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Amgen experimental weight-loss drug needs lower dose to limit side effects
By Deena Beasley - 6/23/2025
By Deena Beasley
(Reuters) -Amgen's long-acting experimental obesity drug MariTide needs to be given at a low starting dose to limit side effects like vomiting, according to mid-stage trial results presented at a medical meeting on Monday that pushed the company's shares down nearly 6%.
To improve the drug's tolerability, Amgen said its recently launched 72-week Phase 3 trial will randomize obese or overweight adults to three different doses, with each group starting at a much lower dose that will be increased over an eight-week period.
"MariTide is a long-acting drug, but side effects are short-lived, which is a great learning and gives us confidence to go into Phase 3," Jay Bradner, executive vice president of research and development at Amgen, told Reuters.
In the mid-stage study, vomiting was reported by nearly 90% of patients started at the highest tested dose, compared with 50% of patients ramped up to a full dose in one step and 22% of those brought to their target dose over eight weeks.
Shares of Amgen fell 5.8% to close at $272.44 on the Nasdaq.
Citi Research analyst Geoff Meacham said the Phase 3 dosing plans will likely improve the drug's tolerability, but MariTide's gastrointestinal side effect rates are concerning "and we increasingly question the unmet need for a monthly injectable."
Amgen previously announced top-line results from the year-long Phase 2 trial showing that MariTide, injected monthly or every other month, helped overweight or obese patients shed up to 20% of their body weight.
The full results were presented at the American Diabetes Association meeting in Chicago and published in the New England Journal of Medicine.
MariTide is an antibody linked to a pair of peptides that activate receptors for the appetite- and blood sugar-reducing hormone GLP-1 while simultaneously blocking a second gut hormone called GIP.
Amgen said no new safety signals were identified in the study and tolerability was consistent with the GLP-1 class.
In late-stage trials, Novo Nordisk's GLP-1 obesity drug Wegovy had a vomiting rate of 24%, while Eli Lilly's Zepbound, which is designed to activate both GLP-1 and GIP, had a rate of 13%. Each of those drugs is given as weekly injections.
Amgen said its Phase 2 trial discontinuation rates due to gastrointestinal issues were lower for groups treated with escalating doses.
The data also show that for people with type 2 diabetes, MariTide lowered blood sugar by up to 2.2 percentage points. Amgen said weight loss with MariTide also improved pre-specified cardiometabolic measures, including waist circumference, blood pressure, inflammation markers and blood lipids.
The company said it plans to start additional Phase 3 studies this year for MariTide in patients with a variety of serious health issues, including cardiovascular disease caused by clogging arteries, heart failure, and obstructive sleep apnea.
(Reporting By Deena BeasleyEditing by Bill Berkrot)