The present disclosure relates to use of GDF-15 as a safety biomarker for determining a toxicological effect of a Mdm2 inhibitor； an ex vivo method for determining a toxicological effect of a Mdm2 inhibitor in a subject, in particular for determining a likelihood of developing thrombocytopenia in a subject in response to administration of a dose of a Mdm2 inhibitor； methods of using a Mdm2 inhibitor in the treatment of cancer in a subject； a kit for use in predicting the likelihood that a patient having cancer will develop thrombocytopenia in response to a treatment with a dose of a Mdm2 inhibitor； a kit for use in treating a patient having cancer and related disclosure embodiments.
