Efficacy and Safety of Hematopoietic Stem Cell Remobilization with Plerixafor (Mozobil^®) + G-CSF In Adult Patients with Non-Hematologic Malignancies

Although high dose chemotherapy followed by autologous hematopoietic stem cell (HSC) transplantation is a potentially curative procedure for patients with hematologic and non-hematologic malignancies, a significant number are unable to mobilize sufficient cells to proceed to transplant. While the safety and efficacy of plerixafor + G-CSF is well established for front-line and salvage mobilization in patients with myeloma and lymphoma, data are limited for patients with non hematological malignancies. We now report on the safety and efficacy of remobilization with plerixafor + G-CSF in patients in this setting.

This is a retrospective analysis of patients >18 years with non hematological malignancies enrolled in the US plerixafor compassionate use program (CUP). In the CUP, patients with previous mobilization failure (defined as the inability to collect ≥2 ×10⁶ CD34+ cells/kg or achieve an adequate peripheral blood (PB) count, typically ≥10 CD34+ cells/μl) were remobilized with plerixafor + G-CSF with the goal of collecting 2 × 10⁶ CD34+ cells/kg to proceed to transplant. G-CSF (10μg/kg SC) was given every morning for 5 days. Plerixafor (0.24 mg/kg SC) was given in the evening on Day 4, ~11 hours prior to apheresis the next day. Plerixafor, G-CSF and apheresis were repeated daily until patients collected ≥2×10⁶ CD34+ cells/kg.

The analysis included 32 patients (median age 32.5 years) with germ cell tumor (n=21), medulloblastoma (n=4), sarcoma (n=3), breast cancer (n=2), cervical cancer (n=1) or chordoma (n=1). Previous mobilization regimens included growth factor alone in 22 patients and growth factor + chemotherapy in 10 patients; 25 patients failed to collect the minimum transplantable cell dose (median yield: 1.27 ×10⁶ CD34+ cells/kg); 7 patients did not undergo apheresis due to low PB CD34+ cells. Remobilization with plerixafor + G-CSF resulted in a median yield of 2.8 × 10⁶ CD34+ cells/kg; the median number of apheresis days was 2 (range 1–4). Twenty-two (69%) patients collected ≥2 × 10⁶ CD34+ cells/kg; the median time to collect the target cell dose was 2 days (range 1–3 days). The median CD34+ cell yield for patients with germ cell tumors was 3.16 × 10⁶ cells/kg. Twenty-four (75%) patients proceeded to transplant; 8/21 patients with germ cell tumors received tandem transplants. Median time to neutrophil and platelet engraftment was 11 and 20 days, respectively. Drug-related adverse events were observed in 12 (38%) patients; most were mild and commonly included injection site reactions (n=6), diarrhea (n=3), nausea (n=2) and bone pain (n=2). None of the patients experienced serious adverse events.

Mobilization with plerixafor + G-CSF facilitates collection of an adequate number of HSC in the majority of adult patients with non-hematologic malignancies who have failed prior mobilization with growth factor ± chemotherapy. Using this salvage approach 75% of patients who otherwise would not have had the option could successfully undergo autologous transplantation.

Horwitz: Genzyme Corporation: Honoraria, Research Funding. Off Label Use: Plerixafor (Mozobil®), a hematopoietic stem cell mobilizer, is approved by the US FDA in combination with granulocyte-colony stimulating factor (G-CSF) to mobilize hematopoietic stem cells to the peripheral blood for collection and subsequent autologous transplantation in patients with non-Hodgkin's lymphoma and multiple myeloma. Huebner: Genzyme Corporation: Employment, Equity Ownership. Mody: Genzyme Corporation: Employment, Equity Ownership. Schriber: Genzyme Corporation: Speakers Bureau.