A novel inhibitor L755507 efficiently blocks c-Myc-MAX heterodimerization and induces apoptosis in cancer cells.

c-Myc is a transcription factor that plays a crucial role in cellular homeostasis, and its deregulation is associated with highly aggressive and chemotherapy-resistant cancers. After binding with partner MAX, the c-Myc-MAX heterodimer regulates the expression of several genes, leading to an oncogenic phenotype. Although considered a crucial therapeutic target, no clinically approved c-Myc-targeted therapy has yet been discovered. Here, we report the discovery via computer-aided drug discovery of a small molecule, L755507, which functions as a c-Myc inhibitor to efficiently restrict the growth of diverse Myc-expressing cells with low micromolar IC50 values. L755507 successfully disrupts the c-Myc-MAX heterodimer, resulting in decreased expression of c-Myc target genes. Spectroscopic and computational experiments demonstrated that L755507 binds to the c-Myc peptide and thereby stabilizes the helix-loop-helix conformation of the c-Myc transcription factor. Taken together, this study suggests that L755507 effectively inhibits the c-Myc-MAX heterodimerization and may be used for further optimization to develop a c-Myc-targeted antineoplastic drug.