, 2026, Pfizer said it was discontinuing two other clinical-stage obesity programs: MET-224o, an oral GLP-1 candidate from the Metsera deal, and PF-07976016, a Phase 2 GIPR antagonist [2]. Berobenatide remains the lead program. On Pfizer's second-quarter earnings call, chief scientific officer Chris Boshoff said an analysis "suggests berobenatide can deliver weight loss comparable to tirzepatide and potentially better than semaglutide," and that with extension data from the Phase 2b Vesper-1 trial, the company believes the drug "can potentially deliver robust efficacy and favorable gastrointestinal tolerability with the convenience of a monthly therapy" [2]. Tirzepatide is the molecule in Mounjaro and Zepbound; semaglutide is the molecule in Ozempic, Wegovy and Rybelsus.
Why it matters for patients
Berobenatide is not approved for any use. The Phase 3 program is meant to produce the large-scale safety and efficacy data regulators require, and no results from these trials have been reported [2]. No head-to-head trial of berobenatide against semaglutide or tirzepatide has been described in the trial records [2]. The comparison Boshoff cited comes from an analysis of existing data, not from a completed study that pitted the drugs against each other [2].
The practical questions for patients are who can enroll and what a monthly shot would change. The studies seek adults with overweight or obesity, some of whom may also have type 2 diabetes, and study doctors review specific age, weight and health requirements before enrollment [2]. Dosing interval is the main difference among the trials: the U.S. and one Japan study use a once-monthly injection, while the other Japan study and the China study use a once-weekly injection [1][2]. Pfizer describes monthly dosing as a convenience factor rather than a proven advantage [2].
Cost, insurance coverage and pricing for berobenatide have not been disclosed, and Pfizer's August 2026 public statements on the program did not include a target approval date [2].
What happens next
The U.S. Phase 3 study NCT07595549 is listed as recruiting as of September 4, 2026 [1]. The two Japan registrations list start dates of September 27, 2026, and the China registration lists August 31, 2026; all are listed as not yet recruiting [2]. Participants in the Japan studies are followed for about 21 to 22 months, so those trials are not expected to report results before then [2]. Berobenatide's listed highest phase remains Phase 3, with no first approval date on record [2].
Sources
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