Hu5F9-G4, an immunoglobulin 4 (IgG4) monoclonal humanized antibody targeting CD47, is under active clinical trials as a novel immunotherapeutic for hematologic and solid malignancies and can cause pretransfusion testing interference. In this study, we demonstrate our first experience of Hu5F9-G4 interference with serologic testing and mitigate this interference through multiple platelet alloadsorption. A 69-year-old woman with a history of ureter cancer presented with anemia. On routine blood group typing, the patient showed strong agglutination (4+) with anti-A, A, and B cells. Unexpectedly, antibody screening and identification showed panreactivity to all panel cells, although the autocontrol result was negative. Medical records revealed that she was enrolled in an anti-CD47 clinical trial. To eliminate interference by the drug, we attempted alloadsorption using pooled platelets that were prepared from segments of random single donor platelets. After seven alloadsorption sessions using pooled allogeneic platelets, the ABO discrepancy and panreactivity was resolved. To our knowledge, this is the first demonstration of anti-CD47 interference elimination in Korea.

Hu5F9-G4, an immunoglobulin 4 (IgG4) monoclonal humanized antibody targeting CD47, is under active clinical trials as a novel immunotherapeutic for hematologic and solid malignancies and can cause pretransfusion testing interference. In this study, we demonstrate our first experience of Hu5F9-G4 interference with serologic testing and mitigate this interference through multiple platelet alloadsorption. A 69-year-old woman with a history of ureter cancer presented with anemia. On routine blood group typing, the patient showed strong agglutination (4+) with anti-A, A, and B cells. Unexpectedly, antibody screening and identification showed panreactivity to all panel cells, although the autocontrol result was negative. Medical records revealed that she was enrolled in an anti-CD47 clinical trial. To eliminate interference by the drug, we attempted alloadsorption using pooled platelets that were prepared from segments of random single donor platelets. After seven alloadsorption sessions using pooled allogeneic platelets, the ABO discrepancy and panreactivity was resolved. To our knowledge, this is the first demonstration of anti-CD47 interference elimination in Korea.