P493-6 treated with KJ-Pyr-9 and/or Doxycycline

In a fluorescence polarization screen for MYC-MAX interaction, we have identified a novel small molecule inhibitor of MYC, KJ-Pyr-9, from a Kröhnke pyridine library. The Kd of KJ-Pyr-9 for MYC in vitro is 6.5 ± 1.0 nM as determined by backscattering interferometry; KJ-Pyr-9 also interferes with MYC-MAX complex formation in the cell as shown in a protein fragment complementation assay. KJ-Pyr-9 specifically inhibits MYC-induced oncogenic transformation in cell culture; it has no or only weak effects on the oncogenic activity of several unrelated oncoproteins. KJ-Pyr-9 preferentially interferes with the proliferation of MYC-overexpressing human and avian cells and specifically reduces the MYC-driven transcriptional signature. In vivo, KJ-Pyr-9 effectively blocks the growth of a xenotransplant of MYC-overexpressing  human cancer cells. 4 treatment groups analyzed in triplicate: no treatment(control), 20uM KJ-Pyr-9, 0.1ug/mL doxycycline and KJ-Pyr-9 in combination with doxycycline