Germany’s Merck KGaA has agreed to sell its 21.8% stake in Schering AG, paving the way for rival Bayer to seize control of Schering AG. Bayer is expected to pay Merck KGaA $4.6 billion for its Schering AG stake upping the total purchase price for Schering AG to nearly $22 billion. The combined companies will form a German drug-manufacturing powerhouse to be  known as Bayer Schering Pharma. Schering AG’s product line includes several oncology drugs, including contraceptives Climara, Yasmin and Yaz — and other specialty brands sold in the US by Schering AG affiliate Berlex.