Monoclonal antibody purging and autologous bone marrow transplantation in acute myelogenous leukemia in complete remission.

A mouse monoclonal antibody (S4-7) reacting with human myelomonocytic cells has been previously shown to be suitable for bone marrow purging in selected acute myelogenous leukemia (AML) patients with S4-7 positive leukemic clonogenic cells at diagnosis. The results obtained in seven AML patients who underwent such a treatment, followed by autologous bone marrow transplantation (ABMT), are now reported. Six patients underwent ABMT in first complete remission (CR), one in second CR, after BAVC conditioning regimen. One patient died of infection 1 month after ABMT; in the other six a complete recovery of hemopoiesis was observed. In spite of S4-7 reactivity with normal myelomonocytic cells, a prompt recovery of granulopoiesis was however observed both in in vitro liquid culture and in vivo with a median time of 20 days to reach granulocyte values of 500 x 10(6)/l. The patient transplanted in 2nd CR relapsed 3 months after ABMT. Of the five evaluable patients transplanted in 1st CR, two relapsed 8 and 9 months post-ABMT while three remain in continuous CR at 35, 47, 57 months. Leukemic cells of two of the three patients with recurrent disease were studied at relapse and in both could be detected a significant percentage of S4-7 negative cells, detectable neither at diagnosis nor (one patient) at the time of first relapse after standard chemotherapy.