Human Bone Marrow Depleted of CD 33-Positive Cells Mediates Delayed but Durable Reconstitution of Hematopoiesis : Clinical Trial of MY 9 Monoclonal Antibody-Purged Autografts for the Treatment of Acute Myeloid Leukemia
The CD33 antigen, identified by murine monoclonal antibody anti-MY9, is expressed by clonogenic leukemic cells from almost all patients with acute myeloid leukemia; it is also expressed by normal myeloid progenitor cells. Twelve consecutive patients with de novo acute myeloid leukemia received myeloablative therapy followed by infusion of autologous marrow previously treated in vitro with anti-MY9 and complement. Anti-MY9 and complement treatment eliminated virtually all committed myeloid progenitors (colony-forming unit granulocyte-macrophage) from the autografts. Nevertheless, in the absence of early relapse of leukemia, all patients showed durable trilineage engraftment. The median interval post bone marrow transplantation (BMT) required t o achieve an absolute neutrophil count greater than 50OlpL was 43 days (range, 16 to 75). t o achieve a platelet count greater than 20,0OQ/pL without transfusion was 92 days (range, 35 to 679). and to achieve red blood cell transfusion independence was 105 days (range, 37 to 670). At the time of BM harvest, 10 patients were in second remission, one patient was in first remission, and one patient was in third remission.