The U.S. drugmaker approached the British company with a $98.9 billion offer in January, but AstraZeneca turned down the proposal. It contacted AstraZeneca again on Saturday to renew takeover talks but the two sides did not reach a deal. This increased investors' expectations that Pfizer would need to raise its offer to successfully take over AstraZeneca.
Such a deal would be one of the largest between two pharmaceutical companies and would mark the largest foreign acquisition of a British company.
AstraZeneca also rose to an all-time high of $79.88 on Monday amid the news. The stock rose 12.13% to $76.99 at the close of trading.
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