Shire agreed to buy US rare disease firm ViroPharma for USD4.2 billion in cash. On Monday, the drugmaker said it would buy the US company for USD50 per share. This move by Shire was its strategy to create a market leader in the rare diseases market. This was according to a report published by Reuters.

Shire is a London-listed specialty biopharmaceutical firm, according to its company website. The firm had already included drugs and treatment for rare diseases in its portfolio. Some of its products were drugs for Gaucher's disease and Fabry disease. After the deal would be finalized, Shire would expect to create a unit that would produce about USD2 billion in annual revenues, Reuters reported.

French healthcare company Sanofi was among the other companies that were interested in buying ViroPharma, the report said.

Many drug companies were said to have lost patent on their conventional drugs. Some of these firms turned to drugs for rare diseases that affect a small population worldwide. This move would help replenish their pipelines with unique products, the report explained.

Shire sought the advice of Lazard and Morgan Stanley on the acquisition deal. ViroPharma was advised by Goldman Sachs, Reuters said.