Pfizer has released its first data on an obesity drug candidate following its acquisition of Metsera, reporting weight loss results that exceed 12% at the highest tested dose. The company presented findings from the Phase IIb VESPER-3 study of PF’3944, formerly known as MET-097i, which is a long-acting GLP-1 injectable.
The study began with weekly subcutaneous injections to start treatment before transitioning patients to monthly dosing. Four different titration protocols were used alongside a placebo group. In the medium dose group—weekly injections ramping up from 0.4 mg to 1.2 mg and then moving to 4.8 mg monthly—patients saw a placebo-adjusted weight loss of 12.3% after 28 weeks. A lower dose group reached a 10% reduction at the same time point.
According to analysts at BMO Capital Markets, these results “look competitive” compared to other available therapies. They cited Novo Nordisk’s semaglutide, which achieved about 9% placebo-adjusted weight loss in the Phase III STEP-1 trial after 28 weeks, and Eli Lilly’s tirzepatide, which saw a 13% reduction in the Phase III SURMOUNT-1 study at the same interval.
Patients in both Pfizer treatment groups did not show signs of plateauing in their weight loss by the time of this interim analysis—a result Pfizer described as evidence of “robust and continuous weight loss” with PF’3944 even after switching to monthly dosing. The company expects further reductions in body weight through a follow-up period lasting up to 64 weeks.
Pfizer plans to advance both low and medium dose regimens into Phase III trials. The company outlined an extensive late-stage development program for PF’3944, including ten planned Phase III studies targeting various patient populations and related conditions. This includes VESPER-4, focusing on people who are overweight or have obesity without type 2 diabetes using weekly doses, and VESPER-5 for those with type 2 diabetes.
Investors are also watching for possible combination treatments involving PF’3944 and MET-233i, another asset acquired from Metsera. BMO analysts stated: “Any data regarding combination with [PF’3944] and the asset’s relative competitive profile . . . will be key as we continue to evaluated [sic] Pfizer’s positioning in the evolving obesity market.”
Pfizer initially offered $4.9 billion for Metsera last September but was outbid by Novo Nordisk’s $8.5 billion proposal before ultimately securing Metsera for around $10 billion after an intense bidding process.
BMO said Tuesday’s data for PF’3944 “appear supportive of a competitive mono-agonist profile,” though they noted that some questions remain ahead of a full data release expected in June.
