AstraZeneca Shares Plummet Amid Bristol Myers Merger Rumors

AstraZeneca's stock plummeted 5.5% on Monday after reports of merger talks with Bristol Myers Squibb, which could create one of the world's largest drugmakers with a combined value of nearly $400 billion.

Investors and analysts were skeptical about the potential deal, with Jefferies analyst Michael Leuchten writing that it would be 'more than a head scratcher' due to AstraZeneca's lack of need for a transformative acquisition despite possible financial benefits.

Bristol Myers shares, on the other hand, saw a 5% increase in U.S. premarket trading.

In related news, Amgen disclosed that hackers had stolen company data and patient health information from cloud storage systems run by third-party providers, marking another major cybersecurity incident in the healthcare sector.