Analysts weigh in on Amgen's bone density data for weight loss drug, causing stock to decline.

• The stock price of Amgen decreased after experts discussed the bone density loss results from a preliminary trial of its weight loss injection, MariTide.
• Some analysts viewed the extra information as a possible safety concern, while others believed the share shift was an exaggerated response and that more data on a larger patient population is necessary.
• The monthly drug is a promising potential competitor in the weight loss drug market, designed to be taken instead of the existing weekly injections from Novo Nordisk and Eli Lilly.

The stock price of MariTide dropped more than 7% on Tuesday due to concerns about bone density loss from an early-stage trial of its experimental weight loss injection.

One analyst suggested that new data indicates a potential safety risk associated with the drug, but others argued that the stock movement was an overreaction and that more data on a larger patient population is necessary.

Amgen did not immediately respond to a request for comment on the data

The drug is a promising potential competitor in the weight loss drug market. Unlike existing injections from and, it is designed to be taken monthly and promotes weight loss differently.

The crucial phase two trial results for MariTide are expected to be released before the end of the year, and Wall Street is eagerly anticipating the results.

On Tuesday, analysts reported that a phase one study's publicly available data showed that the highest dose of MariTide, 420 milligrams, resulted in a 4% decrease in bone mineral density over 12 weeks. This decrease in bone mineral density occurs when bones lose calcium and other minerals, making them weaker and more prone to fractures.

Olivia Brayer, a Cantor Fitzgerald analyst, characterized the data as a "big unknown" and proposed it could pose a potential risk associated with drugs like MariTide, which use GIPR antagonism. Meanwhile, Amgen's injection works by blocking a gut hormone receptor called GIP but also activating another appetite-suppressing hormone called GLP-1.

Unlike Eli Lilly's obesity drug, Zepbound, which activates GIP and GLP-1, Wegovy activates GLP-1 but does not target GIP, which may also affect how the body breaks down sugar and fat.

During weight loss treatment, patients may naturally experience a decrease in bone mineral density, according to Brayer.

On the other hand, this could be a non-starter because there seems to be a dose-dependent increase in bone mineral density loss, meaning patients appear to lose more bone mineral density the higher the dose they take.

Jefferies analyst Michael Yee stated in a note that the additional MariTide data does not appear to be a significant concern. Although Yee acknowledged that individuals on the highest dose of the drug experienced declines in bone density, he noted that the data is inconsistent.

Yee stated that bone mineral density "changes" are a known side effect of weight loss drugs in the first one to three months of use because people lose significant weight quickly.

Yee stated that Amgen is aware of the "hypothetical concern" of bone mineral density loss, as discussed with management.

"Jefferies stated that although they acknowledge that there may be some effect, they do not believe there is a significant drop in bone mineral density over time, and there is no clinical risk or concern associated with it. In their view, the effect is normalized over time and there is no issue."

Evan Seigerman, a BMO analyst, wrote in a note on Tuesday that it is necessary to exercise caution when making a comprehensive assessment of MariTide's safety profile based on the available data.

He stated that we would feel more confident in evaluating the safety profile of the drug if we had access to a larger group of patients. The solution may not be evident until Amgen releases the complete phase two trial data on the medication.

Seigerman wrote that our view on MariTide hasn't changed, and if anything, we see the selling as overdone.