FRANKFURT, Germany (AP) — German drug company Merck says it has agreed to buy St. Louis-based chemical firm Sigma-Aldrich Corp. for $17 billion in a deal Merck says will strengthen its business in chemicals and laboratory equipment.

Darmstadt-based Merck KGaA said Monday it is paying $140 per share in cash for all of Sigma-Aldrich’s shares — a premium of 37 percent over Friday’s closing price of $102.37.