EN4 is a covalent ligand that targets cysteine 171 (C171) of MYC. EN4 is selective for c-MYC over N-MYC and L-MYC. EN4 inhibits MYC transcriptional activity, downregulates MYC targets, and impairs tumorigenesis[1].
EN4 (1-50 μM; for 72 hours) treatment significantly impaires 231MFP breast cancer cell proliferation in a dosedependent manner, with >90% inhibition of proliferation at 50 μM[1].EN4 (50 μM; for 60 hours) treatment significantly decreases the protein levels of representative MYC-regulated target genes, including CDK2 and CDC25A. EN4 treatment also substantially reduces MYC levels[1].EN4 shows the strongest inhibition of both MYC/MAX binding to its DNA consensus sequence in vitro as well as MYC transcriptional activity in cells. EN4 inhibited MYC/MAX binding to the E-box response element DNA consensus sequence in a dose-responsive manner with an IC50 value of 6.7 μM. EN4 also inhibits MYC luciferase reporter activity in a dose-responsive manner with an IC50 value of 2.8 μM[1]. EN4 (50 μM; for 2 hours) treatment significantly reduced MYC thermal stability in 231MFP breast cancer cells[1].
EN4 (50 mg/kg; intraperitoneal injection; daily; for 3 weeks) treatment significantly attenuated tumor growth in 231MFP breast tumor xenograft mice[1].
[1]. Lydia Boike, et al. Discovery of a Functional Covalent Ligand Targeting an Intrinsically Disordered Cysteine within MYC. Cell Chem Biol. 2021 Jan 21;28(1):4-13.e17.