MDM2 and lymphopenia: Because of the expected haematological on-target toxicity of MDM2 inhibitors, haematologic AEs were identified as adverse events of special interest (AESI) and included neutropenia, thrombocytopenia, leucopenia, anaemia and lymphopenia.19 AESIs occurred in 64.7% of patients regardless of study drug relationship, and in 51% as suspected to be treatment-related.