Effect of Reducing Intravascular Hemolysis on Ferritin Homeostasis in Eculizumab Treated Paroxysmal Nocturnal Hemoglobinuria (PNH) Patients.

BACKGROUND: In paroxysmal nocturnal hemoglobinuria (PNH), the lack of the GPI-anchored terminal complement inhibitor CD59 on erythrocytes renders these cells susceptible to continuous complement mediated hemolysis. Hemolysis leads to anemia, fatigue, red blood cell transfusions, renal impairment and increases the risk of thromboembolic events. Urinary iron loss is also common in patients with PNH due to intravascular hemolysis. Eculizumab is a terminal complement inhibitor that has been evaluated in two phase III studies. In previous studies eculizumab significantly reduced intravascular hemolysis (characterized by significant reduction of LDH levels) and significantly reduced transfusion requirements as well as thromboembolic events. In this study we evaluated the change in hemolytic parameters and levels of ferritin parameters in PNH patients treated with eculizumab in two centers (Essen and Homburg/Saar).

METHODS: Nineteen PNH patients were treated with eculizumab as follows: 4 x 600mg IV every 7±2 days; 900 mg 7±2 days later; and then 900 mg every 14±2 days. The median therapy duration was 31 months (range 1–40 months). Hemolysis, transfusion requirements and serum iron parameters were analyzed over time of treatment.

RESULTS: Eculizumab effectively inhibited intravascular hemolysis in all PNH patients as evidenced by an 79% decrease in LDH levels (mean±SD: 2,110±802 to 349±182 U/l (normal range: 100–247); p=0.0001) and reduced transfusion requirements. Persistent elevation of reticulocytes as well as the reduction of haptoglobin and hemopexin were observed in most patients, which suggest continuing extravascular hemolysis. Interestingly, we observed an 709% increase in ferritin levels in patients treated with eculizumab (median from 73 to 965 μg/l (normal range: 20–290 μg/L); p=0.001). This was more pronounced in patients still requiring some transfusions. Three patients were started on oral iron depletion therapy. No thromboembolic or serious adverse events were observed in eculizumab-treated patients. Two PNH patients were diagnosed with PNH-associated hematological disease (MDS, myelofibrosis).

SUMMARY/CONCLUSIONS: Eculizumab is safe and well tolerated in the analyzed cohort of PNH patients. Iron parameters in PNH patients treated with eculizumab should be monitored to determine if iron supplementation should be altered or iron depletion therapy should be considered. While some extravascular hemolysis may persist, intravascular hemolysis is effectively controlled with eculizumab and is associated with a concomitant improvement in anemia and quality of life.