Identification of novel PI3K inhibitors through a scaffold hopping strategy.

A scaffold hopping strategy, including intellectual property availability assessment, was successfully applied for the discovery of novel PI3K inhibitors. Compounds were designed based on the chemical structure of the lead compound ETP-46321, a potent PI3K inhibitor, previously reported by our group. The new generated compounds showed good in vitro potency and selectivity, proved to inhibit potently the phosphorylation of AKTSer473 in cells and demonstrated to be orally bioavailable, thus becoming potential back-up candidates for ETP-46321.

Generation of tricyclic imidazo[1,2-a]pyrazines as novel PI3K inhibitors by application of a conformational restriction strategy.

The involvement of the phosphoinositide 3-kinases (PI3Ks) in several diseases, especially in the oncology area, has singled it as one of the most explored therapeutic targets in the last two decades. Many different inhibitor classes have been developed by the industry and academia with a diverse selectivity profile within the PI3K family. In the present manuscript we report a further exploration of our lead PI3K inhibitor ETP-46321 (Martínez González et al., 2012)1 by the application of a conformational restriction strategy. For that purpose we have successfully synthesized novel tricyclic imidazo[1,2-a]pyrazine derivatives as PI3K inhibitors. This new class of compounds had enable the exploration of the solvent-accessible region within PI3K and resulted in the identification of molecule 8q with the best selectivity PI3Kα/δ isoform profile in vitro, and promising in vivo PK data.

Biological characterization of ETP-46321 a selective and efficacious inhibitor of phosphoinositide-3-kinases.

Inhibitors of PI3K signaling are of great therapeutic interest in oncology. The phosphoinositide-3-kinase signaling pathway is activated in a variety of solid and non-solid tumors. We have identified an imidazopyrazine derivative, ETP-46321, as a potent inhibitor of PI3Kα [Formula: see text]. The compound was 6 times less potent towards PI3Kδ and more than 200 and 60 times less potent at inhibiting PI3Kß and PI3Kγ and did not significantly inhibit the related phosphoinositide-3-kinase-related protein kinase family kinases mTOR or DNA PK (IC(50)'s > 5 µM), or an additional 287 protein kinases that were screened. ETP-46321 inhibited PI3K signaling in treated tumor cell lines, induced cell cycle arrest and inhibited VEGF-dependent sprouting of HUVEC cells. The compound was anti-proliferative and synergized with both cytotoxic and targeted therapeutics. The compound induced a reduction in the phosphorylation of Akt in U87 MG xenografts after a single treatment. The growth of colon and lung cancinoma HT-29 and A549 xenografts was delayed by once a day treatment with ETP-46321. The compound synergized with Doxotaxel in a model of ovarian cancer.

Chemical interrogation of FOXO3a nuclear translocation identifies potent and selective inhibitors of phosphoinositide 3-kinases.

Activation of the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway is one the most frequent genetic events in human cancer. A cell-based imaging assay that monitored the translocation of the Akt effector protein, Forkhead box O (FOXO), from the cytoplasm to the nucleus was employed to screen a collection of 33,992 small molecules. The positive compounds were used to screen kinases known to be involved in FOXO translocation. Pyrazolopyrimidine derivatives were found to be potent FOXO relocators as well as biochemical inhibitors of PI3Kalpha. A combination of virtual screening and molecular modeling led to the development of a structure-activity relationship, which indicated the preferred substituents on the pyrazolopyrimidine scaffold. This leads to the synthesis of ETP-45658, which is a potent and selective inhibitor of phosphoinositide 3-kinases and demonstrates mechanism of action in tumor cell lines and in vivo in treated mice.

Induction of Lysosome Membrane Permeabilization as a Therapeutic Strategy to Target Pancreatic Cancer Stem Cells.

Despite significant efforts to improve pancreatic ductal adenocarcinoma (PDAC) clinical outcomes, overall survival remains dismal. The poor response to current therapies is partly due to the existence of pancreatic cancer stem cells (PaCSCs), which are efficient drivers of PDAC tumorigenesis, metastasis and relapse. To find new therapeutic agents that could efficiently kill PaCSCs, we screened a chemical library of 680 compounds for candidate small molecules with anti-CSC activity, and identified two compounds of a specific chemical series with potent activity in vitro and in vivo against patient-derived xenograft (PDX) cultures. The anti-CSC mechanism of action of this specific chemical series was found to rely on induction of lysosomal membrane permeabilization (LMP), which is likely associated with the increased lysosomal mass observed in PaCSCs. Using the well characterized LMP-inducer siramesine as a tool molecule, we show elimination of the PaCSC population in mice implanted with tumors from two PDX models. Collectively, our approach identified lysosomal disruption as a promising anti-CSC therapeutic strategy for PDAC.

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.

Discovery of mitogen-activated protein kinase-interacting kinase 1 inhibitors by a comprehensive fragment-oriented virtual screening approach.

Mitogen-activated protein kinase-interacting kinases 1 and 2 (MNK1 and MNK2) phosphorylate the oncogene eIF4E on serine 209. This phosphorylation has been reported to be required for its oncogenic activity. To investigate if pharmacological inhibition of MNK1 could be useful for the treatment of cancers, we pursued a comprehensive virtual screening approach to rapidly identify pharmacological tools for target validation and to find optimal starting points for a plausible medicinal chemistry project. A collection of 1236 compounds, selected from a library of 42 168 compounds and a database of 18.8 million structures, were assayed. Of the identified hits, 26 were found to have IC(50) values less than 10 µM (2.10% hit rate). The most potent compound had an IC(50) value of 117 nM, and 73.1% of these hits were fragments. The hits were characterized by a high ligand efficiency (0.32-0.52 kcal/mol per heavy atom). Ten different chemical scaffolds were represented, giving a chemotype/hit ratio of 0.38.