Comparative Efficacy and Selectivity of Pharmacological Inhibitors of DYRK and CLK Protein Kinases.

Dual-specificity, tyrosine phosphorylation-regulated kinases (DYRKs) and cdc2-like kinases (CLKs) play a large variety of cellular functions and are involved in several diseases (cognitive disorders, diabetes, cancers, etc.). There is, thus, growing interest in pharmacological inhibitors as chemical probes and potential drug candidates. This study presents an unbiased evaluation of the kinase inhibitory activity of a library of 56 reported DYRK/CLK inhibitors on the basis of comparative, side-by-side, catalytic activity assays on a panel of 12 recombinant human kinases, enzyme kinetics (residence time and Kd), in-cell inhibition of Thr-212-Tau phosphorylation, and cytotoxicity. The 26 most active inhibitors were modeled in the crystal structure of DYRK1A. The results show a rather large diversity of potencies and selectivities among the reported inhibitors and emphasize the difficulties to avoid "off-targets" in this area of the kinome. The use of a panel of DYRKs/CLKs inhibitors is suggested to analyze the functions of these kinases in cellular processes.

Discovery of Novel Bruton's Tyrosine Kinase PROTACs with Enhanced Selectivity and Cellular Efficacy.

Bruton's tyrosine kinase (BTK) is a target for treating B-cell malignancies and autoimmune diseases, and several BTK inhibitors are already approved for use in humans. Heterobivalent BTK protein degraders are also in development, based on the premise that proteolysis targeting chimeras (PROTACs) may provide additional therapeutic benefits. However, most BTK PROTACs are based on the BTK inhibitor ibrutinib raising concerns about their selectivity profiles, given the known off-target effects of ibrutinib. Here, we disclose the discovery and in vitro characterization of BTK PROTACs based on the selective BTK inhibitor GDC-0853 and the cereblon recruitment ligand pomalidomide. PTD10 is a highly potent BTK degrader (DC50 0.5 nM) that inhibited cell growth and induced apoptosis at lower concentrations than the two parent molecules, as well as three previously reported BTK PROTACs, and had improved selectivity compared to ibrutinib-based BTK PROTACs.

Synthesis and Preclinical Evaluation of a Novel Fluorine-18-Labeled Tracer for Positron Emission Tomography Imaging of Bruton's Tyrosine Kinase.

Bruton's tyrosine kinase (BTK) is a target for treating B-cell malignancies and autoimmune diseases. To aid in the discovery and development of BTK inhibitors and improve clinical diagnoses, we have developed a positron emission tomography (PET) radiotracer based on a selective BTK inhibitor, remibrutinib. [18F]PTBTK3 is an aromatic, 18F-labeled tracer that was synthesized in 3 steps with a 14.8 ± 2.4% decay-corrected radiochemical yield and ≥99% radiochemical purity. The cellular uptake of [18F]PTBTK3 was blocked up to 97% in JeKo-1 cells using remibrutinib or non-radioactive PTBTK3. [18F]PTBTK3 exhibited renal and hepatobiliary clearance in NOD SCID (non-obese diabetic/severe combined immunodeficiency) mice, and the tumor uptake of [18F]PTBTK3 in BTK-positive JeKo-1 xenografts (1.23 ± 0.30% ID/cc) was significantly greater at 60 min post injection compared to the tumor uptake in BTK-negative U87MG xenografts (0.41 ± 0.11% ID/cc). In the JeKo-1 xenografts, tumor uptake was blocked up to 62% by remibrutinib, indicating the BTK-dependent uptake of [18F]PTBTK3 in tumors.

Hit to lead evaluation of 1,2,3-triazolo[4,5-b]pyridines as PIM kinase inhibitors.

PIM kinases have become targets of interest due to their association with biochemical mechanisms affecting survival, proliferation and cytokine production. 1,2,3-Triazolo[4,5-b]pyridines were identified as PIM inhibitors applying a scaffold hopping approach. Initial exploration around this scaffold and X-ray crystallographic data are hereby described.

Pim 1 kinase inhibitor ETP-45299 suppresses cellular proliferation and synergizes with PI3K inhibition.

The serine/threonine Pim 1 kinase is an oncogene whose expression is deregulated in several human cancers. Overexpression of Pim 1 facilitates cell cycle progression and suppresses apoptosis. Hence pharmacologic inhibitors of Pim 1 are of therapeutic interest for cancer. ETP-45299 is a potent and selective inhibitor of Pim 1 that inhibits the phosphorylation of Bad and 4EBP1 in cells and suppresses the proliferation of several non-solid and solid human tumor cell lines. The combination of the PI3K inhibitor GDC-0941 with ETP-45299 was strongly synergistic in MV-4-11 AML cells, indicating that the combination of selective Pim kinase inhibitors and PI3K inhibitor could have clinical benefit.

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.

beta-Catenin and plakoglobin N- and C-tails determine ligand specificity.

beta-Catenin and plakoglobin are related proteins involved in the regulation of adherens junctions and desmosomes. Moreover, by binding to Tcf-4, they can act as transcriptional modulators of genes involved in embryonic development and tumorigenesis. However, they associate to distinct Tcf-4 subdomains causing opposing effects on Tcf-4 binding to DNA: whereas beta-catenin does not affect this binding, plakoglobin prevents it. Both proteins are composed by two N- and C-tails and a central armadillo repeat domain. Interaction of Tcf-4, as well as other desmosomal or adherens junction components, with beta-catenin or plakoglobin takes place through the central armadillo domain. Here we show that, as reported for beta-catenin, plakoglobin terminal tails also interact with the central domain and regulate the ability of this region to bind to different cofactors. Moreover the specificity of the interaction of beta-catenin and plakoglobin with different subdomains in Tcf-4 or with other junctional components resides within the terminal tails and not in the armadillo domain. For instance, a chimeric protein in which the central domain of beta-catenin was replaced by that of plakoglobin presented the same specificity as wild-type beta-catenin. Therefore, the terminal tails of these proteins are responsible for discerning among binding of factors to the armadillo domain. These results contribute to the understanding of the molecular basis of the interactions established by these key regulators of epithelial tumorigenesis.