AstraZeneca stock tumbled as much as 7% on Monday following reports that the drugmaker had been in early talks with Bristol Myers Squibb about joining forces. Bristol Myers Squibb stock rose 6% in U.S. premarket trading.
Should a transaction close, the merged company could be worth close to $400 billion, which would place it among the most consequential deals in pharmaceutical history, according to Reuters. Both companies have stayed silent on the matter. AstraZeneca offered no comment, and Bristol Myers Squibb had not replied to media inquiries at the time of publication.
The Financial Times broke the story. Reuters was unable to confirm whether negotiations are continuing, and sources indicated the process might not result in any agreement.
Before Monday’s session, AstraZeneca’s market capitalization stood at $264 billion. Under CEO Pascal Soriot, who has run the company since 2012, it has set a target of $80 billion in annual revenue by 2030, compared with $58.7 billion last year. Bristol Myers Squibb’s market cap stands at roughly $133 billion.
Analysts expressed skepticism about the strategic rationale. “Given the strength of AZ’s growth and innovation profile, we are a bit perplexed,” Jefferies analysts wrote Monday. “Of course financial accretion can look good and maybe more cash generation would allow for more R&D. But if there is one company that doesn’t need financial engineering, it’s AZ.” Citi analysts called the report a “surprise” given AstraZeneca’s pipeline, according to CNBC.
CNBC suggested that AstraZeneca’s push to expand its American footprint could help explain the reported overtures. The company moved to list its shares directly on the New York Stock Exchange earlier this year. In the first half of 2026, the U.S. represented 42% of AstraZeneca’s total sales, compared with 69% of revenues that Princeton, New Jersey-based Bristol Myers Squibb generated domestically in its most recent quarter.
A deal would likely draw antitrust scrutiny given the two companies’ overlapping oncology portfolios. AstraZeneca’s oncology franchise brought in around $25 billion last year, representing close to half of its overall revenue. At Bristol Myers Squibb, cancer drugs made up more than 40% of sales through the first six months of 2026. “I would expect a Trump FTC to scrutinize the merger, and if there are significant overlaps in certain drugs and late-stage pipeline overlaps, it would require meaningful divestitures,” antitrust lawyer Andre Barlow of DBM Law Group said.