Lilly's Zepbound Outperforms Novo's Wegovy in Weight Loss Efficacy and Safety

Eli Lilly's obesity drug Zepbound (tirzepatide) has demonstrated superior weight loss efficacy and a comparable safety profile to Novo Nordisk's Wegovy (semaglutide) in a head-to-head clinical trial, potentially reshaping the competitive landscape of the rapidly growing obesity treatment market.

SURMOUNT-5 Trial Results

The Phase IIIb SURMOUNT-5 study, involving over 750 overweight and obese patients without diabetes, revealed that Zepbound-treated patients lost an average of 20.2% of their body weight after 72 weeks, compared to 13.7% for those on Wegovy. This represents a 47% relative weight loss advantage for Zepbound.

Key secondary endpoints also favored Zepbound, with a higher percentage of patients achieving at least 25% weight loss compared to Wegovy. The comprehensive data, published in the New England Journal of Medicine, showed that Zepbound's superior efficacy did not come at the expense of safety.

Safety and Tolerability Profile

Despite concerns that greater weight loss might lead to increased side effects, Zepbound demonstrated a safety profile comparable to Wegovy. Common adverse events for both drugs included nausea, constipation, vomiting, and diarrhea. Serious adverse events occurred in 4.8% of Zepbound-treated patients versus 3.5% in the Wegovy group.

The study reported no treatment-related deaths, and an equal number of patients (six) in each group discontinued due to side effects. These findings led Leerink Partners analysts to conclude that Zepbound has a "superior benefit-risk ratio" compared to Wegovy.

Market Implications and Future Developments

The SURMOUNT-5 results could significantly impact the competitive dynamics of the obesity drug market. While Novo Nordisk recently gained an advantage with CVS Caremark selecting Wegovy as its "preferred GLP-1 medicine" effective July 1, Lilly remains confident in its commercial strategy.

Lilly is now focusing on the ATTAIN-MAINTAIN extension study, which will evaluate the efficacy of transitioning patients to orforglipron, an oral obesity drug, for weight maintenance. This next-generation GLP-1 drug showed promising results in recent Phase III trials, with patients experiencing a 7.9% reduction in body weight over 40 weeks.

As the obesity treatment landscape continues to evolve, these latest developments underscore the intense competition between Eli Lilly and Novo Nordisk in their pursuit of dominance in this lucrative market segment.