The PI3K/AKT pathway is commonly activated in human cancer. Multiple small-molecule inhibitors have been developed to target PI3K/mTOR or AKT kinases, but the efficacy of these drugs is compromised by the stimulation of compensatory signaling pathways. The redundancy of oncogenic signaling pathways provides back-up mechanisms that allow cancer cells to escape to targeted therapies. One example of such compensatory pathways is that driven by PIM kinases, which produce parallel oncogenic signals to AKT and mTOR and share several downstream molecular targets. In fact, in mouse lymphoma models chemoresistance to doxorubicin caused by AKT is readily reversed by rapamycin, but PIM mediated resistance is refractory to mTORC1 inhibition. Moreover, PIM2 kinase can confer resistance of primary hematopoietic cells to rapamycin treatment. Furthermore, PIM 1 mediates resistance to AKT and PI3K/mTOR inhibition and suggests co-targeting to improve the efficacy of PI3K/AKT/mTOR inhibitors in anticancer therapy. The PI3K/AKT/mTOR and PIM pathways are activated and seem to be relevant for tumor progression in many lymphomas, leukemias and in some solid tumors. We have previously reported that the combination of PI3K inhibitor GDC-0941 with a PIM selective inhibitor, ETP-45299, was strongly synergistic in antiproliferation experiments in MV-4-11 AML cells. Therefore, combination of such activities in a single molecule might have the potential to achieve better clinical efficacy and prevent/suppress resistance in comparison with classical PI3K/AKT/mTOR inhibitors. During the course of our investigations in this field we have identified a new chemical series of compounds with dual (PIM/PI3K) and triple activity (PIM/PI3K/mTOR inhibitors). (WO2012/156756). In this work, we show the biochemical, cellular and in vivo characterization of dual PIM/PI3K ETP-539/(IBL-202) and triple PIM/PI3K/mTOR ETP-339/(IBL-301) inhibitors. These optimized lead compounds are low nanomolar pan PIM/PI3K and pan PIM/PI3K/mTOR inhibitors respectively. These dual and triple inhibitors show excellent kinase selectivity profile against a panel of 456 kinases. Both compounds have been profiled for their antiproliferative behavior. We have identified leukemia, lymphoma, colon, and NSCLC lines which exhibit a strong sensitivity to dual and triple inhibition with GI80 between 5-10 times more potent than PIM or PI3K selective reference inhibitors. Mechanistically, cells respond to dual and triple inhibitors with a clear cell cycle arrest and marked apoptosis in AML and NSCLC cell lines, and strong down regulation of biomarkers. Our dual and triple inhibitors are optimized with respect to their in vitro ADME properties and have excellent oral bioavailability. These inhibitors have been tested in vivo in xenograft (MV4:11 AML) and transgenic (KRAsV12NSCLC) cancer mouse models. Both compounds have demonstrated down regulation of biomarkers associated with their targeted profile and significant antitumor efficacy in both models after oral administration. These inhibitors have been well tolerated, with no signs of toxicity even 20 times above the efficacious dose.

These results provide the rationale for further preclinical development of ETP-539/(IBL-202 and ETP-339/(IBL-301) and the basis for a potential clinical use in AML and NSCLC tumors.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A275.

Citation Format: Carmen Blanco Aparicio, Oliver Renner, Elena Gomez-Casero, Antonio Cebriá, Nuria Ajenjo, Enara Aguirre, David Cebrián, Ma Carmen Rodriguez de Miguel, Belén Pequeño, MaIsabel Albarrán, Rosario Riesco, Ana Belén García, Rosa Alvarez, Michael O'Neill, Sonia Martinez, Joaquin Pastor. Co-targeting PIM and PI3K/mTOR pathways with a single molecule: Novel orally available combined PIM/PI3K and PIM/PI3K/mTOR kinase inhibitors. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A275.