In order to bolster its immunology and rare disease pipeline, AstraZeneca (AZ) has agreed to purchase Alexion Pharmaceuticals for a total consideration of US$39 B. With the acquisition, AZ will gain access to Alexion’s therapies that inhibit pathways of the complement system, which is led by Soliris® (eculizumab), a first-in-class anti-complement component 5 monoclonal antibody. Alexion will also form the basis of AZ’s dedicated rare disease unit in Boston, Massachusetts.