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.

Abstract B173: Preclinical characterization and antitumor efficacy of DS-5010, a highly potent and selective RET inhibitor

Background: RET gene rearrangement has been detected in several cancers including 1-2% and 50% of non-small cell lung cancer (NSCLC) and papillary thyroid carcinoma, respectively, and it is known as a driver mutation. Several US Food and Drug Administration (FDA)-approved multi-tyrosine kinase inhibitors (MTKIs) have shown inhibitory effects on RET kinase activity and have been tested in several clinical studies. However, MTKIs do not appear potent enough to show clinical benefits. The FDA-approved MTKIs have been reported to exhibit dose-limiting toxicity (DLT) at doses below those suppressing RET kinase activity. Kinase insert domain receptor (KDR) inhibition especially leads to anti-angiogenesis-related DLT such as hypertension. Thus, the development of highly potent and selective second-generation RET inhibitors is desired. DS-5010 is an orally available small-molecule RET inhibitor that shows a specific and highly potent activity against RET and gatekeeper-mutated RET (RET-GKm) and slight KDR activity. In this study, we characterized the in vitro and in vivo activities of DS-5010. Results: In biochemical assays of 106 kinases, RET and platelet-derived growth factor receptor (PDGFR) alpha/beta were inhibited more than 80% by 193 nM DS-5010. The half-maximal inhibitory concentration (IC50) values of DS-5010 against RET, RET-GKm (V804L) were single digit nano-molar even under a condition of high concentration of ATP; besides it against KDR was more than 1000 nM. In a Ba/F3-RET subcutaneous tumor model, DS-5010 dosing at 10 mg/kg twice daily (bid) induced tumor regression. Moreover, DS-5010 exhibited a similar antitumor effect in a Ba/F3-RET-GKm (V804L) subcutaneous tumor model. In contrast, the FDA-approved MTKIs (cabozantinib, vandetanib, and alectinib) showed no significant antitumor effect on a Ba/F3-RET-GKm (V804L) subcutaneous tumor model. In an LC2/ad NSCLC xenograft model, which has the RET-CCDC6 fusion gene, DS-5010 dosing at 1 mg/kg thrice daily (tid) induced tumor regression. To predict acquired mutations against FDA-approved MTKIs, resistant clones were established by prolonged incubation of Ba/F3-RET cells with cabozantinib. A sequence analysis revealed that all the resistant clones possessed V804E mutation in the RET kinase domain and DS-5010 inhibited cell proliferation of Ba/F3-RET (V804E) mutation in the low nano-molar range. However, the FDA-approved MTKIs failed to show strong growth inhibitory effects (half-maximal growth inhibition [GI50]: 1584-5381 nM). Conclusion: These results indicate that DS-5010 has potent in vitro and in vivo activities against RET and RET-GKm, suggesting the potential usefulness of the compound for targeted therapy of cancers with RET gene rearrangements and mutations. Moreover, its potential effectiveness against acquired MTKI-resistant cells was also demonstrated. We are currently performing investigational new drug-enabling studies of DS-5010.

Citation Format: Yasuyuki Kaneta, Takahiro Komatsu, Masashi Miyamoto, Megumi Goto, Hidenori Namiki, Yoshihiro Shibata, Hideaki Kageji, Hiroaki Inagaki, Kiyoshi Nakayama, Yuichi Tominaga, Takeshi Isoyama. Preclinical characterization and antitumor efficacy of DS-5010, a highly potent and selective RET inhibitor [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr B173.

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.

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.

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 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."

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.

Selective cytotoxicity of adriamycin immunoconjugate of monoclonal antibody MSN-1 to endometrial adenocarcinoma in vitro and in vivo

Missile therapy, which destroys cancer cells specifically, has been regarded as an effective treatment modality for carcinoma. The monoclonal antibody MSN-1 (IgM), which reacts strongly with endometrial adenocarcinomas, was combined with adriamycin (ADM) by a disulfide bond using N-succinimidyl-3-(2-pyridyldithio) propionate (SPDP) and 2-iminothiolane. Its selective cytotoxicity against SNG-II was examined in a colony formation in vitro, and on athymic mice in vivo. The results of our study suggest that the <inhibitory concentration> or IC50, of the MSN-1-ADM immunoconjugate against SNG-II to be 57 times that of ADM alone in vitro. The reductions in resected weights of target tumor cells, at the local site of the MSN-1-ADM immunoconjugate treatment, were 25% with caudal vein administration, and 38% with local administration, as compared with the untreated group, in vivo. There was no weight loss in treated mice. Our results suggest that this MSN-1-ADM immunoconjugate has potential clinical application in the treatment of endometrial adenocarcinomas.

Gestational choriocarcinoma whose responsible pregnancy was a complete hydatidiform mole identified by PCR analysis with new sequence tagged site primers

We report a case where the pregnancy responsible for a gestational choriocarcinoma was not the antecedent pregnancy or the second normal term delivery, but a complete hydatidiform mole that had advanced to clinically invasive mole. This responsible pregnancy was identified by polymerase chain reaction analysis (PCR). PCR analysis was performed by using five new sets of sequence-tagged site (STS) primers on four chromosomes (chr. 1, D1S225; chr. 3, D3S1744; chr. 12, D12S1090; chr. 18, D18S849 and D18S877). The constitution of alleles of choriocarcinoma was shown to be almost identical with that of the husband on every marker. The allele patterns of choriocarcinoma on D3S1744 and D12S1090 were not observed with DNA from the patient. The band pattern originating from molar DNA was also identical with those of the husband and choriocarcinomas on D18S849 and D1S225.

Survey of Cryptosporidium oocysts from adult cattle in a slaughter house

Cryptosporidian oocysts were surveyed in rectal stools of adult cattle which were carried into slaughterhouse from April 1995 to July 1996. We morphologically and histologically investigated oocysts, and experimentally infected the isolated oocysts to mice and rats. Cryptosporidian oocysts were detected from 24 of 512 cattle (4.7%). They were spherical or ovoid, and the size was 7.0-7.9 x 5.3-6.1 microm. Mice and rats inoculated orally with 10(5)-10(7) oocysts became infected and discharged oocysts in the feces for a period of more than two months. Developing parasites were detected from the stomach of mice, and not detected from the other digestive tract. From these findings, present isolates from cattle were identified as Cryptosporidium muris.

Effect of gelonin immunoconjugate with monoclonal antibody MSN-1 to endometrial adenocarcinoma on antigen-producing tumor cells in vivo

Missile therapy, which destroys cancer cells specifically, has been advocated as an effective modality for the treatment of carcinoma. We have developed an immunoconjugate consisting of the monoclonal antibody MSN-1 (IgM), which reacts strongly with endometrial adenocarcinomas, combined with a plant hemitoxin named gelonin via a disulfide bond using N-succinimidyl-3-(2-pyridyldithio) propionate and 2-iminothiolane, and examined its selective cytotoxicity in athymic mice. The reductions in resected weights of target tumor cells, at the local site of MSN-1-gelonin immunoconjugate treatment, were 96% with local administration and 75% with caudal vein administration, as compared with the untreated group. There was no weight loss in treated mice. Our results suggest that this MSN-1-gelonin immunoconjugate has potential clinical applications in the treatment of endometrial adenocarcinomas.

Effects of gelonin immunoconjugate of monoclonal antibody MSN-1 to endometrial adenocarcinoma on antigen-producing tumor cells in vitro

Missile therapy, which destroys cancer cells specifically, has been considered to be an effective modality for treatment of carcinoma. We have developed a monoclonal antibody MSN-1 (immunoglobulin class: IgM), of which the immunogen is the endometrial adenocarcinoma cell line SNG-II, which strongly reacts with endometrial adenocarcinomas. We describe an immunoconjugate consisting of the MSN-1 and a plant hemitoxin named gelonin which has revealed to assume selective cytotoxicity against the SNG-II in a colony formation assay in vitro. The results of our study suggest that the 'inhibitory concentration' or IC50, of the MSN-1-gelonin immunoconjugate against the SNG-II was 188 fold that of gelonin alone. These results indicated that the MSN-1-gelonin immunoconjugate exhibited highly selective cytotoxicity to endometrial adenocarcinoma, which expressed an epitope against the MSN-1, and it is suggested that the MSN-1-gelonin immunoconjugate has possibility of clinical application to treatment of endometrial adenocarcinomas.

[Characterization of anti human uterine endometrial cancer antibody (MSN-1) and its usefulness in clinical application]

We have produced a monoclonal antibody (MSN-1), by using our endometrial cancer-cultured cell line (SNG-II) as an immunogen. MSN-1 belongs to the IgM immunoglobulin class and mainly recognized the Lewis carbohydrate moiety. It seldom, reacted immunohistochemically with normal endometrium but with about 90% of endometrial cancer cases. So, we evaluated the effectiveness of its use in clinical application. We studied the relationship between the stage of cancer and reactivity to MSN-1, and that between the reactivity of moderately differentiated endometrial cancer to MSN-1 and a 5-year survival rate. Endometrial cancer with a poor prognosis tended to react poorly to MSN-1, suggesting the possibility that the reactivity to MSN-1 is useful as a new prognostic factor. A study of endometrial hyperplasia revealed that the reactivity to MSN-1 was high in the high risk group (individuals diagnosed as endometrial cancer later). This suggested that the analysis of the expression of the antigen recognized by MSN-1 is useful in selecting the high risk group out of patients with endometrial hyperplasia. Furthermore, we indicated that abnormal expression of the antigen recognized by MSN-1 associated with neoplasia of endometrial cells is useful in developing a new diagnostic method for example our endometrial cell enzyme immunoassay (EmC-EIA) and will be helpful in developing diagnostic approaches, such as missile therapy with a complex of MSN-1 and adriamycin for endometrial cancer.

Lipid analysis of Helicobacter pylori

Lipids from Helicobacter pylori were extracted, isolated by conventional DEAE-Sephadex and silica gel column chromatography, and then purified by preparative thin-layer chromatography. Simple and phospholipids were analyzed by HPTLC and quantitatively determined by densitometry scanning. The fatty acid compositions of simple lipids were estimated by gas-liquid chromatography. The simple lipid composition of H. pylori consisted of wax ester (2.5%), triglycerides (4.9%), free fatty acids (30.0%), cholesterol (6.9%), diacylglycerol (29.1%), and monoacylglycerol (2.6%). The neutral phospholipid composition consisted of phosphatidyl ethanolamine (79.1%), lysophosphatidyl ethanolamine (16%), and phosphatidyl choline (1.9%). That of acidic phospholipids consisted of phosphatidic acid (52.7%) and phosphatidyl serine (47.3%). The major fatty acids of crude lipid, wax, free fatty acids, triglycerides, diacylglycerides, and monoacyl glycerides were C19:1 (cyclo), C18:2, C16:0, C19:1 (cyclo), C22h:0, and C18:0, respectively. These results are new findings and suggest significant characteristics from the metabolic, physiologic, and chemotaxonomic point of view.