Pilot Study of Prophylactic Ex Vivo Costimulated Donor Leukocyte Infusion After Reduced-Intensity Conditioned Allogeneic Stem Cell Transplantation

Donor leukocyte infusion (DLI) can induce potent graft-versus-leukemia (GVL) activity in patients with relapsed hematologic malignancies after allogeneic hematopoietic stem cell transplantation (HSCT). Unfortunately, except in patients with chronic-phase chronic myelogenous leukemia, responses to DLI have been disappointing. GVL induction is likely to be most effective in the setting of minimal residual disease. Prevention of relapse through the provision of prophylactic DLI to high-risk patients may improve the outcome of allogeneic HSCT. We previously reported that ex vivo costimulated T cell infusion of activated DLI (aDLI) as treatment for relapse is safe and has potent GVL effects. We hypothesized that prophylactic aDLI can be given safely and prevent relapse in high-risk patients after allogeneic HSCT. Eighteen patients with acute myeolgenous leukemia (n = 14), acute lymphoblastic leukemia (n = 3), or myelodysplastic syndrome (n = 1) underwent allogeneic HSCT after a reduced-intensity conditioning (RIC) regimen with alemtuzumab, fludarabine, and busulfan. Graft-versus-host-disease (GVHD) prophylaxis consisted of tacrolimus and methotrexate with a planned early and rapid taper of tacrolimus. Patients without GVHD, off immune suppression, and in remission received aDLI at a dose of 1 × 107 CD3+ cells/kg (aDLI 1) at day +120, followed by a second infusion of 1 × 108 CD3 cells/kg (aDLI 2) at day +180. At a median follow-up of 58 months, 5 of the 18 patients (28%) were alive, and 4 patients were in remission. Eleven patients (65%) relapsed, at a median time of 191 days. Twelve of the 18 patients received at least one aDLI, and 6 of these 12 patients also received aDLI 2. Six patients did not receive any aDLI owing to early relapse (n = 2), protocol ineligibility (n = 1), or GVHD (n = 3). Only 2 of the 12 patients who received aDLI 1 developed GVHD. Two out of the 12 patients remain in remission at the time of this report. Disease recurrence was the cause of death in 10 of the 13 patients (77%) who died. Our data indicate that prophylactic ex vivo costimulated CD3/CD28 DLI is safe, feasible, and not associated with significant GVHD. Relapse remains the major cause of treatment failure after RIC HSCT even with rapid withdrawal of immune suppression and the use of prophylactic aDLI, and better strategies to prevent relapse are needed.