Germany’s Merck KGaA is buying a majority stake in Swiss rival Serono in a deal worth approximately $13.3 billion, according to published reports.Merck said it is buying a 64.5% stake in Serono that will give it 75.5% of voting rights, The Wall Street Journal reported.“Details of the financing will be provided prior to closing, early 2007,” a Merck spokesman said. Merck produces chemicals such as liquid crystals and drugs including cancer treatment Erbitux. Merck’s pipeline virtually dried up in June when its Parkinson’s disease drug Sarizotan failed in late-stage clinical tests.Serono’s sales increased 2.8% in the second quarter, with the company’s main product, multiple sclerosis treatment Rebif, contributing to the rise.