Booming Tirzepatide Sales and a Bidding War for Metsera

Yesterday’s news from the business of developing and selling obesity medicines reveals a lot. Lilly told us tirzepatide is now the biggest-selling drug of any kind in the world and Novo Nordisk started a highly unusual bidding war with Pfizer for Metsera.

Metsera is a biotech startup focused on obesity medicines.

Booming Tirzepatide

Lilly announced its business results for the third quarter and, yes, it is clear that demand for tirzeptide is booming. Total sales for the Mounjaro and Zepbound brands came to more than ten billion dollars. That was enough to surpass Keytruda (a Merck cancer drug) and become the world’s biggest selling drug of any kind.

This is especially striking when you consider that the monthly cost of Keytruda is more than ten times what it is for tirzepatide. So by far, tirzepatide is reaching more people.

A couple of other tidbits from Lilly’s news yesterday caught our attention. Tirzepatide now accounts for more than half of Lilly’s sales. All the sales growth it’s enjoying comes despite the fact that pricing pressure brought down the company’s net revenue by 15%. Tirzepatide sales grew by 74% outside of the U.S. – despite the fact that health plans outside the U.S. provide very little coverage for this drug in obesity. People step right up anyway and pay for it out of pocket. Three quarters of revenue in these international markets for tirzepatide comes from people paying for it themselves.

In short the demand for this drug is impressive.

The Bidding War for Metsera

That robust demand explains a lot about the reasons behind the bidding war that erupted for Metsera yesterday. Pfizer had reached a deal last month to buy the company for $7.3 billion. Novo yesterday made an unsolicited bid worth about $9 billion. Of course, Pfizer did not like that much, calling it “reckless and unprecedented.” The company vows a legal fight.

Whether this move by Novo is bold and brilliant or desperate and reckless, one thing is clear. Novo Nordisk is doubling down to regain leadership in this market that they essentially created with the launch of Saxenda and Wegovy. The impressive numbers from Lilly yesterday make it unmistakable that the medical need for obesity medicines represents one of the biggest opportunities for the pharmaceutical industry in years to come.

So the competition to innovate and dominate this market will be intense. Thus, we have good reason to hope that more people living with obesity will benefit as these innovative medicines reach them. Options will proliferate and affordability will improve.

Click here, here, and here for more of this news. For Lilly’s presentation of their business results, click here.

The “L” and Trinity Building, etching by Joseph Pennell / Boston Public Library

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October 31, 2025