CC-4047 inhibits development of CFU-GM osteoclast precursors. Nonadherent bone marrow cells were cultured in methylcellulose culture containing 30% FCS and 100 pg/mL rh CSF-GM in the presence of 100 μM CC-4047, 100 μM thalidomide (Thal), or 0.1% DMSO. After 9 to 10 days of incubation, colony phenotypes and the numbers were determined by inverted microscope. Asterisks indicate a significant difference from control (P < .01). The experiment was performed independently 3 times. Each value is the mean plus or minus SD of CFU colonies per plate.