MK-0812 is an effective and specific CCR2 antagonist.

MK-0812 completely blocks all MCP-1 mediated response in a concentration-dependent manner (IC50: 3.2 nM). This value is similar to the potency observed for the inhibition of 125I-MCP-1 binding by MK-0812 on isolated monocytes (IC50 4.5 nM). The addition of MK-0812 to rhesus blood also inhibits MCP-1 induced monocyte shape change. The IC50 for MK-0812 in whole blood assays is 8 nM [1].

MK0812 (30 mg/kg, p.o.) reduces the frequency of Ly6G-Ly6Chi monocytes in the peripheral blood, while no impact on circulating Ly6G+Ly6C+ neutrophil frequency is observed. In addition, MK0812 treatment causes a dose-dependent reduction in circulating Ly6Chi monocytes and a corresponding elevation in the CCR2 ligand CCL2 [2].

Human whole blood is collected in EDTA tubes and used within 1 h of blood collection. For antagonist treated samples, blood (200 μL) is pre-incubated with MK-0812 (0.1% final DMSO concentration) for 30 min at room temperature. After this, 20 μL of FITC conjugated anti-CD14 antibody and 4 μL of chemokine or buffer is added to each sample and mixed lightly. An aliquot (100 μL) of the blood mixture is incubated for 10 min at 37°C immediately placed on ice and lightly fixed with 250 μL of ice-cold fixative (49 mL PBS, 1.0 mL 4% paraformaldehyde) for 1 min. Red blood cells are lysed by adding 1.0 mL of ice-cold lysis solution (0.15 M NH4Cl2, 10 mM sodium bicarbonate, and 1 mM EDTA), and incubated for 20 min on ice. After complete lysis of red blood cells, 100 μL of 4% para-formaldehyde is added and the samples are analyzed by flow cytometry for forward scattering measurements [1].

Female BALB/c mice are used between 8 and 10 weeks of age. MK0812 are administered in a 0.4% MC solution by 30 mg/kg oral gavage (p.o.). Two hours later, the frequency of CD11b+Ly6G-Ly6Chi monocytes and CD11b+Ly6G+Ly6C+ neutrophils is determined by flow cytometry [2].