Amgen's stock price plummets despite Phase II trial success

Amgen’s headquarters are located in Thousand Oaks, California, USA. Photo credit: JHVEPhoto / Shutterstock.

Amgen’s stock price has fallen despite announcing positive data from the Phase II MariTide (Maridebart cafraglutide, formerly AMG 133) trial, which showed a 20% weight loss.

Data from the phase II trial (NCT05669599) showed an average weight loss of 20% at 52 weeks in overweight or obese patients without type 2 diabetes (T2D).

In patients with overweight or obesity and T2D (who typically lose less weight with GLP-1 therapies), an average weight loss of 17% was achieved. The diabetic group also experienced a decrease in average hemoglobin A1C (HbA1c) by up to 2.2 percentage points at week 52.

In both groups, patients did not plateau in weight, suggesting the possibility of continued weight loss beyond the 52-week mark.

Despite the positive results for MariTide, Amgen’s share price fell 10% following the announcement, suggesting investors were hoping for better. The disappointment may be due in part to adverse events (AEs) in the dose escalation arms of the study, where approximately 11% of patients discontinued treatment.

The most common adverse reactions were related to gastrointestinal (GI) complications and included nausea, vomiting and constipation. In the dose escalation arms, discontinuation due to gastrointestinal side effects was less than 8%. Amgen described the side effects as “predominantly mild to moderate, transient and primarily related to the first dose.” It said nausea generally disappeared within an average window of six days and vomiting within one to two days.

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Today’s news represents the second blow to Amgen’s stock prices this month. On November 12, the company’s stock price fell 7.14% when a Cantor Fitzgerald analyst raised concerns about Phase I investments found in a hidden tab. expressed data suggesting that MariTide negatively affected changes in bone mineral density.

Amgen shared the Phase II trial results during an investor call and briefly addressed the issue, reporting that there was “no association between MariTide administration and changes in bone mineral density.”

Following today’s results, Amgen will move forward with the second part of its Phase II trial for MariTide, including patients who experienced greater than 15% body weight reduction. Of these patients, more than 90% chose to continue their participation. This portion of the study will continue for an additional 52 weeks and will evaluate weight loss with continued treatment, weight maintenance through less frequent or lower doses, and durability of weight loss after stopping MariTide.

Amgen also announced that it will launch MARITIME, a Phase III clinical development program for obesity and obesity-related diseases.

“We are very excited about MariTide’s differentiated profile with clinically meaningful characteristics such as significant and progressive weight loss, monthly or less frequent dosing, significant improvements in cardiometabolic parameters and strong reductions in HbA1C,” said Jay Bradner, Executive Vice President of Research and Development and Chief Scientific Officer at Amgen.

“These results give us the confidence to launch MARITIME, a Phase III program targeting obesity and a range of related diseases, offering a unique potential new treatment option for patients.”

The company also reported that MariTide demonstrated clinically meaningful improvements in cardiometabolic parameters. These included blood pressure, triglycerides and high-sensitivity C-reactive protein (hs-CRP) at all doses. There was no significant increase in free fatty acids.

There is a lot of competition in the weight loss space, primarily due to Novo Nordisk’s Wegovy (semaglutide) and Eli Lilly’s Zepbound (tirzepatide). The Phase II trial of Amgen’s candidate has similar efficacy data but, if approved, could be more attractive to patients due to the once-monthly dosing schedule.