Just call it BristolAstraMyersZenecaSquibb

Investors got to witness one of the rarest sites on Wall Street today: a deal nobody wants done.

AstraZeneca is in talks to merge with Bristol Myers Squibb in a deal that would create a company worth roughly $400 billion, according to a report from the Financial Times on Sunday. If a deal is struck, it would be one of the biggest mergers in history.

AstraZeneca, the UK’s second-largest publicly traded company, is purportedly looking to deepen its US presence after listing on the NYSE earlier this year, trying to make further inroads into a market that accounted for 42% of its revenue in the first half of 2026.

But investors aren’t sold: AstraZeneca shares fell 6.88%, while BMS eked out a 0.24% gain as analysts warned that the merger faces both strategic and financial hurdles.

Wall Street is left wondering

Analysts from RBC Capital Markets, Jefferies, UBS, and Barclays all sounded bewildered in notes this morning, confused by AstraZeneca’s desire to make a deal. The company has a lot of momentum: It has spent the past several years expanding into the rare diseases and obesity markets through its acquisition of Alexion. And it’s on track to grow annual revenue to $80 billion by the end of the decade, up from the roughly $59 billion it generated last year.

By all accounts, AstraZeneca has a strong pipeline of drugs to buoy its business for years to come. BMS, meanwhile, faces the opposite problem: Its two biggest drugs by revenue, Eliquis and Opdivo, begin losing patent protection in 2028. The company is also under pressure to reignite growth after its $74 billion Celgene acquisition in 2019 fell short of expectations.

Then there’s the fact that with cancer treatments accounting for 44% of AstraZeneca’s 2025 revenue and about half of BMS’ sales, regulators would likely scrutinize the deal over antitrust concerns. That could drag out approvals and slow drug development.

The return of M&A

The talks come as US dealmaking hits record levels this year, helped by a friendlier regulatory environment under President Trump. Drugmakers have been especially active as they race to replenish their pipelines before blockbuster medicines lose patent protection.

So far though, most of Big Pharma has favored bolt-on acquisitions worth less than $10 billion, rather than betting on blockbuster mergers. If AstraZeneca goes forward with this deal, it would break from that playbook—and investors may start wondering whether management has doubts about its pipeline after all.—SY