Post-Transplant Blockade of CXCR4 Improves Complete Remission Rates and Donor Stem Cell Engraftment without Aggravating Gvhd

Allogeneic hematopoietic cell transplantation (allo-HCT) is a promising therapeutic option for hematological malignancies, but relapse resulted predominantly from residual disease in bone marrow (BM) remains the major cause of treatment failure. Using immunodeficient mice grafted with laboratory-generated human B-ALL, our previous study suggested that leukemia cells within the BM were resistant to graft-versus-leukemia (GVL) effects, and mobilization with CXCR4 antagonist may dislodge leukemia cells from BM, rendering them destroyed by GVL effects. In this study, we extended this approach to patient-derived xenograft (PDX) and murine T-ALL and AML models for determining its clinical relevance and effects on GVHD and donor hematopoietic engraftment. We found that post-transplant treatment with CXCR4 antagonist AMD3100 significantly improved eradication of leukemia cells in the BM in PDX mice grafted with B-ALL cells from multiple patients. AMD3100 also significantly improved disease-free remission rates in murine T-ALL and AML models, and promoted donor hematopoietic engraftment in mice following non-myeloablative allo-HCT. Furthermore, post-transplant treatment with AMD3100 had no detectable deleterious effect on acute or chronic GVHD. These findings provide important preclinical data supporting the initiation of clinical trials exploring combination therapy with CXCR4 antagonist and allo-HCT.