Magrolimab (Hu5F9-G4) is an Anti-CD47 antibody of IgG4 subtype that is therapeutically used in oncology studies. Tumor cells express increased levels of the CD47 antigen, a "do not eat me" signal, protecting these cells from destruction by the immune system. According to recent literature, Magrolimab interferes heavily with antibody screening, crossmatching and ABO typing. Here, we report our experience in transfusion support for two patients receiving anti-CD47 antibody therapy.

Samples from two male patients suffering from AML or MDS were collected before the first Magrolimab dose and before and immediately after administration of subsequent doses. One Patient received 16 weekly doses of Magrolimab, the other patient 15 doses. Standard serologic tests for ABO blood group typing and detection of red blood cell (RBC) antibodies were performed using the gel card technique (BioRad, Switzerland) and the Capture technique (Werfen, Spain), the latter with an anti-human globulin that does not detect IgG4. Platelet antibodies were analysed by MAIPA and automated platelet crossmatching (Werfen, Spain). Extended blood group genotyping and serological confirmation were performed before the first dose.

At baseline, patients were typed B RhD+ and 0 RhD+, respectively. ABO forward typing, antibody screening and crossmatching was impaired depending on treatment time and method (Table 1). One patient showed a positive DAT only for 24 hours after the first Magrolimab dose and did not receive any transfusions. The other patient had repeatedly positive DAT and required a total of 16 RBC units and 4 platelet concentrates. Platelet serology (MAIPA and crossmatching) was not impaired. Hemoglobin levels dropped in both patients after the initial dose.

Magrolimab may present a challenge for ABO blood group typing and compatibility testing. Our limited experience from two Magrolimab patients suggest that the capture technique could allow safe pretransfusion testing at almost all time points. A good cooperation between clinicians and the immunohematology laboratory is crucial

no conflicts of interest