Pfizer advances monthly GLP-1 obesity injection from its Metsera purchase

Pfizer is developing a monthly GLP-1 obesity injection that came with its acquisition of the obesity biotech Metsera, a program aimed at competing with the weekly injections sold today as Wegovy and Zepbound ^[2][1].

Pfizer closed the Metsera purchase on Nov. 13, 2025, ending a two-week bidding contest with Novo Nordisk ^[2]. Pfizer paid $65.60 per share upfront and agreed to pay up to $20.65 more per share through a contingent value right tied to "the achievement of three specified clinical and regulatory milestones," which Pfizer did not describe in detail ^[2]. The total deal value of about $10 billion was up from $7.3 billion in the companies' original September agreement ^[2]. Novo Nordisk had offered $6.5 billion upfront against Pfizer's original $4.9 billion bid; a Delaware judge blocked Pfizer's attempt to stop Novo's offer, and the U.S. Federal Trade Commission warned that the structure of Novo's proposed buyout might not comply with U.S. merger law ^[2]. Metsera agreed to Pfizer's increased offer late on Nov. 7, 2025 ^[2].

The lead asset behind the deal is MET-097i, which Pfizer described as a weekly and monthly injectable GLP-1 that was "about to begin Phase 3 development" at the time of the acquisition ^[2]. Metsera's pipeline also included MET-233i, a monthly amylin analog in Phase 1 testing both alone and in combination with MET-097i, and an oral GLP-1 candidate also in Phase 1 ^[2]. Metsera is now a wholly owned Pfizer subsidiary, and Pfizer said it expects the acquisition to weigh on earnings over the next several years as it invests in those candidates ^[2]. "By acquiring Metsera, we are directing our resources toward one of the most impactful and high-growth therapeutic areas," Pfizer CEO Albert Bourla said ^[2].

Pfizer has not reported Phase 2b results for a monthly candidate identified as PF-08653944, and it has not disclosed how many obesity trials it plans to run in 2026 or how many of those would be Phase 3 studies. Whether PF-08653944 is the same molecule as MET-097i has likewise not been reported. No weight-loss or side-effect data for a monthly version of the drug have been disclosed.

Dosing frequency is one way companies are trying to separate their products. Amgen's investigational MariTide (maridebart cafraglutide) is given monthly or less often and produced roughly 20% average weight loss at 52 weeks in the data summarized in a pipeline review; it is in Phase 3, with an estimated approval date of May 2028 ^[1]. By comparison, that review lists 16.9% average weight loss at 68 weeks for weekly Wegovy (semaglutide) and 22.5% at 72 weeks for weekly Zepbound (tirzepatide) ^[1]. Those are cross-trial comparisons, not head-to-head results, and the review cautions that trial populations, doses and durations differed ^[1].

Why it matters for patients

Every GLP-1 obesity medicine approved in the United States is either a weekly injection or a daily pill ^[1]. A monthly injection could mean fewer needles and fewer scheduling steps, a practical difference for people who find weekly injections difficult. Amgen's monthly-or-less-frequent candidate is already in late-stage testing ^[1].

But no monthly GLP-1 obesity drug is approved, and Pfizer has not reported how well its monthly candidate works or how well it is tolerated. The pitch is convenience. Whether less frequent dosing matches the weight loss seen with weekly drugs has not been established.

Dosing frequency is also not the only area of competition. Oral options are growing: oral Wegovy (semaglutide) was approved in December 2025, and Foundayo (orforglipron), a daily oral GLP-1, was approved in April 2026 ^[1].

What happens next

As of November 2025, Pfizer said MET-097i was about to begin Phase 3 ^[2]. No start date, completion date or results date for a monthly program has been reported. The three clinical and regulatory milestones attached to the Metsera contingent value right have not been specified ^[2]. Amgen's MariTide carries an estimated approval date of May 2028 in the pipeline review's table ^[1].