Pfizer’s obesity asset berobenatide demonstrated significant weight loss in mid-stage development, with the potential to be administered as a monthly injection, according to data presented at the 2026 annual meeting of the American Diabetes Association. The findings support Pfizer’s $10 billion acquisition of Metsera, the original developer of berobenatide.
Analysts at Guggenheim Partners said, “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.” They added that these results give Pfizer an “entry point into [the] large obesity market,” noting a continued need for additional treatment options. The analysts also said they were encouraged by Pfizer’s plans for a broad Phase 3 program and would focus on results from higher monthly doses.
At ADA, Pfizer shared Phase 2b study results from VESPER-1, VESPER-2 and VESPER-3 trials. These studies evaluated different dosing strengths and frequencies for berobenatide among patients with obesity or overweight—with or without diabetes. In VESPER-1, weekly doses led to a non-placebo-adjusted 15.9% reduction in weight after 32 weeks during an open-label extension phase. A subgroup receiving once-monthly 4.8 mg injections saw a 14.9% weight reduction at 60 weeks versus baseline.
BMO Capital Markets analysts wrote that these results “compare favorably to tirzepatide,” Eli Lilly’s dual agonist marketed as Zepbound for obesity, which showed roughly 17% weight loss at around 32 weeks. BMO further commented that “OLE VESPER-1 and VESPER-2 data demonstrate efficacy near comparable to tirzepatide in obese and T2D patients.” Safety and tolerability were described as consistent with other drugs in this class.
John Buse, investigator for the VESPER studies and professor at University of North Carolina School of Medicine, Chapel Hill, told BioSpace, “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.”
Leerink Partners noted optimism about berobenatide but emphasized waiting for late-stage trial outcomes before making broader conclusions about its place in the market. The group wrote: “Management’s vision is for berobenatide to be a foundational metabolic medicine—both as a single agent and as a combination backbone,” highlighting plans to launch first as a weekly therapy followed by monthly maintenance dosing by 2029.
