Germany’s Bayer AG announced on Friday that it has raised its stake in takeover candidate Schering AG to 40.2% by shelling out for more than 4.6 million shares on the open market.

The group went on a spending spree for Schering stock shortly after rival suitor Merck KGaA backed down from what looked to be challenge to the marriage and agreed to sell Bayer its 21.8% percent stake in the firm.

The deal with Merck clears the path for Bayer to gather the 75% of shares it needs to complete the up to 17-billion euro ($21.3 billion) deal, to create the new entity Bayer Schering Pharma.

The acquisition will be the largest ever undertaken by Bayer, which has been restructuring its business by spinning of certain chemicals interests into an independent company, Lanxess, and re-building the healthcare business in the wake of the damaging withdrawal of cholesterol-lowering drug Baycol/Lipobay (cerivastatin) in 2001.