Our study confirms previous investigations showing that plerixafor in combination with G-CSF is an effective and well-tolerated mobilization regimen with the potential of successful stem cell collection in patients with previous mobilization failure.

Single-donor plateletpheresis results in a temporary increase in serum TPO levels in healthy platelet donors, which may be part of a compensatory response-boosting megakaryocytopoiesis after platelet collection.

In multicomponent apheresis, standardized PLT collection is effective and well tolerated. The higher activation of Amicus(®)-derived PLTs may be because of the divergent centrifugation modalities during collection. Possible consequences for the clinical outcome of thrombocytopenic patients will be evaluated in further trials.

Plerixafor in combination with granulocyte-colony stimulating factor (G-CSF) is approved for autologous stem cell mobilization in poor mobilizing patients with multiple myeloma or malignant lymphoma. The purpose of this study was to evaluate efficacy and safety of plerixafor in an immediate rescue approach, administrated subsequently to G-CSF alone or chemotherapy and G-CSF in patients at risk for mobilization failure. Eighty-five patients mobilized with G-CSF alone or chemotherapy were included. Primary endpoint was the efficacy of the immediate rescue approach of plerixafor to achieve ≥2.0 × 10 CD34 cells/kg for a single or ≥5 × 10 CD34 cells/kg for a double transplantation and potential differences between G-CSF and chemotherapy-based mobilization. Secondary objectives included comparison of stem cell graft composition including CD34 cell and lymphocyte subsets with regard to the mobilization regimen applied. No significant adverse events were recorded. A median 3.9-fold increase in CD34 cells following plerixafor was observed, resulting in 97% patients achieving at least ≥2 × 10 CD34+ cells/kg. Significantly more differentiated granulocyte and monocyte forming myeloid progenitors were collected after chemomobilization whereas more CD19 and natural killer cells were collected after G-CSF. Fifty-two patients underwent transplantation showing rapid and durable engraftment, irrespectively of the stem cell mobilization regimen used. The addition of plerixafor in an immediate rescue model is efficient and safe after both, G-CSF and chemomobilization and results in extremely high success rates. Whether the differences in graft composition have a clinical impact on engraftment kinetics, immunologic recovery, and graft durability have to be analysed in larger prospective studies.

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