Structure-Based Design of Selective Janus Kinase 2 Imidazo[4,5-d]pyrrolo[2,3-b]pyridine Inhibitors

Targeting the JAK/STAT Pathway: A Combined Ligand- and Target-Based Approach

Janus kinases (JAKs) are a family of proinflammatory enzymes able to mediate the immune responses and the inflammatory cascade by modulating multiple cytokine expressions as well as various growth factors. In the present study, the inhibition of the JAK-signal transducer and activator of transcription (STAT) signaling pathway is explored as a potential strategy for treating autoimmune and inflammatory disorders. A computationally driven approach aimed at identifying novel JAK inhibitors based on molecular topology, docking, and molecular dynamics simulations was carried out. For the best candidates selected, the inhibitory activity against JAK2 was evaluated in vitro. Two hit compounds with a novel chemical scaffold, 4 (IC₅₀ = 0.81 μM) and 7 (IC₅₀ = 0.64 μM), showed promising results when compared with the reference drug Tofacitinib (IC₅₀ = 0.031 μM).

Discovery of imidazopyrrolopyridines derivatives as novel and selective inhibitors of JAK2

Herein, we describe the design, synthesis, and structure-activity relationships of a series of imidazopyrrolopyridines derivatives that selectively inhibit Janus kinase 2 (JAK2). These screening cascades revealed that 6k was a preferred compound, with IC₅₀ values of 10 nM for JAK2. Moreover, 6k was a selective JAK2 inhibitor with 19-fold, >30-fold and >30-fold selectivity over JAK1, JAK3 and TYK2 respectively. In cytokine-stimulated cell-based assays, 6k exhibited a higher JAK2 selectivity over JAK1 isoforms. Indeed, at a dose of 20 mg/kg compound 6k, pSTAT3 and pSTAT5 expression was reduced to levels comparable to those of control animals untreated with GM-CSF. Additionally, 6k showed a relatively good bioavailability (F = 38%), a suitable half-life time (T_1/2 = 1.9 h), a satisfactory metabolic stability, suggesting that 6k might be a promising inhibitor of JAK2 for further development research for the treatment of MPNs.

Discovery of novel JAK2 and EGFR inhibitors from a series of thiazole-based chalcone derivatives

The Janus kinase (JAK) and epidermal growth factor receptor (EGFR) have been considered as potential targets for cancer therapy due to their role in regulating proliferation and survival of cancer cells. In the present study, the aromatic alkyl-amino analogs of thiazole-based chalcone were selected to experimentally and theoretically investigate their inhibitory activity against JAK2 and EGFR proteins as well as their anti-cancer effects on human cancer cell lines expressing JAK2 (TF1 and HEL) and EGFR (A549 and A431). In vitro cytotoxicity screening results demonstrated that the HEL erythroleukemia cell line was susceptible to compounds 11 and 12, whereas the A431 lung cancer cell line was vulnerable to compound 25. However, TF1 and A549 cells were not sensitive to our thiazole derivatives. From kinase inhibition assay results, compound 25 was found to be a dual inhibitor against JAK2 and EGFR, whereas compounds 11 and 12 selectively inhibited the JAK2 protein. According to the molecular docking analysis, compounds 11, 12 and 25 formed hydrogen bonds with the hinge region residues Lys857, Leu932 and Glu930 and hydrophobically came into contact with Leu983 at the catalytic site of JAK2, while compound 25 formed a hydrogen bond with Met769 at the hinge region, Lys721 near a glycine loop, and Asp831 at the activation loop of EGFR. Altogether, these potent thiazole derivatives, following Lipinski's rule of five, could likely be developed as a promising JAK2/EGFR targeted drug(s) for cancer therapy.

Janus kinases (JAKs): The efficient therapeutic targets for autoimmune diseases and myeloproliferative disorders

The Janus kinases or JAKs are a family of intracellular tyrosine kinases that play an essential role in the signaling of numerous cytokines that have been implicated in the pathogenesis of autoimmune diseases and myeloproliferative disorders. JAKs are activated upon ligand induced receptor homo- or heterodimerization, which results in the immediate phosphorylation of tyrosine residues and the phosphotyrosines then serve as docking sites for cytoplasmic signal transducer and activator of transcription (STAT) proteins which become phosphorylated by the JAKs upon recruitment to the receptor complex. The phosphorylated STAT proteins dimerize and travel to the cellular nucleus, where they act as transcription factors. Interfering in the JAK-STAT pathway has yielded the only approved small molecule kinase inhibitors for immunological indications. Numerous medicinal chemistry studies are currently aimed at the design of novel and potent inhibitors for JAKs. Additionally, whether the second-generation inhibitors which possessed selectivity for JAKs are more efficient are under research. This Perspective summarizes the progress in the discovery and development of JAKs inhibitors, including the potential binding site and approaches for identifying small-molecule inhibitors, as well as future therapeutic perspectives in autoimmune diseases and myeloproliferative disorders are also put forward in order to provide reference and rational for the drug discovery of novel and potent JAKs inhibitors.

An Update on JAK Inhibitors

Janus kinases (JAKs) are a family of non-receptor tyrosine kinases, composed by four members, JAK1, JAK2, JAK3 and TYK2. JAKs are involved in different inflammatory and autoimmune diseases, as well as in malignancies, through the activation of the JAK/STAT signalling pathway. Furthermore, the V617F mutation in JAK2 was identified in patients affected by myeloproliferative neoplasms. This knowledge prompted researchers from academia and pharmaceutical companies to investigate this field in order to discover small molecule JAK inhibitors. These efforts recently afforded to the market approval of four JAK inhibitors. Despite the fact that all these drugs are pyrrolo[2,3-d]pyrimidine derivatives, many compounds endowed with different heterocyclic scaffolds have been reported in the literature as selective or multi-JAK inhibitors, and a number of them is currently being evaluated in clinical trials. In this review we will report many representative compounds that have been published in articles or patents in the last five years (period 2013-2017). The inhibitors will be classified on the basis of their chemical structure, focusing, when possible, on their structure activity relationships, selectivity and biological activity. For every class of derivatives, compounds disclosed before 2013 that have entered clinical trials will also be briefly reported, to underline the importance of a particular chemical scaffold in the search for new inhibitors.

A Novel Naphthoquinone-Coumarin Hybrid That Inhibits BCR-ABL1-STAT5 Oncogenic Pathway and Reduces Survival in Imatinib-Resistant Chronic Myelogenous Leukemia Cells

BCR-ABL1-STAT5 is an oncogenic signaling pathway in human chronic myelogenous leukemia (CML) and it represents a valid target for anti-CML drug design. Resistance to direct BCR-ABL1 inhibitors is a common clinical issue, so STAT5 inhibition has become an interesting alternative target. In this study, the effects of NPQ-C6, a novel naphtoquinone-coumarin conjugate, were evaluated on human CML-derived K562 cells. Live-Cell Imaging analysis revealed that NPQ-C6 inhibited 2D (IC50_AUC = 1.4 ± 0.6 μM) growth of CML cells. NPQ-C6 increased sub-G1 and reduced G0/G1 cell cycle phases in a dose- and time-dependent manner. This effect on cell cycle was related to increased levels of apoptotic nuclei, cleavage of caspase-3, -9, and PARP and annexin V-positive cells. NPQ-C6 increased γH2AX, a double-strand DNA break marker. NPQ-C6 showed a wide range of modulatory effects on cell signaling through an early increased phosphorylation of JNK, P38-MAPK and AKT, and decreased phosphorylation of ERK1/2, BCR-ABL1, and STAT5. NPQ-C6 inhibited expression of c-MYC and PYM-1, two target gene products of BCR-ABL1/STAT5 signaling pathway. Cytokine-induced activation of STAT5/STAT3-dependent transcriptional and DNA binding activities were also inhibited by NPQ-C6. Notably, NPQ-C6 maintained its activity on BCR-ABL1/STAT5/c-MYC/PIM-1 oncogenic pathway in imatinib-resistant cells. Molecular modeling suggested BCR-ABL1 and JAK2 proteins as NPQ-C6 targets. In summary, our data show a novel multikinase modulator that might be therapeutically effective in BCR-ABL1-STAT5-related malignancies.

Understanding the structural features of JAK2 inhibitors: a combined 3D-QSAR, DFT and molecular dynamics study

JAK2 plays a critical role in JAK/STAT signaling pathway and in patho-mechanism of myeloproliferative disorders and autoimmune diseases. Thus, effective JAK2 inhibitors provide a promising opportunity for the pharmaceutical intervention of many diseases. In this work, 3D-QSAR study was performed on a series of 1-amino-5H-pyrido-indole-4-carboxamide derivatives as JAK2 inhibitors to obtain reliable comparative molecular field analysis (CoMFA) and comparative molecular similarity analysis (CoMSIA) models with three different alignment methods. Among the different alignment methods, ligand-based (CoMFA: q² = 0.676, r² = 0.979; CoMSIA: q² = 0.700, r² = 0.953) and pharmacophore-based alignment (CoMFA: q² = 0.710, r² = 0.982; CoMSIA: q² = 0.686, r² = 0.960) has produced better statistical results when compared to receptor-based alignment (CoMFA: q² = 0.507, r² = 0.979; CoMSIA: q² = 0.544, r² = 0.917). Statistical parameters indicated that data are well fitted and have high predictive ability. The presence of electrostatic and hydrophobic field is highly desirable for potent inhibitory activity, and the steric field plays a minor role in modulating the activity. The contour analysis indicates ARG980, ASN981, ASP939 and LEU937 have more possibility of interacting with bulky, hydrophobic groups in pyrido and positive and negative groups in pyrazole ring. Based on our findings, we have designed sixteen molecules and predicted its activity and drug-like properties. Subsequently, molecular docking, molecular dynamics and DFT calculations were performed to evaluate its potency.

N, Kuppusamy P, Purandare AV. Discovery of a Highly Selective JAK2 Inhibitor, BMS-911543, for the Treatment of Myeloproliferative Neoplasms

JAK2 kinase inhibitors are a promising new class of agents for the treatment of myeloproliferative neoplasms and have potential for the treatment of other diseases possessing a deregulated JAK2-STAT pathway. X-ray structure and ADME guided refinement of C-4 heterocycles to address metabolic liability present in dialkylthiazole 1 led to the discovery of a clinical candidate, BMS-911543 (11), with excellent kinome selectivity, in vivo PD activity, and safety profile.