Out with the old, in with the new. The German drug and chemical conglomerate Merck KGaA says it is exploring the sale of its generic-drug business, one of the world's largest such operations. Merck's comments on Friday about divesting its generics unit as "one strategic option" portends more action in a field that has been filled in recent years with buyouts in the U.S. and overseas. The announcement coincided with Merck's reporting that it has now purchased most of the shares of the Swiss biotechnology company Serono ( SRA). Merck offered $13.3 billion in September for the company whose major product is the multiple sclerosis drug Rebif. All told, it now holds 84% of Serono's capital stock and 89% of the voting rights. Next week, Merck hopes to commence a tender offer for the remaining shares. The deal has been approved by U.S. and European Union regulators. If Merck sells its generics unit -- a decision first reported by a German newspaper on Thursday -- it could use the cash to help pay for Serono, even though it already has lined up a $15 billion loan package through several investment banking firms. "Merck Generics has a strong business with excellent leadership and good growth prospects for the future," said Michael Roemer, chairman of the company. "However, it will need continued investment to fully realize its potential and strengthen its market presence. In light of the far-reaching changes occurring in the market, we are considering as an option the divestiture of Merck Generics to a qualified buyer."