Laboratory course of patient 006. Patient 006 initially received 45 mg/kg (3.4 g once per week, then once every other week) of sutimlimab, and hemoglobin levels increased from 7.1 g/dL to 11.2 g/dL after 6 doses, when she experienced laboratory evidence of biochemical breakthrough. This prompted a subsequent dose increase to 60 mg/kg (4.3 g), which stopped hemolysis and stabilized hemoglobin levels. However, after 8 additional doses, breakthrough hemolysis re-occurred (increased bilirubin and LDH and decreased haptoglobin and C4), which led to a slight dose increase to 65 mg/kg preventing additional breakthrough events. Hemoglobin levels decreased significantly during repeated long washout periods (lengthy holiday and health treatment vacation). She was eventually assigned to a 5.5-g fixed-dose regimen, and after re-commencement of regular infusion therapy, the patient’s hemoglobin improved to a peak level of 11.4 g/dL. In week 75, her hemoglobin dropped to 6.1 g/dL which was a result of gastrointestinal bleeding after the re-operation of a diaphragmatic hernia. At that time, laboratory results revealed a sufficiently inhibited complement system (CH50, 30.8%; C4, 36 mg/dL) but no signs of hemolysis (bilirubin, 0.46 mg/dL; LDH, 213 U/L; and haptoglobin, 80 mg/dL). After transfusion of 4 erythrocyte concentrates, her hemoglobin rose to 10.2 g/dL and remained stable throughout her hospital stay. She continued with regular biweekly infusions of sutimlimab 5.5 g and her hemoglobin levels remained stable (blue arrows denote sutimlimab infusions).