Efficacy of Plerixafor Administered At 5:00PM for Stem Cell Mobilization in Lymphoma and Myeloma Patients Undergoing Autologous Stem Cell Transplant,

High-dose chemotherapy and/or radiotherapy are effective treatment strategies for patients with life-threatening hematologic malignancies. A critical step to the success of transplantation is achieving adequate mobilization of CD34+ stem cells from the bone marrow into the peripheral blood to provide sufficient cell yield after apheresis for the transplant. Plerixafor combined with granulocyte colony-stimulating factor (G-CSF) has proven efficacious in mobilizing CD34+ stem cells in patients with lymphoma and myeloma prior to autologous stem cell transplantation. In the phase 3 clinical trials of plerixafor plus G-CSF for SCM, plerixafor was administered at 10:00 pm on days prior to apheresis. This dosing schedule is based on the peak level of CD34+ cells in the peripheral blood (PB) at 11–14 hours after administration; however PB CD34+ cell levels were elevated from 4–18 hours after plerixafor administration. Due to inconvenience in dosing plerixafor at 10:00pm, we took advantage of its pharmacodynamic profile and explored an alternative dosing schedule, giving plerixafor at 5:00 pm. Here, we report our updated experience with the efficacy of this schedule.

We performed a retrospective study using our Stem Cell Harvest database. A total of 58 patients (31 lymphoma, 27 myeloma) underwent mobilization with G-CSF + plerixafor, either as front-line (n=51) or as salvage (n=7) mobilization strategies between February 2009 through May 2010. Mobilization consisted of G-CSF 10 μg/kg SC administered daily at 6:00 am day 1 through 4 plus plerixafor 0.24 mg/kg SC given once daily at 5:00 pm in an outpatient clinic beginning on day 4. For patients with renal impairment (ie, creatinine clearance ≤50 mL/min), the dose of plerixafor was lowered by a third to 0.16 mg/kg. Daily apheresis began at 8:30 am on the morning of day 5 and continued for up to 4 days, with a minimum collection goal defined as ≥ 2 × 10⁶ CD34+ cells/kg for lymphoma patients and ≥ 4 × 10⁶ CD34+ cells/kg for myeloma patients. Mobilization with G-CSF plus plerixafor and apheresis were halted once the minimum goal was reached between day 2 and 4 of apheresis, or after a single collection achieved the optimal goal which was defined as ≥ 4 × 10⁶ (lymphoma) or ≥ 8 × 10⁶ (myeloma) CD34+ cells/kg. The mobilization strategy was considered a failure if patients did not reach the minimum CD34+ cell collection goal within the 4 days of apheresis.

G-CSF + plerixafor mobilization yielded a median 5.13 × 10⁶ CD34+ cells/kg (range, 0.06–25.8) in a median of 2 apheresis days. Forty-five of 58 (78%) patients achieved the minimum CD34+ cells/kg required for transplantation, including 30 (52%) patients who achieved this goal on the first day of apheresis. Overall, 52 (90%) patients proceeded to transplantation, with median neutrophil and platelet engraftment times of 11 and 18 days, respectively.

In summary, the alternative 5:00 pm dosing of plerixafor for stem cell mobilization provided a more convenient dosing schedule while ensuring that a majority of lymphoma and myeloma patients achieved the minimum CD34+ cell yield required to proceed to transplantation.

Tornatta:Genzyme: Consultancy, Honoraria, Speakers Bureau. Fung:Genzyme: Consultancy, Honoraria, Speakers Bureau.