Discovery of novel triazolo[4,3-b]pyridazin-3-yl-quinoline derivatives as PIM inhibitors.

PIM kinase family (PIM-1, PIM-2 and PIM-3) is an appealing target for the discovery and development of selective inhibitors, useful in various disease conditions in which these proteins are highly expressed, such as cancer. The significant effort put, in the recent years, towards the development of small molecules exhibiting inhibitory activity against this protein family has ended up with several molecules entering clinical trials. As part of our ongoing exploration for potential drug candidates that exhibit affinity towards this protein family, we have generated a novel chemical series of triazolo[4,3-b]pyridazine based tricycles by applying a scaffold hopping strategy over our previously reported potent pan-PIM inhibitor ETP-47453 (compound 2). The structure-activity relationship studies presented herein demonstrate a rather selective PIM-1/PIM-3 biochemical profile for this novel series of tricycles, although pan-PIM and PIM-1 inhibitors have also been identified. Selected examples show significant inhibition of the phosphorylation of BAD protein in a cell-based assay. Moreover, optimized and highly selective compounds, such as 42, did not show significant hERG inhibition at 20 µM concentration, and proved its antiproliferative activity and utility in combination with particular antitumoral agents in several tumor cell lines.

Rapid identification of ETP-46992, orally bioavailable PI3K inhibitor, selective versus mTOR.

Phosphoinositide-3-kinases (PI3K) are a family of lipid kinases mediating numerous cell processes such as proliferation, migration and differentiation. PI3K is an important target for cancer therapeutics due to the deregulation of this signaling pathway in a wide variety of human cancers. Herein, we describe the rapid identification of ETP-46992, within 2-aminocarbonyl imidazo [1,2-a] pyrazine series, with suitable pharmacokinetic (PK) properties that allows the establishment of mechanism of action and efficacy in vivo studies. ETP-46992 showed tumor growth inhibition in a GEMM mouse tumor model driven by a K-Ras(G12V) oncogenic mutation and in tumor xenograft models with PI3K pathway deregulated (BT474).

The essential role of PIM kinases in sarcoma growth and bone invasion.

PIM kinases are a family of serine/threonine kinases composed of three different isoforms (PIM1, PIM 2 and PIM 3) that are highly homologous. Their expression is mediated by the JAK/STAT signalling pathway, providing survival and cell cycle transition signals. PIM kinases are heavily targeted for anticancer drug discovery. However, very little is known about the relative contribution of the different isoforms to the tumourigenesis process in vivo, and how their individual inhibition might affect tumour growth. Taking advantage of genetically modified mice, we explored whether the inhibition of specific isoforms is required to prevent sarcomas induced by 3-methylcholanthrene carcinogenic treatment. We found that absence of Pim2 and Pim3 greatly reduced sarcoma growth to a similar extent to the absence of all three isoforms. This model of sarcoma generally produces bone invasion by the tumour cells. Lack of Pim2 and Pim3 reduced tumour-induced bone invasion by 70%, which is comparable with the reduction of tumour-induced bone invasion in the absence of all three isoforms. Similar results were obtained in mouse embryonic fibroblasts (MEFs) derived from these knockout (KO) mice, where double Pim2/3 KO MEFs already showed reduced proliferation and were resistant to oncogenic transformation by the RAS oncogene. Our data also suggest an important role of Gsk3ß phosphorylation in the process of tumourigenesis.

Identification of ETP-46321, a potent and orally bioavailable PI3K α, δ inhibitor.

Phosphoinositide-3-kinase (PI3K) is an important target for cancer therapeutics due to the deregulation of this signaling pathway in a wide variety of human cancers. Herein, we describe the optimization of imidazo [1,2-a] pyrazines, which allow us to identify compound 14 (ETP-46321), with potent biochemical and cellular activity and good pharmacokinetic properties (PK) after oral dosing. ETP-46321 PK/PD studies showed time dependent downregulation of AKT(Ser473) phosphorylation, which correlates with compound levels in tumor tissue and demonstrating to be efficacious in a GEMM mouse tumor model driven by a K-Ras(G12V) oncogenic mutation. Treatment with ETP-46321 resulted in significant tumor growth inhibition.