Aurora kinase inhibitors: progress towards the clinic

Pharmacological Profile of BI 847325, an Orally Bioavailable, ATP-Competitive Inhibitor of MEK and Aurora Kinases

Although the MAPK pathway is frequently deregulated in cancer, inhibitors targeting RAF or MEK have so far shown clinical activity only in BRAF- and NRAS-mutant melanoma. Improvements in efficacy may be possible by combining inhibition of mitogenic signal transduction with inhibition of cell-cycle progression. We have studied the preclinical pharmacology of BI 847325, an ATP-competitive dual inhibitor of MEK and Aurora kinases. Potent inhibition of MEK1/2 and Aurora A/B kinases by BI 847325 was demonstrated in enzymatic and cellular assays. Equipotent effects were observed in BRAF-mutant cells, whereas in KRAS-mutant cells, MEK inhibition required higher concentrations than Aurora kinase inhibition. Daily oral administration of BI 847325 at 10 mg/kg showed efficacy in both BRAF- and KRAS-mutant xenograft models. Biomarker analysis suggested that this effect was primarily due to inhibition of MEK in BRAF-mutant models but of Aurora kinase in KRAS-mutant models. Inhibition of both MEK and Aurora kinase in KRAS-mutant tumors was observed when BI 847325 was administered once weekly at 70 mg/kg. Our studies indicate that BI 847325 is effective in in vitro and in vivo models of cancers with BRAF and KRAS mutation. These preclinical data are discussed in the light of the results of a recently completed clinical phase I trial assessing safety, tolerability, pharmacokinetics, and efficacy of BI 847325 in patients with cancer. Mol Cancer Ther; 15(10); 2388-98. ©2016 AACR.

Amplification of TLK2 Induces Genomic Instability via Impairing the G2-M Checkpoint

Managing aggressive breast cancers with enhanced chromosomal instability (CIN) is a significant challenge in clinics. Previously, we described that a cell cycle-associated kinase called Tousled-like kinase 2 (TLK2) is frequently deregulated by genomic amplifications in aggressive estrogen receptor-positive (ER⁺) breast cancers. In this study, it was discovered that TLK2 amplification and overexpression mechanistically impair Chk1/2-induced DNA damage checkpoint signaling, leading to a G₂-M checkpoint defect, delayed DNA repair process, and increased CIN. In addition, TLK2 overexpression modestly sensitizes breast cancer cells to DNA-damaging agents, such as irradiation or doxorubicin. To our knowledge, this is the first report linking TLK2 function to CIN, in contrast to the function of its paralog TLK1 as a guardian of genome stability. This finding yields new insight into the deregulated DNA damage pathway and increased genomic instability in aggressive ER⁺ breast cancers.

IMPLICATIONS

Targeting TLK2 presents an attractive therapeutic strategy for the TLK2-amplified breast cancers that possess enhanced genomic instability and aggressiveness. Mol Cancer Res; 14(10); 920-7. ©2016 AACR.

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.

A phase I study of BI 811283, an Aurora B kinase inhibitor, in patients with advanced solid tumors

PURPOSE

This phase I study investigated the maximum tolerated dose (MTD), safety, pharmacokinetics, pharmacodynamics, and antitumor activity of the Aurora B kinase inhibitor BI 811283 in patients with advanced solid tumors.

METHODS

BI 811283 was administered via 24-h infusion on Days 1 and 15 of a 4-week cycle (schedule A) or Day 1 of a 3-week cycle (schedule B) in a modified 3 + 3 dose-escalation design. Pharmacodynamic assessments included immunohistochemistry for phosphorylated histone H3 (pHH3) on skin biopsies to determine Aurora B kinase inhibition and plasma concentrations of caspase-cleaved CK-18 (apoptosis marker).

RESULTS

A total of 121 patients were treated. The MTDs of BI 811283 were 125 mg (schedule A) and 230 mg (schedule B). Dose-limiting toxicities were primarily hematological (febrile neutropenia and grade 4 neutropenia); the most common drug-related adverse effects included neutropenia, fatigue, leukopenia, nausea, alopecia, diarrhea, and decreased appetite. A trend toward a decrease in pHH3 was observed, with increasing BI 811283 doses, indicating target engagement; there was no consistent trend regarding caspase-cleaved CK-18 levels. No objective response was observed although 19 patients in each schedule achieved clinical benefit (stable disease).

CONCLUSIONS

BI 811283 demonstrated a generally manageable safety profile and disease stabilization in some patients.

TRIAL REGISTRATION

EudraCT No: 2007-000191-17, ClinicalTrials.gov Identifier: NCT00701324.

N-(2-methyl-indol-1H-5-yl)-1-naphthalenesulfonamide: A novel reversible antimitotic agent inhibiting cancer cell motility

A series of compounds containing the sulfonamide scaffold were synthesized and screened for their in vitro anticancer activity against a representative panel of human cancer cell lines, leading to the identification of N-(2-methyl-1H-indol-5-yl)-1-naphthalenesulfonamide (8e) as a compound showing a remarkable activity across the panel, with IC50 values in the nanomolar-to-low micromolar range. Cell cycle distribution analysis revealed that 8e promoted a severe G2/M arrest, which was followed by cellular senescence as indicated by the detection of senescence-associated β-galactosidase (SA-β-gal) in 8e-treated cells. Prolonged 8e treatment also led to the onset of apoptosis, in correlation with the detection of increased Caspase 3/7 activities. Despite increasing γ-H2A.X levels, a well-established readout for DNA double-strand breaks, in vitro DNA binding studies with 8e did not support interaction with DNA. In agreement with this, 8e failed to activate the cellular DNA damage checkpoint. Importantly, tubulin staining showed that 8e promoted a severe disorganization of microtubules and mitotic spindle formation was not detected in 8e-treated cells. Accordingly, 8e inhibited tubulin polymerization in vitro in a dose-dependent manner and was also able to robustly inhibit cancer cell motility. Docking analysis revealed a compatible interaction with the colchicine-binding site of tubulin. Remarkably, these cellular effects were reversible since disruption of treatment resulted in the reorganization of microtubules, cell cycle re-entry and loss of senescent markers. Collectively, our data suggest that this compound may be a promising new anticancer agent capable of both reducing cancer cell growth and motility.

Therapeutic polymeric nanoparticles and the methods of making and using thereof: a patent evaluation of WO2015036792

Evaluation of the patent application WO2015036792 claiming therapeutic polymeric nanoparticles loaded with AZD1152-hqpa (aurora kinase inhibitor), and methods of making and using same for the treatment of cancer, is described. The claimed polymeric nano-formulations containing hydrophobic acid significantly improved the pharmacokinetic profiles (slow/sustained drug release profile) of the drug AZD1152-hqpa, as compared to the control agent (AZD1152). Drug efficacy and tolerability were also improved, and toxicity decreased in in vivo animal experiments, resulting in a better therapeutic index for the nano-formulation. Hence, the nano-formulated AZD1152-hqpa could be tested in the clinic at a dose level similar to, or higher than, that used for AZD1152, with lower incidence of toxicity.

Targeting Mitosis in Cancer: Emerging Strategies

The cell cycle is an evolutionarily conserved process necessary for mammalian cell growth and development. Because cell-cycle aberrations are a hallmark of cancer, this process has been the target of anti-cancer therapeutics for decades. However, despite numerous clinical trials, cell-cycle-targeting agents have generally failed in the clinic. This review briefly examines past cell-cycle-targeted therapeutics and outlines how experience with these agents has provided valuable insight to refine and improve anti-mitotic strategies. An overview of emerging anti-mitotic approaches with promising pre-clinical results is provided, and the concept of exploiting the genomic instability of tumor cells through therapeutic inhibition of mitotic checkpoints is discussed. We believe this strategy has a high likelihood of success given its potential to enhance therapeutic index by targeting tumor-specific vulnerabilities. This reasoning stimulated our development of novel inhibitors targeting the critical regulators of genomic stability and the mitotic checkpoint: AURKA, PLK4, and Mps1/TTK.

Aurora kinase targeting in lung cancer reduces KRAS-induced transformation

BACKGROUND

Activating mutations in KRAS are prevalent in lung cancer and have been causally linked to the oncogenic process. However, therapies targeted to oncogenic RAS have been ineffective to date and identification of KRAS targets that impinge on the oncogenic phenotype is warranted. Based on published studies showing that mitotic kinases Aurora A (AURKA) and B (AURKB) cooperate with oncogenic RAS to promote malignant transformation and that AURKA phosphorylates RAS effector pathway components, the aim of this study was to investigate whether AURKA and AURKB are KRAS targets in lung cancer and whether targeting these kinases might be therapeutically beneficial.

METHODS

In order to determine whether oncogenic KRAS induces Aurora kinase expression, we used qPCR and western blotting in three different lung cell-based models of gain- or loss-of-function of KRAS. In order to determine the functional role of these kinases in KRAS-induced transformation, we generated KRAS-positive A549 and H358 cells with stable and inducible shRNA-mediated knockdown of AURKA or AURKB and evaluated transformation in vitro and tumor growth in vivo. In order to validate AURKA and/or AURKB as therapeutically relevant KRAS targets in lung cancer, we treated A549 and H358 cells, as well as two different lung cell based models of gain-of-function of KRAS with a dual Aurora kinase inhibitor and performed functional in vitro assays.

RESULTS

We determined that KRAS positively regulates AURKA and AURKB expression. Furthermore, in KRAS-positive H358 and A549 cell lines, inducible knockdown of AURKA or AURKB, as well as treatment with a dual AURKA/AURKB inhibitor, decreased growth, viability, proliferation, transformation, and induced apoptosis in vitro. In addition, inducible shRNA-mediated knockdown of AURKA in A549 cells decreased tumor growth in vivo. More importantly, dual pharmacological inhibiton of AURKA and AURKB reduced growth, viability, transformation, and induced apoptosis in vitro in an oncogenic KRAS-dependent manner, indicating that Aurora kinase inhibition therapy can specifically target KRAS-transformed cells.

CONCLUSIONS

Our results support our hypothesis that Aurora kinases are important KRAS targets in lung cancer and suggest Aurora kinase inhibition as a novel approach for KRAS-induced lung cancer therapy.

Nuclear AURKA acquires kinase-independent transactivating function to enhance breast cancer stem cell phenotype

Centrosome-localized mitotic Aurora kinase A (AURKA) facilitates G2/M events. Here we show that AURKA translocates to the nucleus and causes distinct oncogenic properties in malignant cells by enhancing breast cancer stem cell (BCSC) phenotype. Unexpectedly, this function is independent of its kinase activity. Instead, AURKA preferentially interacts with heterogeneous nuclear ribonucleoprotein K (hnRNP K) in the nucleus and acts as a transcription factor in a complex that induces a shift in MYC promoter usage and activates the MYC promoter. Blocking AURKA nuclear localization inhibits this newly discovered transactivating function of AURKA, sensitizing resistant BCSC to kinase inhibition. These findings identify a previously unknown oncogenic property of the spatially deregulated AURKA in tumorigenesis and provide a potential therapeutic opportunity to overcome kinase inhibitor resistance.

Preferential Allele Expression Analysis Identifies Shared Germline and Somatic Driver Genes in Advanced Ovarian Cancer

Identifying genes where a variant allele is preferentially expressed in tumors could lead to a better understanding of cancer biology and optimization of targeted therapy. However, tumor sample heterogeneity complicates standard approaches for detecting preferential allele expression. We therefore developed a novel approach combining genome and transcriptome sequencing data from the same sample that corrects for sample heterogeneity and identifies significant preferentially expressed alleles. We applied this analysis to epithelial ovarian cancer samples consisting of matched primary ovary and peritoneum and lymph node metastasis. We find that preferentially expressed variant alleles include germline and somatic variants, are shared at a relatively high frequency between patients, and are in gene networks known to be involved in cancer processes. Analysis at a patient level identifies patient-specific preferentially expressed alleles in genes that are targets for known drugs. Analysis at a site level identifies patterns of site specific preferential allele expression with similar pathways being impacted in the primary and metastasis sites. We conclude that genes with preferentially expressed variant alleles can act as cancer drivers and that targeting those genes could lead to new therapeutic strategies.

Identifying genes that contribute to cancer biology is complicated partly because cancers can have dozens of somatic mutations and thousands of germline variants. Somatic mutations are gene variants that arise after conception in an organism while germline variants are gene variants present at conception in an organism. Most methods to identify cancer drivers have focused on determining somatic mutations. In this study we attempt to identify, from a tumor sample, important germline and somatic variants by determining if a variant is expressed (made into RNA) more than expected from the amount of the variant in the genome. The preferred expression of a variant could benefit cancer cells. When applying our analysis to ovarian cancer samples we found that despite the apparent heterogeneity, different patients frequently share the same genes with preferentially expressed variants. These genes in many cases are known to affect cancer processes such as DNA repair, cell adhesion and cell signaling and are targetable with known drugs. We therefore conclude that our analysis can identify germline and somatic gene variants that contribute to cancer biology and can potentially guide individualized therapies.

A Cell Biologist's Field Guide to Aurora Kinase Inhibitors

Aurora kinases are essential for cell division and are frequently misregulated in human cancers. Based on their potential as cancer therapeutics, a plethora of small molecule Aurora kinase inhibitors have been developed, with a subset having been adopted as tools in cell biology. Here, we fill a gap in the characterization of Aurora kinase inhibitors by using biochemical and cell-based assays to systematically profile a panel of 10 commercially available compounds with reported selectivity for Aurora A (MLN8054, MLN8237, MK-5108, MK-8745, Genentech Aurora Inhibitor 1), Aurora B (Hesperadin, ZM447439, AZD1152-HQPA, GSK1070916), or Aurora A/B (VX-680). We quantify the in vitro effect of each inhibitor on the activity of Aurora A alone, as well as Aurora A and Aurora B bound to fragments of their activators, TPX2 and INCENP, respectively. We also report kinome profiling results for a subset of these compounds to highlight potential off-target effects. In a cellular context, we demonstrate that immunofluorescence-based detection of LATS2 and histone H3 phospho-epitopes provides a facile and reliable means to assess potency and specificity of Aurora A versus Aurora B inhibition, and that G2 duration measured in a live imaging assay is a specific readout of Aurora A activity. Our analysis also highlights variation between HeLa, U2OS, and hTERT-RPE1 cells that impacts selective Aurora A inhibition. For Aurora B, all four tested compounds exhibit excellent selectivity and do not significantly inhibit Aurora A at effective doses. For Aurora A, MK-5108 and MK-8745 are significantly more selective than the commonly used inhibitors MLN8054 and MLN8237. A crystal structure of an Aurora A/MK-5108 complex that we determined suggests the chemical basis for this higher specificity. Taken together, our quantitative biochemical and cell-based analyses indicate that AZD1152-HQPA and MK-8745 are the best current tools for selectively inhibiting Aurora B and Aurora A, respectively. However, MK-8745 is not nearly as ideal as AZD1152-HQPA in that it requires high concentrations to achieve full inhibition in a cellular context, indicating a need for more potent Aurora A-selective inhibitors. We conclude with a set of “good practice” guidelines for the use of Aurora inhibitors in cell biology experiments.

The Aurora-A inhibitor MLN8237 affects multiple mitotic processes and induces dose-dependent mitotic abnormalities and aneuploidy

Inhibition of Aurora kinase activity by small molecules is being actively investigated as a potential anti-cancer strategy. A successful therapeutic use of Aurora inhibitors relies on a comprehensive understanding of the effects of inactivating Aurora kinases on cell division, a challenging aim given the pleiotropic roles of those kinases during mitosis. Here we have used the Aurora-A inhibitor MLN8237, currently under phase-I/III clinical trials, in dose-response assays in U2OS human cancer cells synchronously proceeding towards mitosis. By following the behaviour and fate of single Aurora-inhibited cells in mitosis by live microscopy, we show that MLN8237 treatment affects multiple processes that are differentially sensitive to the loss of Aurora-A function. A role of Aurora-A in controlling the orientation of cell division emerges. MLN8237 treatment, even in high doses, fails to induce efficient elimination of dividing cells, or of their progeny, while inducing significant aneuploidy in daughter cells. The results of single-cell analyses show a complex cellular response to MLN8237 and evidence that its effects are strongly dose-dependent: these issues deserve consideration in the light of the design of strategies to kill cancer cells via inhibition of Aurora kinases.

Recent advances in the development of Aurora kinases inhibitors in hematological malignancies

Over the last two decades, since the discovery of Drosophila mutants in 1995, much effort has been made to understand Aurora kinase biology. Three mammalian subtypes have been identified thus far which include the Aurora A, B and C kinases. These regulatory proteins specifically work at the cytoskeleton and chromosomal structures between the kinetochores and have vital functions in the early phases of the mitotic cell cycle. Today, there are multiple phase I and phase II clinical trials as well as numerous preclinical studies taking place looking at Aurora kinase inhibitors in both hematologic and solid malignancies. This review focuses on the preclinical and clinical development of Aurora kinase inhibitors in hematological malignancy and discusses their therapeutic potential.

Aurora kinase a regulates m1 macrophage polarization and plays a role in experimental autoimmune encephalomyelitis

Macrophage polarization is a dynamic and integral process of tissue inflammation and remodeling. Here we demonstrate an important role of Aurora kinase A in the regulation of inflammatory M1 macrophage polarization. We found that there was an elevated expression of Aurora-A in M1 macrophages and inhibition of Aurora-A by small molecules or specific siRNA selectively led to the suppression of M1 polarization, sparing over the M2 macrophage differentiation. At the molecular level, we found that the effects of Aurora-A in M1 macrophages were mediated through the down-regulation of NF-κB pathway and subsequent IRF5 expression. In an autoimmune disease model, experimental autoimmune encephalitis (EAE), treatment with Aurora kinase inhibitor blocked the disease development and shifted the macrophage phenotype from inflammatory M1 to anti-inflammatory M2. Thus, this study reveals a novel function of Aurora-A in controlling the polarization of macrophages, and modification of Aurora-A activity may lead to a new therapeutic approach for chronic inflammatory diseases.

Danusertib Induces Apoptosis, Cell Cycle Arrest, and Autophagy but Inhibits Epithelial to Mesenchymal Transition Involving PI3K/Akt/mTOR Signaling Pathway in Human Ovarian Cancer Cells

Ovarian carcinoma (OC) is one of the most common gynecological malignancies, with a poor prognosis for patients at advanced stage. Danusertib (Danu) is a pan-inhibitor of the Aurora kinases with unclear anticancer effect and underlying mechanisms in OC treatment. This study aimed to examine the cancer cell killing effect and explore the possible mechanisms with a focus on proliferation, cell cycle progression, apoptosis, autophagy, and epithelial to mesenchymal transition (EMT) in human OC cell lines C13 and A2780cp. The results showed that Danu remarkably inhibited cell proliferation, induced apoptosis and autophagy, and suppressed EMT in both cell lines. Danu arrested cells in G₂/M phase and led to an accumulation of polyploidy through the regulation of the expression key cell cycle modulators. Danu induced mitochondria-dependent apoptosis and autophagy in dose and time-dependent manners. Danu suppressed PI3K/Akt/mTOR signaling pathway, evident from the marked reduction in the phosphorylation of PI3K/Akt/mTOR, contributing to the autophagy inducing effect of Danu in both cell lines. In addition, Danu inhibited EMT. In aggregate, Danu exerts potent inducing effect on cell cycle arrest, apoptosis, and autophagy, but exhibits a marked inhibitory effect on EMT. PI3K/Akt/mTOR signaling pathway contributes, partially, to the cancer cell killing effect of Danu in C13 and A2780cp cells.

Sarcoma Cell Line Screen of Oncology Drugs and Investigational Agents Identifies Patterns Associated with Gene and microRNA Expression

The diversity in sarcoma phenotype and genotype make treatment of this family of diseases exceptionally challenging. Sixty-three human adult and pediatric sarcoma lines were screened with 100 FDA-approved oncology agents and 345 investigational agents. The investigational agents' library enabled comparison of several compounds targeting the same molecular entity allowing comparison of target specificity and heterogeneity of cell line response. Gene expression was derived from exon array data and microRNA expression was derived from direct digital detection assays. The compounds were screened against each cell line at nine concentrations in triplicate with an exposure time of 96 hours using Alamar blue as the endpoint. Results are presented for inhibitors of the following targets: aurora kinase, IGF-1R, MEK, BET bromodomain, and PARP1. Chemical structures, IC50 heat maps, concentration response curves, gene expression, and miR expression heat maps are presented for selected examples. In addition, two cases of exceptional responders are presented. The drug and compound response, gene expression, and microRNA expression data are publicly available at http://sarcoma.cancer.gov. These data provide a unique resource to the cancer research community.

Advances in small-molecule drug discovery for triple-negative breast cancer

Triple-negative breast cancer (TNBC) is a subtype of poor prognosis, highly invasive and difficult-to-treat breast cancers accounting for approximately 15% of clinical cases. Given the poor outlook and lack of sustained response to conventional therapies, TNBC has been the subject of intense studies on new therapeutic approaches in recent years. The development of targeted cancer therapies, often in combination with established chemotherapy, has been applied to a number of new clinical studies in this setting in recent years. This review will highlight recent therapeutic advances in TNBC, focusing on small-molecule drugs and their associated biological mechanisms of action, and offering the possibility of improved prospects for this patient group in the near future.

Molecular Pathways: New Signaling Considerations When Targeting Cytoskeletal Balance to Reduce Tumor Growth

The dynamic balance between microtubule extension and actin contraction regulates mammalian cell shape, division, and motility, which has made the cytoskeleton an attractive and very successful target for cancer drugs. Numerous compounds in clinical use to reduce tumor growth cause microtubule breakdown (vinca alkaloids, colchicine-site, and halichondrins) or hyperstabilization of microtubules (taxanes and epothilones). However, both of these strategies indiscriminately alter the assembly and dynamics of all microtubules, which causes significant dose-limiting toxicities on normal tissues. Emerging data are revealing that posttranslational modifications of tubulin (detyrosination, acetylation) or microtubule-associated proteins (Tau, Aurora kinase) may allow for more specific targeting of microtubule subsets, thereby avoiding the broad disruption of all microtubule polymerization. Developing approaches to reduce tumor cell migration and invasion focus on disrupting actin regulation by the kinases SRC and ROCK. Because the dynamic balance between microtubule extension and actin contraction also regulates cell fate decisions and stem cell characteristics, disrupting this cytoskeletal balance could yield unexpected effects beyond tumor growth. This review will examine recent data demonstrating that cytoskeletal cancer drugs affect wound-healing responses, microtentacle-dependent reattachment efficiency, and stem cell characteristics in ways that could affect the metastatic potential of tumor cells, both beneficially and detrimentally.

7-(Pyrazol-4-yl)-3H-imidazo[4,5-b]pyridine-based derivatives for kinase inhibition: Co-crystallisation studies with Aurora-A reveal distinct differences in the orientation of the pyrazole N1-substituent

Introduction of a 1-benzyl-1H-pyrazol-4-yl moiety at C7 of the imidazo[4,5-b]pyridine scaffold provided 7a which inhibited a range of kinases including Aurora-A. Modification of the benzyl group in 7a, and subsequent co-crystallisation of the resulting analogues with Aurora-A indicated distinct differences in binding mode dependent upon the pyrazole N-substituent. Compounds 7a and 14d interact with the P-loop whereas 14a and 14b engage with Thr217 in the post-hinge region. These crystallographic insights provide options for the design of compounds interacting with the DFG motif or with Thr217.

Exploring a cascade Heck-Suzuki reaction based route to kinase inhibitors using design of experiments

Design of Experiments (DoE) has been used to optimize a diversity oriented palladium catalyzed cascade Heck-Suzuki reaction for the construction of 3-alkenyl substituted cyclopenta[b]indole compounds. The obtained DoE model revealed a reaction highly dependent on the ligand. Guided by the model, an optimal ligand was chosen that selectively delivered the desired products in high yields. The conditions were applicable with a variety of boronic acids and were used to synthesize a library of 3-alkenyl derivatized compounds. Focusing on inhibition of kinases relevant for combating melanoma, the library was used in an initial structure-activity survey. In line with the observed kinase inhibition, cellular studies revealed one of the more promising derivatives to inhibit cell proliferation via an apoptotic mechanism.

ABCG2 impairs the activity of the aurora kinase inhibitor tozasertib but not of alisertib

BACKGROUND

Recently, we have shown that the ATP-binding cassette (ABC) transporter ABCB1 interferes with the anti-cancer activity of the pan-aurora kinase inhibitor tozasertib (VX680, MK-0457) but not of the aurora kinase A and B inhibitor alisertib (MLN8237). Preliminary data had suggested tozasertib also to be a substrate of the ABC transporter ABCG2, another ABC transporter potentially involved in cancer cell drug resistance. Here, we studied the effect of ABCG2 on the activity of tozasertib and alisertib.

RESULTS

The tozasertib concentration that reduces cell viability by 50% (IC50) was dramatically increased in ABCG2-transduced UKF-NB-3(ABCG2) cells (48.8-fold) compared to UKF-NB-3 cells and vector-transduced control cells. The ABCG2 inhibitor WK-X-34 reduced tozasertib IC50 to the level of non-ABCG2-expressing UKF-NB-3 cells. Furthermore, ABCG2 depletion from UKF-NB-3(ABCG2) cells using another lentiviral vector expressing an shRNA against the bicistronic mRNA of ABCG2 and eGFP largely re-sensitised these cells to tozasertib. In contrast, alisertib activity was not affected by ABCG2 expression.

CONCLUSIONS

Tozasertib but not alisertib activity is affected by ABCG2 expression. This should be considered within the design and analysis of experiments and clinical trials investigating these compounds.

Aurora Kinases and Potential Medical Applications of Aurora Kinase Inhibitors: A Review

Aurora kinases (AKs) represent a novel group of serine/threonine kinases. They were originally described in 1995 by David Glover in the course of studies of mutant alleles characterized with unusual spindle pole configuration in Drosophila melanogaster. Thus far, three AKs A, B, and C have been discovered in human healthy and neoplastic cells. Each one locates in different subcellular locations and they are all nuclear proteins. AKs are playing an essential role in mitotic events such as monitoring of the mitotic checkpoint, creation of bipolar mitotic spindle and alignment of centrosomes on it, also regulating centrosome separation, bio-orientation of chromosomes and cytokinesis. Any inactivation of them can have catastrophic consequences on mitotic events of spindle formation, alignment of centrosomes and cytokinesis, resulting in apoptosis. Overexpression of AKs has been detected in diverse solid and hematological cancers and has been linked with a dismal prognosis. After discovery and identification of the first aurora kinase inhibitor (AKI) ZM447439 as a potential drug for targeted therapy in cancer treatment, approximately 30 AKIs have been introduced in cancer treatment.

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.

Phase 1 dose escalation trial of ilorasertib, a dual Aurora/VEGF receptor kinase inhibitor, in patients with hematologic malignancies

BACKGROUND

Ilorasertib (ABT-348) is a novel inhibitor of Aurora kinase, vascular endothelial growth factor (VEGF) and platelet-derived growth factor receptors, and the Src families of tyrosine kinases. Ilorasertib alone or in combination with azacitidine demonstrated activity in preclinical models in various hematological malignancies, indicating that pan-Aurora kinase and multiple kinase inhibition may have preferential antileukemic activity. This phase 1 trial determined the safety, pharmacokinetics, and preliminary antitumor activity of ilorasertib alone or combined with azacitidine in advanced hematologic malignancies.

PATIENTS AND METHODS

Fifty-two patients (median age, 67 years; 35 % with >4 prior regimens) with acute myelogenous leukaemia (AML; n = 38), myelodysplastic syndrome (n = 12), or chronic myelomonocytic leukaemia (n = 2) received 3 or 6 doses of ilorasertib per 28-day cycle and were assigned to arm A (once-weekly oral), B (twice-weekly oral), C (once-weekly oral plus azacitidine), or D (once-weekly intravenous) treatment.

RESULTS

Maximum tolerated doses were not determined; the recommended phase 2 oral monotherapy doses were 540 mg once weekly and 480 mg twice weekly. The most common grade 3/4 adverse events were hypertension (28.8 %), hypokalemia (15.4 %), anemia (13.5 %), and hypophosphatemia (11.5 %). Oral ilorasertib pharmacokinetics appeared dose proportional, with a 15-hour half-life and no interaction with azacitidine. Ilorasertib inhibited biomarkers for Aurora kinase and VEGF receptors, and demonstrated clinical responses in 3 AML patients.

CONCLUSIONS

Ilorasertib exhibited acceptable safety and pharmacokinetics at or below the recommended phase 2 dose, displayed evidence of dual Aurora kinase and VEGF receptor kinase inhibition, and activity in AML.

Benzo[e]pyrimido[5,4-b][1,4]diazepin-6(11H)-one derivatives as Aurora A kinase inhibitors: LQTA-QSAR analysis and detailed systematic validation of the developed model

Aurora kinases are sub-divided into Aurora A, Aurora B, and Aurora C kinases that are considered as prospective targets for a new class of anticancer drugs. In this work, a 4-D-QSAR model using an LQTA-QSAR approach with previously reported 31 derivatives of benzo[e]pyrimido[5,4 -b][1,4]diazepin -6(11H)-one as potent Aurora kinase A inhibitors has been created. Instead of single conformation, the conformational ensemble profile generated for each ligand by using trajectories and topology information retrieved from molecular dynamics simulations from GROMACS package were aligned and used for the calculation of intermolecular interaction energies at each grid point. The descriptors generated on the basis of these Coulomb and Lennard-Jones potentials as independent variables were used to perform a PLS analysis using biological activity as dependent variable. A good predictive model was generated with nine field descriptors and five latent variables. The model showed [Formula: see text]; [Formula: see text] and [Formula: see text]. This model was further validated systematically by using different validation parameters. This 4D-QSAR model gave valuable information to recognize features essential to adapt and develop novel potential Aurora kinase inhibitors.

Novel Aurora/vascular endothelial growth factor receptor dual kinase inhibitor as treatment for hepatocellular carcinoma

We previously identified Aurora B kinase as the only independent factor predictive of the aggressive recurrence of hepatocellular carcinoma (HCC). In this preclinical study, JNJ-28841072, a novel Aurora/vascular endothelial growth factor receptor dual kinase inhibitor, was evaluated for treatment of HCC. In vitro and in vivo effects of JNJ-28841072 were analyzed using human HCC cell cultures and xenograft models. An orthotopic liver xenograft model was used for the pharmacobiological effects on Aurora kinase and vascularization in hepatic tumors. JNJ-28841072 suppressed in vitro phosphorylation of histone H3 with induction of cell polyploidy and death in a dose-dependent manner (IC₅₀ = 0.8–1.2 μM). In s.c. human HCC xenografts, remarkable inhibition of tumor growth was observed after JNJ-28841072 treatment (P = 0.0005). In orthotopic liver xenografts, the treatment with JNJ-28841072 significantly suppressed in vivo phosphorylation of histone H3 (P = 0.0008), vessel formation (P = 0.018), normoxic area (P = 0.0001), and hepatoma growth (P = 0.038). Our preclinical studies indicate that JNJ-28841072 is a promising novel therapeutic approach for the treatment of HCC. It might be worthy of evaluation in further studies.

Combined inhibition of MEK and Aurora A kinase in KRAS/PIK3CA double-mutant colorectal cancer models

Aurora A kinase and MEK inhibitors induce different, and potentially complementary, effects on the cell cycle of malignant cells, suggesting a rational basis for utilizing these agents in combination. In this work, the combination of an Aurora A kinase and MEK inhibitor was evaluated in pre-clinical colorectal cancer models, with a focus on identifying a subpopulation in which it might be most effective. Increased synergistic activity of the drug combination was identified in colorectal cancer cell lines with concomitant KRAS and PIK3CA mutations. Anti-proliferative effects were observed upon treatment of these double-mutant cell lines with the drug combination, and tumor growth inhibition was observed in double-mutant human tumor xenografts, though effects were variable within this subset. Additional evaluation suggests that degree of G2/M delay and p53 mutation status affect apoptotic activity induced by combination therapy with an Aurora A kinase and MEK inhibitor in KRAS and PIK3CA mutant colorectal cancer. Overall, in vitro and in vivo testing was unable to identify a subset of colorectal cancer that was consistently responsive to the combination of a MEK and Aurora A kinase inhibitor.

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.

Small molecule control of chromatin remodeling

Control of cellular transcriptional programs is based on reversible changes in chromatin conformation that affect access of the transcriptional machinery to specific gene promoters. Chromatin conformation is in turn controlled by the concerted effects of reversible, covalent modification of the DNA and histone components of chromatin, along with topographical changes in DNA-histone interactions; all of these chromatin-modifying reactions are catalyzed by specific enzymes and are communicated to the transcriptional machinery by proteins that recognize and bind to unique, covalent modifications at specific chromatin sites (so-called reader proteins). Over the past decade, considerable progress has been made in the discovery of potent and selective small molecule modulators of specific chromatin-modifying proteins. Here we review the progress that has been made toward small molecule control of these mechanisms and the potential clinical applications of such small molecule modulators of chromatin remodeling.

Aurora kinase A in gastrointestinal cancers: time to target

Gastrointestinal (GI) cancers are a major cause of cancer-related deaths. During the last two decades, several studies have shown amplification and overexpression of Aurora kinase A (AURKA) in several GI malignancies. These studies demonstrated that AURKA not only plays a role in regulating cell cycle and mitosis, but also regulates a number of key oncogenic signaling pathways. Although AURKA inhibitors have moved to phase III clinical trials in lymphomas, there has been slower progress in GI cancers and solid tumors. Ongoing clinical trials testing AURKA inhibitors as a single agent or in combination with conventional chemotherapies are expected to provide important clinical information for targeting AURKA in GI cancers. It is, therefore, imperative to consider investigations of molecular determinants of response and resistance to this class of inhibitors. This will improve evaluation of the efficacy of these drugs and establish biomarker based strategies for enrollment into clinical trials, which hold the future direction for personalized cancer therapy. In this review, we will discuss the available data on AURKA in GI cancers. We will also summarize the major AURKA inhibitors that have been developed and tested in pre-clinical and clinical settings.

Repressors of reprogramming

Induced pluripotent stem cells (iPSCs) have been the focal point of ever increasing interest and scrutiny as they hold the promise of personalized regenerative medicine. However, creation of iPSCs is an inefficient process that requires forced expression of potentially oncogenic proteins. In order to unlock the full potential of iPSCs, both for basic and clinical research, we must broaden our search for more reliable ways of inducing pluripotency in somatic cells. This review surveys an area of reprogramming that does not receive as much focus, barriers to reprogramming, in the hope of stimulating new ideas and approaches towards developing safer and more efficient methods of reprogramming. Better methods of iPSC creation will allow for more reliable disease modeling, better basic research into the pluripotent state and safer iPSCs that can be used in a clinical setting.

Clinical next generation sequencing of pediatric-type malignancies in adult patients identifies novel somatic aberrations

Pediatric malignancies in adults, in contrast to the same diseases in children are clinically more aggressive, resistant to chemotherapeutics, and carry a higher risk of relapse. Molecular profiling of tumor sample using next generation sequencing (NGS) has recently become clinically available. We report the results of targeted exome sequencing of six adult patients with pediatric-type malignancies : Wilms tumor(n=2), medulloblastoma(n=2), Ewing's sarcoma( n=1) and desmoplastic small round cell tumor (n=1) with a median age of 28.8 years. Detection of druggable somatic aberrations in tumors is feasible. However, identification of actionable target therapies in these rare adult patients with pediatric-type malignancies is challenging. Continuous efforts to establish a rare disease registry are warranted.

Modeling the mitotic regulatory network identifies highly efficient anti-cancer drug combinations

Targeting mitotic regulation is recognized as an important strategy for cancer therapy. Aurora A/B kinase and polo-like kinase 1 (PLK1) are the key mitotic regulators, and many inhibitors have been developed. Combinations of these inhibitors are anticipated to be more effective therapeutics compared with single-inhibitor treatments; however, a systematic analysis of the combined effects is lacking. Here, we constructed the first mammalian cell mitotic regulation network model, which spans from mitotic entry to anaphase initiation, and contains all key mitotic kinase targets. The combined effects of different kinase inhibitors and microtubule inhibitors were systematically explored. Simultaneous inhibition of Aurora B and PLK1 strongly induces polyploidy. Microtubule inhibitor dosage can be significantly reduced when combined with a PLK1 inhibitor. The efficacy of these inhibitor combinations was validated by our experimental results. The mitotic regulatory network model provides a platform to study the complex interactions during mitosis, enables identification of mitotic regulators, and determines targets for drug discovery research. The suggested use of combining microtubule inhibitors with PLK1 inhibitors is anticipated to enhance microtubule-inhibitor tolerance in a wide range of patients.

Aurora kinase B inhibition reduces the proliferation of metastatic melanoma cells and enhances the response to chemotherapy

BACKGROUND

The poor response to chemotherapy and the brief response to vemurafenib in metastatic melanoma patients, make the identification of new therapeutic approaches an urgent need. Interestingly the increased expression and activity of the Aurora kinase B during melanoma progression suggests it as a promising therapeutic target.

METHODS

The efficacy of the Aurora B kinase inhibitor barasertib-HQPA was evaluated in BRAF mutated cells, sensitive and made resistant to vemurafenib after chronic exposure to the drug, and in BRAF wild type cells. The drug effectiveness has been evaluated as cell growth inhibition, cell cycle progression and cell migration. In addition, cellular effectors of drug resistance and response were investigated.

RESULTS

The characterization of the effectors responsible for the resistance to vemurafenib evidenced the increased expression of MITF or the activation of Erk1/2 and p-38 kinases in the newly established cell lines with a phenotype resistant to vemurafenib. The sensitivity of cells to barasertib-HQPA was irrespective of BRAF mutational status. Barasertib-HQPA induced the mitotic catastrophe, ultimately causing apoptosis and necrosis of cells, inhibited cell migration and strongly affected the glycolytic metabolism of cells inducing the release of lactate. In association i) with vemurafenib the gain in effectiveness was found only in BRAF(V600K) cells while ii) with nab-paclitaxel, the combination was more effective than each drug alone in all cells.

CONCLUSIONS

These findings suggest barasertib as a new therapeutic agent and as enhancer of chemotherapy in metastatic melanoma treatment.

Inhibition of mitotic Aurora kinase A by alisertib induces apoptosis and autophagy of human gastric cancer AGS and NCI-N78 cells

Gastric cancer is one of the most common cancers and responds poorly to current chemotherapy. Alisertib (ALS) is a second-generation, orally bioavailable, highly selective small-molecule inhibitor of the serine/threonine protein kinase Aurora kinase A (AURKA). ALS has been shown to have potent anticancer effects in preclinical and clinical studies, but its role in gastric cancer treatment is unclear. This study aimed to investigate the cancer cell-killing effect of ALS on gastric cancer cell lines AGS and NCI-N78, with a focus on cell proliferation, cell-cycle distribution, apoptosis, and autophagy and the mechanism of action. The results showed that ALS exhibited potent growth-inhibitory, proapoptotic, and proautophagic effects on AGS and NCI-N78 cells. ALS concentration-dependently inhibited cell proliferation and induced cell-cycle arrest at G₂/M phase in both cell lines, with a downregulation of cyclin-dependent kinase 1 and cyclin B1 expression but upregulation of p21 Waf1/Cip1, p27 Kip1, and p53 expression. ALS induced mitochondria-mediated apoptosis and autophagy in both AGS and NCI-N78 cells. ALS induced the expression of proapoptotic proteins but inhibited the expression of antiapoptotic proteins, with a significant increase in the release of cytochrome c and the activation of caspase 9 and caspase 3 in both cell lines. ALS induced inhibition of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) and p38 mitogen-activated protein kinase (MAPK) signaling pathways while activating the 5′-adenosine monophosphate-activated protein kinase (AMPK) signaling pathway as indicated by their altered phosphorylation, contributing to the proautophagic effects of ALS. SB202191 and wortmannin enhanced the autophagy-inducing effect of ALS in AGS and NCI-N78 cells. Notably, ALS treatment significantly decreased the ratio of phosphorylated AURKA over AURKA, which may contribute, at least in part, to the inducing effects of ALS on cell-cycle arrest and autophagy in AGS and NCI-N78 cells. Taken together, these results indicate that ALS exerts a potent inhibitory effect on cell proliferation but inducing effects on cell-cycle arrest, mitochondria-dependent apoptosis, and autophagy with the involvement of PI3K/Akt/mTOR, p38 MAPK, and AURKA-mediated signaling pathways in AGS and NCI-N78 cells.

Alisertib, an Aurora kinase A inhibitor, induces apoptosis and autophagy but inhibits epithelial to mesenchymal transition in human epithelial ovarian cancer cells

Ovarian cancer is a leading killer of women, and no cure for advanced ovarian cancer is available. Alisertib (ALS), a selective Aurora kinase A (AURKA) inhibitor, has shown potent anticancer effects, and is under clinical investigation for the treatment of advanced solid tumor and hematologic malignancies. However, the role of ALS in the treatment of ovarian cancer remains unclear. This study investigated the effects of ALS on cell growth, apoptosis, autophagy, and epithelial to mesenchymal transition (EMT), and the underlying mechanisms in human epithelial ovarian cancer SKOV3 and OVCAR4 cells. Our docking study showed that ALS, MLN8054, and VX-680 preferentially bound to AURKA over AURKB via hydrogen bond formation, charge interaction, and π-π stacking. ALS had potent growth-inhibitory, proapoptotic, proautophagic, and EMT-inhibitory effects on SKOV3 and OVCAR4 cells. ALS arrested SKOV3 and OVCAR4 cells in G₂/M phase and induced mitochondria-mediated apoptosis and autophagy in both SKOV3 and OVCAR4 cell lines in a concentration-dependent manner. ALS suppressed phosphatidylinositol 3-kinase/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) and p38 mitogen-activated protein kinase pathways but activated 5′-AMP-dependent kinase, as indicated by their altered phosphorylation, contributing to the proautophagic activity of ALS. Modulation of autophagy altered basal and ALS-induced apoptosis in SKOV3 and OVCAR4 cells. Further, ALS suppressed the EMT-like phenotype in both cell lines by restoring the balance between E-cadherin and N-cadherin. ALS downregulated sirtuin 1 and pre-B cell colony enhancing factor (PBEF/visfatin) expression levels and inhibited phosphorylation of AURKA in both cell lines. These findings indicate that ALS blocks the cell cycle by G₂/M phase arrest and promotes cellular apoptosis and autophagy, but inhibits EMT via phosphatidylinositol 3-kinase/Akt/mTOR-mediated and sirtuin 1-mediated pathways in human epithelial ovarian cancer cells. Further studies are warranted to validate the efficacy and safety of ALS in the treatment of ovarian cancer.

RNA-seq reveals aurora kinase-driven mTOR pathway activation in patients with sarcomatoid metastatic renal cell carcinoma

Sarcomatoid metastatic renal cell carcinoma (mRCC) is associated with a poor prognosis, and the biology of the disease has been inadequately characterized. RNA sequencing (RNA-seq) was performed on adjacent benign, clear cell, and sarcomatoid components from clinical specimens with sarcomatoid mRCC. M phase and cell-cycle pathways were enriched in sarcomatoid versus adjacent clear cell components, suggesting greater cell proliferation. The expression of aurora kinase A (AURKA) was increased as part of these pathways, and its increased expression was validated by quantitative PCR (qPCR). Immunohistochemical (IHC) analysis revealed that AURKA levels were increased in sarcomatoid tissue compared with their benign or clear cell parts. The increase in AURKA correlated with increased mTOR pathway activity, as evidenced by increased expression of phosphorylated mTOR (S2448) and ribosomal protein S6K (T389). When AURKA was stably expressed in a RCC cell line (Renca), it resulted in increased expression and activity of mTOR, suggesting that overexpression of AURKA can activate the mTOR pathway. These results warrant the analysis of a larger clinical cohort and suggest that targeting AURKA and/or mTOR in patients with sarcomatoid mRCC should be explored.

IMPLICATIONS

Comparative RNA-seq of adjacent sarcomatoid and clear cell histology of RCC indicates a proliferative phenotype and increased AURKA-dependent activation of mTOR signaling in sarcomatoid RCC, which could be targeted by available agents.

An integrated flow and microwave approach to a broad spectrum protein kinase inhibitor

The protein kinase inhibitor CTx-0152960 and the piperazinyl analogue CTx-0294885 were prepared using a hybrid flow and microwave approach.

A phase 1 dose escalation study of BI 831266, an inhibitor of Aurora kinase B, in patients with advanced solid tumors

Purpose BI 831266 is a potent, selective, low-molecular-weight inhibitor of Aurora kinase B. This trial aimed to determine the maximum tolerated dose (MTD) of BI 831266 in patients with advanced solid tumors (NCT00756223; EudraCT 2008-001631-36; 1257.1). Methods BI 831266 (4–130 mg) was administered over 24 h on days 1 and 15 of a 4-week schedule. A modified 3 + 3 dose-escalation design was utilized to evaluate the MTD. Safety, pharmacokinetics, pharmacodynamics, objective response rate, progression-free survival (PFS) and exploratory biomarkers were secondary endpoints. Results Twenty-five patients received BI 831266. The most frequent tumor type was colorectal cancer (48 %). One patient (130 mg) experienced a dose-limiting toxicity of grade 3 febrile neutropenia. The trial was prematurely terminated (sponsor decision) without further dose-escalation. The most frequent treatment-related adverse events (AEs) were fatigue (20 %), neutropenia, alopecia (16 % each), anemia, dry skin, and nausea (12 % each). Treatment-related grade ≥3 AEs were neutropenia (12 %), anemia (8 %), and febrile neutropenia (4 %); 15 patients experienced serious AEs. High variability in the pharmacokinetic profiles precluded definitive pharmacokinetic conclusions. Exploratory biomarker determination revealed consistency with the mode of action as an Aurora kinase B inhibitor. One patient (4 %; 32 mg) with cervical cancer demonstrated a confirmed partial response (duration 141 days, PFS 414 days). Four patients had stable disease. Conclusion The MTD of BI 831266 was not reached because of early trial termination. BI 831266 demonstrated a generally manageable safety profile and signs of antitumor activity in some patients’ solid tumors.

Efficacy and safety of biweekly i.v. administrations of the Aurora kinase inhibitor danusertib hydrochloride in independent cohorts of patients with advanced or metastatic breast, ovarian, colorectal, pancreatic, small-cell and non-small-cell lung cancer: a multi-tumour, multi-institutional phase II study

BACKGROUND

This multi-centre phase II trial assessed the activity, safety (CTCAE 3.0) and pharmacokinetics (PK) of the pan-Aurora kinase inhibitor danusertib hydrochloride (PHA-739358) in breast (BC), ovarian (OC), pancreatic (PC), colorectal (CRC), small-cell (SCLC) and non-small-cell lung (NSCLC) cancers.

METHODS

Consenting adult patients with good performance and organ function with advanced/metastatic tumours who had failed systemic therapy were treated in independent, disease-specific cohorts with danusertib 500 mg/m(2) given as 24-h i.v. infusion every 14 days with until progression or unacceptable toxicity. A two-stage design was applied. Primary end point was the progression-free rate (PFR) at 4 months (RECIST1.1).

RESULTS

A total of 223 patients were enrolled with 219 actively treated. The median relative dose intensity of danusertib was similar for all tumour types (84.6%-99.6%). The median number of biweekly treatment cycles ranged from 3 to 4/patient (maximum 5-40 cycles/entity) and the median treatment duration varied between 7.6 and 10.0 weeks per histotype. Danusertib did not meet pre-specified protocol criteria for clinically relevant activity in any of the treated cancers. The PFR at 4 months was 18.4% in BC, 12.1% in OC, 10.0% in PC, 10.4% in NSCLC (all histotypes), 16.1% in squamous NSCLC and 0% in SCLC and CRC. Some radiological and/or biochemical indication of antitumor activity was seen in BC, OC, PC and NSCLC, including two confirmed partial responses. The most frequent drug-related non-laboratory adverse events (AEs) were fatigue/asthenia, nausea, diarrhoea, anorexia, vomiting, alopecia, constipation and pyrexia. Common laboratory AEs included haematological toxicity, hypalbuminaemia and increases in liver enzymes. Treatment was discontinued due to AEs in only 5.5% of patients. Plasma concentrations of danusertib were in line with results from earlier studies.

CONCLUSION

Single-agent danusertib did show only marginal anti-tumour activity in common solid tumours after failure of prior systemic therapies. The safety and PK profile was consistent with previous experience.

CLINICAL TRIAL NUMBER

2006-003772-35.

P21-activated kinase 7 mediates cisplatin-resistance of esophageal squamous carcinoma cells with Aurora-A overexpression

Aurora-A overexpression is common in various types of cancers and has been shown to be involved in tumorigenesis through different signaling pathways, yet how the deregulation affects cancer therapeutics remains elusive. Here we showed that overexpression of Aurora-A rendered esophageal cancer cells resistance to cisplatin (CDDP) by inhibiting apoptosis. By using an apoptosis array, we identified a downstream gene, p21-activated kinase 7 (PAK7). PAK7 was upregulated by Aurora-A overexpression at both mRNA and protein levels. Importantly, the expression levels of Aurora-A and PAK7 were correlated in ESCC primary samples. Chromatin immunoprecipitation (ChIP) assay revealed that binding of E2F1 to the promoter of PAK7 was significantly enhanced upon Aurora-A activation, and knockdown of transcription factor E2F1 decreased PAK7 expression, suggesting that Aurora-A regulated PAK7 through E2F1. Furthermore, we demonstrated that PAK7 knockdown led to increased apoptosis, and Aurora-A-induced resistance to CDDP was reversed by downregulation of PAK7, suggesting PAK7 was a downstream player of Aurora-A that mediated chemoresistance of ESCC cells to CDDP. Our data suggest that PAK7 may serve as an attractive candidate for therapeutics in ESCC patients with Aurora-A abnormality.

Inhibition of Aurora kinase B is important for biologic activity of the dual inhibitors of BCR-ABL and Aurora kinases R763/AS703569 and PHA-739358 in BCR-ABL transformed cells

ABL tyrosine kinase inhibitors (TKI) like Imatinib, Dasatinib and Nilotinib are the gold standard in conventional treatment of CML. However, the emergence of resistance remains a major problem. Alternative therapeutic strategies of ABL TKI-resistant CML are urgently needed. We asked whether dual inhibition of BCR-ABL and Aurora kinases A-C could overcome resistance mediated by ABL kinase mutations. We therefore tested the dual ABL and Aurora kinase inhibitors PHA-739358 and R763/AS703569 in Ba/F3- cells ectopically expressing wild type (wt) or TKI-resistant BCR-ABL mutants. We show that both compounds exhibited strong anti-proliferative and pro-apoptotic activity in ABL TKI resistant cell lines including cells expressing the strongly resistant T315I mutation. Cell cycle analysis indicated polyploidisation, a consequence of continued cell cycle progression in the absence of cell division by Aurora kinase inhibition. Experiments using drug resistant variants of Aurora B indicated that PHA-739358 acts on both, BCR-ABL and Aurora Kinase B, whereas Aurora kinase B inhibition might be sufficient for the anti-proliferative activity observed with R763/AS703569. Taken together, our data demonstrate that dual ABL and Aurora kinase inhibition might be used to overcome ABL TKI resistant CML.

SAR156497, an exquisitely selective inhibitor of aurora kinases

The Aurora family of serine/threonine kinases is essential for mitosis. Their crucial role in cell cycle regulation and aberrant expression in a broad range of malignancies have been demonstrated and have prompted intensive search for small molecule Aurora inhibitors. Indeed, over 10 of them have reached the clinic as potential anticancer therapies. We report herein the discovery and optimization of a novel series of tricyclic molecules that has led to SAR156497, an exquisitely selective Aurora A, B, and C inhibitor with in vitro and in vivo efficacy. We also provide insights into its mode of binding to its target proteins, which could explain its selectivity.

Identification of ligand efficient, fragment-like hits from an HTS library: structure-based virtual screening and docking investigations of 2H- and 3H-pyrazolo tautomers for Aurora kinase A selectivity

Furanopyrimidine 1 (IC50 = 273 nM, LE = 0.36, LELP = 10.28) was recently identified by high-throughput screening (HTS) of an in-house library (125,000 compounds) as an Aurora kinase inhibitor. Structure-based hit optimization resulted in lead molecules with in vivo efficacy in a mouse tumour xenograft model, but no oral bioavailability. This is attributed to "molecular obesity", a common problem during hit to lead evolution during which degradation of important molecular properties such as molecular weight (MW) and lipophilicity occurs. This could be effectively tackled by the right choice of hit compounds for optimization. In this regard, ligand efficiency (LE) and ligand efficiency dependent lipophilicity (LELP) indices are more often used to choose fragment-like hits for optimization. To identify hits with appropriate LE, we used a MW cut-off <250, and pyrazole structure to filter HTS library. Next, structure-based virtual screening using software (Libdock and Glide) in the Aurora A crystal structure (PDB ID: 3E5A) was carried out, and the top scoring 18 compounds tested for Aurora A enzyme inhibition. This resulted in the identification of a novel tetrahydro-pyrazolo-isoquinoline hit 7 (IC50 = 852 nM, LE = 0.44, LELP = 8.36) with fragment-like properties suitable for further hit optimization. Moreover, hit 7 was found to be selective for Aurora A (Aurora B IC50 = 35,150 nM) and the possible reasons for selectivity investigated by docking two tautomeric forms (2H- and 3H-pyrazole) of 7 in Auroras A and B (PDB ID: 4AF3) crystal structures. This docking study shows that the major 3H-pyrazole tautomer of 7 binds in Aurora A stronger than in Aurora B.

In vitro and in vivo characterization of a benzofuran derivative, a potential anticancer agent, as a novel Aurora B kinase inhibitor

Aurora B is a serine/threonine kinase that has a key role in mitosis and is overexpressed in cancer cells. Aberrations in Aurora B are highly correlated with tumorigenesis and cancer development, so many studies have focused on the development of Aurora B kinase inhibitors. Based on one of our previous high-throughput screening studies, we identified lead compound S6, a small-molecule benzofuran derivative that binds Aurora B and inhibits its kinase activity in vitro. S6 also displayed high selectivity for Aurora B inhibition. The cytotoxicity of S6 was assessed against a panel of 21 cancer cell lines. The cervical cancer cell line HeLa, liver cancer cell line HepG2 and colon cancer cell line SW620 were the most sensitive to S6 treatment. We found that S6 decreased the proliferation and colony formation of these three cell lines and elevated their percentages of cells in the G2/M phase of the cell cycle. S6 also inhibited phospho-histone H3 on Ser 10, a natural biomarker of endogenous Aurora B activity. The growth suppression of liver cancer QGY-7401 xenograft tumors was observed in nude mice after S6 administration, and this effect was accompanied by the in vivo inhibition of phospho-histone H3 (Ser 10). Taken together, we conclude that targeting Aurora B with compound S6 may be a novel strategy for cancer treatment, and additional studies are warranted.