Autologous transplantation with CD52 monoclonal antibody-purged marrow for acute lymphoblastic leukemia: long-term follow-up.

During 1984-86, 23 patients (5-37 years, median 16) with acute lymphoblastic leukemia (ALL) in first remission (n = 11) or beyond (n = 12) underwent autologous transplantation (ABMT) using marrow purged with the rat anti-CD52 monoclonal antibody Campath-1M after melphalan and total-body irradiation (TBI). Median time to 0.5 x 10(9)/L neutrophils and 50 x 10(9)/L platelets was 38 and 51 days respectively. Myeloid engraftment was significantly slower compared with ALL patients receiving unpurged marrow (P = .01). Eight patients died due to transplant-related causes 53-205 days after the procedure. Six of eight patients receiving 1150 cGy TBI died of toxicity compared with two of 15 receiving less than 1150 cGy (P = .006, Fisher's exact test). Nine patients relapsed at 45-195 days (median 97); eight died and one is alive at nine years in a chemotherapy-induced remission. Six patients are alive and well in continuous remission 9-10 years (median 10) after transplant. The 10-year probabilities of disease-free survival and relapse are 26% (95% CI: 11-45%) and 51% (95% CI: 37-59%) respectively. We conclude that it is feasible to purge marrow for autografting using Campath-1M without killing normal stem cells. Myeloid engraftment is slow but consistent, and long-term survival is seen in a proportion of patients. The role of CD52 monoclonal antibodies for purging in ALL still requires further study.