Mounjaro Dethrones Keytruda as World's Top-Selling Drug
Eli Lilly's tirzepatide franchise pulled in $36.5B in 2025, edging past Merck's Keytruda — the first time a GLP-1 has held the global No. 1 sales spot.
May 6, 2026 · 2 min read
Eli Lilly's tirzepatide franchise — sold as Mounjaro for type 2 diabetes and Zepbound for obesity — generated $36.5 billion in 2025, overtaking Merck's Keytruda ($31.7 billion) to become the world's top-selling drug. Bloomberg confirmed the milestone Wednesday based on full-year sales filings. It's the first time a GLP-1 has held the global No. 1 spot.
What happened
Tirzepatide sales nearly doubled year-over-year, driven primarily by Zepbound's obesity indication and aggressive direct-to-consumer pricing through Lilly's self-pay channel. Mounjaro's diabetes use continued to grow as well, but the larger eligible population for obesity treatment is what tipped the franchise past Keytruda.
For context: Keytruda held the top spot for years on the back of expanded oncology indications. The handoff happened gradually — analysts had flagged it was likely after Lilly's strong Q3 2025 numbers, and Q4 cemented it. Combined GLP-1 sales (tirzepatide plus Novo's semaglutide) are now projected above $84 billion globally in 2026.
Why it matters
The shift signals something pharma watchers have been calling for two years: cardiometabolic disease, not oncology, is now the largest single therapeutic revenue category. That has downstream effects on R&D allocation, manufacturing capacity, and payer formulary design — most insurers still treat obesity drugs as discretionary, even as their parent companies report record GLP-1 revenue.
For patients, the immediate practical effect is supply confidence. When a single drug crosses $35B, manufacturers invest in redundant production capacity; the tirzepatide shortage list status has been stable for months, and Lilly's recent capacity expansions reduce the risk of returning to allocations.
What to watch
Two stories will reshape the 2026 ranking: Novo's oral Wegovy pill launch, which is running at roughly $1.4 billion annualized in its first quarter, and the continued ramp of Lilly's Foundayo (orforglipron). If Novo's combined semaglutide franchise — injectable plus oral — passes tirzepatide later this year, the global top spot could change hands again before 2027.
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