Humanized Mcl-1 mice enable accurate preclinical evaluation of MCL-1 inhibitors destined for clinical use

Margs S. Brennan, Catherine Chang, Lin Tai, Guillaume Lessene, Andreas Strasser, Grant Dewson, Gemma L. Kelly and Marco J. Herold

Key Points

  • Due to the higher affinity of current MCL-1 inhibitors, huMcl-1 mice have been established.

  • A therapeutic window for S63845 can be established in huMcl-1 mice transplanted with huMcl-1;Eµ-Myc lymphomas.


Myeloid cell leukemia-1 (MCL-1) is a prosurvival B-cell lymphoma 2 (BCL-2) family member required for the sustained growth of many cancers. Recently, a highly specific MCL-1 inhibitor, S63845, showing sixfold higher affinity to human compared with mouse MCL-1, has been described. To accurately test efficacy and tolerability of this BH3-mimetic (BH3-only protein mimetic) drug in preclinical cancer models, we developed a humanized Mcl-1 (huMcl-1) mouse strain in which MCL-1 was replaced with its human homolog. huMcl-1 mice are phenotypically indistinguishable from wild-type mice but are more sensitive to the MCL-1 inhibitor S63845. Importantly, nontransformed cells and lymphomas from huMcl-1;Eµ-Myc mice are more sensitive to S63845 in vitro than their control counterparts. When huMcl-1;Eµ-Myc lymphoma cells were transplanted into huMcl-1 mice, treatment with S63845 alone or alongside cyclophosphamide led to long-term remission in ∼60% or almost 100% of mice, respectively. These results demonstrate the potential of our huMcl-1 mouse model for testing MCL-1 inhibitors, allowing precise predictions of efficacy and tolerability for clinical translation.

  • Submitted June 22, 2018.
  • Accepted August 19, 2018.
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