Eli Lilly vs Merck: Which Is the Better Buy in 2026?

Lilly is a concentrated bet on one of medicine's most promising categories — GLP-1 drugs for obesity and diabetes that appear to reduce cardiovascular risk and drive weight loss at unprecedented rates. Merck's revenue is diversified across oncology (Keytruda), vaccines (Gardasil), and animal health. Lilly's bet is higher-risk, higher-reward on a single category; Merck's diversification means no single drug makes or breaks it.

Lilly's GLP-1 franchise — Mounjaro for diabetes, Zepbound for obesity — may be the largest new drug category in pharmaceutical history. The obesity market alone represents hundreds of millions of patients globally who currently have no effective medical treatment. That opportunity explains the premium multiple. Merck's Keytruda is arguably the most important cancer drug by revenue in history, with patent protection into the 2030s and approvals expanding into more tumor types each year. Different mega-cycles, similar quality of execution.