Chronic treatment of paroxysmal nocturnal hemoglobinuria patients with eculizumab: safety, efficacy, and unexpected laboratory phenomena

The terminal complement inhibitor eculizumab has become the standard of treatment in patients with symptomatic paroxysmal nocturnal hemoglobinuria (PNH). In this retrospective study, 19 PNH patients received chronic therapy with eculizumab with a median duration of 16 months (range 6–46 months). Parameters of hemolysis, transfusion requirements, and serum iron parameters were analyzed. Lactate dehydrogenase levels were significantly decreased by 85% from a median of 1897 U/l (range 293–3360) to 283 U/l (range 143–667), with an 86% reduction of transfusion requirements, whereas other parameters of hemolysis remained abnormal. Six patients (31.6%) became completely transfusion independent. A significant increase in ferritin levels from a median of 104 μg/l before to a median of 528 μg/l (p = 0.011) during treatment with eculizumab was observed. This was more pronounced in patients with low reticulocyte production index and/or requiring blood transfusions. Monospecific direct Coombs test was positive in most PNH patients, indicating a shift to extravascular hemolysis. Positive immunofixation for IgG kappa was observed, due to the presence of eculizumab in the serum. Eculizumab was safe and well tolerated long term in our study population. Iron should not be routinely supplemented in PNH patients treated with eculizumab without close monitoring of iron parameters, and iron depletion therapy should be considered in the case of overload.