ADA2025: Two Remarkable New Obesity Drugs at an Early Stage
On the closing day of the ADA Scientific Sessions in Chicago, we got a good look at two remarkable new obesity drugs. Both of them have potential to bring important advances. Both of them need more work before they will be ready to go to FDA for approval.
This was a rare treat.
Bimagrumab
The day started with a symposium to present detailed results of a phase two study of bimagrumab by itself and in combination with semaglutide. Bimagrumab is a monoclonal antibody that Lilly acquired in 2023. It works by blocking myostatin from inhibiting muscle growth. Back in 2019, researchers showed this drug had promise for treating obesity because it could help people lose weight at the same time they gained muscle. But Novartis had no interest in developing it because they had already been unsuccessful with it in efforts to treat a condition called myositis.
That was a time when obesity was not very interesting to most pharmaceutical companies. So Novartis spun off the drug to a startup called Versanis. Then, when the obesity market started looking lucrative, Lilly bought Versanis to get the rights to bimagrumab.
The results of the 72-week study we saw yesterday makes this drug look like it might be quite a prize. In combination with semaglutide, it caused people to lose 22% of their body weight, mostly in the form of body fat. For semaglutide alone, the weight loss was 16% and only 72% of it came from losing fat tissue. With the combination, almost all of the weight loss (93%) came from fat tissue.
This means that the reductions in waist circumference were striking. Describing what that change meant to an average person in this trial, Lou Aronne said, “That’s eight notches on a person’s belt. A dramatic reduction from 42 to 34 inches.”
Remember, though, this was just a phase two study and it used semaglutide for the combination. Rather than developing bimagrumab with semaglutide, Lilly is now developing it in combination with its own drug, tirzepatide. So definitive results are a few years off.
But what we saw yesterday gives us reason to believe this drug can offer a leap forward.
MariTide
The other big advance we saw taking shape yesterday is another antibody therapy with a unique mechanism of action. MariTide is the brand name for maridebart cafraglutide. It is an antibody that activates GLP-1 and blocks GIP. It also has a distinctively long duration of action that means it only has to be taken monthly. The phase two study of MariTide was simultaneously presented yesterday and published in the New England Journal of Medicine.
Perhaps because of its unique mechanism of action, it is the first drug where we have seen a degree of weight loss (up to 17%) in people with obesity and diabetes that approached the weight loss seen in people with obesity alone (up to 20%).
But these are only phase two results and Amgen has made further refinements to dosing regimens that the company hopes will help with MariTide’s tolerability. So we will have to wait for the pivotal results to know how much of an advance this one will be.
Click here for the full publication of MariTide results and here for Amgen’s summary. For additional reporting on the bimagrumab study (there’s no publication yet), click here, here, and here.
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June 24, 2025
