The Food and Drug Administration approved a request by Eli Lilly on Wednesday to begin marketing its tirzepatide medication, which is branded as Mounjaro for diabetes, under a new brand for weight loss as well.

While Mounjaro had already been used by some patients “off-label” for weight loss, the new FDA approval will allow the drugmaker to begin officially selling and marketing tirzepatide — branded as Zepbound — for weight loss too.

Zepbound will be available for patients in the U.S. by the end of the year, the drugmaker said.

The company said Wednesday in a news release that the medication, administered with an injection pen, will be sold at a cheaper list price than its semaglutide competitors from Novo Nordisk, which are branded as Wegovy for weight loss and Ozempic for diabetes. 

“New treatment options bring hope to the many people with obesity who struggle with this disease and are seeking better options for weight management,” Joe Nadglowski, CEO of the Obesity Action Coalition, said in Eli Lilly’s release. The group receives funding from Eli Lilly and other pharmaceutical and health care companies.

The FDA’s approval of Zepbound was partially based on a trial of adults without diabetes, which found that participants — who averaged 231 pounds at the start of the trial — who were given the highest approved dose lost around 18% of their body weight compared to placebo.

“In light of increasing rates of both obesity and overweight in the United States, today’s approval addresses an unmet medical need,” the FDA’s Dr. John Sharretts, director of the agency’s Division of Diabetes, Lipid Disorders, and Obesity, said in a news release.

While there have not been results from large clinical trials comparing Novo Nordisk’s and Eli Lilly’s medications head-to-head, there is some research to suggest Zepboud could outperform Ozempic. 

A meta-analysis presented at the annual meeting of the European Association for the Study of Diabetes in October concluded tirzepatide was “more effective for weight loss than semaglutide, with a larger weight-loss effect at higher doses,” but acknowledged limitations in trying to make a direct comparisons of the two.

In a report earlier this year comparing semaglutide and tirzepatide for diabetics, the Institute for Clinical and Economic Review concluded that tirzepatide showed “greater reduction” in weight and other key markers, but “had a greater incidence of gastrointestinal side effects, severe adverse events, and discontinuation compared with semaglutide.”

Zepbound carries the risk of an array of potential side effects, the FDA says, including nausea, diarrhea, vomiting, constipation, and hair loss. 

Like with other weight loss drugs in this class, some of Zepbound’s side effects could be serious.  

People with a history of severe gastroparesis, or stomach paralysis, should not use the drug, the FDA says. 

Eli Lilly and Novo Nordisk have both faced claims that their drugs can cause stomach paralysis. The FDA recently moved to acknowledge reports of ileus, or a blockage in the intestines, on Ozempic’s label.

The agency also notes that other people could be at higher risk of more severe issues from Zepbound, including patients with a history of medullary thyroid cancer, pancreas inflammation, or severe gastrointestinal disease.

It also should not be combined with other so-called GLP-1 receptor agonist drugs, which include its sibling Mounjaro, as well as Wegovy and Ozempic. 

“The safety and effectiveness of coadministration of Zepbound with other medications for weight management have not been established,” the agency says.