Previous mega blockbusters took years to reach their peak sales. Lilly’s tirzepatide franchise is on course to exceed them just a few years in.
Eli Lilly is rewriting the rules of pharma. Not only did sales of the company’s tirzepatide franchise exceed Keytruda for the first time in the third quarter, the steep pace of growth has it on a trajectory to far surpass Merck’s cancer stalwart.
Indeed, Lilly’s Mounjaro, Zepbound and the yet-to-be-approved orforglipron are collectively expected to reach peak sales of $101 billion, according to a recent estimate from Truist Securities. The firm previously estimated the diabetes version Mounjaro to reach peak sales of $40 billion and the weight loss injectable Zepbound to acheive $30 billion.
Keytruda, on the other hand, brought in $29.5 billion in 2024, and it took Merck 11 years to grow the checkpoint inhibitor to that level. It now faces patent expiration in just a few years’ time.
Previous mega-blockbuster drugs similarly pale in comparison to projections for the trio of diabetes/weight loss products. Before Keytruda, there was AbbVie’s Humira, which peaked at $21.2 billion in 2022 before losing ground to generic copies. Even further back, it was Pfizer’s Lipitor. The drug achieved nearly $13 billion in sales in 2006 before declining.
Like Keytruda, all of these drugs had a slow and steady climb to the top. Humira was on the market for nearly 20 years before reaching that peak.
That isn’t the story for Lilly’s tirzepatide franchise, or for Novo Nordisk’s rival medicine semaglutide. Both drugs have climbed precipitously since getting their medicines approved for weight loss. Lilly’s franchise has hit $24.8 billion in the first nine months of 2025—and it’s only year 4.
“We are kind of in a rare situation right now, in that our growth rate is high and our profitability is expanding, and we are early in the cycle of this invention,” Lilly CEO Dave Ricks said during an appearance on the Cheeky Pint podcast.
Novo initially saw a slower climb, more akin to Keytruda’s growth curve, after its initial approval as Ozempic for diabetes in 2017. But four years later, when Wegovy was approved for weight loss, semaglutide sales began exploding, reaching $26.6 billion in 2024.
But Lilly has quickly proven itself to be the victor in this market battle as tirzepatide has reigned supreme in head-to-head trials with semaglutide, proving to be potentially more efficacious and tolerable. The Indianapolis-based pharma has also exceled at advertising its products; one expert recently referred to Lilly as a “marketing machine.” This sales prowess has led Lilly to quickly overtake Novo, sending its Nordic rival’s growth curve back down south this year.
How high can Lilly go?
