Alexion Phamaceuticals Inc, drug-maker for rare blood diseases, could potentially break some records for the most expensive acquisition in the field of biotechnology. 

To date, Roche Holding AG is trying to raise US $21 billion from old and new investors to purchase Alexion which is selling its shares to as much as US $148, accordimg to a Bloomberg report. Interestingly, Roche was also involved in the record-setting purchase of Genentech Inc. for US $46.8 billion in 2009. Up to today, the transaction is still considered the biggest deal in biotech.

Roche withdrew its earlier plan to buy Ilumina Inc. due to the high asking price but Alexion is a more attractive option because of Soliris, an an orphan drug that costs $400,000 a year.

Soliris is an extremely exclusive medicine that is treating rare blood diseases affecting about 20,000 patients. Even if the orphan drug is very expensive, the cost is covered by medical insurance which adds value for investors.