Merck & Co., Inc.

Merck & Co., Inc. is an American global pharmaceutical company that discovers, develops, manufactures, and markets prescription medicines, biologic therapies, vaccines, and animal health products, generating $65.0 billion in revenue in fiscal 2025. Headquartered in Rahway, New Jersey, the company operates through two segments: Pharmaceutical, which includes oncology, vaccines, hospital acute care, cardiometabolic, and virology products, and Animal Health, which sells veterinary pharmaceuticals, vaccines, and health management solutions across livestock and companion animal species. Merck is a component of both the S&P 500 and the Dow Jones Industrial Average, employs roughly 75,000 people, and spent $12.5 billion on research and development in 2025.

This is a story about a pharmaceutical titan executing a deliberate and expensive portfolio transformation in full view of a known patent cliff. Keytruda, the anti-PD-1 therapy that generated $31.7 billion in 2025 — 49% of total company sales — loses its primary U.S. compound patent in December 2028. Between now and then, the company must prove that the 20-plus new products it has assembled through a mix of internal R&D and over $60 billion in business development since 2021 can collectively replace what will be one of the largest revenue holes in pharmaceutical history. Management has put a number on it: over $70 billion in commercial opportunity from these new growth drivers by the mid-2030s, a figure that has grown by $20 billion in the past year alone.

The file turns on whether that number is credible. The bull case is visible in the early launch trajectories of Winrevair, Capvaxive, and Welireg, and in a late-stage pipeline that includes an oral PCSK9 inhibitor, a TROP2-directed ADC in 17 Phase 3 trials, a TL1A antibody for inflammatory bowel disease, and a once-weekly oral HIV regimen. The bear case lives in the sheer arithmetic of replacing $32 billion in single-product revenue, in the regulatory and competitive risks that attend every pipeline asset, and in an IRA drug price-setting framework whose full effect on industry economics is still being discovered.