Navtemadlin is a potent small moeclule inhibitor of the p53-MDM2 protein-protein interaction, that is being tested in Phase II/III clinical trials for the treatment of cancer. In this experiment, we compare the whole proteme of MCF-7 and SJSA-1 cells following Navtemadlin treatment in order to gain an insight into the cause of the observed differences in the off-target profile of this molecule in the two cell lines.