The MCL1 inhibitor S63845 is tolerable and effective in diverse cancer models

Avoidance of apoptosis is critical for the development and sustained growth of tumours. The pro-survival protein myeloid cell leukemia 1 (MCL1) is overexpressed in many cancers, but the development of small molecules targeting this protein that are amenable for clinical testing has been challenging. Here we describe S63845, a small molecule that specifically binds with high affinity to the BH3-binding groove of MCL1. Our mechanistic studies demonstrate that S63845 potently kills MCL1-dependent cancer cells, including multiple myeloma, leukaemia and lymphoma cells, by activating the BAX/BAK-dependent mitochondrial apoptotic pathway. In vivo , S63845 shows potent anti-tumour activity with an acceptable safety margin as a single agent in several cancers. Moreover, MCL1 inhibition, either alone or in combination with other anti-cancer drugs, proved effective against several solid cancer-derived cell lines. These results point towards MCL1 as a target for the treatment of a wide range of tumours. S63845 specifically inhibits MCL1 and induces tumour cell death in vitro and in vivo in diverse cancer-derived cell lines with an acceptable safety margin. MCL1 protein as a possible anti-cancer target These authors report the discovery and characterization of a novel inhibitor of the anti-apoptotic pro-survival protein MCL1, which is expressed by multiple tumour types. The compound, termed S63845, activates the BAX/BAK-dependent mitochondrial apoptotic pathway and shows efficacy in several solid tumour models, suggesting that inhibition of MCL1 could be a viable anti-cancer strategy, alone or in combination with other anti-cancer drugs.