Discovery, Structure-Activity Relationship and In Vitro Anticancer Activity of Small-Molecule Inhibitors of the Protein-Protein Interactions between AF9/ENL and AF4 or DOT1L

Simple Summary: Chromosomal translocations involving the mixed lineage leukemia (MLL) gene generate potent fusion oncogenes and cause acute myeloid leukemia or lymphocytic leukemia, which account for similar to 75% infant and 5-10% child/adult acute leukemia cases with a poor prognosis (5-year survival rates < 45%). Protein-protein interactions between the most frequent MLL fusion partner proteins AF9/ENL and AF4 or histone methyltransferase DOT1L are critical to malignant gene expression and are therefore a potential drug target for cancer. Compound screening followed by medicinal chemistry studies identified several novel small-molecule inhibitors showing strong inhibition of these protein-protein interactions, significant suppression of characteristic gene expression, and robust cellular anticancer activities with negligible cytotoxicity. These compounds are useful chemical probes for biological studies of these protein-protein interactions, as well as pharmacological leads for further drug development against MLL-rearranged and other leukemias. Chromosomal translocations involving the mixed lineage leukemia (MLL) gene cause 5-10% acute leukemias with poor clinical outcomes. Protein-protein interactions (PPI) between the most frequent MLL fusion partner proteins AF9/ENL and AF4 or histone methyltransferase DOT1L are drug targets for MLL-rearranged (MLL-r) leukemia. Several benzothiophene-carboxamide compounds were identified as novel inhibitors of these PPIs with IC50 values as low as 1.6 mu M. Structure-activity relationship studies of 77 benzothiophene and related indole and benzofuran compounds show that a 4-piperidin-1-ylphenyl or 4-pyrrolidin-1-ylphenyl substituent is essential for the activity. The inhibitors suppressed expression of MLL target genes HoxA9, Meis1 and Myc, and selectively inhibited proliferation of MLL-r and other acute myeloid leukemia cells with EC50 values as low as 4.7 mu M. These inhibitors are useful chemical probes for biological studies of AF9/ENL, as well as pharmacological leads for further drug development against MLL-r and other leukemias.

Automated summary

This study identified several small-molecule inhibitors that target MLL rearranged leukemia. These inhibitors showed significant suppression of characteristic gene expression, strong cellular anticancer activities, and low cytotoxicity. They serve as useful chemical probes for studying protein-protein interactions and as leads for developing drugs against MLL rearranged and other leukemias.