Eli Lilly's Tirzepatide Becomes World's Best-Selling Drug

Eli Lilly (LLY) is experiencing significant growth driven by its GLP-1 drug, tirzepatide. Marketed as Mounjaro for type 2 diabetes and Zepbound for weight loss, tirzepatide has quickly become the world's best-selling drug, surpassing Merck's Keytruda. In the U.S. incretin analog market, Eli Lilly holds a 57.9% share of total prescriptions.

The company's Q3 2025 revenues increased by 54% year-over-year to $17.6 billion, with adjusted EPS soaring by 495% to $7.02. Eli Lilly has raised its full-year revenue guidance to $63 billion - $65 billion. It is also developing an oral GLP-1 candidate, orforglipron, which has shown promising results in Phase 3 trials. If approved, this could further boost Eli Lilly's market share. The company is awaiting results from Phase 3 trials for another GLP-1 candidate, retatrutide, expected by the end of 2026.

Eli Lilly's success in the GLP-1 market is driven by the high clinical need for effective diabetes and weight loss treatments. With a diversified portfolio that includes drugs for oncology, immunology, and neuroscience, Eli Lilly is poised for continued growth.

Actionable Takeaways:

Tirzepatide is a GLP-1 dual receptor agonist manufactured by Eli Lilly, sold as Mounjaro for type 2 diabetes and Zepbound for weight loss.

Tirzepatide became the world's best-selling drug in Q3 2025, with $10.1 billion in sales. Mounjaro's U.S. prescriptions rose by over 60%, and Zepbound prescriptions tripled year-over-year in Q3.

Eli Lilly's tirzepatide has become the world's best-selling drug, driven by the increasing demand for GLP-1-based treatments. The company's strong financial performance and diversified portfolio suggest continued growth potential. Key actions for readers include monitoring the development of Eli Lilly's oral GLP-1 candidate and tracking the company's progress in the incretin analog market.

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