In vitro activity: INCB3344 is a novel, potent, selective, orally bioavailable small molecule antagonist of the CCR2 receptor with IC50 values of 5.1 nM (hCCR2) and 9.5 nM (mCCR2) in binding antagonism and 3.8 nM (hCCR2) and 7.8 nM (mCCR2) in antagonism of chemotaxis activity. INCB3344 is a selective hCCR2 antagonist, exhibiting IC50 values of more than 1 μM against a panel of>50 ion channels, transporters, chemokine receptors and other selected GPCRs. It is also a selective mCCR2 antagonist, showing IC50 values of>1 μM and>3 μM against murine CCR1 and murine CCR5, respectively, the two most homologous chemokine receptors to mCCR2. Characterization of the pharmacological activity of INCB3344 is first evaluated by testing its ability to inhibit CCL2 binding to CCR2 in a whole cell binding assay using a murine monocyte cell line, WEHI-274.1 and 125I-labeled mCCL2 as a tracer. The binding IC50 of INCB3344 in this assay is determined to be 10±5 nM, and inhibition of>90% binding is observed at a concentration of 90 nM.

Kinase Assay: WEHI 274.1 (murine monocytic cell line) cells are used in a whole cell binding assay. Cells (5×105) in RPMI 1640 (VWR), +0.1% BSA+20 mM HEPES (VWR), are added to various concentrations of INCB3344 in RPMI 1640 follow immediately by the addition of 150 pM 125I-labeled mCCL2 (mouse CCL2(JE)) and incubated for 30 min at room temperature (RT). For the nonspecific control, 0.3 μM mCCL2 is added in place of INCB3344. Cells are then harvested through 1.2-μm polyvinylidene difluoride filters, the filters are air-dried, and binding is determined by counting in a gamma counter. Antagonist activity is reported as the inhibitor concentration required for IC50 of specific binding. Specific binding is defined as the total binding minus the nonspecific binding and typically represents 97% of the total binding.

Cell Assay: WEHI-274.1 cells (5×105) in RPMI 1640 (VWR) with or without various concentrations of INCB3344 in RPMI 1640 are loaded in the wells on top of an 8-μm polycarbonate filter in a 96-well-modified Boyden chamber. Beneath the filter, 30 nM mCCL2 with or without INCB3344 or media is placed in a corresponding 96-well plate. The sealed chambers are incubated for 45 min at 37°C, 5% CO2. Filters are washed, stained with Wright-Giemsa, and the number of cells that migrate toward mCCL2 in the bottom chamber counted by microscopy. The ability of INCB3344 to antagonize CCR2-mediated chemotaxis is reported as the inhibitor concentration required for IC50 values of specific migration to mCCL2. Specific migration is defined as the total migration minus the background migration. A similar assay is used to determine the impact of INCB3344 on CCR1-mediated chemotaxis of WEHI-274.1 cells, by using mouse MIP-1α as a ligand. In addition C5a, FMLP and RANTES are similarly tested in the presence of INCB3344 for migration of WEHI-274.1 cells. For the studies on the impact of INCB3344 on CCR5-mediated chemotaxis, murine T cells are used as the cell system with mouse MIP-1β as the ligand.

Rats: Adult male Sprague-Dawley rats (200-250 g) are used. After t=0 baseline measurement, rats are lightly anesthetized under an isoflurane/oxygen (5%; 2 L/min) flow and 25 μL of either saline (vehicle), 1 μg of CCL2 and/or 1 mM of INCB3344 is administered intrathecally between L5 and L6 vertebrae. Animals are tested once at 30, 60, 90, 120, and 240 min following drug administration. The percentage of maximal potential effect (MPE) is calculated for every time point.