GSK 2830371 potently inhibits Wip1 (2-420) dephosphorylation of FDP and the endogenous substrates phospho-p38 MAPK (T180) with IC50 values of 6 nM and 13 nM, respectively. In the PPM1D-amplified MCF7 breast carcinoma cells, treatment with GSK 2830371 (0.04, 0.11, 0.33, 1, 3, and 9 μM) increased phosphorylation of substrates in a concentration-dependent manner. Treatment of MX-1 and MCF7 cells (Wip1amplified, p53 wild type) with GSK 2830371 (0.001, 0.01, 0.1, 1, and 10 μM) causes concentration-dependent effects in cell growth assays. GSK2830371 has a 50% growth inhibitory concentration (GI50) of 2.65 μM±0.54 (SEM) in MCF-7 cells. Treatment of MCF-7 cells with 2.5μM GSK2830371 results in marked time-dependent degradation of both isoforms of WIP1 over 8 hours which correlated with p53 stabilisation and phospho-p53 (pp53).