US drugs giant Pfizer on Sunday announced it had made a final improved bid for British competitor AstraZeneca, valuing the company at £69 billion ($117 billion). In a letter written from Pfizer chairman and chief executive officer Ian Read to AstraZeneca chairman Leif Johansson, the US giant said that Pfizer and AstraZeneca shareholders would own "approximately 73 percent and 27 percent, respectively, of the combined company. "The improved proposal values AstraZeneca today at approximately £69 billion," it added.