Lilly's Obesity Drug Zepbound Becomes World's Best-Selling Medicine, Driving Revenue Surge

Eli Lilly's groundbreaking obesity and diabetes medication, tirzepatide, has claimed the title of the world's best-selling drug, propelling the company to raise its full-year financial forecasts. The pharmaceutical giant's third-quarter results have sent ripples through the industry, highlighting the growing dominance of GLP-1 medicines in the global market.

Tirzepatide Sales Soar, Outpacing Competitors

Tirzepatide, marketed as Zepbound for obesity and Mounjaro for diabetes, generated a staggering $10.1 billion in combined sales during the third quarter of 2025. This represents a significant leap from $4.37 billion in the same period last year, surpassing Merck & Co.'s cancer drug Keytruda, which brought in $8.1 billion.

The meteoric rise of tirzepatide has not only reshaped Lilly's product portfolio but has also redefined the company's market position. Once known primarily for Prozac and insulin products, Lilly's fortunes are now inextricably linked to the burgeoning GLP-1 market, which analysts project could exceed $100 billion by the next decade.

Financial Outlook and Market Response

Buoyed by the exceptional performance of its obesity and diabetes franchise, Lilly has revised its financial projections upward. The company now anticipates full-year revenue between $63 billion and $63.5 billion, a substantial increase from its previous estimate of $60 billion to $62 billion. Earnings per share are expected to reach $21.80 to $22.50, up from the earlier forecast of $20.85 to $22.10.

Despite these impressive figures, Lilly's share price has remained relatively stable over the past year. The market's muted response can be attributed to several factors, including occasional sales figures falling short of high analyst expectations and mixed investor sentiment regarding an experimental obesity pill in development.

Strategic Moves in a Competitive Landscape

Lilly is not resting on its laurels in the face of fierce competition, particularly from Novo Nordisk. The company has taken strategic steps to differentiate its products and expand market access:

1. Head-to-head studies: Lilly has conducted research showing Zepbound's superiority over Novo Nordisk's Wegovy in weight loss efficacy.

2. Manufacturing investments: To avoid production shortfalls that have plagued injectable GLP-1 drugs, Lilly is making significant investments in manufacturing capabilities for its experimental obesity pill.

3. Accessibility initiatives: The company has launched an online service offering self-paying customers new options and recently announced a partnership with Walmart to provide discounted drugs to customers by mid-November.

These moves come as Novo Nordisk faces its own challenges, including recent layoffs and a contentious bid to acquire obesity drug developer Metsera for up to $9 billion, competing against Pfizer's offer.

As the obesity and diabetes drug market continues to evolve rapidly, Lilly's record-breaking sales and strategic positioning suggest that the company is well-placed to maintain its leadership in this highly competitive and lucrative sector.