Background:

MIM1 effectively competed with FITC-MCL-1 SAHBA and FITC-BID BH3 for MCL-1ΔNΔC binding with IC50 values of 4.7 and 4.8 mM, respectively. And MIN1 shows a combination of favorable biophysical and biological properties including its solubility, stability, nonreactivity, MCL-1 binding potency and selectivity, compatibility with and activity in a BAX-mediated liposomal release assay and relatively little to no toxicity in Bax-/-Bak-/- MEFs [1].

As an MCL-1 inhibitor, MIM1 selectively targets the BH3-binding groove of MCL-1, neutralizes its biochemical lockhold on apoptosis, and induces caspase activation and leukemia cell death in the specific context of MCL-1 dependence.

The activity and specificity of MIM1 in cancer cells was dependable for assessing MCL-1 and BCL-XL dependence by employing murine BCRABL (p185)-transformed, Arf null, B-lineage acute lymphoblastic leukemia cells. Comparing to the effect of ABT-737 on p185+Arf-/-/Mcl-1-deleted B-ALL cells, MIM1 had the exact opposite effect, impacting the viability of the MCL-1-dependent cells (IC50, 4.2 mM), including dose-dependent induction of caspase 3/7 activity, but having no effect on the BCL-XL-dependent cells. A combination of MIM1 (IC50, 10.6 mM) and ABT-737 (IC50, 5.1 mM) resulted in synergistic cytotoxicity. Strikingly, when the MIM1/ABT-737 combination was applied to MCL-1-reconstituted p185+Arf-/-/Mcl-1-deleted B-ALL cells, the addition of ABT-737 had little effect [1].

MIM1 emerged as a potent and selective small molecule inhibitor of MCL-1 DNDC, capable of targeting the canonical BH3-binding point of MCL-1 and blocking MCL-1-mediated suppression of tBID-induced BAX activation in vitro. MIM1 may serve as a prototype for the development of next generation small molecules that effectively reduce the apoptotic threshold in cancers specifically driven by antiapoptotic MCL-1 [1].

Reference:
[1].  Cohen NA, Stewart ML, Gavathiotis E, et al. A Competitive Stapled Peptide Screen Identifies a Selective Small Molecule that Overcomes MCL-1-Dependent Leukemia Cell Survival. Chemistry & Biology, 2012, 19(9): 1175-1186.