Paroxysmal Nocturnal Hemoglobinuria
PNH is an ultra-rare, life-threatening and debilitating disease of the blood with an estimated 8,000-10,000 patients across North America and Europe. Due to an acquired genetic deficiency, uncontrolled complement activation in PNH patients allows their own complement system to attack and destroy blood cells, leading to life-threatening complications.

Patients with PNH suffer from chronic complement activation and destruction of some of their blood cells, known as hemolysis, caused by the C5 cleavage product C5b-9 (the membrane attack complex). This hemolysis is associated with further clinical symptoms and negative outcomes, including kidney disease, thrombosis (blood clots), liver dysfunction, fatigue, impaired quality of life, recurring pain, shortness of breath, pulmonary hypertension, intermittent episodes of dark-colored urine (hemoglobinuria), and anemia. When the destruction of red blood cells is sufficiently large, recurrent blood transfusions may be necessary.

Before the introduction of eculizumab, PNH patients, many of whom were in young adulthood, faced a life of repeated blood transfusions, thromboembolic complications and typical life expectancies of only 8-10 years from diagnosis. There are no animal models of the autoimmune hematological condition paroxysmal nocturnal haemoglobinuria (PNH). The advent of eculizumab, the first effective complement C5 inhibitor, transformed this bleak outlook, and most of these patients now enjoy a more normal life expectancy.