Synthesis, activity, and their relationships of 2,4-diaminonicotinamide derivatives as EGFR inhibitors targeting C797S mutation.

The C797S mutation is one of the major factors behind resistance to the third-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors. Herein, we describe the discovery of the 2,4-diaminonicotinamide derivative 5j, which shows potent inhibitory activity against EGFR del19/T790M/C797S and L858R/T790M/C797S. We also report the structure-activity relationship of the 2,4-diaminonicotinamide derivatives and the co-crystal structure of 5j and EGFR del19/T790M/C797S.

Discovery of DS-9300: A Highly Potent, Selective, and Once-Daily Oral EP300/CBP Histone Acetyltransferase Inhibitor.

Histone acetylation is a post-translational modification of histones that is catalyzed by histone acetyltransferases (HATs) and plays an essential role in cellular processes. The HAT domain of EP300/CBP has recently emerged as a potential drug target for cancer therapy. Here, we describe the identification of the novel, highly potent, and selective EP300/CBP HAT inhibitor DS-9300. Our optimization efforts using a structure-based drug design approach based on the cocrystal structures of the EP300 HAT domain in complex with compounds 2 and 3 led to the identification of compounds possessing low-nanomolar EP300 HAT inhibitory potency and the ability to inhibit cellular acetylation of histone H3K27. Optimization of the pharmacokinetic properties in this series resulted in compounds with excellent oral systemic exposure, and once-daily oral administration of 16 (DS-9300) demonstrated potent antitumor effects in a castrated VCaP xenograft mouse model without significant body weight loss.

Discovery of EP300/CBP histone acetyltransferase inhibitors through scaffold hopping of 1,4-oxazepane ring.

EP300 and its paralog CBP play an important role in post-translational modification as histone acetyltransferases (HATs). EP300/CBP inhibition has been gaining attention as an anticancer treatment target in recent years. Herein, we describe the identification of a novel, highly selective EP300/CBP inhibitor, compound 11 (DS17701585), by scaffold hopping and structure-based optimization of a high-throughput screening hit 1. Compound 11 (DS17701585) shows dose-dependent inhibition of SRY-box transcription factor 2 (SOX2) mRNA expression in a human lung squamous cell carcinoma cell line LK2-xenografted mouse model.

U.S. Phase I First-in-human Study of Taletrectinib (DS-6051b/AB-106), a ROS1/TRK Inhibitor, in Patients with Advanced Solid Tumors.

PURPOSE: Taletrectinib (DS-6051b/AB-106) is an oral, tyrosine kinase inhibitor of ROS1 and NTRK with potent preclinical activity against ROS1 G2032R solvent-front mutation among others. We report the first-in-human U.S. phase I results of taletrectinib. PATIENTS AND METHODS: Patients ≥18 years old with neuroendocrine tumors, with tumor-induced pain, or tumors harboring ROS1/NTRK rearrangements were eligible. Accelerated titration followed by modified continuous reassessment method and escalation with overdose control was used (50-1,200 mg once daily or 400 mg twice daily). Primary objectives were safety/tolerability, and MTD determination. Secondary objectives were food-effect pharmacokinetics and antitumor activity. RESULTS: A total of 46 patients were enrolled. Steady-state peak concentration (C max) and exposure (AUC0-8) increased dose dependently from 50-mg to 800-mg once-daily doses. The ratio of the geometric mean of AUC0-24 between low-fat-diet-fed/fasted state was 123% (90% confidence interval, 104%-149%). Dose-limiting toxicities (grade 3 transaminases increase) occurred in two patients (1,200-mg once-daily dose). MTD was 800 mg once daily. Most common treatment-related adverse events were nausea (47.8%), diarrhea (43.5%), and vomiting (32.6%). Pain score reductions were observed in the 800-mg once-daily dose cohort. Confirmed objective response rate was 33.3% among the six patients with RECIST-evaluable crizotinib-refractory ROS1+ NSCLC. One patient with TPM3-NTRK1 differentiated thyroid cancer achieving a confirmed partial response of 27 months at data cutoff. We identified a cabozantinib-sensitive ROS1 L2086F as an acquired taletrectinib-resistance mutation. CONCLUSIONS: Taletrectinib has manageable toxicities at the MTD of 800 mg daily. Preliminary efficacy was observed in patients with crizotinib-refractory ROS1+ NSCLC.

Quizartinib, a selective FLT3 inhibitor, maintains antileukemic activity in preclinical models of RAS-mediated midostaurin-resistant acute myeloid leukemia cells.

FLT3 internal tandem duplication (ITD) mutations are associated with poor prognosis in patients with acute myeloid leukemia (AML). In this preclinical study, we characterized the binding affinity and selectivity of quizartinib, a small-molecule inhibitor of FLT3, and AC886, the active metabolite of quizartinib, compared with those of other FLT3 inhibitors. Selectivity profiling against >400 kinases showed that quizartinib and AC886 were highly selective against FLT3. Quizartinib and AC886 inhibited FLT3 signaling pathways in FLT3-ITD-mutated AML cells, leading to potent growth inhibition with IC50 values of <1 nM. When quizartinib was administered to mice bearing FLT3-ITD mutated tumors, AC886 was rapidly detected and tumor regression was observed at doses of ≥1 mg/kg without severe body weight loss. In addition, quizartinib inhibited the viability of midostaurin-resistant MOLM-14 cells and exerted potent antitumor activity in mouse xenograft models without severe body weight loss, while midostaurin and gilteritinib did not show significant antitumor effects. This is the first detailed characterization of quizartinib and AC886 in comparison with other FLT3 inhibitors under the same experimental conditions. Preclinical antileukemic activity in midostaurin-resistant FLT3-ITD-mutated AML cells suggests the potential value of quizartinib following midostaurin failure in patients with FLT3-ITD mutated AML.

DS-1205b, a novel selective inhibitor of AXL kinase, blocks resistance to EGFR-tyrosine kinase inhibitors in a non-small cell lung cancer xenograft model.

The AXL receptor tyrosine kinase is involved in signal transduction in malignant cells. Recent studies have shown that the AXL upregulation underlies epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI) resistance in EGFR-mutant non-small cell lung cancer (NSCLC). In this study, we investigated the effect of DS-1205b, a novel and selective inhibitor of AXL, on tumor growth and resistance to EGFR TKIs. In AXL-overexpressing NIH3T3 cells, DS-1205b potently inhibited hGAS6 ligand-induced migration in vitro and exerted significant antitumor activity in vivo. AXL was upregulated by long-term erlotinib or osimertinib treatment in HCC827 EGFR-mutant NSCLC cells, and DS-1205b treatment in combination with osimertinib or erlotinib effectively inhibited signaling downstream of EGFR in a cell-based assay. In an HCC827 EGFR-mutant NSCLC xenograft mouse model, combination treatment with DS-1205b and erlotinib significantly delayed the onset of tumor resistance compared to erlotinib monotherapy, and DS-1205b restored the antitumor activity of erlotinib in erlotinib-resistant tumors. DS-1205b also delayed the onset of resistance when used in combination with osimertinib in the model. These findings strongly suggest that DS-1205b can prolong the therapeutic benefit of EGFR TKIs in nonclinical as well as clinical settings.

The new-generation selective ROS1/NTRK inhibitor DS-6051b overcomes crizotinib resistant ROS1-G2032R mutation in preclinical models.

ROS1 gene rearrangement was observed in around 1-2 % of NSCLC patients and in several other cancers such as cholangiocarcinoma, glioblastoma, or colorectal cancer. Crizotinib, an ALK/ROS1/MET inhibitor, is highly effective against ROS1-rearranged lung cancer and is used in clinic. However, crizotinib resistance is an emerging issue, and several resistance mechanisms, such as secondary kinase-domain mutations (e.g., ROS1-G2032R) have been identified in crizotinib-refractory patients. Here we characterize a new selective ROS1/NTRK inhibitor, DS-6051b, in preclinical models of ROS1- or NTRK-rearranged cancers. DS-6051b induces dramatic growth inhibition of both wild type and G2032R mutant ROS1-rearranged cancers or NTRK-rearranged cancers in vitro and in vivo. Here we report that DS-6051b is effective in treating ROS1- or NTRK-rearranged cancer in preclinical models, including crizotinib-resistant ROS1 positive cancer with secondary kinase domain mutations especially G2032R mutation which is highly resistant to crizotinib as well as lorlatinib and entrectinib, next generation ROS1 inhibitors.

A novel inhibitor stabilizes the inactive conformation of MAPK-interacting kinase 1.

Mitogen-activated protein kinase (MAPK)-interacting kinases 1 (Mnk1) and 2 (Mnk2) modulate translation initiation through the phosphorylation of eukaryotic translation initiation factor 4E, which promotes tumorigenesis. However, Mnk1 and Mnk2 are dispensable in normal cells, suggesting that the inhibition of Mnk1 and Mnk2 could be effective in cancer therapy. To provide a structural basis for Mnk1 inhibition, a novel Mnk1 inhibitor was discovered and the crystal structure of Mnk1 in complex with this inhibitor was determined. The crystal structure revealed that the inhibitor binds to the autoinhibited state of Mnk1, stabilizing the Mnk-specific DFD motif in the DFD-out conformation, thus preventing Mnk1 from switching to the active conformation and thereby inhibiting the kinase activity. These results provide a valuable platform for the structure-guided design of Mnk1 inhibitors.

NTRK3 kinase fusions in Spitz tumours.

Oncogenic fusions in TRK family receptor tyrosine kinases have been identified in several cancers and can serve as therapeutic targets. We identified ETV6-NTRK3, MYO5A-NTRK3 and MYH9-NTRK3 fusions in Spitz tumours, and demonstrated that NTRK3 fusions constitutively activate the mitogen-activated protein kinase, phosphoinositide 3-kinase and phospholipase Cγ1 pathways in melanocytes. This signalling was inhibited by DS-6051a, a small-molecule inhibitor of NTRK1/2/3 and ROS1. NTRK3 fusions expand the range of oncogenic kinase fusions in melanocytic neoplasms and offer targets for a small subset of melanomas for which no targeted options currently exist. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Anti-tumour activity of CS-7017, a selective peroxisome proliferator-activated receptor gamma agonist of thiazolidinedione class, in human tumour xenografts and a syngeneic tumour implant model.

The anti-tumour activity of the novel thiazolidinedione class peroxisome proliferator-activated receptor gamma (PPARgamma) agonist CS-7017 was investigated. CS-7017 activated PPARgamma-mediated luciferase expression with an EC(50) of 0.20 nM. In addition, CS-7017 was shown to be highly selective for PPARgamma amongst other PPAR subfamilies. CS-7017 inhibited the proliferation of the human anaplastic thyroid tumour cell line DRO and the pancreatic tumour cell line AsPC-1 in vitro at concentrations as low as 10 nM. In xenograft studies, CS-7017 inhibited the growth of the human colorectal tumour cell line HT-29 in nude mice as well as DRO in nude rats in a dose-dependent manner. At the same dose, an increase in the levels of adiponectin, a surrogate marker for PPARgamma activation, was also observed. CS-7017 prolonged the survival of mice inoculated with murine colorectal tumour Colon 38 with marginal tumour growth inhibition. These preclinical results support the potential utility of CS-7017 in a clinical setting.

The core protein of hepatitis C virus is imported into the nucleus by transport receptor Kap123p but inhibits Kap121p-dependent nuclear import of yeast AP1-like transcription factor in yeast cells.

The core protein of hepatitis C virus (HCV) is a major component of the viral nucleocapsid. The HCV core protein includes nuclear localization signal-like sequences and has various effects on cellular metabolism, playing roles, for example, in the regulation of transcription, apoptosis, and transformation. To examine the possibility of an effect of the core protein on nucleocytoplasmic transport, we used the yeast Saccharomyces cerevisiae as a model system. The core protein (p23) is processed to p21 and is localized in both the cytoplasm and nucleus in yeast cells, similar to that observed in mammalian cells in several cases. The nuclear import of the core protein requires the activity of small GTPase Ran/Gsp1p and is mediated by Kap123p in yeast cells. When the core protein was expressed in yeast cells, the import of the yeast AP1-like transcription factor Yap1p into the nucleus was inhibited. Experiments in vitro involving Kap121p, also known as Pse1p, a receptor for the nuclear import of Yap1p, indicated that the amount of Yap1p bound to Kap121p was reduced in the presence of core protein. These results suggest that the HCV core protein affects cellular metabolism by disturbing transport of proteins to the nucleus.

Lower concentration of La protein required for internal ribosome entry on hepatitis C virus RNA than on poliovirus RNA.

Translation initiation of poliovirus and hepatitis C virus (HCV) RNA occurs by entry of ribosomes to the internal RNA sequence, called the internal ribosomal entry site (IRES). Both IRES bind to the La protein and are thought to require the protein for their translation initiation activity, although they are greatly different in both the primary and predicted secondary structures. To compare the La protein requirement for these IRES, we took advantage of I-RNA from the yeast Saccharomyces cerevisiae, which has been reported to bind to La protein and block poliovirus IRES-mediated translation initiation. In a cell-free translation system prepared from HeLa cells, yeast I-RNA inhibited translation initiation on poliovirus RNA as expected, but did not significantly inhibit translation initiation on HCV RNA. However, the translation initiation directed by either IRES was apparently inhibited by I-RNA in rabbit reticulocyte lysates, in which La protein is limiting. I-RNA-mediated inhibition of HCV IRES-dependent translation in rabbit reticulocyte lysates was reversed by exogenous addition of purified recombinant La protein of smaller amounts than necessary to reverse poliovirus IRES-dependent translation. These results suggest that HCV IRES requires lower concentrations of La protein for its function than does poliovirus IRES. Immunofluorescence studies showed that HCV infection appeared not to affect the subcellular localization of La protein, which exists mainly in the nucleus, although La protein redistributed to the cytoplasm after poliovirus infection. The data are compatible with the low requirement of La protein for HCV IRES activity.