Pfizer Inc. proposed buying AstraZeneca Plc for about $98.7 billion in what would rank as the biggest-ever takeover of a U.K. company and continues to be interested in a deal after being spurned.

Pfizer offered 46.61 pounds a share in cash and stock for London-based AstraZeneca last January, and AstraZeneca declined to pursue negotiations, New York-based company Pfizer said in a statement today. The proposal is about 14 percent above the April 25 close for AstraZeneca. The stock today climbed above that price, gaining the most in more than two decades.