Pharmaceutical giant Merck will acquire its rival Schering-Plough in a US$41-billion deal announced on 9 March and unanimously approved by the boards of the New Jersey-based companies.

The move is seen as a way to protect the company's drug-development pipeline. The new company, which will be called Merck, would have 18 drugs in phase-III development, double what Merck had before. It also opens new markets for Merck: Schering-Plough earns 70% of its annual revenue outside the United States, including more than $2 billion from emerging markets.

The deal is the latest in a series of drug-industry marriages: Pfizer paid $68 billion in January to acquire Wyeth, and Roche recently boosted its offer to buy out Genentech to $46 billion.