A genetic mutation in PNH patients leads to the generation of populations of abnormal RBCs (known as PNH cells) that are deficient in terminal complement inhibitors (CD-59), rendering PNH RBCs sensitive to persistent terminal complement-mediated destruction. The destruction and loss of these PNH cells (intravascular hemolysis) results in low RBC counts (anemia) and also fatigue, difficulty in functioning, pain, dark urine, shortness of breath, and blood clots. Eculizumab, the active ingredient in Soliris, is a monoclonal antibody that binds to the complement protein C5 specifically and with high affinity, thereby inhibiting its cleavage to C5a and C5b and subsequent generation of the terminal complement complex C5b-9. Soliris inhibits terminal complement mediated intravascular hemolysis in PNH patients and therefore the destruction of PNH erythrocytes that lack complement protection with CD-59.
Eculizumab is a monoclonal antibody directed against the complement protein C5. This antibody blocks the cleavage of C5 and halts the process of complement-mediated cell destruction. Eculizumab is a product of Alexion Pharmaceuticals and has been shown to be effective in treating paroxysmal nocturnal hemoglobinuria. Eculizumab was approved by the FDA in March, 2007.