Pharmacquired: What a surprise deal does for AstraZeneca and Alexion

One of the largest pharmaceutical deals in recent years is also one of the most curious.

On Saturday, AstraZeneca announced plans to acquire Alexion Pharmaceuticals for just shy of $40 billion. The deal would combine two companies working in very different areas of drug research, with Alexion focused on rare diseases and AstraZeneca mostly invested in medicines for cancer, diabetes and respiratory conditions.