A rumored megamerger between pharmaceutical giants AstraZeneca and Bristol Myers Squibb is facing backlash on Wall Street — confusing analysts and spurring a significant stock sell-off.
According to people “familiar with the matter,” The Financial Times reported on Sunday that AstraZeneca and Bristol Myers have discussed a tie-up in recent months; and, though a deal could soon solidify, it may also break down or be delayed. Reuters later echoed some of these details, citing a person familiar with the situation who said the companies had held initial talks about a possible combination.
The market reaction indicates investors aren’t keen to see this deal materialize. Bristol Myers shares were down almost 1.5% at one point early Monday, while AstraZeneca’s fell more than 8%, wiping out roughly $22 billion from the U.K.-based company’s market value. AstraZeneca completed a direct listing on the New York Stock Exchange early this year, though its primary listing is still on the London Stock Exchange.
If the deal were to happen, it would be one of the pharmaceutical industry’s largest, creating a combined entity worth nearly $400 billion. It would also supercharge AstraZeneca’s two biggest product categories, cancer and cardiovascular drugs, which last year respectively accounted for 44% and 22% of the company’s $59 billion in revenue.
Bristol Myers’ top-sellers include the immunotherapy Opdivo, the blood thinner Eliquis and the immune system regulator Orencia. Those first two drugs are at risk of losing key patent protections in the next couple years, which has put pressure on Bristol Myers to deliver new drugs that can offset the coming decline.
On that front, the company has had mixed success. Its latest earnings report surpassed analyst expectations, in part because of the strong showing of newer medicines like Reblozyl, Breyanzi and Camzyos. However, Eliquis’ performance bolstered the quarter. And other so-called growth products like the schizophrenia medication Cobenfy, which Bristol Myers paid $14 billion to acquire, have yet to impress commercially.
To Michael Leuchten, an analyst at Jefferies who covers AstraZeneca, a buyout of Bristol Myers would be a “head scratcher,” namely because, under the direction of CEO Pascal Soriot, AstraZeneca has notched a series of major wins over the past several years. At the end of 2025, the company had 16 products generating $1 billion or more in annual sales. By 2030, it expects that number to surpass 25 and sales to exceed $80 billion.
AstraZeneca’s revenue rose 8% last year, and its stock price has surged around 37% since mid-2021.
Given the company’s existing growth and promising research projects, “we are a bit perplexed by the news,” Leuchten wrote in a note to clients. “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 [AstraZeneca].”
The market’s skepticism is “understandable,” according to Alex Torgerson, an M&A partner at consulting firm West Monroe.
“AstraZeneca has been one of the industry's strongest organic growth stories, so investors are naturally asking why it would take on the complexity of a potential $400 billion megamerger instead of continuing to execute its current strategy,” Torgerson wrote in an email to BioPharma Dive.
Analysts anticipate that such a deal might not be easy to close. First, it would likely raise flags with antitrust regulators. The scrutiny would be particularly acute in the U.K., according to William Blair analyst Matt Phipps, because AstraZeneca is “arguably the cornerstone” of the country’s biopharma R&D ecosystem.
Price may also be challenging to hammer out. On one hand, Bristol Myers’ top products are under patent pressure. On the other, the company is expecting in the coming months data from important clinical trials of Cobenfy, a blood thinner called milvexian and other experimental medicines.
“Achieving alignment on value may prove difficult,” wrote RBC Capital Markets analyst Trung Huynh. “Both sides will need compelling economic and strategic rationale to support a merger.”
More broadly, a merger of this size may have knock-on effects for dealmaking.
Not only would it probably keep two prominent acquirers mostly on the sidelines for some time, it could also sow the seeds that “transformational” deals are back on the table for big pharma after a period where “bolt-on” deals in the range of $5 billion to $10 billion were more in vogue.
“Regardless of whether this deal occurs, it signals that large pharmaceutical companies may be thinking differently about growth,” Torgerson wrote.
“For the past several years, the industry has favored targeted biotech acquisitions over megamergers,” he added. “If AstraZeneca is exploring a transaction of this scale, it could encourage other large pharmaceutical companies to reassess whether transformational deals belong back in the M&A playbook.”
Bristol Myers did not respond to a BioPharma Dive request to comment. AstraZeneca declined to comment.
