Eli Lilly said on Sunday its drug Zepbound was superior to Novo Nordisk's Wegovy across five weight-loss targets such as reducing waist circumference, citing data from a head-to-head trial.

Novo Nordisk's shares slipped 3% in overnight trading.

Lilly reported in December that its obesity drug had already met the main goal, leading to 47% more weight loss than those who received Wegovy. Full data from the study was reported by the company in a press release and presented at the European Congress on Obesity.

The data is the first head-to-head trial comparing the wildly popular medicines, and gives Lilly more firepower as it seeks to gain wider insurance coverage in an obesity drug market estimated to reach more than $150 billion annually by the next decade.

It comes days after CVS Health's decision to drop Zepbound from some lists of medicines it covers for reimbursement, instead favoring Wegovy.

Zepbound helped nearly 25% more participants lose more than 15% of their weight compared to Wegovy, Lilly said on Sunday.

The trial also showed that treatment with Zepbound achieved a superior average waist circumference reduction of 18.4 centimeters (cm), while those treated with Wegovy saw an average reduction of 13 cm.

While Lilly's drug mimics two gut hormones to help reduce weight, Wegovy has a single mode of action.

U.S. approvals for Zepbound and Wegovy were based on separate trials in which Lilly's drug helped patients lose more than 22% of their weight after 72 weeks, while Wegovy led to 15% weight loss after 68 weeks.