Eli Lilly’s highly popular weight loss drug reduced the risk of developing Type 2 diabetes by 94% in obese or overweight adults with prediabetes compared with a placebo, according to initial results from a long-term study released Tuesday. 

The late-stage trial on tirzepatide, the active ingredient in the company’s weight loss injection Zepbound and diabetes drug Mounjaro, also found that patients experienced sustained weight loss over the roughly three-year treatment period. Adults on the highest weekly dose of the drug saw a 22.9% decrease in body weight on average after 176 weeks, compared with 2.1% for those who received a placebo. 

Shares of the pharmaceutical giant rose almost 3% on Tuesday.

The results suggest that Eli Lilly’s treatment could meaningfully delay a potential diagnosis for people with prediabetes, or those with blood sugar levels that are higher than normal but not high enough to be classified as Type 2 diabetes. 

More than 1 in 3 Americans have prediabetes, according to the latest government data, which health experts say can be reversed with lifestyle changes such as diet and exercise. People who are overweight or have obesity are at a higher risk for prediabetes. 

The new data also shows the potential long-term health benefits of taking a buzzy class of obesity and diabetes medications called GLP-1s, which mimic hormones produced in the gut to tamp down appetite and regulate blood sugar. As Eli Lilly’s Zepbound and Mounjaro and injections from rival Novo Nordisk have skyrocketed in popularity over the last two years, the companies have raced to study other clinical uses for their drugs.

The results are “another reminder of the huge investment which Lilly has made to prove not only do you lose weight but when you do on this medicine, it converts to health benefits. This is our fourth study this year that does such a thing,” Eli Lilly CEO David Ricks told CNBC in an interview, adding that tirzepatide has shown promise as a treatment for heart failure, sleep apnea and fatty liver disease in three other clinical trials.

Eli Lilly tested tirzepatide in more than 1,000 adults over 176 weeks in the phase three trial, followed by a 17-week period where patients stopped treatment. It is the longest completed study on the drug to date, according to the company. 

The drugmaker will submit the latest results to a peer-reviewed journal and present them at an upcoming medical conference in November. Eli Lilly published 72-week weight loss results on a larger group of patients from the same trial, called SUMOUNT-1, back in 2022. 

Patients in the trial who stopped taking tirzepatide during the 17 weeks began to regain weight and saw an increase in progression to diabetes. But those participants still had an 88% lower risk of developing diabetes compared with a placebo, according to the latest phase three results.

“On the drug, we can keep healthy body weight down for three years and ward off diabetes,” Ricks told CNBC. “When you come of the drug, a percentage of people do begin to gain weight and then…begin the advance again toward diabetes.” 

Still, Ricks noted that patients don’t “snap all the way back as if they were never on the drug.”

The safety data on tirzepatide during the trial was consistent with previous studies on the drug, according to Eli Lilly. The most common side effects were gastrointestinal, such as diarrhea, nausea, constipation and vomiting, and were generally mild to moderate in severity.

Eli Lilly’s Zepbound works by imitating two naturally produced gut hormones called GLP-1 and GIP. 

GLP helps reduce food intake and appetite. GIP, which also suppresses appetite, may also improve how the body breaks down sugar and fat.