India Pharma Outlook Team | Wednesday, 04 February 2026
Pfizer Inc. today announced positive topline results from the phase 2b VESPER-3 study evaluating PF’3944 monthly dosing, an ultra-long-acting injectable GLP-1 receptor agonist, in adults with obesity or overweight without type 2 diabetes.
The study met both primary goals, showing the drug could maintain strong weight loss when patients switched from weekly to monthly injections while keeping a favorable safety profile.
At week 28, PF’3944 monthly dosing achieved up to 12.3% mean placebo-adjusted weight loss, with all four dose regimens beating placebo (P < 0.001). Participants received weekly doses through week 12, then transitioned to monthly maintenance dosing through week 28. Notably, no weight-loss plateau was seen, suggesting further reductions are likely as the study continues to week 64.
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The ongoing randomized, double-blind trial includes five arms, with roughly 54 participants per group. The low- and mid-dose monthly regimens planned for phase 3 delivered 10% and 12.3% placebo-adjusted weight loss, reinforcing Pfizer’s confidence in advancing the program.
PF’3944 maintained a safety profile consistent with the GLP-1 class. Gastrointestinal side effects were mostly mild or moderate, with no severe diarrhea reported and only isolated cases of severe nausea or vomiting. Discontinuations due to adverse events were limited, and none occurred in the placebo group.
“These topline results from the phase 2b VESPER-3 study reinforce the potential of PF’3944 as a monthly treatment with competitive efficacy,” said Jim List, MD, PhD, chief internal medicine officer.
Following its acquisition of Metsera, Pfizer plans more than 20 obesity trials in 2026, including 10 phase 3 studies of PF’3944 across weekly and monthly dosing strategies.
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