Much work needs to be done for Pfizer to be able to catch up to the weight-loss frontrunners, according to Guggenheim Partners, but new data from Metsera’s lead asset could set the pharma apart from competitors with a monthly injection.
Pfizer’s newly obtained obesity asset berobenatide not only showed robust weight loss across a broad mid-stage development program but also demonstrated the potential to be a monthly injection option.
These findings, presented at the 2026 annual meeting of the American Diabetes Association, bolster Pfizer’s $10 billion gamble on Metsera, the asset’s original developer.
“Overall we found the berobenatide data to be solid, but also relatively undifferentiated from other options that are either already on the market or ahead of berobenatide in development,” analysts at Guggenheim Partners wrote in a Saturday note to investors.
Still, the data give Pfizer an “entry point into large obesity market,” they continued, as “there remains a need for additional options to meet the diverse needs that patients have.”
“We are encouraged to see the company moving forward with a broad Phase 3 program for berobenatide, but await more data from the monthly doses,” the firm added. The group will pay particular focus on “the higher 9.6mg monthly dose to see how differentiated the program can become.”
At ADA, Pfizer presented data from the Phase 2b studies VESPER-1, VESPER-2 and VESPER-3, which together sought out the ideal dosing strength and frequency for the GLP-1 agonist, according to a company release on Saturday. The trials enrolled patients with obesity oroverweight, with or without diabetes.
VESPER-1 looked at weekly doses of berobenatide—formerly known as MET-097—with an open-label exploratory extension phase during which patients who had originally been assigned to placebo were transitioned to 2.4-mg weekly doses of the GLP-1 drug after an initial 24-week randomized period. Meanwhile, patients who were originally assigned to berobenatide continued active treatment during the open-label extension phase.
Results presented at ADA showed a non-placebo-adjusted 15.9% reduction in weight at 32 weeks into the extension phase, according to a Pfizer presentation at the conference. At this point in VESPER-1, Pfizer hadn’t yet detected plateauing.
A subgroup treated with 4.8-mg berobenatide once-monthly saw a 14.9% drop in weight at 60 weeks versus baseline, Pfizer added.
These results “compare favorably to tirzepatide,” analysts at BMO Capital Markets wrote in a note on Saturday, noting that Eli Lilly’s GLP-1/GIP dual-agonist—marketed as Zepbound for obesity—elicited roughly 17% weight loss at around 32 weeks.
Meanwhile, Pfizer shared data from VESPER-2—which tested out four different once-weekly dosing regimens against placebo among patients with obesity and overweight, plus type 2 diabetes—for the first time. At week 28, participants saw up to 10.2% weight reduction at the highest weekly maintenance dose of 1.6 mg.
“OLE VESPER-1 and VESPER-2 data demonstrate efficacy near comparable to tirzepatide in obese and T2D patients, potentially providing more validation of Pfizer’s broader development plan,” BMO analysts noted.
The safety and tolerability profile was on par with the drug class, Pfizer said.
While the mid-stage data arestill early, “it looks like it’s in the same range of efficacy as the most effective products that are put on the marketplace now, with similar—maybe better—tolerability,” John Buse, VESPER investigator and professor at the University of North Carolina School of Medicine, Chapel Hill, told BioSpace.
Pfizer at ADA also presented data from VESPER-3, an ongoing 64-week weight loss study focusing on patients without type 2 diabetes. Here, BMO focused on tolerability, highlighting that study dropouts ranged from 11.1% at the second-lowest dose to 20.8% at the highest dose. Overall, 9.3% of patients across VESPER-3’s berobenatide arms discontinued due to treatment-emergent adverse events (TEAE). None of the patients in the placebo group dropped out because of TEAEs.
BMO called this profile “manageable,” contending that it “supports further development in Ph 3 studies.” Discontinuations were “largely acceptable,” the analysts said, adding that with Pfizer implementing dosing flexibility in its late-stage program, “initial once monthly tolerability appears at minimum encouraging with improvement possible in later development.”
Like BMO and Guggenheim, Leerink Partners were optimistic about berobenatide—but with the similar caveat of needing to see further late-stage data before drawing any broader conclusions about the drug’s positioning in the market.
“Management’s vision is for berobenatide to be a foundational metabolic medicine—both as a single agent and as a combination backbone,” the group wrote on Sunday, noting that Pfizer plans to first launch the drug as a weekly medicine, with a monthly injection to follow as a maintenance option in 2029. Pfizer plans to advance 10 Phase 3 studies for berobenatide this year alone.
Berobenatide’s value as a monthly therapy, Leerink said, “hinges on Phase 3 results in 2028.”
Editor’s note: This story includes reporting by Gabrielle Masson.
