A monthly weight loss injection could soon compete with the weekly options patients use today.
In a mid-stage trial reported by Pfizer, the experimental drug berobenatide produced up to 12.3% more weight loss than placebo at 28 weeks when patients switched from weekly to monthly injections. All four dosing regimens tested beat placebo.
The results come from VESPER-3, a Phase 2b study of about 270 adults with obesity or overweight but without type 2 diabetes.
Berobenatide, also known internally as PF'3944 (previously MET-097i), is an ultra-long-acting GLP-1 receptor agonist.
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That means it activates the same appetite-regulating hormone pathway as GLP-1 drugs like Ozempic and Wegovy, but it stays active in the body long enough to be dosed just once every four weeks.
How the weekly-to-monthly design worked
Patients started on weekly injections for the first 12 weeks. This titration phase lets the body adjust and helps limit gastrointestinal side effects, which are common with GLP-1 medications.
From week 12 onward, they switched to a single monthly injection through week 28.
Pfizer reported that weight loss did not plateau after the switch. The highest placebo-adjusted loss, 12.3%, came from an arm ending on a 4.8 mg monthly dose.
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Side effects were mostly mild to moderate gastrointestinal symptoms, in line with the wider GLP-1 class.
In the two arms Pfizer highlighted for Phase 3 (the low- and medium-dose monthly regimens), five participants discontinued because of adverse events during the weekly phase and five during the monthly phase.
Where it sits next to weekly rivals
Existing weekly GLP-1 drugs have set a high bar. In the STEP 1 trial published in The New England Journal of Medicine, weekly semaglutide (the active ingredient in Novo Nordisk's Wegovy and Ozempic) produced 14.9% mean weight loss at 68 weeks.
Weekly tirzepatide (the active ingredient in Eli Lilly's Zepbound and Mounjaro) reached up to 22.5% at 72 weeks in the SURMOUNT-1 trial. Berobenatide's 12.3% figure is placebo-adjusted at just 28 weeks, so direct comparisons are limited.
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For patients who struggle to keep up a weekly injection routine, a once-a-month shot could be easier to maintain. Adherence to weekly GLP-1 medications is one of the biggest real-world barriers to how well they work.
When it might be available
Berobenatide is not approved anywhere. Pfizer said it plans to advance 10 Phase 3 studies in 2026 across chronic weight management and obesity-related conditions including knee osteoarthritis and obstructive sleep apnea.
Those are the pivotal trials regulators would review before any decision on approval. VESPER-4, a once-weekly Phase 3 study, has already been initiated, and VESPER-6, the once-monthly Phase 3 study, is planned.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.