All patients who participated in the 3 clinical trials described above were eligible for the extension study in which patients contined to receive eculizumab. Of 195 eligible patients, 187 enrolled in this long-term extension study which lasted 104 weeks. All patients sustained a reduction in intravascular hemolysis over a total eculizumab exposure time ranging from 10 to 54 months. There were fewer thrombotic events with eculizumab treatment than during the same period of time prior to treatment. However, the majority of patients received concomitant anticoagulants; the effects of anti-coagulant withdrawal during eculizumab therapy was not studied.