AMG 900, a small-molecule inhibitor of aurora kinases, potentiates the activity of microtubule-targeting agents in human metastatic breast cancer models

Exploration of the VEGFR-2 inhibition activity of phthalazine derivatives: design, synthesis, cytotoxicity, ADMET, molecular docking and dynamic simulation

Novel phthalazine derivatives were designed, synthesized and evaluated against Hep G2 and MCF-7 as VEGFR-2 inhibitors. In particular, compounds 2g and 4a were found to be the most potent derivatives among all the tested compounds against MCF-7 and Hep G2 cancer cell lines with IC50 values of 0.15 and 0.12 and 0.18 and 0.09 μM respectively. Moreover, compounds 3a, 3c, 5a and 5b displayed excellent anticancer activities against MCF-7 and Hep G2 cancer cell lines. The highly active derivatives 2g, 3a, 3c, 4a, 5a and 5b were evaluated for their inhibitory activities against VEGFR-2. The tested compounds displayed high to low inhibitory activities with IC50 values ranging from 0.148 to 0.892 μM. Among them, compounds 2g and 4a were found to be the most potent derivatives that inhibited VEGFR-2 with IC50 values of 0.148 and 0.196 μM respectively. Compounds 3a, 3c, 5a and 5b exhibited good activity with IC50 values of 0.375, 0.892, 0.548 and 0.331 μM respectively. Sorafenib was used as a reference drug in this study. Molecular modeling studies were carried out for all compounds against the VEGFR-2 active site. The data obtained from biological testing highly correlated with those obtained from molecular modeling studies. Moreover, MD simulation results indicated the stability of ligand-target interaction. Furthermore, our derivatives 2g and 4a showed a good in silico calculated ADMET profile.

Preclinical Evaluation of JAB-2485, a Potent AURKA Inhibitor with High Selectivity and Favorable Pharmacokinetic Properties

As a critical mitotic regulator, Aurora kinase A (AURKA) is aberrantly activated in a wide range of cancers. Therapeutic targeting of AUKRA is a promising strategy for the treatment of solid tumors. In this study, we evaluated the preclinical characteristics of JAB-2485, a small-molecule inhibitor of AURKA currently in Phase I/IIa clinical trial in the US (NCT05490472). Biochemical studies demonstrated that JAB-2485 is potent and highly selective on AURKA, with subnanomolar IC50 and around 1500-fold selectivity over AURKB or AURKC. In addition, JAB-2485 exhibited favorable pharmacokinetic properties featured by low clearance and good bioavailability, strong dose-response relationship, as well as low risk for hematotoxicity and off-target liability. As a single agent, JAB-2485 effectively induced G2/M cell cycle arrest and apoptosis and inhibited the proliferation of small cell lung cancer, triple-negative breast cancer, and neuroblastoma cells. Furthermore, JAB-2485 exhibited robust in vivo antitumor activity both as monotherapy and in combination with chemotherapies or the bromodomain inhibitor JAB-8263 in xenograft models of various cancer types. Together, these encouraging preclinical data provide a strong basis for safety and efficacy evaluations of JAB-2485 in the clinical setting.

Boosting edgeR (Robust) by dealing with missing observations and gene-specific outliers in RNA-Seq profiles and its application to explore biomarker genes for diagnosis and therapies of ovarian cancer

The edgeR (Robust) is a popular approach for identifying differentially expressed genes (DEGs) from RNA-Seq profiles. However, it shows weak performance against gene-specific outliers and is unable to handle missing observations. To address these issues, we proposed a pre-processing approach of RNA-Seq count data by combining the iLOO-based outlier detection and random forest-based missing imputation approach for boosting the performance of edgeR (Robust). Both simulation and real RNA-Seq count data analysis results showed that the proposed edgeR (Robust) outperformed than the conventional edgeR (Robust). To investigate the effectiveness of identified DEGs for diagnosis, and therapies of ovarian cancer (OC), we selected top-ranked 12 DEGs (IL6, XCL1, CXCL8, C1QC, C1QB, SNAI2, TYROBP, COL1A2, SNAP25, NTS, CXCL2, and AGT) and suggested hub-DEGs guided top-ranked 10 candidate drug-molecules for the treatment against OC. Hence, our proposed procedure might be an effective computational tool for exploring potential DEGs from RNA-Seq profiles for diagnosis and therapies of any disease.

Small-molecule inhibition of kinesin KIF18A reveals a mitotic vulnerability enriched in chromosomally unstable cancers

Chromosomal instability (CIN) is a hallmark of cancer, caused by persistent errors in chromosome segregation during mitosis. Aggressive cancers like high-grade serous ovarian cancer (HGSOC) and triple-negative breast cancer (TNBC) have a high frequency of CIN and TP53 mutations. Here, we show that inhibitors of the KIF18A motor protein activate the mitotic checkpoint and selectively kill chromosomally unstable cancer cells. Sensitivity to KIF18A inhibition is enriched in TP53-mutant HGSOC and TNBC cell lines with CIN features, including in a subset of CCNE1-amplified, CDK4-CDK6-inhibitor-resistant and BRCA1-altered cell line models. Our KIF18A inhibitors have minimal detrimental effects on human bone marrow cells in culture, distinct from other anti-mitotic agents. In mice, inhibition of KIF18A leads to robust anti-cancer effects with tumor regression observed in human HGSOC and TNBC models at well-tolerated doses. Collectively, our results provide a rational therapeutic strategy for selective targeting of CIN cancers via KIF18A inhibition.

The Aurora kinase B relocation blocker LXY18 triggers mitotic catastrophe selectively in malignant cells

The mitotic regulator, Aurora kinase B (AURKB), is frequently overexpressed in malignancy and is a target for therapeutic intervention. The compound, LXY18, is a potent, orally available small molecule that inhibits the proper localization of AURKB during late mitosis, without affecting its kinase activity. In this study, we demonstrate that LXY18 elicits apoptosis in cancer cells derived from various indications, but not in non-transformed cell lines. The apoptosis is p53-independent, triggered by a prolonged mitotic arrest and occurs predominantly in mitosis. Some additional cells succumb post-mitotic slippage. We also demonstrate that cancer cell lines refractory to AURKB kinase inhibitors are sensitive to LXY18. The mitotic proteins MKLP2, NEK6, NEK7 and NEK9 are known regulators of AURKB localization during the onset of anaphase. LXY18 fails to inhibit the catalytic activity of these AURKB localization factors. Overall, our findings suggest a novel activity for LXY18 that produces a prolonged mitotic arrest and lethality in cancer cells, leaving non-transformed cells healthy. This new activity suggests that the compound may be a promising drug candidate for cancer treatment and that it can also be used as a tool compound to further dissect the regulatory network controlling AURKB localization.

Chemical biology fluorescent tools for in vitro investigation of the multidrug resistant P-glycoprotein (P-gp) expression in tumor cells

Selective P-glycoprotein (P-gp)-targeted fluorescent conjugates are desirable tools to investigate the role of P-gp, a protein strongly implicated in mediating multidrug resistance and a major cause of chemotherapy failure. Herein, we report the development of 25 novel fluorescent small-molecule conjugates with varying physicochemical and optical properties, and their biological evaluation in a cell model as P-gp targeted constructs. This investigation revealed relationships between molecular structure and cell behavior and uncovered the capacity of conjugates with varying fluorophores to selectively target P-gp. Sulfocyanine 3 labeled conjugates (5, 10, 24, 29, 34) showed a particular intracellular staining pattern. Other conjugates bearing a boron dipyrromethene (BODIPY) core (3, 8, 13, 22, 27 (BODIPY FL), 12 (BODIPY 564/570) and 4, 9 (BODIPY 650/665)) or a 7-nitrobenz-2-oxa-1,3-diazole (NBD) core (11, 30) showed potential for global P-gp direct detection and quantification. These fluorescent conjugates holds key advantages over existing methods for drug resistance evaluation with regards to P-gp expression and could be used as innovative tools in preclinical assays and clinical diagnosis.

The heterogeneous transition state of resistance to RET kinase inhibitors converges on ERK1/2-driven Aurora A/B kinases

AIM

While most patients with RET-altered cancer responded to the RET protein tyrosine kinase inhibitors (TKIs) pralsetinib (BLU667) and selpercatinib (LOXO292), few achieved a complete response. Heterogeneity in residual tumors makes it difficult to target their diverse genetic alterations individually. The aim of this study is to characterize the cancer cells that persist under continuous RET TKI treatment and identify the shared vulnerability of these cells.

METHODS

We analyzed residual RET-altered cancer cells under prolonged RET TKI treatment by whole exome sequencing (WES), RNA-seq analysis, and drug-sensitivity screening. These were followed by tumor xenograft experiments of mono- and combinational drug treatments.

RESULTS

BLU667- and LOXO292-tolerated persisters were cellularly heterogeneous, contained slowly proliferating cells, regained low levels of active ERK1/2, and displayed plasticity in growth rate, which we designated as in the transition state of resistance (TSR). TSR cells were genetically heterogeneous. Aurora A/B kinases were among the most significantly upregulated genes and that the MAPK pathway activity had significantly higher transcript footprints. MEK1/2 and Aurora kinase inhibitors were the most effective drugs when combined with a RET kinase inhibitor. In a TSR tumor model, combination of BLU667 with an Aurora kinase or a MEK1/2 kinase inhibitor caused TSR tumor regression.

CONCLUSION

Our experiments reveal that the heterogeneous TSR cancer cells under continuous RET TKI treatment converge on the targetable ERK1/2-driven Aurora A/B kinases. The discovery of the targetable convergent point in the genetically heterogeneous TSR points to an effective combination therapy approach to eliminate the residual tumors.

Aurora B Inhibitors as Cancer Therapeutics

The Aurora kinases (A, B, and C) are a family of three isoform serine/threonine kinases that regulate mitosis and meiosis. The Chromosomal Passenger Complex (CPC), which contains Aurora B as an enzymatic component, plays a critical role in cell division. Aurora B in the CPC ensures faithful chromosome segregation and promotes the correct biorientation of chromosomes on the mitotic spindle. Aurora B overexpression has been observed in several human cancers and has been associated with a poor prognosis for cancer patients. Targeting Aurora B with inhibitors is a promising therapeutic strategy for cancer treatment. In the past decade, Aurora B inhibitors have been extensively pursued in both academia and industry. This paper presents a comprehensive review of the preclinical and clinical candidates of Aurora B inhibitors as potential anticancer drugs. The recent advances in the field of Aurora B inhibitor development will be highlighted, and the binding interactions between Aurora B and inhibitors based on crystal structures will be presented and discussed to provide insights for the future design of more selective Aurora B inhibitors.

Design, synthesis, docking, and anticancer evaluations of phthalazines as VEGFR-2 inhibitors

Twenty new N-substituted-4-phenylphthalazin-1-amine derivatives were designed, synthesized, and evaluated for their anticancer activities against HepG2, HCT-116, and MCF-7 cells as VEGFR-2 inhibitors. HCT-116 was the most sensitive cell line to the influence of the new derivatives. In particular, compound 7f was found to be the most potent derivative among all the tested compounds against the three cancer cell lines, with 50% inhibition concentration, IC₅₀  = 3.97, 4.83, and 4.58 µM, respectively, which is more potent than both sorafenib (IC₅₀  = 9.18, 5.47, and 7.26 µM, respectively) and doxorubicin (IC₅₀  = 7.94, 8.07, and 6.75 µM, respectively). Fifteen of the synthesized derivatives were selected to evaluate their inhibitory activities against VEGFR-2. Compound 7f was found to be the most potent derivative that inhibited VEGFR-2 at an IC₅₀ value of 0.08 µM, which is more potent than sorafenib (IC₅₀  = 0.10 µM). Compound 8c inhibited VEGFR-2 at an IC₅₀ value of 0.10 µM, which is equipotent to sorafenib. Moreover, compound 7a showed very good activity with IC₅₀ values of 0.11 µM, which is nearly equipotent to sorafenib. In addition, compounds 7d, 7c, and 7g possessed very good VEGFR-2-inhibitory activity, with IC₅₀ values of 0.14, 0.17, and 0.23 µM, respectively.

LightSpot®-FL-1 Fluorescent Probe: An Innovative Tool for Cancer Drug Resistance Analysis by Direct Detection and Quantification of the P-glycoprotein (P-gp) on Monolayer Culture and Spheroid Triple Negative Breast Cancer Models

Simple Summary

Tumoral drug resistance is mainly caused by multidrug resistance transporters (MDR), such as the P-gp, which presents high clinical interest. For this reason, the P-gp-mediated drug resistance diagnosis may be very relevant for optimizing anticancer treatment efficacy. However, the lack of effective analytical tools limits this clinical diagnostic approach. Therefore, our group has developed LightSpot^®-FL-1, a new cell-permeant fluorescent probe able to specifically localize and quantify the P-gp inside unicellular, monolayer, and cellular mass models. The application of this innovative tool was firstly demonstrated in the preclinical field, using five triple-negative breast cancer (TNBC) cell models. The comparison between classical anti-P-gp immunostaining and LightSpot^®-FL-1 P-gp staining highlighted a strong similarity with P-gp localization and expression level quantification. LightSpot^®-FL-1 P-gp detection and quantification, using several fluorescence imaging methods, are easy, direct, and cost-effective and are, therefore, very promising for future clinical diagnosis development.

Abstract

P-gp is the most widely studied MDR protein conferring cellular resistance to many standard or targeted therapeutic agents. For this reason, P-gp chemoresistance evaluation, established before or during chemotherapy, can be very relevant in order to optimize the efficacy of treatments, particularly for aggressive tumoral subtypes such as triple-negative breast cancer (TNBC). In this context, our team developed an innovative cell-permeant fluorescent probe called the LightSpot^®-FL-1, which is able to specifically localize and quantify the P-gp in cells or cell masses, as evidenced on different TNBC cell models. First, flow cytometry analysis showed LightSpot^®-FL-1 cell penetration and persistence in time, in TNBC cells. Then, LightSpot^®-FL-1 staining was compared to anti-P-gp immunostaining by fluorescence microscopy on five TNBC cell lines. Results showed a clear similarity of P-gp localization and expression level, confirmed by Pearson’s and Mander’s colocalization coefficients with 92.1% and 100.0%, and a strong correlation coefficient of R² = 0.99. In addition, the LightSpot^®-FL-1 staining allowed the quantification of a P-gp induction (33% expression increase) following a 6-hour spheroid model exposure to the anti-PARP Olaparib. Thus, the new LightSpot^®-FL-1 cell-permeant probe, targeting P-gp, appears to be an effective tool for drug resistance evaluation in preclinical models and shows promising possibilities for future use in clinical diagnosis.

N-Substituted-4-phenylphthalazin-1-amine-derived VEGFR-2 inhibitors: Design, synthesis, molecular docking, and anticancer evaluation studies

In accordance with the significant impetus of the discovery of potent vascular endothelial growth factor receptor 2 (VEGFR-2) inhibitors, herein, we report the design, synthesis, and anticancer evaluation of 12 new N-substituted-4-phenylphthalazin-1-amine derivatives against HepG2, HCT-116, and MCF-7 cells as VEGFR-2 inhibitors. The results of the cytotoxicity investigation indicated that HCT-116 and MCF-7 were the most sensitive cell lines to the influence of the newly synthesized derivatives. In particular, compound 7a was found to be the most potent derivative among all the tested compounds against the three cancer cell lines, HepG2, HCT116, and MCF-7, with IC₅₀  = 13.67 ± 1.2, 5.48 ± 0.4, and 7.34 ± 0.6 µM, respectively, which is nearly equipotent to that of sorafenib (IC₅₀  = 9.18 ± 0.6, 5.47 ± 0.3, and 7.26 ± 0.3 µM, respectively). All synthesized derivatives, 4a,b-8a-c, were evaluated for their inhibitory activities against VEGFR-2. The tested compounds displayed high to low inhibitory activity, with IC₅₀ values ranging from 0.14 ± 0.02 to 9.54 ± 0.85 µM. Among them, compound 7a was found to be the most potent derivative that inhibited VEGFR-2 at an IC₅₀ value of 0.14 ± 0.02 µM, which is nearly 72% of that of the sorafenib IC₅₀ value (0.10 ± 0.02 µM). Compounds 7b, 8c, 8b, and 8a exhibited very good activity with IC₅₀ values of 0.18 ± 0.02, 0.21 ± 0.03, 0.24 ± 0.02, and 0.35 ± 0.04 µM, respectively. Molecular modeling studies were carried out for all compounds against the VEGFR-2 active site. The data obtained from biological testing highly correlated with that obtained from molecular modeling studies. However, these modifications led to new phthalazine derivatives with higher VEGFR-2 inhibitory activities than vatalanib and which are nearly equipotent to sorafenib.

Anticancer potential of new 3-nitroaryl-6-(N-methyl)piperazin-1,2,4-triazolo[3,4-a]phthalazines targeting voltage-gated K+ channel: Copper-catalyzed one-pot synthesis from 4-chloro-1-phthalazinyl-arylhydrazones

A series of six 3-aryl-6-(N-methylpiperazin)-1,2,4-triazolo[3,4-a]phthalazines were prepared through a facile and efficient one-pot copper-catalyzed procedure from 4-chloro-1-phthalazinyl-arylhydrazones with relatively good yields (62-83%). The one-pot copper-catalytic procedure consists of two simultaneous reactions: (i) a direct intramolecular dehydrogentaive cyclization between ylidenic carbon and adjacent pyrazine nitrogen to form 1,2,4-triazolo ring and, (ii) a direct N-amination on carbon-chlorine bond. Then, an in vitro anticancer evaluation was performed for the synthesized compounds against five selected human cancer cells (A549, MCF-7, SKBr3, PC-3 and HeLa). The nitro-derivatives were significantly more active against cancer strains than against the rest of tested compounds. Specifically, compound 8d was identified as the most promising anticancer agent with significant biological responses and low relative toxicities on human dermis fibroblast. The cytotoxic effect of compound 8d was more significant on PC3, MCF-7 and SKBr3 cancer cells with low-micromolar IC₅₀ value ranging from 0.11 to 0.59 μM, superior to Adriamycin drug. Mechanistic experimental and theoretical studies demonstrated that compounds 8d act as a K⁺ channel inhibitor in cancer models. Further molecular docking studies suggest that the EGFR Tyrosine Kinase enzyme may be a potential target for the most active 3-aryl-6-(N-methylpiperazin)-1,2,4-triazolo[3,4-a]phthalazines.

Alterations and molecular targeting of the GSK-3 regulator, PI3K, in head and neck cancer

Head and neck squamous cell carcinoma (HNSCC) is a highly morbid, genetically unstable disease derived from the mucoepithelium of the upper aerodigestive tract. Recent characterization of this disease has implicated the PI3K-Akt-mTOR pathway as one of the most frequently dysregulated pathways. As such, there are several classes of PI3K inhibitors currently undergoing clinical trials. In this article, we review the PI3K pathway, mutations of this pathway in HNSCC, drugs that target PI3K, the impact of these agents on the PI3K and GSK-3 signaling axes, ongoing clinical trials evaluating PI3K inhibitors, and the challenges of using these drugs in the clinic. This article is part of a Special Issue entitled: GSK-3 and related kinases in cancer, neurological and other disorders edited by James McCubrey, Agnieszka Gizak and Dariusz Rakus.

The therapeutic potential of Aurora kinases targeting in glioblastoma: from preclinical research to translational oncology

Glioblastoma is the most common aggressive primary brain tumor. Standard care includes maximal safe surgical resection, radiation, and chemotherapy with temozolomide. However, the impact of this therapeutic approach on patient survival is disappointing and poor outcomes are frequently observed. Therefore, new therapeutic targets are needed to treat this potentially deadly tumor. Aurora kinases are one of today's most sought-after classes of therapeutic targets to glioblastoma therapy. They are a family of proteins composed of three members: Aurora-A, Aurora-B, and Aurora-C that play different roles in the cell division through regulation of chromosome segregation. Deregulation of these genes has been reported in glioblastoma and a progressive number of studies have shown that inhibition of these proteins could be a promising strategy for the treatment of this tumor. This review discusses the preclinical and early clinical findings on the potential use of the Aurora kinases as new targets for the treatment of glioblastoma. KEY MESSAGES: GBM is a very aggressive tumor with limited therapeutic options. Aurora kinases are a family of serine/threonine kinases implicated in GBM pathology. Aurora kinases are critical for glioblastoma cell growth, apoptosis, and chemoresistance. Inhibition of Aurora kinases has a synergistic or sensitizing effect with chemotherapy drugs, radiotherapy, or with other targeted molecules in GBM. Several Aurora kinase inhibitors are currently in clinical trials.

Aurora kinase A stabilizes FOXM1 to enhance paclitaxel resistance in triple-negative breast cancer

Triple-negative breast cancer (TNBC) has a relatively poor outcome. Acquired chemoresistance is a major clinical challenge for TNBC patients. Previously, we reported that kinase-dead Aurora kinase A (Aurora-A) could effectively transactivate the FOXM1 promoter. Here, we demonstrate an additional pathway through which Aurora-A stabilizes FOXM1 by attenuating its ubiquitin in TNBC. Specifically, Aurora-A stabilizes FOXM1 in late M phase and early G1 phase of the cell cycle, which promotes proliferation of TNBC cells. Knock-down of Aurora-A significantly suppresses cell proliferation in TNBC cell lines and can be rescued by FOXM1 overexpression. We observe that paclitaxel-resistant TNBC cells exhibit high expression of Aurora-A and FOXM1. Overexpression of Aurora-A offers TNBC cells an additional growth advantage and protection against paclitaxel. Moreover, Aurora-A and FOXM1 could be simultaneously targeted by thiostrepton. Combination of thiostrepton and paclitaxel treatment reverses paclitaxel resistance and significantly inhibits cell proliferation. In conclusion, our study reveals additional mechanism through which Aurora-A regulates FOXM1 and provides a new therapeutic strategy to treat paclitaxel-resistant triple-negative breast cancer.

Recent therapeutic trends and promising targets in triple negative breast cancer

Breast cancer accounts for 25% of all types of cancer in women, and triple negative breast cancer (TNBC) comprises around 15~20% of breast cancers. Conventional chemotherapy and radiation are the primary systemic therapeutic strategies; no other FDA-approved targeted therapies are yet available as for TNBC. TNBC is generally characterized by a poor prognosis and high rates of proliferation and metastases. Due to these aggressive features and lack of targeted therapies, numerous attempts have been made to discover viable molecular targets for TNBC. Massive cohort studies, clinical trials, and in-depth analyses have revealed diverse molecular alterations in TNBC; however, controversy exists as to whether many of these changes are beneficial or detrimental in caner progression. Here we review the complicated tumorigenic processes and discuss critical findings and therapeutic trends in TNBC with a focus on promising therapeutic approaches, the clinical trials currently underway, and potent experimental compounds under preclinical and evaluation.

Dual Targeting of Aurora Kinases with AMG 900 Exhibits Potent Preclinical Activity Against Acute Myeloid Leukemia with Distinct Post-Mitotic Outcomes

Aurora kinase A and B have essential and non-overlapping roles in mitosis, with elevated expression in a subset of human cancers, including acute myeloid leukemia (AML). In this study, pan-aurora kinase inhibitor (AKI) AMG 900 distinguishes itself as an anti-leukemic agent that is more uniformly potent against a panel of AML cell lines than are isoform-selective AKIs and classic AML drugs. AMG 900 inhibited AML cell growth by inducing polyploidization and/or apoptosis. AMG 900 and aurora-B-selective inhibitor AZD1152-hQPA showed comparable cellular effects on AML lines that do not harbor a FLT3-ITD mutation. AMG 900 was active against P-glycoprotein-expressing AML cells resistant to AZD1152-hQPA and was effective at inducing expression of megakaryocyte-lineage markers (CD41, CD42) on human CHRF-288-11 cells and mouse Jak2 V617F cells. In MOLM-13 cells, inhibition of p-histone H3 by AMG 900 was associated with polyploidy, extra centrosomes, accumulation of p53 protein, apoptosis, and cleavage of Bcl-2 protein. Co-administration of cytarabine (Ara-C) with AMG 900 potentiated cell killing in a subset of AML lines, with evidence of attenuated polyploidization. AMG 900 inhibited the proliferation of primary human bone marrow cells in culture, with a better proliferation recovery profile relative to classic antimitotic drug docetaxel. In vivo, AMG 900 significantly reduced tumor burden in a systemic MOLM-13 xenograft model where we demonstrate the utility of 3'-deoxy-3'-18F-fluorothymidine [18F]FLT positron emission tomographic (PET)-CT imaging to measure the antiproliferative effects of AMG 900 in skeletal tissues in mice.

Mitosis inhibitors in anticancer therapy: When blocking the exit becomes a solution

Current microtubule-targeting agents (MTAs) remain amongst the most important antimitotic drugs used against a broad range of malignancies. By perturbing spindle assembly, MTAs activate the spindle assembly checkpoint (SAC), which induces mitotic arrest and subsequent apoptosis. However, besides toxic side effects and resistance, mitotic slippage and failure in triggering apoptosis in various cancer cells are limiting factors of MTAs efficacy. Alternative strategies to target mitosis without affecting microtubules have, thus, led to the identification of small molecules, such as those that target spindle Kinesins, Aurora and Polo-like kinases. Unfortunately, these so-called second-generation of antimitotics, encompassing mitotic blockers and mitotic drivers, have failed in clinical trials. Our recent understanding regarding the mechanisms of cell death during a mitotic arrest pointed out apoptosis as the main variable, providing an opportunity to control the cell fates and influence the effectiveness of antimitotics. Here, we provide an overview on the second-generation of antimitotics, and discuss possible strategies that exploit SAC activity, mitotic slippage/exit and apoptosis induction, in order to improve the efficacy of anticancer strategies that target mitosis.

An Aurora kinase inhibitor, AMG900, inhibits glioblastoma cell proliferation by disrupting mitotic progression

The Aurora kinase family of serine/threonine protein kinases comprises Aurora A, B, and C and plays an important role in mitotic progression. Several inhibitors of Aurora kinase have been developed as anti‐cancer therapeutics. Here, we examined the effects of a pan‐Aurora kinase inhibitor, AMG900, against glioblastoma cells. AMG900 inhibited proliferation of A172, U‐87MG, and U‐118MG glioblastoma cells by upregulating p53 and p21 and subsequently inducing cell cycle arrest and senescence. Abnormal cell cycle progression was triggered by dysregulated mitosis. Mitosis was prolonged due to a defect in mitotic spindle assembly. Despite the presence of an unattached kinetochore, BubR1, a component of the spindle assembly checkpoint, was not recruited. In addition, Aurora B was not recruited to central spindle at anaphase. Abnormal mitotic progression resulted in accumulation of multinuclei and micronuclei, a type of chromosome missegregation, and ultimately inhibited cell survival. Therefore, the data suggest that AMG900‐mediated inhibition of Aurora kinase is a potential anti‐cancer therapy for glioblastoma.

A phase 1, first-in-human study of AMG 900, an orally administered pan-Aurora kinase inhibitor, in adult patients with advanced solid tumors

Background Aurora kinase overexpression or amplifications are associated with high proliferation, poor prognosis, and therapeutic resistance in human tumors. AMG 900 is an investigational, oral, selective pan-Aurora kinase inhibitor. Methods This first-in-human trial included dose-escalation and dose-expansion phases ( ClinicalTrials.gov : NCT00858377). Dose escalation evaluated the safety, tolerability, and pharmacokinetics of AMG 900 in advanced solid tumors and determined the maximum tolerated dose (MTD) with/without granulocyte colony-stimulating factor (G-CSF) prophylaxis. Dose expansion evaluated clinical activity in three tumor types: taxane- and platinum-resistant ovarian cancer, taxane-resistant triple-negative breast cancer (TNBC), and castration-resistant and taxane- or cisplatin/etoposide-resistant prostate cancer (CRPC). AMG 900 was administered 4 days on/10 days off at 1-50 mg/day during escalation and at the MTD with G-CSF during expansion. Results AMG 900 showed rapid absorption with fast clearance, supporting once-daily dosing. The MTD was 25 mg/day, increasing to 40 mg/day with G-CSF. Grade ≥ 3 treatment-related adverse events included neutropenia (37%), anemia (23%), leukopenia (14%), and thrombocytopenia (12%). During dose expansion, 3/29 (10.3%, 95% CI: 2.0%-28.0%) evaluable patients with ovarian cancer experienced partial response by central imaging per RECIST 1.1; median duration of response was 24.1 weeks (95% CI: 16.1-34.1). Seven patients (24.1%, 95% CI: 10.3%-43.5%) experienced partial response per Gynecologic Cancer InterGroup criteria; 5/9 patients positive for p53 expression responded to treatment. No objective responses were observed in patients with TNBC or CRPC per RECIST 1.1. Conclusions AMG 900 40 mg/day with G-CSF had manageable toxicity and demonstrated single-agent activity in patients with heavily pretreated, chemotherapy-resistant ovarian cancer.

Aurora A kinase activity is required to maintain an active spindle assembly checkpoint during prometaphase

During the prometaphase stage of mitosis, the cell builds a bipolar spindle of microtubules that mechanically segregates sister chromatids between two daughter cells in anaphase. The spindle assembly checkpoint (SAC) is a quality control mechanism that monitors proper attachment of microtubules to chromosome kinetochores during prometaphase. Segregation occurs only when each chromosome is bi-oriented with each kinetochore pair attached to microtubules emanating from opposite spindle poles. Overexpression of the protein kinase Aurora A is a feature of various cancers and is thought to enable tumour cells to bypass the SAC, leading to aneuploidy. Here, we took advantage of a chemical and chemical-genetic approach to specifically inhibit Aurora A kinase activity in late prometaphase. We observed that a loss of Aurora A activity directly affects SAC function, that Aurora A is essential for maintaining the checkpoint protein Mad2 on unattached kinetochores and that inhibition of Aurora A leads to loss of the SAC, even in the presence of nocodazole or Taxol. This is a new finding that should affect the way Aurora A inhibitors are used in cancer treatments.This article has an associated First Person interview with the first authors of the paper.

A Novel Dual HDAC6 and Tubulin Inhibitor, MPT0B451, Displays Anti-tumor Ability in Human Cancer Cells in Vitro and in Vivo

The combination cancer therapy is a new strategy to circumvent drug resistance for the treatment of high metastasis and advanced malignancies. Herein, we developed a synthesized compound MPT0B451 that display inhibitory effect against histone deacetylase (HDAC) 6 and tubulin assembly. Our data demonstrated that MPT0B451 significantly inhibited cancer cell growths in HL-60 and PC-3 cells due to inhibition of HDAC activity. MPT0B451 also markedly increased caspase-mediated apoptosis in these cells. The cell cycle analysis showed mitotic arrest induced by MPT0B451 with enhanced expression of G2/M transition proteins. Moreover, molecular docking analysis supported MPT0B451 as a dual HDAC6 and tubulin inhibitor. Finally, MPT0B451 led to tumor growth inhibition (TGI) in HL-60 and PC-3 xenograft models. These findings indicated that MPT0B451 has dual inhibition effects for HDAC6 and tubulin, and also contributed to G2/M arrest followed by apoptotic induction. Together, our results suggested that MPT0B451 may serve as a potent anti-cancer treatment regimen in human prostate cancer and acute myeloid leukemia.

A phase 1 study of AMG 900, an orally administered pan-aurora kinase inhibitor, in adult patients with acute myeloid leukemia

Aurora kinases are involved in the pathophysiology of several cancers including acute myeloid leukemia (AML). In this phase 1 study, we investigated the safety and efficacy of AMG 900, an orally administered, highly potent, selective, small-molecule inhibitor of both Aurora kinase A and B, in patients with AML . Patients with pathologically documented AML who either declined standard treatments or had relapsed from or were refractory to previous therapies were enrolled. Two every-2-week dose-escalation schedules using a modified 3 + 3 + 3 design were evaluated AMG 900 given daily for 4 days with 10 days off (4/10 schedule), and AMG 900 given daily for 7 days with 7 days off (7/7 schedule). Thirty-five patients were enrolled at 9 different dose levels: 22 patients on the 4/10 schedule (doses from 15 to 100 mg daily), and 13 patients on the 7/7 schedule (doses from 30 to 50 mg daily). Both schedules were tolerated; nausea (31%), diarrhea (29%), febrile neutropenia (29%), and fatigue (23%) were the most common treatment-related adverse events. Three patients (9%) achieved complete response with incomplete count recovery. Patients with higher baseline expression of a set of specific pathway-related genes (BIRC5, AURKA, TTK, CDC2, and CCNB1) were more likely to respond in an exploratory biomarker analysis. AMG 900 was tolerated in a general AML population, and pathway-specific biomarkers identified a potential target population. Future research efforts will be directed toward further exploration of biomarkers of response and combination of AMG 900 with other anticancer agents.

WX-132-18B, a novel microtubule inhibitor, exhibits promising anti-tumor effects

Cancer drug researchers have been seeking microtubule-inhibiting agents (MIAs) with higher bioactivity and lower toxicity than currently marketed drugs. WX-132-18B, a novel structural compound synthesized at our institute, specifically bound to the colchicine-binding site on tubulin rather than the vinblastine site, and concentration-dependently reduced microtubule content via depolymerization. It exhibited the same cellular phenotypic profiles as the classic MIAs (colchicine, vincristine, and taxol), including inducing cell cycle arrest at the G2/M phase, triggering tumor cell apoptosis, promoting nuclear membrane permeability, reducing mitochondrial membrane potential, and disrupting the redox system balance. Importantly, WX-132-18B displayed more potent in vitro bioactivity (IC₅₀ 0.45–0.99 nM) than did the classic MIAs; it inhibited the proliferation of human umbilical vein endothelial cells and seven types of human tumor cells, especially the taxol-resistant breast cancer cells MX-1/T. WX-132-18B also dose-dependently inhibited mice sarcoma, human lung, and gastric cancer xenograft tumors and the formation of tumor blood vessels in mice. In conclusion, WX-132-18B is a novel microtubule-depolymerizing agent that selectively acts on the colchicine-binding site of tubulin and exerts potent in vitro and in vivo anti-tumor effects. These characteristics, along with its anti-angiogenesis and anti-drug resistance properties, make WX-132-18B a promising anti-tumor drug candidate.

Recent advances in hyaluronic acid-decorated nanocarriers for targeted cancer therapy

The cluster-determinant 44 (CD44) receptor has a high affinity for hyaluronic acid (HA) binding and is a desirable receptor for active targeting based on its overexpression in cancer cells compared with normal body cells. The nanocarrier affinity can be increased by conjugating drug-loaded carriers with HA, allowing enhanced cancer cell uptake via the HA-CD44 receptor-mediated endocytosis pathway. In this review, we discuss recent advances in HA-based nanocarriers and micelles for cancer therapy. In vitro and in vivo experiments have repeatedly indicated HA-based nanocarriers to be a target-specific drug and gene delivery platform with great promise for future applications in clinical cancer therapy.

Targeting oncogenic vulnerabilities in triple negative breast cancer: biological bases and ongoing clinical studies

Triple negative breast cancer (TNBC) is still an incurable disease despite the great scientific effort performed during the last years. The huge heterogeneity of this disease has motivated the evaluation of a great number of therapies against different molecular alterations. In this article, we review the biological bases of this entity and how the known molecular evidence supports the current preclinical and clinical development of new therapies. Special attention will be given to ongoing clinical studies and potential options for future drug combinations.

Cell cycle proteins as promising targets in cancer therapy

Cancer is characterized by uncontrolled tumour cell proliferation resulting from aberrant activity of various cell cycle proteins. Therefore, cell cycle regulators are considered attractive targets in cancer therapy. Intriguingly, animal models demonstrate that some of these proteins are not essential for proliferation of non-transformed cells and development of most tissues. By contrast, many cancers are uniquely dependent on these proteins and hence are selectively sensitive to their inhibition. After decades of research on the physiological functions of cell cycle proteins and their relevance for cancer, this knowledge recently translated into the first approved cancer therapeutic targeting of a direct regulator of the cell cycle. In this Review, we focus on proteins that directly regulate cell cycle progression (such as cyclin-dependent kinases (CDKs)), as well as checkpoint kinases, Aurora kinases and Polo-like kinases (PLKs). We discuss the role of cell cycle proteins in cancer, the rationale for targeting them in cancer treatment and results of clinical trials, as well as the future therapeutic potential of various cell cycle inhibitors.

Aurora-A Kinase: A Potent Oncogene and Target for Cancer Therapy

The Aurora kinase family is comprised of three serine/threonine kinases, Aurora-A, Aurora-B, and Aurora-C. Among these, Aurora-A and Aurora-B play central roles in mitosis, whereas Aurora-C executes unique roles in meiosis. Overexpression or gene amplification of Aurora kinases has been reported in a broad range of human malignancies, pointing to their role as potent oncogenes in tumorigenesis. Aurora kinases therefore represent promising targets for anticancer therapeutics. A number of Aurora kinase inhibitors (AKIs) have been generated; some of which are currently undergoing clinical evaluation. Recent studies have unveiled novel unexpected functions of Aurora kinases during cancer development and the mechanisms underlying the anticancer actions of AKIs. In this review, we discuss the most recent advances in Aurora-A kinase research and targeted cancer therapy, focusing on the oncogenic roles and signaling pathways of Aurora-A kinases in promoting tumorigenesis, the recent preclinical and clinical AKI data, and potential alternative routes for Aurora-A kinase inhibition.

PEG10 promotes human breast cancer cell proliferation, migration and invasion

Paternally expressed imprinted gene 10 (PEG10), derived from the Ty3/Gypsy family of retrotransposons, has been implicated as a genetic imprinted gene. Accumulating evidence suggests that PEG10 plays an important role in tumor growth in various cancers, including hepatocellular carcinoma, lung cancer and prostate cancer. However, the correlation between PEG10 and breast cancer remains unclear. In the present study, we evaluated and characterized the role of PEG10 in human breast cancer proliferation, cell cycle, clone formation, migration and invasion. The expression level of PEG10 was significantly elevated in breast cancer tissues and associated with distant metastasis and poor clinical outcome. Gene set enrichment analysis indicated that high expression of PEG10 could enrich cell cycle-related processes in breast cancer tissues. Ectopic overexpression of PEG10 in breast cancer cells enhanced cell proliferation, cell cycle, clone formation along with migration and invasion. Cell-to-cell junction molecule E-cadherin was downregulated and matrix degradation proteases MMP-1, MMP-2, MMP-9 were up-regulated after PEG10 overexpression. Our results demonstrated that PEG10 is a crucial oncogene and has prognostic value for breast cancer, which could be applied in breast cancer diagnosis and targeting therapy in future.

Evaluation of the pharmacokinetics of ixabepilone for the treatment of breast cancer

INTRODUCTION

Chemotherapeutic agents, such as anthracyclines, taxanes and fluoropyrimidines, have significantly improved the outcome of breast cancer patients. However, mechanisms of resistance limit the effectiveness of these drugs. The microtubule-stabilizing agent ixabepilone has been approved for treatment of metastatic breast cancer (MBC) patients resistant or refractory to taxanes, anthracycline and capecitabine.

AREAS COVERED

In this review, we summarized data on pharmacodynamics, pharmacokinetics, preclinical and clinical studies of ixabepilone in breast cancer. This article was compiled through searches on ixabepilone up to March 2015 in the PubMed and the clinicaltrials.gov databases; the FDA and European Medicine Agency (EMA) websites; and the ASCO and AACR proceedings.

EXPERT OPINION

Ixabepilone is a well-tolerated and effective drug in MBC at the approved dose. The most important challenges that ongoing clinical trials are still addressing are: the optimal dosing schedule that might improve the risk/benefit ratio, the clinical efficacy of ixabepilone in early breast cancer, the efficacy in triple-negative breast cancer (TNBC) patients and the identification of biomarkers predictive of response.

Aurora Kinase Inhibitors: Current Status and Outlook

The Aurora kinase family comprises of cell cycle-regulated serine/threonine kinases important for mitosis. Their activity and protein expression are cell cycle regulated, peaking during mitosis to orchestrate important mitotic processes including centrosome maturation, chromosome alignment, chromosome segregation, and cytokinesis. In humans, the Aurora kinase family consists of three members; Aurora-A, Aurora-B, and Aurora-C, which each share a conserved C-terminal catalytic domain but differ in their sub-cellular localization, substrate specificity, and function during mitosis. In addition, Aurora-A and Aurora-B have been found to be overexpressed in a wide variety of human tumors. These observations led to a number of programs among academic and pharmaceutical organizations to discovering small molecule Aurora kinase inhibitors as anti-cancer drugs. This review will summarize the known Aurora kinase inhibitors currently in the clinic, and discuss the current and future directions.

Aurora Kinase Inhibitors in Oncology Clinical Trials: Current State of the Progress

The Aurora kinase family of kinases (Aurora A, B, and C) are involved in multiple mitotic events, and aberrant expression of these kinases is associated with tumorigenesis. Aurora A and Aurora B are validated anticancer targets, and the development of Aurora kinase inhibitors has progressed from preclinical to clinical studies. A variety of Aurora A, B and pan-Aurora kinase inhibitors have entered the clinic. The main side effects include febrile neutropenia, stomatitis, gastrointestinal toxicity, hypertension, and fatigue. Responses including complete remissions have been described in diverse, advanced malignancies, most notably ovarian cancer and acute myelogenous leukemia. This review highlights the biologic rationale for Aurora kinase as a target, and clinical trials involving Aurora kinase inhibitors, with particular emphasis on published early phase studies, and the observed anti-tumor activity of these agents.

Functions of Aurora kinase C in meiosis and cancer

The mammalian genome encodes three Aurora kinase protein family members: A, B, and C. While Aurora kinase A (AURKA) and B (AURKB) are found in cells throughout the body, significant protein levels of Aurora kinase C (AURKC) are limited to cells that undergo meiosis (sperm and oocyte). Despite its discovery nearly 20 years ago, we know little about the function of AURKC compared to that of the other 2 Aurora kinases. This lack of understanding can be attributed to the high sequence homology between AURKB and AURKC preventing the use of standard approaches to understand non-overlapping and meiosis I (MI)-specific functions of the two kinases. Recent evidence has revealed distinct functions of AURKC in meiosis and may aid in our understanding of why chromosome segregation during MI often goes awry in oocytes. Many cancers aberrantly express AURKC, but because we do not fully understand AURKC function in its normal cellular context, it is difficult to predict the biological significance of this expression on the disease. Here, we consolidate and update what is known about AURKC signaling in meiotic cells to better understand why it has oncogenic potential.

The Discovery of Novel Biomarkers Improves Breast Cancer Intrinsic Subtype Prediction and Reconciles the Labels in the METABRIC Data Set

BACKGROUND

The prediction of breast cancer intrinsic subtypes has been introduced as a valuable strategy to determine patient diagnosis and prognosis, and therapy response. The PAM50 method, based on the expression levels of 50 genes, uses a single sample predictor model to assign subtype labels to samples. Intrinsic errors reported within this assay demonstrate the challenge of identifying and understanding the breast cancer groups. In this study, we aim to: a) identify novel biomarkers for subtype individuation by exploring the competence of a newly proposed method named CM1 score, and b) apply an ensemble learning, as opposed to the use of a single classifier, for sample subtype assignment. The overarching objective is to improve class prediction.

METHODS AND FINDINGS

The microarray transcriptome data sets used in this study are: the METABRIC breast cancer data recorded for over 2000 patients, and the public integrated source from ROCK database with 1570 samples. We first computed the CM1 score to identify the probes with highly discriminative patterns of expression across samples of each intrinsic subtype. We further assessed the ability of 42 selected probes on assigning correct subtype labels using 24 different classifiers from the Weka software suite. For comparison, the same method was applied on the list of 50 genes from the PAM50 method.

CONCLUSIONS

The CM1 score portrayed 30 novel biomarkers for predicting breast cancer subtypes, with the confirmation of the role of 12 well-established genes. Intrinsic subtypes assigned using the CM1 list and the ensemble of classifiers are more consistent and homogeneous than the original PAM50 labels. The new subtypes show accurate distributions of current clinical markers ER, PR and HER2, and survival curves in the METABRIC and ROCK data sets. Remarkably, the paradoxical attribution of the original labels reinforces the limitations of employing a single sample classifiers to predict breast cancer intrinsic subtypes.

Discovery of N-(4-(3-(2-aminopyrimidin-4-yl)pyridin-2-yloxy)phenyl)-4-(4-methylthiophen-2-yl)phthalazin-1-amine (AMG 900), a highly selective, orally bioavailable inhibitor of aurora kinases with activity against multidrug-resistant cancer cell lines

Efforts to improve upon the physical properties and metabolic stability of Aurora kinase inhibitor 14a revealed that potency against multidrug-resistant cell lines was compromised by increased polarity. Despite its high in vitro metabolic intrinsic clearance, 23r (AMG 900) showed acceptable pharmacokinetic properties and robust pharmacodynamic activity. Projecting from in vitro data to in vivo target coverage was not practical due to disjunctions between enzyme and cell data, complex and apparently contradictory indicators of binding kinetics, and unmeasurable free fraction in plasma. In contrast, it was straightforward to relate pharmacokinetics to pharmacodynamics and efficacy by following the time above a threshold concentration. On the basis of its oral route of administration, a selectivity profile that favors Aurora-driven pharmacology and its activity against multidrug-resistant cell lines, 23r was identified as a potential best-in-class Aurora kinase inhibitor. In phase 1 dose expansion studies with G-CSF support, 23r has shown promising single agent activity.

p53 Family Members Regulate Phenotypic Response to Aurora Kinase A Inhibition in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive disease with a poor prognosis. Advances in the treatment of TNBC have been hampered by the lack of novel effective targeted therapies. The primary goal of this study was to evaluate the efficacy of targeting Aurora kinase A (AurA), a key regulator of mitosis, in TNBC models. A secondary objective was to determine the role of the p53 family of transcriptional regulators, commonly mutated in TNBC, in determining the phenotypic response to the AurA inhibitor alisertib (MLN8237). Alisertib exhibited potent antiproliferative and proapoptotic activity in a subset of TNBC models. The induction of apoptosis in response to alisertib exposure was dependent on p53 and p73 activity. In the absence of functional p53 or p73, there was a shift in the phenotypic response following alisertib exposure from apoptosis to cellular senescence. In addition, senescence was observed in patient-derived tumor xenografts with acquired resistance to alisertib treatment. AurA inhibitors are a promising class of novel therapeutics in TNBC. The role of p53 and p73 in mediating the phenotypic response to antimitotic agents in TNBC may be harnessed to develop an effective biomarker selection strategy in this difficult to target disease.

Aurora kinase inhibitor patents and agents in clinical testing: an update (2011 - 2013)

INTRODUCTION

Aurora kinase A, B and C, members of serine/threonine kinase family, are key regulators of mitosis. As Aurora kinases are overexpressed in many of the human cancers, small-molecule inhibitors of Aurora kinase have emerged as a possible treatment option for cancer.

AREAS COVERED

In 2009 and 2011, the literature pertaining to Aurora kinase inhibitors and their patents was reviewed. Here, the aim is to update the information for Aurora kinase inhibitors in clinical trials and the patents filed between the years 2011 and 2013. Pubmed, Scopus®, Scifinder®, USPTO, EPO and www.clinicaltrials.gov databases were used for searching the literature and patents for Aurora kinase inhibitors.

EXPERT OPINION

Even though both Aurora sub-type selective as well as pan-selective inhibitors show preclinical and clinical efficacy, so far no Aurora kinase inhibitor has been approved for clinical use. Particularly, dose-limiting toxicity (neutropenia) is a key issue that needs to be addressed. Preliminary evidence suggests that the use of selective Aurora A inhibitors could avoid Aurora B-mediated neutropenia in clinical settings. Also, use of adjunctive agents such as granulocyte stimulating factor to overcome neutropenia associated with Aurora B inhibition could be an answer to overcome the toxicity and bring Aurora inhibitors to market in the future.