Optimization of Novel Pyrido-pyridazinone Derivatives as FER Tyrosine Kinase Inhibitors, Leading to the Potent DS08701581.

Previously, we reported the new pyrido-pyridazinone template as a feline sarcoma-related (FER) tyrosine kinase inhibitor. Representative compound 1 (DS21360717) showed strong enzyme inhibitory activity (IC50 = 0.5 nM), however, its antitumor effect was insufficient, probably due to poor solubility and resultant low bioavailability (BA). In addition, the kinase selectivity was inadequate, which may result in certain safety risks. Here, we focused on derivatization of the unoptimized C-5 position to obtain promising FER inhibitors possessing strong antitumor effects and improved selectivity, referring to their X-ray crystal structure and the docking model with FES proto-oncogene tyrosine kinase as an FER surrogate. While establishing the synthetic route of the pyrido-pyridazinone scaffold, we obtained a desired compound via our derivatization. Our optimized compound 17c (DS08701581) showed the highest class cell-free and cell activities in this template, good oral BA, and improved kinase selectivity, resulting in significant tumor growth inhibition in the Ba/F3-FER tumor model without body weight loss.

Discovery of a Novel ATP-Competitive MEK Inhibitor DS03090629 that Overcomes Resistance Conferred by BRAF Overexpression in BRAF-Mutated Melanoma.

Patients with melanoma with activating BRAF mutations (BRAF V600E/K) initially respond to combination therapy of BRAF and MEK inhibitors. However, their clinical efficacy is limited by acquired resistance, in some cases driven by amplification of the mutant BRAF gene and subsequent reactivation of the MAPK pathway. DS03090629 is a novel and orally available MEK inhibitor that inhibits MEK in an ATP-competitive manner. In both in vitro and in vivo settings, potent inhibition of MEK by DS03090629 or its combination with the BRAF inhibitor dabrafenib was demonstrated in a mutant BRAF-overexpressing melanoma cell line model that exhibited a higher MEK phosphorylation level than the parental cell line and then became resistant to dabrafenib and the MEK inhibitor trametinib. DS03090629 also exhibited superior efficacy against a melanoma cell line-expressing mutant MEK1 protein compared with dabrafenib and trametinib. Biophysical analysis revealed that DS03090629 retained its affinity for the MEK protein regardless of its phosphorylation status, whereas the affinity of trametinib declined when the MEK protein was phosphorylated. These results suggest that DS03090629 may be a novel therapeutic option for patients who acquire resistance to the current BRAF- and MEK-targeting therapies.

Novel protein kinase cAMP-Activated Catalytic Subunit Alpha (PRKACA) inhibitor shows anti-tumor activity in a fibrolamellar hepatocellular carcinoma model.

Fibrolamellar hepatocellular carcinoma (FL-HCC) is known as a highly aggressive liver cancer that typically affects young adults without virus infection. Since this type of cancer does not respond to chemotherapy, surgery is the only known effective therapeutic option. Most FL-HCC patients express the fusion gene DNAJB1-PRKACA, which has been recognized as the signature of FL-HCC. It has also been reported that PRKACA kinase activity is essential for its oncogenic activity, suggesting that PRKACA kinase inhibition could be considered as an useful therapeutic target. In this study, we established an evaluation system for PRKACA kinase inhibitors and synthesized DS89002333, a novel PRKACA inhibitor. DS89002333 showed potent PRKACA inhibitory activity and inhibited fusion protein-dependent cell growth both in vitro and in vivo. Furthermore, this compound showed anti-tumor activity in an FL-HCC patient-derived xenograft model expressing the DNAJB1-PRKACA fusion gene. Our data suggest that DS89002333 could be considered as a potential therapeutic agent for FL-HCC.

Discovery of Novel Pyrido-pyridazinone Derivatives as FER Tyrosine Kinase Inhibitors with Antitumor Activity.

To obtain a new anticancer drug, we focused on FER tyrosine kinase. Starting with high-throughput screening with our in-house chemical library, compound 1, which has a pyridine moiety, was found. Referring to their X-ray crystal structure with FES proto-oncogene tyrosine kinase, as a surrogate of FER followed by chemical modification including scaffold hopping of the pyridine template, we discovered pyrido-pyridazinone derivatives with potent FER kinase inhibitory activity. Here, we disclose the structure-activity relationship on the scaffold and representative compound 21 (DS21360717), which showed in vivo antitumor efficacy in a subcutaneous tumor model.

NEK9 depletion induces catastrophic mitosis by impairment of mitotic checkpoint control and spindle dynamics.

NEK9 is known to play a role in spindle assembly and in the control of centrosome separation, but the consequences of NEK9 targeting in cancer cells remain to be elucidated. In this study, we used siRNA to investigate the consequences of targeting NEK9 in glioblastoma and kidney cancer cells as a first step in assessing its potential as an anti-cancer therapeutic target. Live cell imaging revealed that NEK9 depletion of U1242 glioblastoma and Caki2 kidney carcinoma cells resulted in failure of cytokinesis. Interestingly, NEK9-depleted Caki2 cells overrode mitosis under incorrect chromosome alignment and were converted to a micronucleated phenotype, leading to cell death. Whereas, the RPE1 normal epithelium cell line was refractory to abnormal mitosis upon NEK9 knockdown. Nocodazole-induced mitotic arrest was compromised after NEK9 depletion, indicating that NEK9 has an important role in mitotic checkpoint system. Taken together, we propose that NEK9 inhibition represents a novel anti-cancer strategy by induction of mitotic catastrophe via impairment of spindle dynamics, cytokinesis and mitotic checkpoint control.

Identification of physiologically active substances as novel ligands for MRGPRD.

Mas-related G-protein coupled receptor member D (MRGPRD) is a G protein-coupled receptor (GPCR) which belongs to the Mas-related GPCRs expressed in the dorsal root ganglia (DRG). In this study, we investigated two novel ligands in addition to beta-alanine: (1) beta-aminoisobutyric acid, a physiologically active substance, with which possible relation to tumors has been seen together with beta-alanine; (2) diethylstilbestrol, a synthetic estrogen hormone. In addition to the novel ligands, we found that transfection of MRGPRD leads fibroblast cells to form spheroids, which would be related to oncogenicity. To understand the MRGPRD novel character, oncogenicity, a large chemical library was screened in order to obtain MRGPRD antagonists to utilize in exploring the character. The antagonist in turn inhibited the spheroid proliferation that is dependent on MRGPRD signaling as well as MRGPRD signals activated by beta-alanine. The antagonist, a small-molecule compound we found in this study, is a potential anticancer agent.

MRGD, a MAS-related G-protein coupled receptor, promotes tumorigenisis and is highly expressed in lung cancer.

To elucidate the function of MAS-related GPCR, member D (MRGD) in cancers, we investigated the in vitro and in vivo oncogenic function of MRGD using murine fibroblast cell line NIH3T3 in which MRGD is stably expressed. The expression pattern of MRGD in clinical samples was also analyzed. We found that overexpression of MRGD in NIH3T3 induced focus formation and multi-cellular spheroid formation, and promoted tumors in nude mice. In other words, overexpression of MRGD in NIH3T3 induced the loss of contact inhibition, anchorage-independent growth and in vivo tumorigenesis. Furthermore, it was found that the ligand of MRGD, beta-alanine, enhanced spheroid formation in MRGD-expressing NIH3T3 cells. From investigation of clinical cancer tissues, we found high expression of MRGD in several lung cancers by immunohistochemistry as well as real time PCR. Based on these results, MRGD could be involved in tumorigenesis and could also be a novel anticancer drug target.

Genome-wide analysis of gene-expression profiles in chronic myeloid leukemia cells using a cDNA microarray.

To characterize molecular mechanisms operating in chronic myeloid leukemia (CML) cells with a view toward development of novel therapeutic targets, we analyzed gene-expression profiles of cancer cells from 27 CML patients using a cDNA microarray representing 23,040 human genes. By comparing expression patterns of CML with those of normal cells, we identified 150 genes that were commonly highly up-regulated in CML cells. In addition to 54 genes (34 of them ESTs) whose functions are currently unknown, the up-regulated elements included genes encoding cell-cycle regulators, transcriptional activators, transcriptional factors, and protein kinases as well as proteins already known to be induced in CML, such as some hemoglobins, haptoglobin (HP1), and matrix metalloproteinase 9 (MMP-9), a protein involved in tissue remodeling and tumor invasion. On the other hand, our protocol selected 106 genes, including 13 of unknown function, as being commonly significantly down-regulated in all phases of CML. The results of semiquantitative RT-PCR experiments with 11 representatives of the up-regulated group supported the reliability of our microarray analysis. These data should provide useful information for finding candidate genes whose products might serve as molecular targets for treatment of CML patients.

Prediction of chemosensitivity for patients with acute myeloid leukemia, according to expression levels of 28 genes selected by genome-wide complementary DNA microarray analysis.

To identify genes involved in the sensitivity of acute myeloid leukemia (AML) cells to chemotherapy, we monitored gene-expression profiles of cancer cells from 76 AML patients using a cDNA microarray consisting of 23,040 genes. We identified 63 genes that were commonly overexpressed and 372 genes suppressed in AML. Because these genes represent key molecules for disclosing the molecular mechanisms of AML, they may be potential targets for drug development. We also found 28 that revealed different expression levels between good and poor responders to chemotherapy and appeared to be associated with chemosensitivity. On that basis, we developed a "Drug Response Scoring" system that was correlated well with individual sensitivity to an anticancer drug regimen. Among the 44 cases with positive drug-response scores by our definition, 40 achieved complete remission after treatment, whereas the only 3 of the 20 cases with negative scores responded well to the treatment. An ability to predict chemosensitivity should eventually lead to achievement of our goal of "personalized therapy."

Interleukin-11 as a stimulatory factor for bone formation prevents bone loss with advancing age in mice.

Cytokines in interleukin (IL)-11 subfamily participate in the regulation of bone cell proliferation and differentiation. We report here positive effects of IL-11 on osteoblasts and bone formation. Overexpression of human IL-11 gene in transgenic mice resulted in the stimulation of bone formation to increase cortical thickness and strength of long bones, and in the prevention of cortical bone loss with advancing age. Bone resorption and osteoclastogenesis were not affected in IL-11 transgenic mice. In experiments in vitro, IL-11 stimulated transcription of the target gene for bone morphogenetic protein (BMP) via STAT3, leading to osteoblastic differentiation in the presence of BMP-2, but inhibited adipogenesis in bone marrow stromal cells. These results indicate that IL-11 is a stimulatory factor for osteoblastogenesis and bone formation to conserve cortical bone, possibly by enhancing BMP actions in bone. IL-11 may be a new therapeutic target for senile osteoporosis.

Prediction of sensitivity to STI571 among chronic myeloid leukemia patients by genome-wide cDNA microarray analysis.

One of the most critical issues to be solved in regard to cancer chemotherapy is the establishment of ways to predict the efficacy of anti-cancer drugs for individual patients. To develop a prediction system based on expression of specific genes, we analyzed expression profiles of mononuclear cells from 18 chronic myeloid leukemia (CML) patients who were treated with the tyrosine kinase inhibitor STI571. cDNA microarrays representing 23 040 genes identified 79 genes that were expressed differentially between responders and non-responders to STI571. On the basis of the expression patterns of 15 or 30 of these genes among the patients, we developed a "Prediction Score" system that could clearly separate the responder group from the non-responder group. Verification of this system using four additional ("test") cases succeeded in predicting the response of each of those four patients to the drug. These results provide the first evidence that gene-expression profiles can predict sensitivity of CML cells to STI571, and may eventually lead to the achievement of "personalized therapy" for this disease.