Adoptive Immunotherapy with Donor Lymphocyte Infusions after T-Cell Depleted Allogeneic Stem Cell Transplantation for Patients with Acute Myeloid Leukemia.

In this study we analyzed 40 patients with AML who received donor lymphocyte infusions (DLI) after allogeneic stem cell transplantation (alloSCT). Patients with a median age of 42 (range, 11–66) were transplanted with an in vitro T-cell depleted (Campath in the bag) graft from an HLA matched sibling following a myeloablative (n=35) or a nonmyeloablative conditioning regimen (n=5). Patients received DLI for relapsed AML (n=28) or for mixed chimerism (n=12). All patients with relapsed AML were treated with a cytarabine-containing chemotherapy regimen or with gemtuzumab ozogamycin immediately prior to DLI treatment and received daily 3 x 10⁶ U α-IFN sc. The DLI dose administered was depending on the protocol used. Fourteen relapsed patients received high dose DLI with a median of 50 x 10⁶ CD3⁺ cells/kg and 14 low dose DLI with a median of 5 x 10⁶ CD3+ cells/kg. Ten of 28 patients with relapsed AML obtained a complete remission after the combination of chemotherapy and DLI. One patient obtained a partial remission and fourteen patients showed no response. Three patients were not evaluable. No effect of cell dose was observed on the clinical response after DLI. The median percentage of donor chimerism in patients with relapsed AML before DLI was 74% (range, 5–96%) and increased after DLI to 97% (range, 5–100%). Six patients with relapsed AML became complete chimera after DLI. DLI caused in 12 of 28 relapsed patients grade 3–4 GVHD. cGVHD was observed in 3 patients of whom 2 developed extensive GVHD. With a median follow up of 11 months only 1 pt in the high dose and 4 pts in the low dose group are alive in CR and 23 have died due to progressive disease (16) or GVHD (7).

Due to this low rate of long-term survival of relapsed AML patients treated with DLI, we recently developed a new DLI protocol for AML patients. Twelve patients with mixed chimerism at 6 months after T-cell depleted alloSCT were pre-emptively treated with 3 x 10⁶ CD3⁺ cells/kg. Complete chimeric response was observed in 6 of these 12 patients. Two patients showed increasing mixed chimerism and three patients showed no response. Two of 12 patients treated for mixed chimerism developed aGVHD gr 1–2. No severe aGVHD was observed in this group. Two patients developed chronic GVHD, both after nonmyeloablative conditioning. Incidence of GVHD was significantly lower in this group compared to the relapsed patients. Currently, 7 patients are alive in CR. In conclusion: 1) Long term survival of patients with overt relapse AML after alloSCT treated with DLI remains poor 2) High dose DLI appeared to be less effective than low dose DLI due to increased toxicity 3) DLI for AML may be more successful when it is administered pre-emptively for mixed chimerism after T-cell depleted alloSCT.