Amgen’s MariTide Achieves Up to 20% Weight Loss in Phase 2 Trial, Despite Mixed Market Reaction

Amgen’s investigational weight loss drug, MariTide, has shown promising results in its Phase 2 clinical trial, achieving up to 20% average weight loss in individuals with obesity or overweight over a 52-week period. The drug, formerly known as AMG 133, is a bispecific glucagon-like peptide 1 (GLP-1) receptor agonist and glucose-dependent insulinotropic polypeptide receptor (GIPR) antagonist.

The trial, announced on November 26, 2024, enrolled 592 adults into two cohorts: one without type 2 diabetes (T2D) and one with T2D. Participants without T2D achieved up to a 20% average weight loss, while those with T2D achieved up to a 17% average weight loss, both without experiencing a weight loss plateau. This suggests the potential for further weight loss beyond 52 weeks.

MariTide also demonstrated significant improvements in cardiometabolic parameters, including blood pressure, triglyceride levels, and high-sensitivity C-reactive protein, along with a substantial reduction in HbA1C levels up to 2.2 percentage points in patients with T2D. The drug’s monthly dosing regimen is a notable differentiation from other GLP-1 weight loss drugs, such as Novo Nordisk’s Wegovy and Eli Lilly’s Zepbound, which require weekly administration.

Despite the clinical success, Amgen’s stock fell approximately 11% following the announcement, as investors had expected more significant weight loss outcomes compared to competitors. Analysts are closely watching how MariTide will perform against other weight loss treatments, particularly given that Zepbound showed slightly better results with an average weight loss of around 25% over a year.

The most common adverse events associated with MariTide were gastrointestinal, including nausea, vomiting, and constipation, which were reduced with dose escalation. The discontinuation rate due to adverse events was around 11%, which is between the rates seen with Zepbound and Wegovy.

Amgen plans to proceed with the second part of the Phase 2 study to evaluate the weight loss effects of MariTide beyond 52 weeks, including weight maintenance through less frequent or reduced dosing and the durability of weight loss after drug discontinuation. Over 90% of eligible patients have chosen to continue participating in the second part of the study.