Alexion Pharmaceuticals (NASDAQ:ALXN), formed in 1992, focuses on a strong scientific and product development base to develop novel antibody therapeutics targeting the treatment of patients with a wide array of severe disease states, including autoimmune and cardiovascular disorders, inflammation and cancer. Alexion is dedicated to developing effective and safe treatments for human diseases for which treatment options are either non-existent or inadequate. The company's clinical efforts have focused on treating disease by blocking formation of the terminal components of complement. Complement is an important and natural part of the human immune system that is comprised of a cascade of proteins, one protein leading to formation of the next. The earlier-formed components of the "complement cascade" are generally beneficial, but the later-formed, or terminal, components can have significant and deleterious effects. Alexion's sole marketed drug Soliris remains the only drug specifically indicated as a treatment for paroxysmal nocturnal hemoglobinuria (PNH)(as of April 2011).^[1] Soliris is highly sought after by PNH patients because there aren't many useful alternatives; The fatal effects of the disease are blood clots which spread rapidly throughout the body, blood vessels become blocked; the blocked vessels cause damage to organs downstream.^[2] On September 23, 2011 it was announced that Soliris was approved by the U.S. Food and Drug Administration for the treatment of all pediatric and adult patients with atypical hemolytic-uremic syndrome (aHUS) (rare genetic disease that affects vital organs especially the kidney, killing more than half of the people who have it, the atypical cases account for roughly 10% all HUS cases). According to the Director of Pediatric Nephrology at Emory University and Children’s Healthcare of Atlanta the FDA's decision "marks the most important advance that has been made for patients and families with this disease".^[3]

Alexion's lead FDA approved product, Soliris (eculizumab), is a humanized monoclonal antibody complement inhibitor. Specifically, eculizumab blocks cleavage of the C5 component of the complement system, thereby preventing the final stages of complement activation. Alexion developed Soliris for the treatment of Paroxysmal Nocturnal Hemoglobinuria (PNH). PNH is a rare blood disorder characterized by the onset of severe hemolytic anemia, chronic fatigue and intermittent episodes of dark colored urine, known as hemoglobinuria. PNH is a chronic disease where a portion of a patient's oxygen-carrying red blood cells are missing the normally present complement inhibitors and are therefore abnormally fragile and inadvertently destroyed by normal complement activation. PNH has been identified more commonly among patients with disorders of bone marrow, including aplastic anemia (AA, is an anemia of all three blood cells types because the bone marrow isn't producing enough to replenish the body) and myelodysplastic syndromes (MDS). Underlying bone marrow dysfunction can complicate the clinical course of PNH, contributing to anemia, a greater dependence on transfusion support, an increased risk of infection and life-threatening hemorrhage. Other than Soliris, currently there is no drug specifically available for treatment of patients with PNH. At present (2011) Soliris is approved for use in at least 35 countries. With the acquisition of Enobia Pharma Alexion will be a more diversified pharmaceutical company with key therapeutic drugs used in treating patients with aHUS (organs) and hypophosphatasia (skeleton).

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