KM871 retains effector function in vivo. Patient 13 sera were collected before infusion 3 (20 mg/m² KM871 dose level), KM871 levels were determined, and sera were complement-inactivated by heat treatment. CDC analyses on target SK-MEL-28 cells were performed with heat-inactivated patient sera alone (triangles) or with healthy donor complement added (squares). Control healthy donor sera with equivalent levels of exogenous KM871 added are also shown (circles).