Discovery of indazole-pyridinone derivatives as a novel class of potent and selective MNK1/2 kinase inhibitors that protecting against endotoxin-induced septic shock.

The mitogen-activated protein kinase (MAPK)-interacting kinases 1 and 2 (MNKs 1/2) and their downstream target eIF4E, play a role in oncogenic transformation, progression and metastasis. These results provided rationale for development of first MNKs inhibitors, currently in clinical trials for cancer treatment. Inhibitors of the MNKs/eIF4E pathway are also proposed as treatment strategy for inflammatory conditions. Here we present results of optimization of indazole-pyridinone derived MNK1/2 inhibitors among which compounds 24 and 26, selective and metabolically stable derivatives. Both compounds decreased levels of eIF4E Ser206 phosphorylation (pSer209-eIF4E) in MOLM16 cell line. When administered in mice compounds 24 and 26 significantly improved survival rates of animals in the endotoxin lethal dose challenge model, with concomitant reduction of proinflammatory cytokine levels - TNFα and IL-6 in serum. Identified MNK1/2 inhibitors represent a novel class of immunomodulatory compounds with a potential for the treatment of inflammatory diseases including sepsis.

How to design potent and selective DYRK1B inhibitors? Molecular modeling study.

DYRK1B protein kinase is an emerging anticancer target due to its overexpression in a variety of cancers and its role in cancer chemoresistance through maintaining cancer cells in the G0 (quiescent) state. Consequently, there is a growing interest in the development of potent and selective DYRK1B inhibitors for anticancer therapy. One of the major off-targets is another protein kinase, GSK3ß, which phosphorylates an important regulator of cell cycle progression on the same residue as DYRK1B and is involved in multiple signaling pathways. In the current work, we performed a detailed comparative structural analysis of DYRK1B and GSK3ß ATP-binding sites and identified key regions responsible for selectivity. As the crystal structure of DYRK1B has never been reported, we built and optimized a homology model by comparative modeling and metadynamics simulations. Calculation of interaction energies between docked ligands in the ATP-binding sites of both kinases allowed us to pinpoint key residues responsible for potency and selectivity. Specifically, the role of the gatekeeper residues in DYRK1B and GSK3ß is discussed in detail, and two other residues are identified as key to selectivity of DYRK1B inhibition versus GSK3ß. The analysis presented in this work was used to support the design of potent and selective azaindole-quinoline-based DYRK1B inhibitors and can facilitate development of more selective inhibitors for DYRK kinases.

MNK1/2 inhibition limits oncogenicity and metastasis of KIT-mutant melanoma.

Melanoma can be stratified into unique subtypes based on distinct pathologies. The acral/mucosal melanoma subtype is characterized by aberrant and constitutive activation of the proto-oncogene receptor tyrosine kinase C-KIT, which drives tumorigenesis. Treatment of these melanoma patients with C-KIT inhibitors has proven challenging, prompting us to investigate the downstream effectors of the C-KIT receptor. We determined that C-KIT stimulates MAP kinase-interacting serine/threonine kinases 1 and 2 (MNK1/2), which phosphorylate eukaryotic translation initiation factor 4E (eIF4E) and render it oncogenic. Depletion of MNK1/2 in melanoma cells with oncogenic C-KIT inhibited cell migration and mRNA translation of the transcriptional repressor SNAI1 and the cell cycle gene CCNE1. This suggested that blocking MNK1/2 activity may inhibit tumor progression, at least in part, by blocking translation initiation of mRNAs encoding cell migration proteins. Moreover, we developed an MNK1/2 inhibitor (SEL201), and found that SEL201-treated KIT-mutant melanoma cells had lower oncogenicity and reduced metastatic ability. Clinically, tumors from melanoma patients harboring KIT mutations displayed a marked increase in MNK1 and phospho-eIF4E. Thus, our studies indicate that blocking MNK1/2 exerts potent antimelanoma effects and support blocking MNK1/2 as a potential strategy to treat patients positive for KIT mutations.

SEL120-34A is a novel CDK8 inhibitor active in AML cells with high levels of serine phosphorylation of STAT1 and STAT5 transactivation domains.

Inhibition of oncogenic transcriptional programs is a promising therapeutic strategy. A substituted tricyclic benzimidazole, SEL120-34A, is a novel inhibitor of Cyclin-dependent kinase 8 (CDK8), which regulates transcription by associating with the Mediator complex. X-ray crystallography has shown SEL120-34A to be a type I inhibitor forming halogen bonds with the protein's hinge region and hydrophobic complementarities within its front pocket. SEL120-34A inhibits phosphorylation of STAT1 S727 and STAT5 S726 in cancer cells in vitro. Consistently, regulation of STATs- and NUP98-HOXA9- dependent transcription has been observed as a dominant mechanism of action in vivo. Treatment with the compound resulted in a differential efficacy on AML cells with elevated STAT5 S726 levels and stem cell characteristics. In contrast, resistant cells were negative for activated STAT5 and revealed lineage commitment. In vivo efficacy in xenotransplanted AML models correlated with significant repression of STAT5 S726. Favorable pharmacokinetics, confirmed safety and in vivo efficacy provide a rationale for the further clinical development of SEL120-34A as a personalized therapeutic approach in AML.

Mitogen-activated Protein Kinase (MAPK) Interacting Kinases 1 and 2 (MNK1 and MNK2) as Targets for Cancer Therapy: Recent Progress in the Development of MNK Inhibitors.

MAP kinase-interacting kinases (MNK1 and MNK2) are often activated downstream of ERK and p38 MAPK in the MAP kinase family. The role of MNKs in the development and progression of solid tumors and hematological malignancies has been widely discussed, particularly in the context of cap dependent translation, regulated by phosphorylation of eIF4E. MNK/eIF4E axis is involved in the expression of pro angiogenic, antiapoptotic, cell cycle, and motility proteins, such as MCL1, VEGF, MMP3, SNAIL, SMAD2, ß-catenin or cyclin D1, and is essential during Ras and c Myc-induced transformation. MNK1/2 emerged as eligible targets for drug discovery in oncology, based on the antitumor effects observed in genetic knockout and RNA interference experiments and at the same time lack of adverse effects in dual knockout animals. There is a high interest in the development of pharmacological inhibitors of MNK1/2 as not only tools for further basic research studies but also potential drugs in diseases characterized by deregulated translation. Unfortunately, the role of MNK1/2 in cancer still remains elusive due to the absence of potent and selective probes. Moreover, in many instances, hypotheses have been built reliant upon unspecific MNK1/2 inhibitors such as CGP57380 or cercosporamide. Lately, the first two clinical programs targeting MNKs in oncology have been revealed (eFT508 and BAY 1143269), although several other MNK programs are currently running at the preclinical stage. This review aims to provide an overview of recent progress in the development of MNK inhibitors.