Impact of plerixafor use in the mobilization of blood grafts for autologous hematopoietic cell transplantation

Plerixafor (PLER), a reversible antagonist of the CXC chemokine receptor type 4, has been in clinical use for mobilization of blood grafts for autologous hematopoietic cell transplantation (AHCT) for about 15 years. Initially PLER was investigated in placebo-controlled trials with the granulocyte colony-stimulating factor (G-CSF) filgrastim. It has also been used in combination with chemotherapy plus G-CSF in patients who had failed a previous mobilization attempt or appeared to mobilize poorly with current mobilization (preemptive use). This review summarizes what is known regarding addition of PLER to standard mobilization regimens. PLER increases mobilization of CD34+ cells, decreases the number of apheresis sessions needed to achieve collection targets and increases the proportion of patients who can proceed to AHCT. It appears also to increase the amount of various lymphocyte subsets in the grafts collected. In general, hematologic recovery after AHCT has been comparable to patients mobilized without PLER, although slower platelet recovery has been observed in some studies of patients who mobilize poorly. In phase III studies, long-term outcome has been comparable to patients mobilized without PLER. This also appears to be the case in patients receiving plerixafor for poor or suboptimal mobilization of CD34+ cells. In practice, PLER is safe and has not been shown to increase tumor cell mobilization.

A Prospective Study of an HLA-Haploidentical Peripheral Blood Stem Cell Transplantation Regimen Based on Modification of the Dose of Posttransplant Cyclophosphamide for Poor Prognosis or Refractory Hematological Malignancies

The optimal dose of posttransplant cyclophosphamide (PTCy) for use in patients undergoing HLA-haploidentical hematopoietic cell transplantation with posttransplant cyclophosphamide (PTCy-haplo) has not been sufficiently examined. This study evaluates the safety and efficacy of HLA-haploidentical hematopoietic cell transplantation with a reduced dose of PTCy for patients with a poor prognosis or those with refractory hematological malignancies. We conducted a prospective clinical study of PTCy-haplo with peripheral blood stem cells (PBSCs) using a modified PTCy dosage regimen consisting of 50 mg/kg on day 3 posttransplantation and a reduced dose of 25 mg/kg on day 4. The cumulative incidences of grades II to III and IV acute graft-versus-host disease (GVHD) at day 100 posttransplantation were 30% and 0%, respectively. The cumulative incidence of moderate-to-severe chronic GVHD after transplantation was 7.0%. The cumulative incidence of nonrelapse mortality at 1 year posttransplantation was 6.1%. Overall survival (OS) at 1 year was 66%. In addition, the restricted cubic-spline Cox regression analysis showed nonlinear relationship between the number of infused CD34⁺ cells and CD3⁺ cells, and OS. A graft composition of >4.54 × 10⁶/kg CD34⁺ cells and >1.85 × 10⁸/kg but ≤3.70 × 10⁸/kg CD3⁺ cells was significantly associated with better survival, irrespective of the disease status (hazard ratio, 0.13; 95% confidence interval, 0.04–0.41; P < 0.001). These results suggest that PTCy-haplo with PBSCs using a de-escalated dose of 50 mg/kg on day 3 and 25 mg/kg on day 4 posttransplantation is a feasible option.

Plerixafor for mobilization of blood stem cells in autologous transplantation: an update

INTRODUCTION

About 99% of all autologous transplants are now performed with blood stem cells. G-CSF alone or combined with chemotherapy have been used to mobilize CD34(+) cells. Plerixafor is a novel drug used for mobilization purposes.

AREAS COVERED

We have evaluated recent data in regard to plerixafor use in predicted or proven poor mobilizers. In addition, we have looked for preemptive strategies to optimize the use of this expensive drug. Also cost-efficacy issues and effects of plerixafor on graft composition and post-transplant outcomes will be discussed.

EXPERT OPINION

Plerixafor added to G-CSF is superior than G-CSF alone for mobilization of CD34(+) cells. This combination is also efficient in patients who have failed a previous mobilization attempt with other methods or in patients with risk factors for poor mobilization. Addition of plerixafor to G-CSF or chemotherapy plus G-CSF mobilization in patients who appear to mobilize poorly is under active investigation and algorithms for a preemptive use of this expensive agent have been proposed. Grafts collected after plerixafor appear to contain more lymphoid cells than the grafts collected without it. Whether this affects post-transplant outcomes such as immune reconstitution and risk of relapse needs to be evaluated.