Lineage of drug discovery research on fluorinated pyrimidines: chronicle of the achievements accomplished by Professor Setsuro Fujii.

Prof. Setsuro Fujii achieved significant results in the field of drug discovery research in Japan. He developed nine well-known drugs: FT, UFT, S-1 and FTD/TPI are anticancer drugs, while cetraxate hydrochloride, camostat mesilate, nafamostat mesilate, gabexate mesilate and pravastatin sodium are therapeutic drugs for various other diseases. He delivered hope to patients with various diseases across the world to improve their condition. Even now, drug discovery research based on Dr. Fujii's ideas is continuing.

Activity of TAS4464, a novel NEDD8 activating enzyme E1 inhibitor, against multiple myeloma via inactivation of nuclear factor κB pathways.

The ubiquitin proteasome pathway is essential for the proliferation and survival of multiple myeloma (MM) cells. TAS4464, a novel highly potent inhibitor of NEDD8 activating enzyme, selectively inactivates cullin-RING ubiquitin E3 ligases, resulting in accumulation of their substrates. Here, we examined 14 MM cell lines treated with TAS4464. TAS4464 induced growth arrest and cell death in the MM cell lines even in the presence of bone marrow stromal cells. It also induced the accumulation of phospho-inhibitor of κBα and phospho-p100, impaired the activities of nuclear factor κB (NF-κB) transcription factors p65 and RelB, and decreased the expression of NF-κB target genes, suggesting that TAS4464 inhibits both the canonical and non-canonical NF-κB pathways. TAS4464 had similar effects in an in vivo human-MM xenograft mouse model in which it was also observed to have strong antitumor effects. TAS4464 synergistically enhanced the antitumor activities of the standard MM chemotherapies bortezomib, lenalidomide/dexamethasone, daratumumab and elotuzumab. Together, these results suggest that the anti-MM activity of TAS4464 occurs via inhibition of the NF-κB pathways, and that treatment with TAS4464 is a potential approach for treating MM by single and combination therapies.

The anti-tumor effect of trifluridine via induction of aberrant mitosis is unaffected by mutations modulating p53 activity.

The fluorinated thymidine analog trifluridine (FTD) is a chemotherapeutic drug commonly used to treat cancer; however, the mechanism by which FTD induces cytotoxicity is not fully understood. In addition, the effect of gain-of-function (GOF) missense mutations of the TP53 gene (encoding p53), which promote cancer progression and chemotherapeutic drug resistance, on the chemotherapeutic efficacy of FTD is unclear. Here, we revealed the mechanisms by which FTD-induced aberrant mitosis and contributed to cytotoxicity in both p53-null and p53-GOF missense mutant cells. In p53-null mutant cells, FTD-induced DNA double-stranded breaks, single-stranded DNA accumulation, and the associated DNA damage responses during the G2 phase. Nevertheless, FTD-induced DNA damage and the related responses were not sufficient to trigger strict G2/M checkpoint arrest. Thus, these features were carried over into mitosis, resulting in chromosome breaks and bridges, and subsequent cytokinesis failure. Improper mitotic exit eventually led to cell apoptosis, caused by the accumulation of extensive DNA damage and the presence of micronuclei encapsulated in the disrupted nuclear envelope. Upon FTD treatment, the behavior of the p53-GOF-missense mutant, isogenic cell lines, generated by CRISPR/Cas9 genome editing, was similar to that of p53-null mutant cells. Thus, our data suggest that FTD treatment overrode the effect on gene expression induced by p53-GOF mutants and exerted its anti-tumor activity in a manner that was independent of the p53 function.

Fragment-Based Discovery of Allosteric Inhibitors of SH2 Domain-Containing Protein Tyrosine Phosphatase-2 (SHP2).

The ubiquitously expressed protein tyrosine phosphatase SHP2 is required for signaling downstream of receptor tyrosine kinases (RTKs) and plays a role in regulating many cellular processes. Genetic knockdown and pharmacological inhibition of SHP2 suppresses RAS/MAPK signaling and inhibit the proliferation of RTK-driven cancer cell lines. Here, we describe the first reported fragment-to-lead campaign against SHP2, where X-ray crystallography and biophysical techniques were used to identify fragments binding to multiple sites on SHP2. Structure-guided optimization, including several computational methods, led to the discovery of two structurally distinct series of SHP2 inhibitors binding to the previously reported allosteric tunnel binding site (Tunnel Site). One of these series was advanced to a low-nanomolar lead that inhibited tumor growth when dosed orally to mice bearing HCC827 xenografts. Furthermore, a third series of SHP2 inhibitors was discovered binding to a previously unreported site, lying at the interface of the C-terminal SH2 and catalytic domains.

TAS4464, a NEDD8-activating enzyme inhibitor, activates both intrinsic and extrinsic apoptotic pathways via c-Myc-mediated regulation in acute myeloid leukemia.

TAS4464, a potent, selective small molecule NEDD8-activating enzyme (NAE) inhibitor, leads to inactivation of cullin-RING E3 ubiquitin ligases (CRLs) and consequent accumulations of its substrate proteins. Here, we investigated the antitumor properties and action mechanism of TAS4464 in acute myeloid leukemia (AML). TAS4464 induced apoptotic cell death in various AML cell lines. TAS4464 treatments resulted in the activation of both the caspase-9-mediated intrinsic apoptotic pathway and caspase-8-mediated extrinsic apoptotic pathway in AML cells; combined treatment with inhibitors of these caspases markedly diminished TAS4464-induced apoptosis. In each apoptotic pathway, TAS4464 induced the mRNA transcription of the intrinsic proapoptotic factor NOXA and decreased that of the extrinsic antiapoptotic factor c-FLIP. RNA-sequencing analysis showed that the signaling pathway of the CRL substrate c-Myc was enriched after TAS4464 treatment. Chromatin immunoprecipitation (ChIP) assay revealed that TAS4464-induced c-Myc bound to the PMAIP1 (encoding NOXA) and CFLAR (encoding c-FLIP) promoter regions, and siRNA-mediated c-Myc knockdown neutralized both TAS4464-mediated NOXA induction and c-FLIP downregulation. TAS4464 activated both caspase-8 and caspase-9 along with an increase in NOXA and a decrease in c-FLIP, resulting in complete tumor remission in a human AML xenograft model. These findings suggest that NAE inhibition leads to anti-AML activity via a novel c-Myc-dependent apoptosis induction mechanism.

Futibatinib Is a Novel Irreversible FGFR 1-4 Inhibitor That Shows Selective Antitumor Activity against FGFR-Deregulated Tumors.

FGFR signaling is deregulated in many human cancers, and FGFR is considered a valid target in FGFR-deregulated tumors. Here, we examine the preclinical profile of futibatinib (TAS-120; 1-[(3S)-[4-amino-3-[(3,5-dimethoxyphenyl)ethynyl]-1H-pyrazolo[3, 4-d] pyrimidin-1-yl]-1-pyrrolidinyl]-2-propen-1-one), a structurally novel, irreversible FGFR1-4 inhibitor. Among a panel of 296 human kinases, futibatinib selectively inhibited FGFR1-4 with IC50 values of 1.4 to 3.7 nmol/L. Futibatinib covalently bound the FGFR kinase domain, inhibiting FGFR phosphorylation and, in turn, downstream signaling in FGFR-deregulated tumor cell lines. Futibatinib exhibited potent, selective growth inhibition of several tumor cell lines (gastric, lung, multiple myeloma, bladder, endometrial, and breast) harboring various FGFR genomic aberrations. Oral administration of futibatinib led to significant dose-dependent tumor reduction in various FGFR-driven human tumor xenograft models, and tumor reduction was associated with sustained FGFR inhibition, which was proportional to the administered dose. The frequency of appearance of drug-resistant clones was lower with futibatinib than a reversible ATP-competitive FGFR inhibitor, and futibatinib inhibited several drug-resistant FGFR2 mutants, including the FGFR2 V565I/L gatekeeper mutants, with greater potency than any reversible FGFR inhibitors tested (IC50, 1.3-50.6 nmol/L). These results indicate that futibatinib is a novel orally available, potent, selective, and irreversible inhibitor of FGFR1-4 with a broad spectrum of antitumor activity in cell lines and xenograft models. These findings provide a strong rationale for testing futibatinib in patients with tumors oncogenically driven by FGFR genomic aberrations, with phase I to III trials ongoing. SIGNIFICANCE: Preclinical characterization of futibatinib, an irreversible FGFR1-4 inhibitor, demonstrates selective and potent antitumor activity against FGFR-deregulated cancer cell lines and xenograft models, supporting clinical evaluation in patients with FGFR-driven tumors. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/80/22/4986/F1.large.jpg.

TAS4464, A Highly Potent and Selective Inhibitor of NEDD8-Activating Enzyme, Suppresses Neddylation and Shows Antitumor Activity in Diverse Cancer Models.

NEDD8-activating enzyme (NAE) is an essential E1 enzyme of the NEDD8 conjugation (neddylation) pathway, which controls cancer cell growth and survival through activation of cullin-RING ubiquitin ligase complexes (CRL). In this study, we describe the preclinical profile of a novel, highly potent, and selective NAE inhibitor, TAS4464. TAS4464 selectively inhibited NAE relative to the other E1s UAE and SAE. TAS4464 treatment inhibited cullin neddylation and subsequently induced the accumulation of CRL substrates such as CDT1, p27, and phosphorylated IκBα in human cancer cell lines. TAS4464 showed greater inhibitory effects than those of the known NAE inhibitor MLN4924 both in enzyme assay and in cells. Cytotoxicity profiling revealed that TAS4464 is highly potent with widespread antiproliferative activity not only for cancer cell lines, but also patient-derived tumor cells. TAS4464 showed prolonged target inhibition in human tumor xenograft mouse models; weekly or twice a week TAS4464 administration led to prominent antitumor activity in multiple human tumor xenograft mouse models including both hematologic and solid tumors without marked weight loss. As a conclusion, TAS4464 is the most potent and highly selective NAE inhibitor reported to date, showing superior antitumor activity with prolonged target inhibition. It is, therefore, a promising agent for the treatment of a variety of tumors including both hematologic and solid tumors. These results support the clinical evaluation of TAS4464 in hematologic and solid tumors.

The novel VEGF receptor/MET-targeted kinase inhibitor TAS-115 has marked in vivo antitumor properties and a favorable tolerability profile.

VEGF receptor (VEGFR) signaling plays a key role in tumor angiogenesis. Although some VEGFR signal-targeted drugs have been approved for clinical use, their utility is limited by associated toxicities or resistance to such therapy. To overcome these limitations, we developed TAS-115, a novel VEGFR and hepatocyte growth factor receptor (MET)-targeted kinase inhibitor with an improved safety profile. TAS-115 inhibited the kinase activity of both VEGFR2 and MET and their signal-dependent cell growth as strongly as other known VEGFR or MET inhibitors. On the other hand, kinase selectivity of TAS-115 was more specific than that of sunitinib and TAS-115 produced relatively weak inhibition of growth (GI50 > 10 µmol/L) in VEGFR signal- or MET signal-independent cells. Furthermore, TAS-115 induced less damage in various normal cells than did other VEGFR inhibitors. These data suggest that TAS-115 is extremely selective and specific, at least in vitro. In in vivo studies, TAS-115 completely suppressed the progression of MET-inactivated tumor by blocking angiogenesis without toxicity when given every day for 6 weeks, even at a serum-saturating dose of TAS-115. The marked selectivity of TAS-115 for kinases and targeted cells was associated with improved tolerability and contributed to the ability to sustain treatment without dose reduction or a washout period. Furthermore, TAS-115 induced marked tumor shrinkage and prolonged survival in MET-amplified human cancer-bearing mice. These data suggest that TAS-115 is a unique VEGFR/MET-targeted inhibitor with improved antitumor efficacy and decreased toxicity.