Mounjaro Generic May Soon Join Wegovy as a Weight Loss

Tirzepatide, the active ingredient in the diabetes medication Mounjaro, can help patients lose almost 16% of their body weight, according to trial data shared by pharmaceutical company Eli Lilly.

The weight loss seen in this study was greater than that seen from other medications for obesity and type 2 diabetes, according to Lilly. The company said it will ask the Food and Drug Administration (FDA) to grant an indication for weight management—something the drug is not currently approved for, despite its off-label use.

“It’s great that we have another medication that helps people to lose weight as well as improving glycemic control. If [tirzepatide] is approved for the management of obesity, I think that’s a welcome addition for us as obesity experts to prescribe,” David Lau, MD, PhD, adjunct professor in the departments of medicine, biochemistry and molecular biology, and kinesiology at the University of Calgary, told Verywell.

Wegovy (semaglutide) is currently the most effective drug indicated for weight loss in the United States. Approving tirzepatide for weight loss would add another strong obesity treatment option, both for people with and without diabetes, said Dan Bessesen, MD, an endocrinologist and a professor of medicine at the University of Colorado. 

“I think it is terrific for the field and for patients to have a second medication available. Over time, my sense is the medications available for treating obesity are becoming more effective and will become more widely-used,” Bessesen told Verywell in an email.

If tirzepatide is approved for weight loss, it will likely get a new brand name and dosage to differentiate it from Mounjaro, which is the same drug but only labeled for diabetes treatment. Wegovy and diabetes drug Ozempic provide a similar example; both contain semaglutide, but in different concentrations—so only Wegovy is technically approved for weight management in people without diabetes. When Ozempic is used this way, it’s considered off-label.

Lilly said it will present its full study results at a conference in late June and will apply for FDA approval of a weight loss indication. The company said it expects an FDA decision in late 2023.

The new study included 938 adults who were overweight or living with obesity as well as type 2 diabetes. People taking 10 milligrams (mg) of Mounjaro saw an average of 12.8% body weight reduction while those taking 15 mg lost up to 15.7% of their weight.

It is well established that people with type 2 diabetes tend to have a harder time losing weight than those without diabetes, said Angela Fitch, MD, FACP, FOMA, president of the Obesity Medicine Association.

“When we look at patients with type two diabetes and obesity, the people with diabetes consistently lose less weight than the people with just obesity alone,” Fitch told Verywell. “What is being shown here is that Mounjaro is better for weight loss, even in people with diabetes.”

In an earlier phase 3 trial this year, Lilly showed that people with obesity or who are overweight without diabetes lost up to 22.5% of their body weight while taking tirzepatide.

Wegovy works by mimicking the hormone glucagon-like peptide-1 (GLP-1), which boosts insulin production. This lowers blood sugar and makes people feel full for longer.

Mounjaro also increases GLP-1 as well as the hormone glucose-dependent insulinotropic polypeptide (GIP). Acting on both GIP and GLP-1 can boost metabolism and decrease appetite, causing even greater weight loss and management of blood sugar than GLP-1 agonists alone.

“[The data] are certainly very impressive because not only do you see a slightly greater percent body weight loss with tirzepatide, but you also see better glycemic control,” Lau said. “Most of us in the field feel that this is an unexpected finding in the sense that it has a more profound effect.”

Wegovy, which is FDA-approved for weight management, causes an average of 12.4% weight loss in people without diabetes and 6.2% in those with type 2 diabetes.

It’s challenging to know exactly how Wegovy and Mounjaro stack up as there have been no completed trials directly comparing the two drugs.

“The study design is slightly different from clinical trial to clinical trial. So you can’t really compare the efficacy unless you do a head-to-head comparison,” Lau, who is a principal investigator for the STEP 10 semaglutide trials, said.

Lilly only just began a 700-person study, called SURMOUNT-5, to test tirzepatide against semaglutide directly.

Wegovy and Ozempic manufacturer Novo Nordisk is years ahead of Eli Lilly in terms of testing its drug for outcomes beyond weight loss. The company is now testing how semaglutide effects overall cardiovascular health, and the data is expected to be shared this year.

“If it’s shown that Wegovy has a cardiovascular benefit, it would trump [Mounjaro] anytime when it comes to prescription because now you have a drug that has been shown to have safety data and, if anything, cardiovascular benefits,” Lau said.

While Mounjaro appears to be better for weight management, Lau said providers will look to prescribe a drug that has proven health benefits beyond shedding pounds. For patients with heart disease, for instance, it will be helpful to have data showing that Wegovy can support heart health while reducing body weight.

“The data from the SURMOUNT-1 trial is very encouraging. It looks great,” Lau said. “But my recommendation is let’s wait and see. Let’s not jump the gun and say tirzepatide will torpedo semaglutide because it showed better weight loss data.”

Ultimately, having more obesity treatment options in the toolbox will help clinicians to tailor their treatment for each individual patient, Fitch said.

“It’s nice to have multiple options so that we can balance the outcomes with the side effects,” she said.

For months, patients have been scrambling to get their hands on weight loss medications, which have become increasingly popular even among people without obesity. As with Wegovy and Ozempic, Mounjaro is an injectable medication that cannot be mass-produced as easily as an oral medication, so it’s not clear how the new indication would help the drug supply problem, Lau said.

It’s also too soon to know how expensive and accessible Mounjaro will be as a weight loss medication. Some insurance plans may cover obesity medications. But most insurers, including Medicare don’t. Medicare Part D has excluded anti-obesity medications from coverage for two decades, despite general recognition of obesity as a disease.

If tirzepatide is FDA-approved for weight management, it will be up to insurance companies to decide whether they will cover the medication.

“Having another large and successful pharmaceutical company involved in this therapeutic area will be helpful for patients,” Bessesen said. “Over time, it will help people see obesity as the chronic metabolic disease that it is.”

It will likely be months before the FDA decides whether to indicate tirzepatide for weight loss. In the meantime, ask a trusted provider about what treatment options are available to you for weight management.