Macrophage inhibitory cytokine (MIC-1, a secreted protein that is strongly induced by activated p53) serum levels has been used to assess pharmacodynamic (PD) effects in this Phase I study. Analysis of patients on 100 to 800 mg/day of RG7388 showed that the minimum level for p53 induction occurs at a dose of 100 mg/day or a corresponding plasma level of 500 ng/mL of RG7388. Preliminary analysis of PK and safety data showed that there is an apparent PK/PD relationship between an AUC per cycle and Cycle 1 platelet nadir.