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Figure 4. Screening of clinical and preclinical drugs to identify novel candidates targeting breast cancer brain metastases. A: Preliminary screening of 1,650 compounds for their efficacy against BBM1 cells. BBM1 cells were grown overnight prior to treatment with the compounds at a final concentration 1 µmol/L for 48 or 72 h (n = 2). The percentages of viable cells in each treatment group relative to viable control cells treated with DMSO are shown for data collected after 72-h treatment. Compounds that suppressed viability below 70% compared to control (107 total, separated by a dashed line) were selected for secondary screening using both BBM1 and BBM2 cells lines; B, C: tertiary screening of the active compounds based on cell type-specific effects. Human astrocytes and BBM1 cells were grown overnight prior to treatment with the 35 active compounds identified in the secondary screening at a final concentration of 1 µmol/L for 48 or 72 h (n = 6). The percentages of viable cells relative to viable control cells treated with DMSO are shown for data collected after 72-h treatment; C: relative viability of BBM1 cells treated with compounds (12) that reduced BBM1 cell viability by at least two-fold compared to that of astrocytes at a concentration of 1 µmol/L for 72 h; D: concentration-dependent effects of six potent active compounds. BBM1 cells were grown overnight prior to treatment with the compounds at final concentrations ranging from 0, 31.2, 62.5, 125, 250, 500, 1000 nmol/L (n = 8). The viability of the cells at 72 h post-treatment is shown. The IC50 values of the compounds are shown in parenthesis