CHIR-258 inhibits the viability of FGFR3-expressing B9 cells but not parental IL-6-stimulated cells. Cells were exposed to CHIR-258 for 48 hours, and viability was assessed by an MTT-based assay. ⋄ indicates J807C cells; □, Y373C; ▵, K650E; ○, G384D; ▪, wild type (WT); ▴, F384L; and +, B9-MINV cells stimulated with IL-6. Untreated cells were defined as 100%. Values represent mean ± SD of 4 independent experiments.