Pfizer has announced early data from its Phase IIb VESPER-3 trial of PF’3944, an obesity drug acquired through Metsera. The company reported that patients receiving monthly doses of 4.8 mg and 3.2 mg achieved a weight loss of 12.3% at week 28.
BMO Capital Markets described the data as “competitive” in a note after the release. However, some analysts expressed reservations due to the limited information provided. Notably, Pfizer did not disclose specific results for the placebo group. Chief Scientific Officer Chris Boshoff stated during an earnings call that the placebo group's weight remained “stable.” Leerink Partners calculated that this implies about a 12% absolute weight loss on a placebo-adjusted basis, which is lower than Eli Lilly’s Zepbound, which achieved 16% at week 28.
Leerink also estimated a discontinuation rate of around 10% for VESPER-3, compared to Zepbound’s 6%, though Zepbound's study involved more participants.
Boshoff said the study met its two main objectives: continued weight loss when switching from weekly to monthly dosing and maintaining safety and tolerability. CEO Albert Bourla added, “For the first time, we have shown that GLP-1 receptor agonist peptides can be administered monthly, while maintaining the potential for competitive efficacy and sale.”
Pfizer plans to start Phase III trials later this year with the highest tested dose (9.6 mg), which is already being evaluated in another trial using weekly administration of divided doses. The company predicts this higher dose could result in approximately 15.8% weight loss but will present more detailed findings at the American Diabetes Association conference in June.
Boshoff declined to provide further details on the placebo group or participant demographics but noted that only one severe case of nausea was observed and no severe diarrhea occurred.
The company intends to launch two Phase III studies for PF’3944 this year targeting overweight or obese patients and will conduct seven additional trials focusing on related health conditions and patient access strategies. Pfizer is also exploring other molecules for less frequent dosing schedules.
Chief Commercial Officer Aamir Malik commented on market prospects: “What you need to win in a market like that is, one, you need a great portfolio of products that can serve all those patient needs. And two, you need really differentiated capabilities,” Malik said. “We have a lot of confidence in our ability to win commercially in this market with these assets.”
PF’3944 is being positioned as a monthly maintenance therapy with plans to test switching strategies from other GLP-1 drugs in future studies.
In addition to clinical updates, Pfizer reported quarterly sales of $17.56 billion—exceeding estimates—with strong performance from its vaccine portfolio including Comirnaty (COVID-19), Abrysvo (RSV), and Prevnar (pneumococcal). Sales of COVID-19 treatment Paxlovid were down sharply by 70% compared to last year.
“Commercially Pfizer printed another solid quarter, beating on both the top and bottom line supported across all three key pillars of the company,” BMO Capital Markets wrote.
CEO Bourla noted satisfaction with COVID-19 franchise performance given mild viral activity this year. The company reaffirmed its annual sales guidance between $59.5 billion and $62.5 billion for 2026.
CFO Dave Denton mentioned that Pfizer’s business development capacity has increased slightly beyond its previously stated $6 billion limit but did not specify figures.
