Chinese prosecutors have formally filed charges against couple linked to bribery claims.
The Basel-based drugmaker is looking to bolster its offering of breast cancer drugs with the purchase.
Deal will allow the U.S. medical device maker to reduce its overall global tax burden.
Drugs giant is to have its "commercial practices" investigated by the Serious Fraud Office.
AstraZeneca rejected a final offer from Pfizer earlier this month, saying the proposal undervalued the company.
Rejection undermines U.S. drugmaker's plan for a merger to create the world's biggest pharma group.
AstraZeneca's boss said on Wednesday he would engage with Pfizer if the price was right.
The U.S. drugmaker pressed the scientific case for its controversial plan to acquire AstraZeneca.
Deal with Germany's Bayer AG adds to a string of major cross-border healthcare deals.
Pfizer's pursuit of AstraZeneca comes amid a wave of deal-making in the healthcare sector.
Copyright © 2014. All rights reserved.