The α-chemokine receptor, CXCR4, on CD4⁺T-cells is used by CXCR4-selective HIV forms as a gateway for T-cell infection. In mammalian cell signaling, CXCR4 activation promotes the homing of hematopoietic stem cells, chemotaxis and quiescence of lymphocytes, and growth and metastasis of certain cancer cell types. Plerixafor is a partial antagonist of chemokine receptor 4 (CXCR4) with IC₅₀values ranging from 0.02 to 0.13 µg/ml for inhibiting calcium flux in peripheral blood mononuclear cells (PBMCs), various types of T cells, and mouse lymphocytic leukemia cells.¹It is selective for CXCR4 over CXCR1-3 and CXCR5-9 (IC₅₀s = >25 µg/ml). Plerixafor decreases infectious virus content in the supernatant of Jurkat cells chronically infected with HIV-1(III_B) (EC₅₀= ~0.02 µg/ml).²It rapidly mobilizes murine and human hematopoietic stem and murine long-term repopulating cells for transplantation alone and, with a synergistic effect, when used in combination with G-CSF.³Plerixafor also increases T cell trafficking in mouse blood, spleen, and central nervous system.^4,5Plerixafor (1.25 mg/kg twice per day) decreases the number of 4T1 murine mammary carcinoma cells in the lung in a mouse model of lung metastasis.⁶

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