Addition of plerixafor to G-CSF is useful to achieve efficient collection even in very poor mobilizers: hope for patients with diminished hematopoietic function

Stem cell mobilization in multiple myeloma: challenges, strategies, and current developments

Among hematological malignancies, multiple myeloma (MM) represents the leading indication of autologous hematopoietic stem cell transplantation (auto-HCT). Auto-HCT is predominantly performed with peripheral blood stem cells (PBSCs), and the mobilization and collection of PBSCs are essential steps for auto-HCT. Despite the improved success of conventional methods with the incorporation of novel agents for PBSC mobilization in MM, mobilization failure is still a concern. The current review comprehensively summarizes various mobilization strategies for mobilizing PBSCs in MM patients and the evolution of these strategies over time. Moreover, existing evidence substantiates that the mobilization regimen used may be an important determinant of graft content. However, limited data are available on the effects of graft characteristics in patient outcomes other than hematopoietic engraftment. In this review, we discussed the effect of graft characteristics on clinical outcomes, mobilization failure, factors predictive of poor mobilization, and potential mobilization regimens for such patients.

Getting blood out of a stone: Identification and management of patients with poor hematopoietic cell mobilization

Hematopoietic cell transplantation (HCT) has become a primary treatment for many cancers. Nowadays, the primary source of hematopoietic cells is by leukapheresis collection of these cells from peripheral blood, after a forced egress of hematopoietic cells from marrow into blood circulation, a process known as "mobilization". In this process, mobilizing agents disrupt binding interactions between hematopoietic cells and marrow microenvironment to facilitate collection. As the first essential step of HCT, poor mobilization, i.e. failure to obtain a desired or required number of hematopoietic cell, is one of the major factors affecting engraftment or even precluding transplantation. This review summarizes the available mobilization regimens using granulocyte-colony stimulating factor (G-CSF) and plerixafor, as well as the current understanding of the factors that are associated with poor mobilization. Strategies to mobilize patients or healthy donors who failed previous mobilization are discussed. Multiple novel agents are under investigation and some of them have shown the potential to enhance the mobilization response to G-CSF and/or plerixafor. Further investigation of the risk factors including genetic factors will offer an opportunity to better understand the molecular mechanism of mobilization and help develop new therapeutic strategies for successful mobilizations.

Plerixafor for patients who fail cytokine-or chemotherapy-based stem cell mobilization: Results of a prospective study by the Polish Lymphoma Research Group (PLRG)

Autologous hematopoietic stem cell transplantation (autoHSCT) requires collection of sufficient number of hematopoietic stem cells. The goal of this study was to evaluate efficacy of plerixafor used in patients with lymphoid malignancies failing conventional stem cell mobilization.

This was a prospective, non-interventional study. All consecutive patients (n = 109) treated with plerixafor in 11 centers were reported. The drug was used either in case of previous mobilization failure (n = 67) or interventionally, in case of insufficient CD34+ cell output during current mobilization (n = 42). Successful mobilization was defined as resulting in collection of ≥ 2 × 106 CD34+ cells/kg for single autoHSCT or ≥ 4 × 106 CD34+ cells/kg for double procedure.

The overall rate of successful mobilization was 55% (55% for single and 56% for double autoHSCT). The median total number of collected CD34+ cells/kg was 2.4 (range, 0-11.5) for patients intended for a single transplantation while 4.0 (0.6-16.9) for double procedure. The number of circulating CD34+ cells increased after the use of plerixafor regardless of baseline values. The median fold increase was 3.3 (0.3-155). Data from this observational study confirm high efficacy of plerixafor used in routine clinical practice as salvage for patients with lymphoid malignancies failing conventional stem cell mobilization.