Alexion Pharmaceuticals Inc. is an American pharmaceutical company best known for its development of Soliris, a drug used to treat the rare disorders atypical hemolytic uremic syndrome (aHUS) and paroxysmal nocturnal hemoglobinuria (PNH). 

The company is also involved in immune system research related to autoimmune diseases. It employs around 2,400 people worldwide.

Alexion Pharmaceuticals was founded in 1992 at Science Park in New Haven, Connecticut by Steven Squinto and Leonard Bell. 

In 2000, Alexion moved its headquarters from New Haven to Cheshire, Connecticut. Alexion moved back to New Haven following the completion of New Haven's Downtown Crossing project in December 2015.

According to en.wikipedia