Pfizer starts 954-person Phase 3 trial of obesity drug berobenatide

Pfizer has begun enrolling adults in a 954-participant Phase 3 trial of berobenatide, an experimental obesity medicine also known as PF-08653944, according to the study's federal registration ^[1]. The trial is testing the drug in people with overweight or obesity and lists a primary completion date of May 4, 2028 ^[1].

The registration identifies the study as Phase 3, the stage of testing that companies run before asking the FDA to approve a medicine ^[1]. Berobenatide is not approved for any use in the United States; the registration calls it a study medicine ^[1]. No results from the trial have been released, so how much weight participants may lose, how well the drug is tolerated, and how it compares with existing treatments have not been reported.

Pfizer is also testing berobenatide at a longer dosing interval outside the United States. A Phase 3 study registered for Japan, listed as VESPER-JM, is testing a once-monthly version of the drug in adults with obesity ^[2]. Pfizer has registered a once-weekly Phase 3 program in Japan as well; enrollment targets and completion dates for that program have not been reported.

The US registration does not disclose which doses are being tested, whether the trial includes a placebo or an active comparator, or how long participants will be followed ^[1]. The study listing appears under the identifier NCT07595549 ^[1].

Why it matters for patients

Berobenatide cannot be prescribed today. It is an investigational drug, and the start of a Phase 3 trial does not change the treatments available to patients now ^[1]. Even if the trial stays on schedule, its primary completion date falls in 2028, and a completion date is not an approval date. A company still has to review the data and submit an application before the FDA could decide ^[1].

For people who take a GLP-1 medicine, how often it has to be injected is one of the practical differences between products. Pfizer's decision to test a once-monthly version in Japan shows that longer dosing intervals are part of how companies are competing in this drug class ^[2]. Whether a monthly injection controls appetite and weight as well as more frequent dosing has not been reported.

A trial is one route to an unapproved drug for people who qualify. Enrollment is set at 954 participants, and eligibility is decided by the study's own criteria ^[1]. Whether the trial is open to people who already take another GLP-1 medicine has not been disclosed.

What happens next

• Enrollment in the US Phase 3 trial continues, with a primary completion date of May 4, 2028 ^[1]. That is when researchers expect to finish collecting the main outcome measurements, not a date for results or an FDA decision.
• The Japanese once-monthly study is registered as NCT07794774 ^[2]. Its start and completion dates have not been reported.
• No timeline has been reported for the once-weekly Phase 3 program in Japan.