Shares of Novo-Nordisk A/S (NVO) plummeted 5.70% in pre-market trading on Monday, following news that rival Eli Lilly's weight loss drug Zepbound outperformed Novo-Nordisk's Wegovy in a head-to-head trial. This development could potentially reshape the competitive landscape in the rapidly growing obesity drug market.

According to data presented by Eli Lilly on Sunday at the European Congress on Obesity, Zepbound demonstrated superiority across five weight-loss targets compared to Wegovy. The trial showed that Zepbound helped nearly 25% more participants lose over 15% of their weight compared to Wegovy. Additionally, Zepbound achieved a superior average waist circumference reduction of 18.4 centimeters, while Wegovy led to an average reduction of 13 centimeters.

This head-to-head comparison provides Eli Lilly with significant leverage as it seeks to gain wider insurance coverage in the obesity drug market, which is estimated to reach over $150 billion annually by the next decade. The news is particularly impactful for Novo-Nordisk, as Wegovy has been a key driver of the company's recent success in the weight loss medication segment. Investors are likely reassessing Novo-Nordisk's market position and future growth prospects in light of this strong competition from Eli Lilly's Zepbound.