Nonmyeloablative Versus Myeloablative Allogeneic Hematopoietic Stem Cell Transplant for GATA2 Deficiency

Background: Mutations in the zinc finger transcription factor GATA2 are responsible for: MonoMAC, monocytopenia with nontuberculous mycobacterial (NTM) infections; DCML, dendritic cell, monocyte and lymphoid cell deficiency; Emberger's syndrome with lymphedema and monosomy 7; and familial myelodysplastic syndrome (MDS)/acute myelogenous leukemia (AML). Allogeneic hematopoietic stem cell transplant (HSCT) is the only definitive therapy for GATA2 deficiency.

Methods: We used matched related donors (MRD), matched unrelated donors (URD), umbilical cord blood (UCB), and haploidentical related donors in allogeneic HSCT for GATA2 deficiency. Fourteen patients received a nonmyeloablative conditioning regimen (4 MRD, 4 URD, 4 UCB, and 2 haplo donors). Five patients received a myeloablative conditioning regimen (1 MRD, 2 URD, and 2 haplo donors). In the nonmyeloablative group, MRD and MUD recipients received fludarabine and 200cGy of total body irradiation (TBI), UCB recipients received cyclophosphamide 50mg/kg, fludarabine 150 mg/m2, and 200cGy of TBI, and haploidentical related donor recipients received cyclophosphamide 29 mg/kg, fludarabine 150 mg/m², and 200 cGy TBI. In the myeloablative group, MRD and URD received busulfan 12.8 mg/kg and fludarabine 160 mg/m², and haploidentical related donors received the same regimen as in the nonmyeloablative regimen except for the addition of two days of busulfan 6.4 mg/kg total dose. Nonmyeloablative MRD and URD recipients received tacrolimus and sirolimus post-transplant, and myeloablative MRD and URD recipients received tacrolimus and short course methotrexate post-transplant. All haploidentical related donor recipients received cyclophosphamide 50 mg/kg/day on days + 3 and +4 followed by tacrolimus and mycophenolate mofetil. Three patients in the nonmyeloablative cohort required one or more rounds of pre-transplant chemotherapy because of an increased number of blasts, whereas none of the 5 patients in the myeloablative arm required pre-transplant chemotherapy.

Results: In the nonmyeloablative cohort, 8 of 14 (57%) of patients are alive at a median follow-up of 3.7 years (range 12 months to 5 years). One MRD recipient died of GVHD and one relapsed, one URD recipient rejected the donor stem cells and died, three UCB recipient died (one rejection, one early death, and one donor cell leukemia), and one haploidentical recipient died from regimen-related toxicity. All 5 patients (100%) in the myeloablative group, including two recipients of haploidentical related donors, are alive at a median follow-up of 9.2 months (range 6 to 12 months). All patients who survived had complete reconstitution of the monocyte, NK, and B-lymphocyte compartments, the three cell compartments that were severely deficient pre-transplant, and all had reversal of the infection susceptibility phenotype, characteristic of the disease. In particular, there were no recurrences of non-tuberculous mycobacterial (NTM) infections.

Conclusions: Nonmyeloablative HSCT results in reversal of the hematologic and clinical manifestations of GATA2 deficiency. However, a more intensive conditioning regimen with busulfan resulted in more uniform engraftment, a reduced risk of relapse, avoidance of pre-transplant chemotherapy, and a low regimen-related toxicity. We anticipate that with the use of a high-dose regimen with busulfan, the replacement of UCB with haploidentical related donors, and HSCT earlier in the clinical course, before significant organ damage or clonal evolution of MDS to AML or CMML, the outcome of allogeneic HSCT in patients with GATA2 deficiency will continue to improve.