Plerixafor is a hematopoietic stem cell (HSC) mobilizer that inhibits the CXCR4 chemokine receptor and blocks binding of its ligand, stromal cell-derived factor-1-alpha (SDF-1-alpha). This agent was approved on December 15, 2008, as treatment in combination with granulocyte-colony stimulating factor (G-CSF) to mobilize HSCs to the peripheral blood for collection and subsequent autologous transplantation in patients with non-Hodgkin's lymphoma (NHL) and multiple myeloma (MM).

Efficacy. The efficacy of this agent was assessed in 2 placebo-controlled studies in which patients were treated with either plerixafor 0.24 mg/kg or placebo on each evening before apheresis. Patients also received G-CSF 10 mcg/kg every morning for 4 days before the first dose of plerixafor or placebo and on every morning before apheresis. Study 1 included patients with NHL; Study 2 included patients with MM. In Study 1, 59% of plerixafor-treated patients collected ≥5×10⁶ CD34⁺ cells/kg from peripheral blood in ≤4 apheresis sessions versus 20% of placebo-treated patients (P<.001). In Study 2, 72% of plerixafor-treated patients collected ≥6×10⁶ CD34⁺ cells/kg from peripheral blood in ≤2 apheresis sessions versus 34% of placebo-treated patients (P<.001).

Safety. Plerixafor may cause mobilization of leukemic cells, which may cause contamination of the apheresis product; therefore, this agent is not approved for use in patients with leukemia. Administration of plerixafor and G-CSF increases the levels of circulating leukocytes and HSCs. Patients treated with plerixafor have also experienced thrombocytopenia. Treatment with plerixafor and G-CSF may lead to a release of tumor cells from the marrow. Patients treated with plerixafor and G-CSF should be evaluated for splenic integrity if they report left upper abdominal pain and/or scapular or shoulder pain. Women should avoid becoming pregnant during treatment with plerixafor, as this agent may cause fetal harm. The most common adverse events associated with plerixafor treatment include diarrhea, nausea, fatigue, injection-site reactions, headache, arthralgia, dizziness, and vomiting.