Pfizer confirmed in a statement on Monday morning that it had approached the Anglo-Swedish company in January with an initial offer.
"After limited high-level discussions, AstraZeneca declined to pursue negotiations," Pfizer wrote, adding that discussions ceased mid-January.
Pfizer, however, made a second move on Saturday seeking to renew discussions, citing "recent market developments".
AstraZeneca once again declined to engage.
More to follow