Mounjaro Overtakes Keytruda as World's Top-Selling Drug — $8.66B Lilly Q1 vs $7.9B Merck Q1, Ending Keytruda's Two-Year Reign
Bloomberg reported May 6 that Eli Lilly's Mounjaro displaced Merck's Keytruda as the world's best-selling pharmaceutical in Q1 2026 — $8.66B Mounjaro Q1 sales vs Keytruda's $7.9B Q1 sales. The Mounjaro+Zepbound combined tirzepatide platform generated $36.5B in 2025, outpacing Keytruda's $31.6B. Keytruda had held the #1 ranking since Q1 2023, when it displaced AbbVie's Humira. The shift is the first time a peptide therapeutic has taken the top spot since the historical run of insulin biosimilars. The narrative also frames Lilly's $4.5B Lebanon Indiana manufacturing recommitment and the broader $21B Indiana capital plan as the supply-chain answer to demand at that scale.