In a recent battle of GLP-1 weight loss drugs, Eli Lilly’s Zepbound came out on top.

Lilly’s obesity drug Zepbound outperformed Novo Nordisk’s GLP-1s Ozempic and Wegovy in a head-to-head weight loss study published in JAMA Internal Medicine on Monday.

In a test cohort of adult patients that are overweight or living with obesity, researchers found that tirzepatide — the active ingredient in Zepbound and its sibling drug Mounjaro — was associated with significantly greater weight loss than semaglutide — the active ingredient in rivals Ozempic and Wegovy. 

The study period lasted from May 2022 to September 2023 and while most patients experienced 5% weight loss or greater, those who took Zepbound experienced the greatest benefit.

Additionally, on-treatment changes in weight were larger for patients receiving tirzepatide at three months, six months and 12 months compared to semaglutide, though rates of gastrointestinal adverse events were similar between the groups.

The researchers concluded that while tirzepatide was associated with greater weight loss than semaglutide, future study is needed to understand differences in other important outcomes.

After the study’s findings were released, Lilly’s stock price rose while Novo’s dipped. Novo is slated to report its latest earnings on August 7, while Lilly is set to report on August 8.

This research provides an update on the efficacy of these specific GLP-1 drugs, which have received significant attention for their ability to treat diabetes and obesity — while also contributing to widespread off-label use for weight loss. 

Notably, while Ozempic and Wegovy were both on the market by mid-2021, Zepbound only received approval from the Food and Drug Administration to treat obesity in November 2023. At the time of that approval, many industry stakeholders viewed the regulatory greenlight of this medication as one that could reshape the weight loss market.

Since then, the drug has proven its worth and served as a boon to Lilly’s bottom line by boosting the performance of its diabetes and obesity treatments segment. 

During its first quarter on the market, Zepbound brought home nearly $176 million, followed up by $517.4 million in Q1 2024.

This successful launch prompted Lilly to raise its financial guidance as the GLP-1 space continues to prove itself as a lucrative therapeutic area.

Still, all of that promise and interest from the general public has prompted questions about which drug — tirzepatide or semaglutide — is more effective for weight loss. This study sought to provide a snapshot of the competitive landscape as it currently stands.

While this study focused on the effects of taking the drug, there has been additional research conducted into what happens when patients stop receiving treatment. 

Results from a previous study conducted by Lilly found that patients who took Zepbound regained weight after stopping treatment.