Development of the pyridopyrimidine derivative KC12 as a selective dual Pim/Mnk inhibitor to inhibit leukemia cell growth

Myeloid leukemia is an abnormal proliferative disease relying on fast cap-dependent protein translation. Both provirus integration in Maloney murine leukemia virus (Pim) kinases and mitogen-activated protein kinase-interacting kinases (Mnk) play key roles in activating cap-dependent translation, making them attractive targets for anticancer drug development. Although several selective Pim or Mnk inhibitors entered clinical trials, their efficacy was limited. We propose that concurrent inhibition of both Pim/Mnk kinases is necessary for effective treatment. Previously, we reported the first dual Pim and Mnk inhibitor 21o with a pyrido[3,2- d ]pyrimidine core (IC 50 Mnk1: 9 nM, Mnk2: 5 nM, Pim1: 120 nM), but suffered from poor solubility. We optimized 21o based on molecular docking and obtained a compound KC12 with enhanced kinase inhibitory activity (IC 50 Mnk1:32 nM, Mnk2 3 nM; Pim 1 32 nM) and improved selectivity (only 4 out of 42 tested kinases showed >40% inhibition at 100 nM). KC12 exhibits increased aqueous solubility and superior anti-proliferative activity compared to 21o, as well as to the Pim inhibitor TP-3654 and the Mnk inhibitor eFT508. KC12 induced G0/G1 phase cell cycle arrest in K562 cells and apoptosis in MOLM-13 cells, correlated to the suppression of both eIF4E and 4EBP1 phosphorylation, and the cap-dependent translation products c-Myc and Mcl-1. Moreover, KC12 demonstrated a more favorable pharmacokinetic profile than 21o and exhibited enhanced antitumor efficacy in MOLM-13 xenograft models. These findings suggest that KC12 acts as a novel, potent, and selective dual Pim/Mnk inhibitor and is worthy of further development as a therapeutic agent.