AstraZeneca tie-up talks with Bristol-Myers Squibb are moving stocks. Analysts are puzzled.

AstraZeneca shares were slumping while Bristol-Myers Squibb was jumping on Monday on reported deal talks. But the big question is why these two pharmaceutical giants would want to come together in the first place.

A deal by AstraZeneca chief executive Sir Pascal Soriot would extend the drugmaker's footprint in the US market.

AstraZeneca Shares Drop After Reports of Bristol Myers Squibb Merger Talks  WSJ

The companies have discussed a potential merger over several months, the Financial Times reported on Sunday.

A deal by AstraZeneca chief executive Sir Pascal Soriot would extend the drugmaker's footprint in the US market.

AstraZeneca shares tumble 7% after reported Bristol Myers talks  Reuters

AstraZeneca shares fall on Bristol Myers Squibb merger talks  The Times

Tie-up would be one of the biggest pharmaceutical deals ever and create the world’s fourth-largest drugmaker Business live – latest updates Britain’s biggest drugmaker AstraZeneca is in discussions to take over its US rival Bristol Myers Squibb in a deal that would create a near-$400bn (£300bn) pharmaceutical group.

Astrazeneca is exploring a $400bn (£300bn) merger with US rival Bristol Myers Squibb, in a deal that would create one of the world’s largest pharmaceutical groups. The FTSE 100 giant has held talks with the US group in recent months about a possible tie-up, according to reports in the Financial Times.  Talks could lead

The deal could create one of the world's biggest pharmaceutical groups with a combined value of nearly $400 billion.

Bristol Myers Squibb, which has a $133 billion market capitalization, could provide AstraZeneca with a bigger foothold in the US market.

The deal could create one of the world’s biggest pharmaceutical groups with a combined value of nearly US$400 billion.

Tie-up would create one of the world’s biggest drugmakers