Infusion of Haploidentical Stem Cell after Consolidation in Younger Patients with Acute Myeloid Leukemia: Preliminary Results of a Phase I-II Study

Introduction

Intensive consolidation chemotherapy in acute myeloid leukemia (AML) patients induces important hematologic toxicity with potential life-threatening infections that can lead to delays in further treatment or death in complete remission (CR). Recent single and multi-center studies (Guo et al. Blood 2011, JCO 2012, ASH 2015) have shown that the infusion of HLA-mismatched peripheral stem cell without immunosuppressive prophylaxis can accelerate hematologic recovery after chemotherapy, without developing graft versus host disease (GVHD).

Objectives

The primary objective of this phase I-II trial is to confirm the safety (absence of GVHD) and efficacy (reduction of neutropenia duration) of HLA-mismatched stem cells infusion after consolidation chemotherapy with idarubicine and cytarabine (3+7) in 50 younger patients with intermediate/high-risk AML. Herein we present the preliminary results of the phase I trial with 9 adult patients (safety cohort).

Methods

Patients younger than 65 years old with AML in CR after induction therapy that were assigned to receive consolidation course with idarubicin (12 mg/m²/day IV 1-3) and cytarabine (200 mg/m²/day IV 1-7) according to PETHEMA protocol were enrolled in this study in a single Spanish institution. To determine safety of HLA-mismatched stem cells infusion a standard 3+3 design was used in this preliminary study: cohorts of 3 patients were established with decreasing immunosuppressive prophylaxis, 3 additional patients would be enrolled with the same immunosuppression if limiting toxicity (LT) was observed in 1 out of 3 patients. LT was defined as global GVHD>grade 2 or grade 4 infusion related reactions. The first cohort of 3 patients was assigned to receive immunosuppression with cyclosporine (1-1.5 mg/kg/bid) and prednisone (0.5 mg/kg/qid), the second cohort to receive only prednisone (0.5 mg/kg/qid), and the third would not receive immunosuppressive treatment. The immunosuppression resulting of this phase would be used in an expansion cohort. Stem cells were obtained after mobilization with G-CSF and apheresis from HLA-mismatched family-related donors and were infused the day 9 of the consolidation course. The donor and recipient HLA-A, HLA-B, HLA-C, HLA-DRB1 and HLA-DQB1 alleles were genotyped using a PCR-SSP method. Hematologic recovery was defined as days from start of chemotherapy to neutrophil count >0.5x10⁹/L and to platelet count >50x10⁹/L. G-CSF was administered only in case of severe infection. This study was approved by the Ethical Committee, and inform consent was obtained from all patients and donors.

Results

From March 2015 to June 2016, 9 patients were enrolled in this study. Median age was 46 (28-64) and 6 were male. All were in CR after induction therapy, 6 had intermediate risk cytogenetic, and 3 high risk cytogenetic/molecular AML. All the donors were family-related and HLA compatibility was 3/6 for 8 patients and 5/6 in one patient. HLA-mismatched stem cells infusion characteristics were: median number of mononuclear cells, CD34+ and CD3+ T cells infused per course was 4.5 (2.1-6.6)x10⁸/kg, 3.3 (0.7-4.9)x10⁶/kg and 1.7 (0.8-2.3)x10⁸/kg, respectively. LT was not reached and no diagnosis of GVHD was made. Two patients developed cytarabine related rash and other 2 patients infectious diarrhea. No patient needed further immunosuppressive treatment. Median duration of neutropenia and thrombocytopenia was 30 (27-50) and 44 (22-51) days, respectively. 3 patients received G-CSF and 2 developed severe infections. Median blood cell unit and platelet units transfused was 4 (2-20) and 8 (2-32). These results are similar to those observed in a historical cohort (non-matched) of 59 patients with AML who received consolidation with 3+7 at the same institution between January 2010 to January 2015 (median duration of neutropenia and thrombocytopenia was 29 (17-57) and 36 (18-206) days, respectively).

Conclusion

The infusion of HLA-mismatched stem cell is safe after consolidation with idarubicin and cytarabine in younger patients. The methodology and in consequence the results of our safety cohort (with immunosuppressive prophylaxis) are not comparable to the previous experience reported by other groups. The reduction of hematologic recovery remains to be confirmed with this schedule in a larger cohort without immunosuppressive prophylaxis.

Research granted by IIS La Fe (2014/0368)