Patients with paroxysmal nocturnal hemoglobinuria (PNH) given eculizumab, a novel terminal complement inhibitor, have shown sustained and significant reductions in red blood cell destruction and in the need for blood transfusions, according to preliminary three-year cumulative results of an open-label extension study being conducted by Leeds Teaching Hospital and St. George's Hospital in the UK.

The 10 patient open-label extension program of an initial pilot trial is being conducted in the UK at two sites. All patients have now completed at least three years of chronic eculizumab therapy. In addition to reductions in hemolysis and the need for transfusions, the results also showed a sustained and stable increase in PNH red blood cell counts. PNH is a rare form of anemia for which there is no currently specific treatment.

Eculizumab is a monoclonal antibody drug that blocks the terminal complement pathway of the immune system. Terminal complement has been linked to the destruction of red blood cells, or hemolysis, characteristic of PNH, as PNH blood cells are deficient in natural inhibitors of the complement cascade.