The invention relates to a combination of a compound of formula (I) or a pharmaceutically acceptable salt thereof, and at least one second agent selected from the group consisting of proteasome inhibitors, tumour immunotherapeutics or immunomodulatory agents, signal transduction pathway inhibitors, agents inhibiting the BCL2 family of proteins, agents inhibiting Mcl-1, poly (ADP-ribose) polymerase (PARP) Inhibitors, aromatase inhibitors, conventional cytotoxic agents or a miscellaneous agent selected from abiraterone, ARN-509 and MYC inhibitors.