UK drugmaker AstraZeneca has been exploring a deal to combine with US rival Bristol Myers Squibb in a tie-up that would create one of the world's biggest pharmaceutical groups valued at nearly $400bn. The companies have held discussions about a tie-up in recent months, according to people familiar with the matter. Talks could yield a deal in the near future but may be delayed or fall apart, the people said.

AstraZeneca, the UK's second most valuable listed company, has a market valuation of about £196bn while BMS is worth roughly $133bn, making any deal one of the biggest mergers of all time. A deal by longtime AstraZeneca chief executive Sir Pascal Soriot would extend the British drugmaker's pivot towards the US market.

The company in June elevated the FTSE 100 company's New York listing, in a blow to the London stock market. AstraZeneca declined to comment, while Bristol Myers Squibb did not immediately respond to requests for comment. This is a developing story.