Background:

S63845 is a small molecule MCL1 inhibitor with Ki < 1.2 nM [1].

Myeloid cell leukemia 1 (MCL1) is a pro-survival protein and belongs to BCL-2 family proteins. BCL-2 family proteins are key regulators of the mitochondrial apoptotic pathway. MCL1 is overexpressed in many cancers, so inhibitors targeting this protein may kills MCL1-dependent cancer cells [1].

S63845 is a highly selective and potent MCL1 inhibitor. S63845 bound human MCL1 with KD value of 0.19 nM. S63845 was approximately 1,000-fold more potent in killing MCL1-dependent H929 multiple myeloma cells than MCL1 inhibitor A-1210477. S63845 also induced caspase-dependent phosphatidyl-serine exposure, PARP cleavage and cytochrome c release from mitochondria. In HeLa cells, S63845 disrupted binding of BAK and BAX to MCL1. S63845 killed cancer cells through activation of the BAX/BAK-dependent mitochondrial apoptotic pathway by direct inhibition of MCL1 [1].

In immunocompromised mice with human multiple myeloma (H929 and AMO1) xenografts, intravenously injected (i.v.) S63845 showed dose-dependent anti-tumour activity with maximal tumour growth inhibition (TGImax) of 103% and 114% in the H929 and AMO1 model, respectively [1].

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Reference:

1.Kotschy A, Szlavik Z, Murray J, et al. The MCL1 inhibitor S63845 is tolerable and effective in diverse cancer models. Nature. 2016 Oct 19;538(7626):477-482.