Eli Lilly & Co.’s blockbuster diabetes drug Mounjaro was about as good at preventing heart attacks and strokes as its older medicine Trulicity in a head-to-head study of the two treatments.

The trial — Lilly’s largest and longest of Mounjaro to date — was designed to prove what’s called non-inferiority to Trulicity, meaning the company set out to show that Mounjaro was an acceptable alternative when it comes to reducing risks from major cardiovascular events.

While it achieved that target, the study dashed investors hopes that Mounjaro would be meaningfully better than its older drug. Shares in the obesity-drug maker dropped 3% in premarket trading in New York.

More than 13,000 people with type 2 diabetes and a history of heart disease were enrolled in Lilly’s trial, during which they were treated with either Mounjaro or Trulicity and followed for an average of about four years. The results showed that Mounjaro was effective at reducing the risk of heart attacks and strokes and cardiovascular death, but not significantly better than the older drug, according to results shared by Lilly on Thursday.

Mounjaro was tied to other positive health impacts. Patients on the drug were 16% less likely to die from any cause than those on Trulicity. Mounjaro patients also saw greater improvements in blood sugar levels, weight loss and blood pressure, Lilly said. The most commonly reported side effects were mild and gastrointestinal-related with both drugs.

The fact that patients lost more weight on Mounjaro but saw about the same reduction in risk from cardiovascular events suggests the class of medications — known as GLP-1s — may have protective effects on the heart that are independent of weight loss.

Lilly will present the study at a medical conference in September. Mounjaro is already approved as a treatment for type 2 diabetes, but Lilly plans to submit the new findings to global drug regulators by the end of the year in hopes of expanding its label to include cardiovascular risk reduction.

“These findings strengthen the case for Mounjaro as a potential front-line treatment for people with type 2 diabetes and cardiovascular disease,” Ken Custer, president of Lilly’s cardiometabolic business, said in a statement.

Trulicity has established heart benefits. Back in 2020, US regulators gave it an expanded label for risk reduction from major cardiovascular events in people with type 2 diabetes.

Lilly and rival Novo Nordisk A/S — the maker of Ozempic and Wegovy — have been racing to study their drugs in a range of conditions beyond obesity and diabetes. While most insurers cover the treatments for diabetes, many have been reluctant to cover them for weight loss.

Novo has already demonstrated that both Ozempic and Wegovy reduce the risk of heart attacks and strokes in patients with obesity and diabetes. Both drugs carry labels reflecting those benefits, giving Novo an advantage in coverage negotiations with insurers and government programs.

Lilly, however, has managed to take significant market share from Novo — even without a label for heart disease.

Lilly isn’t running trials of its obesity drug Zepbound specifically for cardiovascular risk reduction. Instead, it’s studying whether the drug can reduce the risk of death from all causes in a large, multiyear trial. Those results aren’t expected until 2027.