Tomohiro Kawamoto

TAK-242 selectively suppresses Toll-like receptor 4-signaling mediated by the intracellular domain

TAK-242, a small-molecule antisepsis agent, has shown to suppress lipopolysaccharide (LPS)-induced inflammation. In this study, we demonstrate that TAK-242 is a selective inhibitor of Toll-like receptor (TLR)-4 signaling. TAK-242 almost completely suppressed production of nitric oxide (NO) or tumor necrosis factor (TNF)-alpha induced by a TLR4-specific ligand, ultra-pure LPS, in mouse RAW264.7, human U-937 and P31/FUJ cells, whereas this agent showed little effect on other TLR ligands, Pam(3)CSK(4) (TLR1/2), peptidoglycan (TLR2/6), double strand RNA (TLR3), R-848 (TLR7) and CpG oligonucleotide (TLR9). Furthermore, TAK-242 potently inhibited nuclear factor (NF)-kappaB activation induced by ultra-pure LPS in HEK293 cells transiently expressing TLR4 and co-receptors, myeloid differentiation protein-2 (MD2) and CD14, whereas this agent showed little effect on other TLRs, TLR1/2, TLR2/6, TLR3, TLR5, TLR7 and TLR9. TAK-242 also inhibited ligand-independent NF-kappaB activation resulting from over-expression of TLR4. Although chimera receptors, which are consist of the extracellular domain of CD4 and the intracellular domain of human or mouse TLR4, showed constitutive NF-kappaB activation, TAK-242 potently inhibited the signaling from CD4-TLR4 chimera receptors. In contrast, the NF-kappaB activation mediated by TLR4 adaptors, myeloid differentiation factor 88 (MyD88), TIR-associated protein (TIRAP), Toll/IL-1R homology (TIR)-domain-containing adaptor protein-inducing interferon-beta (TRIF) or TRIF-related adaptor molecule (TRAM) was not affected by TAK-242. TAK-242 is therefore a selective inhibitor of signaling from the intracellular domain of TLR4 and represents a novel therapeutic approach to the treatment of TLR4-mediated diseases.

2-{3-[4-(Alkylsulfinyl)phenyl]-1-benzofuran-5-yl}-5-methyl-1,3,4-oxadiazole derivatives as novel inhibitors of glycogen synthase kinase-3beta with good brain permeability.

Glycogen synthase kinase 3beta (GSK-3beta) inhibition is expected to be a promising therapeutic approach for treating Alzheimers disease. Previously we reported a series of 1,3,4-oxadiazole derivatives as potent and highly selective GSK-3beta inhibitors, however, the representative compounds 1a,b showed poor pharmacokinetic profiles. Efforts were made to address this issue by reducing molecular weight and lipophilicity, leading to the identification of oxadiazole derivatives containing a sulfinyl group, (S)-9b and (S)-9c. These compounds exhibited not only highly selective and potent inhibitory activity against GSK-3beta but also showed good pharmacokinetic profiles including favorable BBB penetration. In addition, (S)-9b and (S)-9c given orally to mice significantly inhibited cold water stress-induced tau hyperphosphorylation in mouse brain.

Design, synthesis and structure-activity relationships of 1,3,4-oxadiazole derivatives as novel inhibitors of glycogen synthase kinase-3beta.

Glycogen synthase kinase-3beta (GSK-3beta) is implicated in abnormal hyperphosphorylation of tau protein and its inhibitors are expected to be a promising therapeutic agents for the treatment of Alzheimers disease. Here we report design, synthesis and structure-activity relationships of a novel series of oxadiazole derivatives as GSK-3beta inhibitors. Among these inhibitors, compound 20x showed highly selective and potent GSK-3beta inhibitory activity in vitro and its binding mode was determined by obtaining the X-ray co-crystal structure of 20x and GSK-3beta.

TAK-960, a Novel, Orally Available, Selective Inhibitor of Polo-Like Kinase 1, Shows Broad-spectrum Preclinical Antitumor Activity in Multiple Dosing Regimens

Polo-like kinase 1 (PLK1) is a serine/threonine protein kinase involved in key processes during mitosis. Human PLK1 has been shown to be overexpressed in various human cancers, and elevated levels of PLK1 have been associated with poor prognosis, making it an attractive target for anticancer therapy. TAK-960 [4-[(9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino]-2-fluoro-5-methoxy-N-(1-methylpiperidin-4-yl) benzamide] is a novel, investigational, orally bioavailable, potent, and selective PLK1 inhibitor that has shown activity in several tumor cell lines, including those that express multidrug-resistant protein 1 (MDR1). Consistent with PLK1 inhibition, TAK-960 treatment caused accumulation of G2–M cells, aberrant polo mitosis morphology, and increased phosphorylation of histone H3 (pHH3) in vitro and in vivo. TAK-960 inhibited proliferation of multiple cancer cell lines, with mean EC50 values ranging from 8.4 to 46.9 nmol/L, but not in nondividing normal cells (EC50 >1,000 nmol/L). The mutation status of TP53 or KRAS and MDR1 expression did not correlate with the potency of TAK-960 in the cell lines tested. In animal models, oral administration of TAK-960 increased pHH3 in a dose-dependent manner and significantly inhibited the growth of HT-29 colorectal cancer xenografts. Treatment with once daily TAK-960 exhibited significant efficacy against multiple tumor xenografts, including an adriamycin/paclitaxel-resistant xenograft model and a disseminated leukemia model. TAK-960 has entered clinical evaluation in patients with advanced cancers. Mol Cancer Ther; 11(3); 700–9. ©2011 AACR.

Discovery of potent Mcl-1/Bcl-xL dual inhibitors by using a hybridization strategy based on structural analysis of target proteins.

Mcl-1 and Bcl-xL are crucial regulators of apoptosis, therefore dual inhibitors of both proteins could serve as promising new anticancer drugs. To design Mcl-1/Bcl-xL dual inhibitors, we performed structure-guided analyses of the corresponding selective Mcl-1 and Bcl-xL inhibitors. A cocrystal structure of a pyrazolo[1,5-a]pyridine derivative with Mcl-1 protein was successfully determined and revealed the protein-ligand binding mode. The key structure for Bcl-xL inhibition was further confirmed through the substructural analysis of ABT-263, a representative Bcl-xL/Bcl-2/Bcl-w inhibitor developed by Abbott Laboratories. On the basis of the structural data from this analysis, we designed hybrid compounds by tethering the Mcl-1 and Bcl-xL inhibitors together. The results of X-ray crystallographic analysis of hybrid compound 10 in complexes with both Mcl-1 and Bcl-xL demonstrated its binding mode with each protein. Following further optimization, compound 11 showed potent Mcl-1/Bcl-xL dual inhibitory activity (Mcl-1, IC50 = 0.088 μM; and Bcl-xL, IC50 = 0.0037 μM).

Discovery of a Selective Kinase Inhibitor (TAK-632) Targeting Pan-RAF Inhibition: Design, Synthesis, and Biological Evaluation of C-7-Substituted 1,3-Benzothiazole Derivatives.

With the aim of discovering a selective kinase inhibitor targeting pan-RAF kinase inhibition, we designed novel 1,3-benzothiazole derivatives based on our thiazolo[5,4-b]pyridine class RAF/VEGFR2 inhibitor 1 and developed a regioselective cyclization methodology for the C-7-substituted 1,3-benzothiazole scaffold utilizing meta-substituted anilines. Eventually, we selected 7-cyano derivative 8B (TAK-632) as a development candidate and confirmed its binding mode by cocrystal structure with BRAF. Accommodation of the 7-cyano group into the BRAF-selectivity pocket and the 3-(trifluoromethyl)phenyl acetamide moiety into the hydrophobic back pocket of BRAF in the DFG-out conformation contributed to enhanced RAF potency and selectivity vs VEGFR2. Reflecting its potent pan-RAF inhibition and slow off-rate profile, 8B demonstrated significant cellular activity against mutated BRAF or mutated NRAS cancer cell lines. Furthermore, in both A375 (BRAF(V600E)) and HMVII (NRAS(Q61K)) xenograft models in rats, 8B demonstrated regressive antitumor efficacy by twice daily, 14-day repetitive administration without significant body weight loss.

Discovery, synthesis and biological evaluation of isoquinolones as novel and highly selective JNK inhibitors (2)

A novel series of 4-phenylisoquinolones were synthesized and evaluated as c-Jun N-terminal kinase (JNK) inhibitors. Initial modification at the 2- and 3-positions of the isoquinolone ring of hit compound 4, identified from high-throughput screening, led to the lead compound 6b. The optimization was carried out using a JNK1-binding model of 6b and several compounds exhibited potent JNK inhibition. Among them, 11g significantly inhibited cardiac hypertrophy in rat pressure-overload models without affecting blood pressure and the concept of JNK inhibitors as novel therapeutic agents for heart failure was confirmed.

Aneuploidy generates proteotoxic stress and DNA damage concurrently with p53-mediated post-mitotic apoptosis in SAC-impaired cells

The molecular mechanism responsible that determines cell fate after mitotic slippage is unclear. Here we investigate the post-mitotic effects of different mitotic aberrations—misaligned chromosomes produced by CENP-E inhibition and monopolar spindles resulting from Eg5 inhibition. Eg5 inhibition in cells with an impaired spindle assembly checkpoint (SAC) induces polyploidy through cytokinesis failure without a strong anti-proliferative effect. In contrast, CENP-E inhibition causes p53-mediated post-mitotic apoptosis triggered by chromosome missegregation. Pharmacological studies reveal that aneuploidy caused by the CENP-E inhibitor, Compound-A, in SAC-attenuated cells causes substantial proteotoxic stress and DNA damage. Polyploidy caused by the Eg5 inhibitor does not produce this effect. Furthermore, p53-mediated post-mitotic apoptosis is accompanied by aneuploidy-associated DNA damage response and unfolded protein response activation. Because Compound-A causes p53 accumulation and antitumour activity in an SAC-impaired xenograft model, CENP-E inhibitors could be potential anticancer drugs effective against SAC-impaired tumours.

Design and synthesis of novel DFG-out RAF/vascular endothelial growth factor receptor 2 (VEGFR2) inhibitors. 1. Exploration of [5,6]-fused bicyclic scaffolds

To develop RAF/VEGFR2 inhibitors that bind to the inactive DFG-out conformation, we conducted structure-based drug design using the X-ray cocrystal structures of BRAF, starting from an imidazo[1,2-b]pyridazine derivative. We designed various [5,6]-fused bicyclic scaffolds (ring A, 1-6) possessing an anilide group that forms two hydrogen bond interactions with Cys532. Stabilizing the planarity of this anilide and the nitrogen atom on the six-membered ring of the scaffold was critical for enhancing BRAF inhibition. The selected [1,3]thiazolo[5,4-b]pyridine derivative 6d showed potent inhibitory activity in both BRAF and VEGFR2. Solid dispersion formulation of 6d (6d-SD) maximized its oral absorption in rats and showed significant suppression of ERK1/2 phosphorylation in an A375 melanoma xenograft model in rats by single administration. Tumor regression (T/C = -7.0%) in twice-daily repetitive studies at a dose of 50 mg/kg in rats confirmed that 6d is a promising RAF/VEGFR2 inhibitor showing potent anticancer activity.

Design and biological evaluation of imidazo[1,2-a]pyridines as novel and potent ASK1 inhibitors

Imidazo[1,2-a]pyridine derivatives were designed, synthesized, and evaluated as inhibitors of the apoptosis signal-regulating kinase 1 (ASK1). These were based on a benzothiazole derivative that was discovered from high-throughput screening of our compound library. As a result, we identified potent, selective, and orally bioavailable ASK1 inhibitors for wide range of therapeutic targets.