Abstract B227: Discovery of 3-aryl-3H-[1,2,3]triazolo[4,5-b]pyridin-5-ylamine compounds as potent, selective and orally bioavailable inhibitors of PIM kinases.

Abstract

Abstract The PIM family of serine/threonine kinases (PIM-1, 2 and 3) has been originally identified as proviral integration sites involved in lymphomagenesis induced by murine leukemia virus. In almost all of the MuLV-induced lymphomas in Eμ-Pim-1 transgenic mice either c-MYC or N-MYC is activated by proviral insertion. The oncogenic properties of Pim kinases were shown to encompass their capacity to counteract the increased sensitivity to apoptosis induction that is associated with MYC-driven tumorigenesis. Pim-1, 2 and 3 are highly conserved kinases that have unique structural properties, and are characterized by a constitutive serine/threonine activity that does not depend on post-translational modifications for activation. Pim kinases activity supports in vitro and in vivo tumor cell growth and survival through modification of an increasing number of common as well as isoform-specific substrates. Pim expression is driven by oncogenes as BCR-ABL, JAK2, FLT3 and KRas. Pim kinases are overexpressed in a range of haematopoietic malignancies and solid cancers, and its overexpression is associated with drug resistance. Inhibition of PIM kinase activity may be an attractive therapeutic strategy with possible favourable toxicity profiles due to minimal phenotype of mice mutant for all Pim family members. Based on the knowledge of complexes of ligands with PIM1 protein, previously reported, as well as known PIM1 inhibitors coming from and internal HTS campaign, we carried out a scaffold hopping strategy for hit generation. We identified triazolopyridine compounds with potent activity against PIM and FLT3 kinases. We have explored different substitution patterns to improve selectivity of PIM vs FLT3 activity. Here, we describe the exploration and biological characterization of this bicyclic series, reporting its SAR/SPR (ADME). We identified lead compounds with potency in the low nanomolar range vs. PIM1, 2 and 3 and high selectivity versus a panel of 24 protein kinases. The compounds display cellular activity by blocking PIM signaling, S112 P-Bad in H1299 Pim1 cells, in the low nanomolar range. The combination of the PI3K inhibitor GDC-0941 with Pim inhibitors was strongly synergistic in vitro in non solid and solid tumoral cell lines. Finally, we assessed the effect of Pim kinase inhibition on Pim signaling and tumor growth in vivo in a mouse intravenous tumor xenograft model employing tumoral cells coming from E myc mice and in an inducible transgenic KRasV12 mouse model. When delivered orally, ETP-995 inhibited phosphorylation of bad and 4EBP and reduced c-myc expression in vivo, and the compound significantly inhibited tumor growth. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B227.