AstraZeneca shares drop 7% after report on $400 billion merger talks with Bristol Myers Squibb

AstraZeneca shares dropped as much as 7% after a report that the U.K.'s largest drugmaker was in talks with U.S. peer Bristol Myers Squibb over a megadeal that, if completed, could value the companies at roughly $400 billion.AstraZeneca declined to comment. Bristol Myers Squibb didn't immediately respond to a request to comment outside of normal working hours. The companies have discussed a potential merger over several months, the Financial Times reported on Sunday. It would be one of the biggest deals ever. AstraZeneca's London-listed shares were last seen trading 6.5% lower in early morning trading, weighing on the U.K.'s blue-chip index FTSE 100, which was largely flat.This is breaking news. Please refresh for updates.