In vitro activity: GW2580 completely inhibits human cFMS kinase in vitro at 0.06 μM. GW2580 inhibits the growth of CSF-1 stimulated M-NFS-60 myeloid tumor cells, serum stimulated NSO myeloid tumor cells, CSF-1 stimulated freshly isolated human monocytes, and VEGF stimulated human umbilical vein vascular endothelial cells with IC50 of 0.33, 13.5, 0.47 and 12 μM, respectively. 1 μM GW2580 completely inhibits CSF-1-induced growth of mouse M-NFS-60 myeloid cells and human monocytes and completely inhibits bone degradation in cultures of human osteoclasts, rat calvaria, and rat fetal long bone. GW2580 inhibits CSF1R phosphorylation in RAW264.7 murine macrophages stimulated with 10 ng/mL with IC50 of approximately 10 NM. GW2580 also inhibits TRKA activity with IC50 of 0.88 μM.

Kinase Assay: The enzyme is activated by autophosphorylation by incubating 10 μM enzyme, 100 μM ATP, and 5 mM MgCl2 in 50 mM Tris HCL for 90 min at room temperature. Enzyme reactions are performed in a volume of 45 μL, by using round-bottom polystyrene 96-well plates on a Biomek 2000. Compound in 1 μL DMSO or DMSO alone are added to each well containing 30 μL of a 1.5× substrate reaction mix containing 50 mM Mops (3-[N-Morpholino]propanesulfonic acid), pH 7.5, 15 mM MgCl2, 6 μM peptide substrate, biotin-EAIYAPFAKKK-NH2 7.5 mM DTT, 75 mM NaCl, 10 μM ATP, and 0.5 μCi (1 Ci = 37 GBq) [33P-γ] ATP per assay. The reaction is initiated by the addition of 15 μL of diluted enzyme solution, resulting in a final enzyme concentration 20 nM. EDTA is added to control wells for determination of background. The reaction is allowed to proceed for 40 min and stopped by the addition of an equal volume of 0.5% phosphoric acid, and 75 μL is transferred to a 96-well phosphocellulose filter plate that has been prewet with 100 μL of 0.5% phosphoric acid. The plate is filtered on a Millipore filter-plate vacuum manifold and washed three times with the phosphoric acid solution, followed by the addition of 40 μL of scintillation solution. The plates are sealed and counted in a Packard Topcount NXT scintillation counter.

Cell Assay: One day before the start of the cell growth assay the cells are spun down and placed in a depleted media at 2× 106 cells per ml for 24 h. Depleted medium for M-NSF60 cells lacks MCSF. The next day, GW2580 at 10 mM in DMSO is diluted to 20 μM and 0.2% DMSO in medium containing 10% serum and serially diluted to yield a 10-point concentration curve. The M-NFS-60 cells are resuspended in medium at 0.5× 106 cells/mL with 10% serum and 20 ng/mL mouse MCSF. Cells (50 μL) are added to each well containing inhibitor (50 μL), and, 3 days later, 10 μL of WST-1 reagent is added to each well. After a 4-h incubation, the absorbance is measured at 440 nm and growth calculated as the difference between wells with full medium and wells with depleted medium.

Proc Natl Acad Sci U S A. 2005 Nov 1;102(44):16078-83; Blood. 2010 Feb 18;115(7):1461-71.