Eli Lilly & Co.’s blockbuster diabetes drug Mounjaro has surpassed Merck & Co.’s cancer therapy Keytruda as the world’s best-selling medication.
Mounjaro generated $8.7 billion for Lilly in the first quarter of 2026, outperforming Merck’s Keytruda, which posted sales of $7.9 billion. Keytruda has been the world’s top-selling drug since the first quarter of 2023, when it displaced AbbVie Inc.’s autoimmune disorder drug Humira.
Lilly is doing even better if both Mounjaro and its weight-loss drug Zepbound are considered together. They use the same active ingredient, known as tirzepatide. The combination generated $36.5 billion in 2025, outpacing Keytruda’s $31.6 billion for the year.
“It makes sense that we’re shifting from King Keytruda to King Tirzepatide,” said Evan Seigerman, managing director at BMO Capital Markets Corp, noting how well the medicines work and how safe they are. “It’s not a surprise to me.”
The business of cancer drugs is vastly different from the market for obesity and diabetes treatments, he said. At the time of its approval in 2014, Keytruda was revolutionary, extending the lives of patients who previously were given a death sentence. It was priced accordingly.
Tirzepatide, meanwhile, offers low-cost options for millions of people with life-limiting, but not deadly, obesity, he said.
Analysts have predicted for years that Lilly’s drugs would be among the best-selling medicines of all time, though they came to market after Novo Nordisk A/S’ Ozempic and Wegovy. Lilly’s sales have continued to skyrocket even as copycat medicines were launched during shortages and despite pressure from the Trump administration’s affordability push pressured prices in the GLP-1 market.
At the same time, Merck has been staring down a patent cliff for Keytruda, an immunotherapy that is used to treat many different types of cancer. Its patent expires in 2028, prompting the company to bolster its pipeline in other areas. Thus far, obesity isn’t one of them.
Source : Businessstandard
