Portrait of Professor Michelle Garrett

Professor Michelle Garrett

Professor of Cancer Therapeutics
Faculty Director of Medical Sciences

About

Michelle Garrett is Professor of Cancer Therapeutics in the School of Biosciences at the University of Kent and Visiting Professor of Cancer Therapeutics at the Institute of Cancer Research, London, UK.
Michelle received her undergraduate degree from the University of Leeds and then joined The Institute of Cancer Research (ICR) London, to undertake her PhD research with Alan Hall on the role of the RhoA small GTPase in cancer. After gaining her PhD in 1991, Michelle took up a Lucille Markey International Research Fellowship and moved to the USA to undertake post-doctoral studies with Peter Novick at Yale University School of Medicine on regulation of small GTPases in the yeast Saccharomyces cerevisiae.
In 1994 Michelle joined Onyx Pharmaceuticals, California, USA, where she went on to become a team leader involved in the development of cancer drugs targeting the cell division cycle, a collaboration with Pfizer. This included the CDK4 inhibitor project, which went onto deliver Ibrance® (Palbociclib) now a registered treatment for breast cancer. She then returned to the ICR in 1999 to take up a team leader position in the Cancer Research UK (CRUK) Cancer Therapeutics Unit. Her research there specialised in the discovery and development of novel small molecule cancer therapeutics targeting cell signalling and the cell cycle. Whilst at the ICR, Michelle became a Reader in Cancer Therapeutics and Head of Biology for the CRUK Cancer Therapeutics Unit. In September 2014 Michelle joined the School of Biosciences at the University of Kent and currently has three cancer drugs in the clinic.

ORCID ID:0000-0002-3939-1673

Research interests

Understanding the molecular and cellular effects of new drugs for the treatment of cancer

One of the principal characteristics of human cancer is abnormal cell growth caused by deregulation of key cellular processes including signalling and cell division. In fact we now know that signalling pathways can act directly on the cell division cycle: for example, through growth factor regulated signal transduction pathways or via activation of cell cycle checkpoints in response to DNA damage. My research has therefore focussed on how signalling and cell division can be targeted for the treatment of cancer. This has led to the discovery of a number of innovative small molecule therapeutics including the AKT inhibitor AZD5363 the AGC kinase inhibitor AT13148, and the CHK1 kinase inhibitor CCT245737 (SRA737), which are all currently in clinical trial for the treatment of cancer. 

Research in the lab is now focussed on understanding the molecular and cellular effects of these and other functionally related drugs on the cancer cell. This research is being done using molecular and genetic technologies, including genome wide screening and high throughput cellular analysis. The long term aim of this work is to; (i) identify biomarkers for both patient stratification and drug-target engagement for these drugs in the clinic (ii) predict mechanisms of resistance that may arise to these drugs and (iii) develop strategies to prevent or overcome drug resistance, all of which have the potential to lead to the identification of new drugs targets for cancer drug discovery. The ultimate goal of this research is to improve the lives of individuals living with cancer. 

Teaching

Stage 1 

  • BI307 Human physiology and disease 

Stage 2 

  •  BI525 Investigation of Disease 

Stage 3 

  • BI642 Cancer Biology 
  • BI600 Research project 

MSc Cancer Biology (Programme Director) 

  • BI857 Cancer Research in Focus 
  • BI845 Research Project

Professional

  • Committee Member, Cancer Research UK New Agents Committee (NAC) 
  • Panel member, Cancer Research UK Small Molecule Expert Review Panel (SMERP) 
  • Panel member, MRC Developmental Pathways Funding Scheme (DPFS) 
  • Committee member, Breast Cancer Now Catalyst Fund Committee 
  • Committee member, Science AdvisoryCommittee (SAC), Worldwide Cancer Research 
  • General Secretary, British Association for Cancer Research (BACR) 
  • Committee member, Genes and CancerConference (UK) organising committee 
  • Committee member, National Cancer Research Institute (NCRI) Annual Cancer Conference organising committee 
  • Editorial Board member, Molecular Cancer Therapeutics (AACR)

Publications

Article

  • Fenton, T. et al. (2018). Meeting Abstracts of the BACR conference: response and resistance in cancer therapy. Cancer Drug Resistance [Online] 1:266-302. Available at: https://doi.org/10.20517/cdr.2018.18.
  • Fenton, T. et al. (2018). What really matters - response and resistance in cancer therapy. Cancer Drug Resistance [Online] 2018:200-203. Available at: https://doi.org/10.20517/cdr.2018.19.
  • Whittaker, S. et al. (2018). Molecular profiling and combinatorial activity of CCT068127: A potent CDK2 and CDK9 inhibitor. Molecular Oncology [Online] 12:287-304. Available at: https://doi.org/10.1002/1878-0261.12148.
    Deregulation of the cyclin-dependent kinases (CDKs) has been implicated in the pathogenesis of multiple cancer types. Consequently, CDKs have garnered intense interest as therapeutic targets for the treatment of cancer. We describe herein the molecular and cellular effects of CCT068127, a novel inhibitor of CDK2 and CDK9. Optimised from the purine template of seliciclib, CCT068127 exhibits greater potency and selectivity against purified CDK2 and CDK9 and superior antiproliferative activity against human colon cancer and melanoma cell lines. X-ray crystallography studies reveal that hydrogen bonding with the DFG motif of CDK2 is the likely mechanism of greater enzymatic potency. Commensurate with inhibition of CDK activity, CCT068127 treatment results in decreased retinoblastoma protein (RB) phosphorylation, reduced phosphorylation of RNA polymerase II and induction of cell cycle arrest and apoptosis. The transcriptional signature of CCT068127 shows greatest similarity to other small molecule CDK and also HDAC inhibitors. CCT068127 caused a dramatic loss in expression of DUSP6 phosphatase, alongside elevated ERK phosphorylation and activation of MAPK pathway target genes. MCL1 protein levels are rapidly decreased by CCT068127 treatment and this associates with synergistic antiproliferative activity after combined treatment with CCT068127 and ABT263, a BCL2-family inhibitor. These findings support the rational combination of this series of CDK2/9 inhibitors and BCL2 family inhibitors for the treatment of human cancer.
  • Moreno, L. et al. (2017). Accelerating drug development for neuroblastoma - New Drug Development Strategy: an Innovative Therapies for Children with Cancer, European Network for Cancer Research in Children and Adolescents and International Society of Paediatric Oncology Europe Neuroblastoma project. Expert Opinion on Drug Discovery [Online] 12:801-811. Available at: http://dx.doi.org/10.1080/17460441.2017.1340269.
    Introduction: Neuroblastoma, the commonest paediatric extra-cranial tumour, remains a leading cause of death from cancer in children. There is an urgent need to develop new drugs to improve cure rates and reduce long-term toxicity and to incorporate molecularly targeted therapies into treatment. Many potential drugs are becoming available, but have to be prioritised for clinical trials due to the relatively small numbers of patients.
    Areas covered: The current drug development model has been slow, associated with significant attrition, and few new drugs have been developed for neuroblastoma. The Neuroblastoma New Drug Development Strategy (NDDS) has: 1) established a group with expertise in drug development; 2) prioritised targets and drugs according to tumour biology (target expression, dependency, pre-clinical data; potential combinations; biomarkers), identifying as priority targets ALK, MEK, CDK4/6, MDM2, MYCN (druggable by BET bromodomain, aurora kinase, mTORC1/2) BIRC5 and checkpoint kinase 1; 3) promoted clinical trials with target-prioritised drugs. Drugs showing activity can be rapidly transitioned via parallel randomised trials into front-line studies.
    Expert opinion: The Neuroblastoma NDDS is based on the premise that optimal drug development is reliant on knowledge of tumour biology and prioritisation. This approach will accelerate neuroblastoma drug development and other poor prognosis childhood malignancies.
  • Saintas, E. et al. (2017). Acquired resistance to oxaliplatin is not directly associated with increased resistance to DNA damage in SK-N-ASrOXALI4000, a newly established oxaliplatin-resistant sub-line of the neuroblastoma cell line SK-N-AS. PLoS ONE [Online] 12:e0172140. Available at: http://dx.doi.org/10.1371/journal.pone.0172140.
    The formation of acquired drug resistance is a major reason for the failure of anti-cancer therapies after initial response. Here, we introduce a novel model of acquired oxaliplatin resistance, a sub-line of the non-MYCN-amplified neuroblastoma cell line SK-N-AS that was adapted to growth in the presence of 4000 ng/mL oxaliplatin (SK-N-ASrOXALI4000). SK-N-ASrOXALI4000 cells displayed enhanced chromosomal aberrations compared to SK-N-AS, as indicated by 24-chromosome fluorescence in situ hybridisation. Moreover, SK-N-ASrOXALI4000 cells were resistant not only to oxaliplatin but also to the two other commonly used anti-cancer platinum agents cisplatin and carboplatin. SK-N-ASrOXALI4000 cells exhibited a stable resistance phenotype that was not affected by culturing the cells for 10 weeks in the absence of oxaliplatin. Interestingly, SK-N-ASrOXALI4000 cells showed no cross resistance to gemcitabine and increased sensitivity to doxorubicin and UVC radiation, alternative treatments that like platinum drugs target DNA integrity. Notably, UVC-induced DNA damage is thought to be predominantly repaired by nucleotide excision repair and nucleotide excision repair has been described as the main oxaliplatin-induced DNA damage repair system. SK-N-ASrOXALI4000 cells were also more sensitive to lysis by influenza A virus, a candidate for oncolytic therapy, than SK-N-AS cells. In conclusion, we introduce a novel oxaliplatin resistance model. The oxaliplatin resistance mechanisms in SK-N-ASrOXALI4000 cells appear to be complex and not to directly depend on enhanced DNA repair capacity. Models of oxaliplatin resistance are of particular relevance since research on platinum drugs has so far predominantly focused on cisplatin and carboplatin.
  • Banerji, U. et al. (2017). A Phase 1 open-label study to identify a dosing regimen of the pan-AKT inhibitor AZD5363 for evaluation in solid tumors and in PIK3CA-mutated breast and gynecologic cancers. Clinical Cancer Research [Online]. Available at: http://dx.doi.org/10.1158/1078-0432.CCR-17-2260.
    Purpose: This Phase 1, open-label study (Study 1, D3610C00001; NCT01226316) was the first-in-human evaluation of oral AZD5363, a selective pan-AKT inhibitor, in patients with advanced solid malignancies. The objectives were to investigate the safety, tolerability and pharmacokinetics of AZD5363, define a recommended dosing schedule, and evaluate preliminary clinical activity.
    Experimental design: Patients were aged ?18 years with WHO performance status 0–1. Dose escalation was conducted within separate continuous and intermittent (4 days/week [4/7] or 2 days/week [2/7]) schedules with safety, pharmacokinetic and pharmacodynamic analyses. Expansion cohorts of approximately 20 patients each explored AZD5363 activity in PIK3CA-mutant breast and gynecologic cancers.
    Results: Maximum tolerated doses were 320 mg, 480 mg and 640 mg for continuous (n=47), 4/7 (n=21) and 2/7 (n=22) schedules, respectively. Dose-limiting toxicities were rash and diarrhea for continuous, hyperglycemia for 2/7, and none for 4/7. Common adverse events were diarrhea (78%) and nausea (49%) and, for CTCAE grade ?3 events, hyperglycemia (20%). The recommended Phase 2 dose (480 mg bid, 4/7 intermittent) was assessed in PIK3CA-mutant breast and gynecologic expansion cohorts: 46% and 56% of patients, respectively, showed a reduction in tumor size, with RECIST responses of 4% and 8%. These responses were less than the pre-specified 20% response rate; therefore, the criteria to stop further recruitment to the PIK3CA cohort were met.
    Conclusions: At the recommended Phase 2 dose, AZD5363 was well tolerated and achieved plasma levels and robust target modulation in tumors. Proof-of-concept responses were observed in patients with PIK3CA-mutant cancers treated with AZD5363.
  • Sumbayev, V. et al. (2016). Expression of functional neuronal receptor latrophilin 1 in human acute myeloid leukaemia cells. Oncotarget [Online]. Available at: http://dx.doi.org/10.18632/oncotarget.10039.
    Acute myeloid leukaemia (AML) is a blood cancer affecting cells of myeloid lineage. It is characterised by rapid growth of malignant leukocytes that accumulate in the bone marrow and suppress normal haematopoiesis. This systemic disease remains a serious medical burden worldwide. Characterisation of protein antigens specifically expressed by malignant cells, but not by healthy leukocytes, is vital for the diagnostics and targeted treatment of AML. Here we report, for the first time, that the neuronal receptor latrophilin-1 is expressed in human monocytic leukaemia cell lines and in primary human AML cells. However, it is absent in healthy leukocytes. Latrophilin-1 is functional in leukaemia cells tested, and its biosynthesis is controlled through the mammalian target of rapamycin (mTOR), a master regulator of myeloid cell translational pathways. Our findings demonstrate that latrophilin-1 could be considered as a novel biomarker of human AML, which offers potential new avenues for AML diagnosis and treatment.
  • Smith, J. et al. (2016). Novel pharmacodynamic biomarkers for MYCN protein and PI3K/AKT/mTOR pathway signaling in children with neuroblastoma. Molecular Oncology [Online] 10:538-552. Available at: http://doi.org/10.1016/j.molonc.2015.11.005.
    There is an urgent need for improved therapies for children with high-risk neuroblastoma
    where survival rates remain low. MYCN amplification is the most common genomic change
    associated with aggressive neuroblastoma and drugs targeting PI3K/AKT/mTOR, to activate
    MYCNoncoprotein degradation, are entering clinical evaluation. Our aim was to develop and
    validate pharmacodynamic (PD) biomarkers to evaluate both proof of mechanism and proof
    of concept for drugs that block PI3K/AKT/mTOR pathway activity in children with neuroblastoma.
    Wehave addressed the issue of limited access to tumor biopsies for quantitative detection
    of protein biomarkers by optimizing a three-color fluorescence activated cell sorting
    (FACS) method to purify CD45?/GD2+/CD56+ neuroblastoma cells from bone marrow. We
    then developed a novel quantitative measurement of MYCN protein in these isolated neuroblastoma
    cells, providing the potential to demonstrate proof of concept for drugs that inhibit
    PI3K/AKT/mTOR signaling in this disease. In addition we have established quantitative
    detection of three biomarkers for AKT pathway activity (phosphorylated and total AKT,
    GSK3b and P70S6K) in surrogate platelet-rich plasma (PRP) frompediatric patients. Together
    ournewapproachto neuroblastomacell isolation for protein detection and suite ofPD assays
    provides for the first time the opportunity for robust, quantitative measurement of proteinbased
    PD biomarkers in this pediatric patient population. These will be ideal tools to support
    clinical evaluation of PI3K/AKT/mTOR pathway drugs and their ability to target MYCN oncoprotein
    in upcoming clinical trials in neuroblastoma.
  • Osborne, J. et al. (2016). Multiparameter Lead Optimization to Give an Oral Checkpoint Kinase 1 (CHK1) Inhibitor Clinical Candidate: (R)-5-((4-((Morpholin-2-ylmethyl)amino)-5-(trifluoromethyl)pyridin-2-yl)amino)pyrazine-2-carbonitrile (CCT245737). Journal of Medicinal Chemistry [Online] 59:5221-5237. Available at: http://doi.org/10.1021/acs.jmedchem.5b01938.
    Multiparameter optimization of a series of 5-((4-aminopyridin-2-yl)amino)pyrazine-2-carbonitriles resulted in the identification of a potent and selective oral CHK1 preclinical development candidate with in vivo efficacy as a potentiator of deoxyribonucleic acid (DNA) damaging chemotherapy and as a single agent. Cellular mechanism of action assays were used to give an integrated assessment of compound selectivity during optimization resulting in a highly CHK1 selective adenosine triphosphate (ATP) competitive inhibitor. A single substituent vector directed away from the CHK1 kinase active site was unexpectedly found to drive the selective cellular efficacy of the compounds. Both CHK1 potency and off-target human ether-a-go-go-related gene (hERG) ion channel inhibition were dependent on lipophilicity and basicity in this series. Optimization of CHK1 cellular potency and in vivo pharmacokinetic–pharmacodynamic (PK–PD) properties gave a compound with low predicted doses and exposures in humans which mitigated the residual weak in vitro hERG inhibition.
  • Sadok, A. et al. (2015). Rho Kinase Inhibitors Block Melanoma Cell Migration and Inhibit Metastasis. Cancer Research [Online] 75:2272-2284. Available at: http://doi.org/10.1158/0008-5472.CAN-14-2156.
    There is an urgent need to identify new therapeutic opportunities for metastatic melanoma. Fragment-based screening has led to the discovery of orally available, ATP-competitive AKT kinase inhibitors, AT13148 and CCT129254. These compounds also inhibit the Rho-kinases ROCK 1 and ROCK 2 and we show they potently inhibit ROCK activity in melanoma cells in culture and in vivo. Treatment of melanoma cells with CCT129254 or AT13148 dramatically reduces cell invasion, impairing both “amoeboid-like” and mesenchymal-like modes of invasion in culture. Intravital imaging shows that CCT129254 or AT13148 treatment reduces the motility of melanoma cells in vivo. CCT129254 inhibits melanoma metastasis when administered 2 days after orthotopic intradermal injection of the cells, or when treatment starts after metastases have arisen. Mechanistically, our data suggest that inhibition of ROCK reduces the ability of melanoma cells to efficiently colonize the lungs. These results suggest that these novel inhibitors of ROCK may be beneficial in the treatment of metastasis.
  • Walton, M. et al. (2015). The clinical development candidate CCT245737 is an orally active CHK1 inhibitor with preclinical activity in RAS mutant NSCLC and Eµ-MYC driven B-cell lymphoma. Oncotarget [Online] 7:2329-2342. Available at: http://doi.org/10.18632/oncotarget.4919.
    CCT245737 is the first orally active, clinical development candidate CHK1 inhibitor to be described. The IC50 was 1.4nM against CHK1 enzyme and it exhibited>1,000-fold selectivity against CHK2 and CDK1. CCT245737 potently inhibited cellular CHK1 activity (IC50 30-220nM) and enhanced gemcitabine and SN38 cytotoxicity in multiple human tumor cell lines and human tumor xenograft models. Mouse oral bioavailability was complete (100%) with extensive tumor exposure. Genotoxic-induced CHK1 activity (pS296 CHK1) and cell cycle arrest (pY15 CDK1) were inhibited both in vitro and in human tumor xenografts by CCT245737, causing increased DNA damage and apoptosis. Uniquely, we show CCT245737 enhanced gemcitabine antitumor activity to a greater degree than for higher doses of either agent alone, without increasing toxicity, indicating a true therapeutic advantage for this combination. Furthermore, development of a novel ELISA assay for pS296 CHK1 autophosphorylation, allowed the quantitative measurement of target inhibition in a RAS mutant human tumor xenograft of NSCLC at efficacious doses of CCT245737. Finally, CCT245737 also showed significant single-agent activity against a MYC-driven mouse model of B-cell lymphoma. In conclusion, CCT245737 is a new CHK1 inhibitor clinical development candidate scheduled for a first in man Phase I clinical trial, that will use the novel pS296 CHK1 ELISA to monitor target inhibition.
  • Yap, T. et al. (2014). Interrogating Two Schedules of the AKT Inhibitor MK-2206 in Patients with Advanced Solid Tumors Incorporating Novel Pharmacodynamic and Functional Imaging Biomarkers. Clinical Cancer Research [Online] 20:5672-5685. Available at: http://doi.org/10.1158/1078-0432.CCR-14-0868.
    Purpose: Multiple cancers harbor genetic aberrations that impact AKT signaling. MK-2206 is a potent pan-AKT inhibitor with a maximum tolerated dose (MTD) previously established at 60 mg on alternate days (QOD). Due to a long half-life (60–80 hours), a weekly (QW) MK-2206 schedule was pursued to compare intermittent QW and continuous QOD dosing.

    Experimental Design: Patients with advanced cancers were enrolled in a QW dose-escalation phase I study to investigate the safety and pharmacokinetic–pharmacodynamic profiles of tumor and platelet-rich plasma (PRP). The QOD MTD of MK-2206 was also assessed in patients with ovarian and castration-resistant prostate cancers and patients with advanced cancers undergoing multiparametric functional magnetic resonance imaging (MRI) studies, including dynamic contrast-enhanced MRI, diffusion-weighted imaging, magnetic resonance spectroscopy, and intrinsic susceptibility-weighted MRI.

    Results: A total of 71 patients were enrolled; 38 patients had 60 mg MK-2206 QOD, whereas 33 received MK-2206 at 90, 135, 150, 200, 250, and 300 mg QW. The QW MK-2206 MTD was established at 200 mg following dose-limiting rash at 250 and 300 mg. QW dosing appeared to be similarly tolerated to QOD, with toxicities including rash, gastrointestinal symptoms, fatigue, and hyperglycemia. Significant AKT pathway blockade was observed with both continuous QOD and intermittent QW dosing of MK-2206 in serially obtained tumor and PRP specimens. The functional imaging studies demonstrated that complex multiparametric MRI protocols may be effectively implemented in a phase I trial.

    Conclusions: Treatment with MK-2206 safely results in significant AKT pathway blockade in QOD and QW schedules. The intermittent dose of 200 mg QW is currently used in phase II MK-2206 monotherapy and combination studies (NCT00670488). Clin Cancer Res; 20(22); 5672–85. ©2014 AACR.
  • Wang, Q. et al. (2013). Fragment-Based Screening Maps Inhibitor Interactions in the ATP-Binding Site of Checkpoint Kinase 2. PLoS ONE [Online] 8:e65689. Available at: http://doi.org/10.1371/journal.pone.0065689.
    Checkpoint kinase 2 (CHK2) is an important serine/threonine kinase in the cellular response to DNA damage. A fragment-based screening campaign using a combination of a high-concentration AlphaScreen™ kinase assay and a biophysical thermal shift assay, followed by X-ray crystallography, identified a number of chemically different ligand-efficient CHK2 hinge-binding scaffolds that have not been exploited in known CHK2 inhibitors. In addition, it showed that the use of these orthogonal techniques allowed efficient discrimination between genuine hit matter and false positives from each individual assay technology. Furthermore, the CHK2 crystal structures with a quinoxaline-based fragment and its follow-up compound highlight a hydrophobic area above the hinge region not previously explored in rational CHK2 inhibitor design, but which might be exploited to enhance both potency and selectivity of CHK2 inhibitors.
  • Touchefeu, Y. et al. (2013). Optimising measles virus-guided radiovirotherapy with external beam radiotherapy and specific checkpoint kinase 1 inhibition. Radiotherapy and Oncology [Online] 108:24-31. Available at: http://doi.org/10.1016/j.radonc.2013.05.036.
    Abstract
    Background and purpose

    We previously reported a therapeutic strategy comprising replication-defective NIS-expressing adenovirus combined with radioiodide, external beam radiotherapy (EBRT) and DNA repair inhibition. We have now evaluated NIS-expressing oncolytic measles virus (MV-NIS) combined with NIS-guided radioiodide, EBRT and specific checkpoint kinase 1 (Chk1) inhibition in head and neck and colorectal models.

    Materials and methods

    Anti-proliferative/cytotoxic effects of individual agents and their combinations were measured by MTS, clonogenic and Western analysis. Viral gene expression was measured by radioisotope uptake and replication by one-step growth curves. Potential synergistic interactions were tested in vitro by Bliss independence analysis and in in vivo therapeutic studies.

    Results

    EBRT and MV-NIS were synergistic in vitro. Furthermore, EBRT increased NIS expression in infected cells. SAR-020106 was synergistic with EBRT, but also with MV-NIS in HN5 cells. MV-NIS mediated 131I-induced cytotoxicity in HN5 and HCT116 cells and, in the latter, this was enhanced by SAR-020106. In vivo studies confirmed that MV-NIS, EBRT and Chk1 inhibition were effective in HCT116 xenografts. The quadruplet regimen of MV-NIS, virally-directed 131I, EBRT and SAR-020106 had significant anti-tumour activity in HCT116 xenografts.

    Conclusion

    This study strongly supports translational and clinical research on MV-NIS combined with radiation therapy and radiosensitising agents.
  • Borst, G. et al. (2012). Targeted Radiosensitization by the Chk1 Inhibitor SAR-020106. International Journal of Radiation Oncology Biology Physics [Online] 85:1110-1118. Available at: http://doi.org/10.1016/j.ijrobp.2012.08.006.
    Purpose

    To explore the activity of a potent Chk1 inhibitor (SAR-020106) in combination with radiation.

    Methods and Materials

    Colony and mechanistic in vitro assays and a xenograft in vivo model.

    Results

    SAR-020106 suppressed-radiation-induced G2/M arrest and reduced clonogenic survival only in p53-deficient tumor cells. SAR-020106 promoted mitotic entry following irradiation in all cell lines, but p53-deficient cells were likely to undergo apoptosis or become aneuploid, while p53 wild-type cells underwent a postmitotic G1 arrest followed by subsequent normal cell cycle re-entry. Following combined treatment with SAR-020106 and radiation, homologous-recombination-mediated DNA damage repair was inhibited in all cell lines. A significant increase in the number of pan-?H2AX-staining apoptotic cells was observed only in p53-deficient cell lines. Efficacy was confirmed in vivo in a clinically relevant human head-and-neck cell carcinoma xenograft model.

    Conclusion

    The Chk1 inhibitor SAR-020106 is a potent radiosensitizer in tumor cell lines defective in p53 signaling.
  • Bernhard, E. et al. (2012). Mechanism-Based Screen for G1/S Checkpoint Activators Identifies a Selective Activator of EIF2AK3/PERK Signalling. PLoS ONE [Online] 7:e28568. Available at: http://doi.org/10.1371/journal.pone.0028568.
    Human cancers often contain genetic alterations that disable G1/S checkpoint control and loss of this checkpoint is thought to critically contribute to cancer generation by permitting inappropriate proliferation and distorting fate-driven cell cycle exit. The identification of cell permeable small molecules that activate the G1/S checkpoint may therefore represent a broadly applicable and clinically effective strategy for the treatment of cancer. Here we describe the identification of several novel small molecules that trigger G1/S checkpoint activation and characterise the mechanism of action for one, CCT020312, in detail. Transcriptional profiling by cDNA microarray combined with reverse genetics revealed phosphorylation of the eukaryotic initiation factor 2-alpha (EIF2A) through the eukaryotic translation initiation factor 2-alpha kinase 3 (EIF2AK3/PERK) as the mechanism of action of this compound. While EIF2AK3/PERK activation classically follows endoplasmic reticulum (ER) stress signalling that sets off a range of different cellular responses, CCT020312 does not trigger these other cellular responses but instead selectively elicits EIF2AK3/PERK signalling. Phosphorylation of EIF2A by EIF2A kinases is a known means to block protein translation and hence restriction point transit in G1, but further supports apoptosis in specific contexts. Significantly, EIF2AK3/PERK signalling has previously been linked to the resistance of cancer cells to multiple anticancer chemotherapeutic agents, including drugs that target the ubiquitin/proteasome pathway and taxanes. Consistent with such findings CCT020312 sensitizes cancer cells with defective taxane-induced EIF2A phosphorylation to paclitaxel treatment. Our work therefore identifies CCT020312 as a novel small molecule chemical tool for the selective activation of EIF2A-mediated translation control with utility for proof-of-concept applications in EIF2A-centered therapeutic approaches, and as a chemical starting point for pathway selective agent development. We demonstrate that consistent with its mode of action CCT020312 is capable of delivering potent, and EIF2AK3 selective, proliferation control and can act as a sensitizer to chemotherapy-associated stresses as elicited by taxanes.
  • Banerji, U. et al. (2012). A Phase I Pharmacokinetic and Pharmacodynamic Study of CHR-3996, an Oral Class I Selective Histone Deacetylase Inhibitor in Refractory Solid Tumors. Clinical Cancer Research [Online] 18:2687-2694. Available at: http://doi.org/10.1158/1078-0432.CCR-11-3165.
    Purpose: This clinical trial investigated the safety, tolerability, pharmacokinetic (PK), and pharmacodynamic (PD) profile of CHR-3996, a selective class I histone deacetylase inhibitor.

    Patients and Methods: CHR-3996 was administered orally once a day. This phase I trial used a 3+3 dose-escalation design. PK profiles were analyzed by liquid chromatography–tandem mass spectroscopic methods and PD studies were conducted using ELISA studying histone H3 acetylation in peripheral blood mononuclear cells.

    Results: Thirty-nine patients were treated at dose levels of 5 mg (n = 3), 10 mg (n = 4), 20 mg (n = 3), 40 mg (n = 10), 80 mg (n = 10), 120 mg (n = 4), and 160 mg (n = 5) administered orally once daily. The dose-limiting toxicities seen were thrombocytopenia (160 mg), fatigue (80 and 120 mg), plasma creatinine elevation (80 and 120 mg), and atrial fibrillation (40 mg). The area under the curve was proportional to the administered dose and a maximal plasma concentration of 259 ng/mL at a dose of 40 mg exceeded the concentrations required for antitumor efficacy in preclinical models. Target inhibition measured by quantification of histone acetylation was shown at doses of 10 mg/d and was maximal at 40 mg. A partial response was seen in one patient with metastatic acinar pancreatic carcinoma.

    Conclusions: Taking the toxicity and PK/PD profile into consideration, the recommended phase II dose (RP2D) is 40 mg/d. At this dose, CHR-3996 has a favorable toxicologic, PK, and PD profile. CHR-3996 has shown preliminary clinical activity and should be evaluated in further clinical trials.
  • Yap, T. et al. (2012). AT13148 Is a Novel, Oral Multi-AGC Kinase Inhibitor with Potent Pharmacodynamic and Antitumor Activity. Clinical Cancer Research [Online] 18:3912-3923. Available at: http://doi.org/10.1158/1078-0432.CCR-11-3313.
    Purpose: Deregulated phosphatidylinositol 3-kinase pathway signaling through AGC kinases including AKT, p70S6 kinase, PKA, SGK and Rho kinase is a key driver of multiple cancers. The simultaneous inhibition of multiple AGC kinases may increase antitumor activity and minimize clinical resistance compared with a single pathway component.

    Experimental Design: We investigated the detailed pharmacology and antitumor activity of the novel clinical drug candidate AT13148, an oral ATP-competitive multi-AGC kinase inhibitor. Gene expression microarray studies were undertaken to characterize the molecular mechanisms of action of AT13148.

    Results: AT13148 caused substantial blockade of AKT, p70S6K, PKA, ROCK, and SGK substrate phosphorylation and induced apoptosis in a concentration and time-dependent manner in cancer cells with clinically relevant genetic defects in vitro and in vivo. Antitumor efficacy in HER2-positive, PIK3CA-mutant BT474 breast, PTEN-deficient PC3 human prostate cancer, and PTEN-deficient MES-SA uterine tumor xenografts was shown. We show for the first time that induction of AKT phosphorylation at serine 473 by AT13148, as reported for other ATP-competitive inhibitors of AKT, is not a therapeutically relevant reactivation step. Gene expression studies showed that AT13148 has a predominant effect on apoptosis genes, whereas the selective AKT inhibitor CCT128930 modulates cell-cycle genes. Induction of upstream regulators including IRS2 and PIK3IP1 as a result of compensatory feedback loops was observed.

    Conclusions: The clinical candidate AT13148 is a novel oral multi-AGC kinase inhibitor with potent pharmacodynamic and antitumor activity, which shows a distinct mechanism of action from other AKT inhibitors. AT13148 will now be assessed in a first-in-human phase I trial
  • Walton, M. et al. (2012). CCT244747 Is a Novel Potent and Selective CHK1 Inhibitor with Oral Efficacy Alone and in Combination with Genotoxic Anticancer Drugs. Clinical Cancer Research [Online] 18:5650-5661. Available at: http://doi.org/10.1158/1078-0432.CCR-12-1322.
    Purpose: Many tumors exhibit defective cell-cycle checkpoint control and increased replicative stress. CHK1 is critically involved in the DNA damage response and maintenance of replication fork stability. We have therefore discovered a novel potent, highly selective, orally active ATP-competitive CHK1 inhibitor, CCT244747, and present its preclinical pharmacology and therapeutic activity.

    Experimental Design: Cellular CHK1 activity was assessed using an ELISA assay, and cytotoxicity a SRB assay. Biomarker modulation was measured using immunoblotting, and cell-cycle effects by flow cytometry analysis. Single-agent oral CCT244747 antitumor activity was evaluated in a MYCN-driven transgenic mouse model of neuroblastoma by MRI and in genotoxic combinations in human tumor xenografts by growth delay.

    Results: CCT244747 inhibited cellular CHK1 activity (IC50 29–170 nmol/L), significantly enhanced the cytotoxicity of several anticancer drugs, and abrogated drug-induced S and G2 arrest in multiple tumor cell lines. Biomarkers of CHK1 (pS296 CHK1) activity and cell-cycle inactivity (pY15 CDK1) were induced by genotoxics and inhibited by CCT244747 both in vitro and in vivo, producing enhanced DNA damage and apoptosis. Active tumor concentrations of CCT244747 were obtained following oral administration. The antitumor activity of both gemcitabine and irinotecan were significantly enhanced by CCT244747 in several human tumor xenografts, giving concomitant biomarker modulation indicative of CHK1 inhibition. CCT244747 also showed marked antitumor activity as a single agent in a MYCN-driven neuroblastoma.

    Conclusion: CCT244747 represents the first structural disclosure of a highly selective, orally active CHK1 inhibitor and warrants further evaluation alone or combined with genotoxic anticancer therapies.
  • Carden, C. et al. (2012). The Association of PI3 Kinase Signaling and Chemoresistance in Advanced Ovarian Cancer. Molecular Cancer Therapeutics [Online] 11:1609-1617. Available at: http://doi.org/10.1158/1535-7163.MCT-11-0996.
    Evidence that the phosphoinositide 3-kinase (PI3K) pathway is deregulated in ovarian cancer is largely based on the analysis of surgical specimens sampled at diagnosis and may not reflect the biology of advanced ovarian cancer. We aimed to investigate PI3K signaling in cancer cells isolated from patients with advanced ovarian cancer. Ascites samples were analyzed from 88 patients, of whom 61 received further treatment. Cancer cells were immunomagnetically separated from ascites, and the signaling output of the PI3K pathway was studied by quantifying p-AKT, p-p70S6K, and p-GSK3? by ELISA. Relevant oncogenes, such as PIK3CA and AKT, were sequenced by PCR-amplified mass spectroscopy detection methods. In addition, PIK3CA and AKT2 amplifications and PTEN deletions were analyzed by FISH. p-p70S6K levels were significantly higher in cells from 37 of 61 patients who did not respond to subsequent chemotherapy (0.7184 vs. 0.3496; P = 0.0100), and this difference was greater in patients who had not received previous chemotherapy. PIK3CA and AKT mutations were present in 5% and 0% of samples, respectively. Amplification of PIK3CA and AKT2 and deletion of PTEN was seen in 10%, 10%, and 27% of samples, respectively. Mutations of PIK3CA and amplification of PIK3CA/AKT2 or deletion of PTEN did not correlate with levels of p-AKT, p-p70S6K, and p-GSK3?. In patients with advanced ovarian cancer, there is an association between levels of p-p70S6K and response to subsequent chemotherapy. There is no clear evidence that this is driven specifically by PIK3CA or AKT mutations or by amplifications or deletion of PTEN.
  • Lainchbury, M. et al. (2012). Discovery of 3-Alkoxyamino-5-(pyridin-2-ylamino)pyrazine-2-carbonitriles as Selective, Orally Bioavailable CHK1 Inhibitors. Journal of Medicinal Chemistry [Online] 55:10229-10240. Available at: http://doi.org/10.1021/jm3012933.
  • Reader, J. et al. (2011). Structure-Guided Evolution of Potent and Selective CHK1 Inhibitors through Scaffold Morphing. Journal of Medicinal Chemistry [Online] 54:8328-8342. Available at: http://doi.org/10.1021/jm2007326.
    Pyrazolopyridine inhibitors with low micromolar potency for CHK1 and good selectivity against CHK2 were previously identified by fragment-based screening. The optimization of the pyrazolopyridines to a series of potent and CHK1-selective isoquinolines demonstrates how fragment-growing and scaffold morphing strategies arising from a structure-based understanding of CHK1 inhibitor binding can be combined to successfully progress fragment-derived hit matter to compounds with activity in vivo. The challenges of improving CHK1 potency and selectivity, addressing synthetic tractability, and achieving novelty in the crowded kinase inhibitor chemical space were tackled by multiple scaffold morphing steps, which progressed through tricyclic pyrimido[2,3-b]azaindoles to N-(pyrazin-2-yl)pyrimidin-4-amines and ultimately to imidazo[4,5-c]pyridines and isoquinolines. A potent and highly selective isoquinoline CHK1 inhibitor (SAR-020106) was identified, which potentiated the efficacies of irinotecan and gemcitabine in SW620 human colon carcinoma xenografts in nude mice.
  • Anderson, V. et al. (2011). CCT241533 Is a Potent and Selective Inhibitor of CHK2 that Potentiates the Cytotoxicity of PARP Inhibitors. Cancer Research [Online] 71:463-472. Available at: http://doi.org/10.1158/0008-5472.CAN-10-1252.
    CHK2 is a checkpoint kinase involved in the ATM-mediated response to double-strand DNA breaks. Its potential as a drug target is still unclear, but inhibitors of CHK2 may increase the efficacy of genotoxic cancer therapies in a p53 mutant background by eliminating one of the checkpoints or DNA repair pathways contributing to cellular resistance. We report here the identification and characterization of a novel CHK2 kinase inhibitor, CCT241533. X-ray crystallography confirmed that CCT241533 bound to CHK2 in the ATP pocket. This compound inhibits CHK2 with an IC50 of 3 nmol/L and shows minimal cross-reactivity against a panel of kinases at 1 ?mol/L. CCT241533 blocked CHK2 activity in human tumor cell lines in response to DNA damage, as shown by inhibition of CHK2 autophosphorylation at S516, band shift mobility changes, and HDMX degradation. CCT241533 did not potentiate the cytotoxicity of a selection of genotoxic agents in several cell lines. However, this compound significantly potentiates the cytotoxicity of two structurally distinct PARP inhibitors. Clear induction of the pS516 CHK2 signal was seen with a PARP inhibitor alone, and this activation was abolished by CCT241533, implying that the potentiation of PARP inhibitor cell killing by CCT241533 was due to inhibition of CHK2. Consequently, our findings imply that CHK2 inhibitors may exert therapeutic activity in combination with PARP inhibitors.
  • McHardy, T. et al. (2010). Discovery of 4-Amino-1-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperidine-4-carboxamides As Selective, Orally Active Inhibitors of Protein Kinase B (Akt). Journal of Medicinal Chemistry [Online] 53:2239-2249. Available at: http://dx.doi.org/10.1021/jm901788j.
    Protein kinase B (PKB or Akt) is an important component of intracellular signaling pathways regulating growth and survival. Signaling through PKB is frequently deregulated in cancer, and inhibitors of PKB therefore have potential as antitumor agents. The optimization of lipophilic substitution within a series of 4-benzyl-1-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperidin-4-amines provided ATP-competitive, nanomolar inhibitors with up to 150-fold selectivity for inhibition of PKB over the closely related kinase PKA. Although active in cellular assays, compounds containing 4-amino-4-benzylpiperidines underwent metabolism in vivo, leading to rapid clearance and low oral bioavailability. Variation of the linker group between the piperidine and the lipophilic substituent identified 4-amino-1-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)piperidine-4-carboxamides as potent and orally bioavailable inhibitors of PKB. Representative compounds modulated biomarkers of signaling through PKB in vivo and strongly inhibited the growth of human tumor xenografts in nude mice at well-tolerated doses.
  • Matthews, T. et al. (2010). Design and evaluation of 3,6-di(hetero)aryl imidazo[1,2-a]pyrazines as inhibitors of checkpoint and other kinases. Bioorganic & Medicinal Chemistry Letters [Online] 20:4045-4049. Available at: http://doi.org/10.1016/j.bmcl.2010.05.096.
    A range of 3,6-di(hetero)arylimidazo[1,2-a]pyrazine ATP-competitive inhibitors of CHK1 were developed by scaffold hopping from a weakly active screening hit. Efficient synthetic routes for parallel synthesis were developed to prepare analogues with improved potency and ligand efficiency against CHK1. Kinase profiling showed that the imidazo[1,2-a]pyrazines could inhibit other kinases, including CHK2 and ABL, with equivalent or better potency depending on the pendant substitution. These 3,6-di(hetero)aryl imidazo[1,2-a]pyrazines appear to represent a general kinase inhibitor scaffold.
  • Walton, M. et al. (2010). The Preclinical Pharmacology and Therapeutic Activity of the Novel CHK1 Inhibitor SAR-020106. Molecular Cancer Therapeutics [Online] 9:89-100. Available at: http://doi.org/10.1158/1535-7163.MCT-09-0938.
    Genotoxic antitumor agents continue to be the mainstay of current cancer chemotherapy. These drugs cause DNA damage and activate numerous cell cycle checkpoints facilitating DNA repair and the maintenance of genomic integrity. Most human tumors lack functional p53 and consequently have compromised G1-S checkpoint control. This has led to the hypothesis that S and G2-M checkpoint abrogation may selectively enhance genotoxic cell killing in a p53-deficient background, as normal cells would be rescued at the G1-S checkpoint. CHK1 is a serine/threonine kinase associated with DNA damage–linked S and G2-M checkpoint control. SAR-020106 is an ATP-competitive, potent, and selective CHK1 inhibitor with an IC50 of 13.3 nmol/L on the isolated human enzyme. This compound abrogates an etoposide-induced G2 arrest with an IC50 of 55 nmol/L in HT29 cells, and significantly enhances the cell killing of gemcitabine and SN38 by 3.0- to 29-fold in several colon tumor lines in vitro and in a p53-dependent fashion. Biomarker studies have shown that SAR-020106 inhibits cytotoxic drug–induced autophosphorylation of CHK1 at S296 and blocks the phosphorylation of CDK1 at Y15 in a dose-dependent fashion both in vitro and in vivo. Cytotoxic drug combinations were associated with increased ?H2AX and poly ADP ribose polymerase cleavage consistent with the SAR-020106–enhanced DNA damage and tumor cell death. Irinotecan and gemcitabine antitumor activity was enhanced by SAR-020106 in vivo with minimal toxicity. SAR-020106 represents a novel class of CHK1 inhibitors that can enhance antitumor activity with selected anticancer drugs in vivo and may therefore have clinical utility.
  • Caldwell, J. et al. (2010). Structure-Based Design of Potent and Selective 2-(Quinazolin-2-yl)phenol Inhibitors of Checkpoint Kinase 2. Journal of Medicinal Chemistry [Online] 54:580-590. Available at: http://doi.org/10.1021/jm101150b.
    Structure-based design was applied to the optimization of a series of 2-(quinazolin-2-yl)phenols to generate potent and selective ATP-competitive inhibitors of the DNA damage response signaling enzyme checkpoint kinase 2 (CHK2). Structure?activity relationships for multiple substituent positions were optimized separately and in combination leading to the 2-(quinazolin-2-yl)phenol 46 (IC50 3 nM) with good selectivity for CHK2 against CHK1 and a wider panel of kinases and with promising in vitro ADMET properties. Off-target activity at hERG ion channels shown by the core scaffold was successfully reduced by the addition of peripheral polar substitution. In addition to showing mechanistic inhibition of CHK2 in HT29 human colon cancer cells, a concentration dependent radioprotective effect in mouse thymocytes was demonstrated for the potent inhibitor 46 (CCT241533).
  • Yap, T. et al. (2010). Preclinical Pharmacology, Antitumor Activity, and Development of Pharmacodynamic Markers for the Novel, Potent AKT Inhibitor CCT128930. Molecular Cancer Therapeutics [Online] 10:360-371. Available at: http://doi.org/10.1158/1535-7163.MCT-10-0760.
    AKT is frequently deregulated in cancer, making it an attractive anticancer drug target. CCT128930 is a novel ATP-competitive AKT inhibitor discovered using fragment- and structure-based approaches. It is a potent, advanced lead pyrrolopyrimidine compound exhibiting selectivity for AKT over PKA, achieved by targeting a single amino acid difference. CCT128930 exhibited marked antiproliferative activity and inhibited the phosphorylation of a range of AKT substrates in multiple tumor cell lines in vitro, consistent with AKT inhibition. CCT128930 caused a G1 arrest in PTEN-null U87MG human glioblastoma cells, consistent with AKT pathway blockade. Pharmacokinetic studies established that potentially active concentrations of CCT128930 could be achieved in human tumor xenografts. Furthermore, CCT128930 also blocked the phosphorylation of several downstream AKT biomarkers in U87MG tumor xenografts, indicating AKT inhibition in vivo. Antitumor activity was observed with CCT128930 in U87MG and HER2-positive, PIK3CA-mutant BT474 human breast cancer xenografts, consistent with its pharmacokinetic and pharmacodynamic properties. A quantitative immunofluorescence assay to measure the phosphorylation and total protein expression of the AKT substrate PRAS40 in hair follicles is presented. Significant decreases in pThr246 PRAS40 occurred in CCT128930-treated mouse whisker follicles in vivo and human hair follicles treated ex vivo, with minimal changes in total PRAS40. In conclusion, CCT128930 is a novel, selective, and potent AKT inhibitor that blocks AKT activity in vitro and in vivo and induces marked antitumor responses. We have also developed a novel biomarker assay for the inhibition of AKT in human hair follicles, which is currently being used in clinical trials.
  • Grimshaw, K. et al. (2010). AT7867 Is a Potent and Oral Inhibitor of AKT and p70 S6 Kinase That Induces Pharmacodynamic Changes and Inhibits Human Tumor Xenograft Growth. Molecular Cancer Therapeutics [Online] 9:1100-1110. Available at: http://doi.org/10.1158/1535-7163.MCT-09-0986.
    The serine/threonine kinase AKT plays a pivotal role in signal transduction events involved in malignant transformation and chemoresistance and is an attractive target for the development of cancer therapeutics. Fragment-based lead discovery, combined with structure-based drug design, has recently identified AT7867 as a novel and potent inhibitor of both AKT and the downstream kinase p70 S6 kinase (p70S6K) and also of protein kinase A. This ATP-competitive small molecule potently inhibits both AKT and p70S6K activity at the cellular level, as measured by inhibition of GSK3? and S6 ribosomal protein phosphorylation, and also causes growth inhibition in a range of human cancer cell lines as a single agent. Induction of apoptosis was detected by multiple methods in tumor cells following AT7867 treatment. Administration of AT7867 (90 mg/kg p.o. or 20 mg/kg i.p.) to athymic mice implanted with the PTEN-deficient U87MG human glioblastoma xenograft model caused inhibition of phosphorylation of downstream substrates of both AKT and p70S6K and induction of apoptosis, confirming the observations made in vitro. These doses of AT7867 also resulted in inhibition of human tumor growth in PTEN-deficient xenograft models. These data suggest that the novel strategy of AKT and p70S6K blockade may have therapeutic value and supports further evaluation of AT7867 as a single-agent anticancer strategy.
  • Hilton, S. et al. (2009). Identification and characterisation of 2-aminopyridine inhibitors of checkpoint kinase 2. Bioorganic & Medicinal Chemistry [Online] 18:707-718. Available at: http://doi.org/10.1016/j.bmc.2009.11.058.
    5-(Hetero)aryl-3-(4-carboxamidophenyl)-2-aminopyridine inhibitors of CHK2 were identified from high throughput screening of a kinase-focussed compound library. Rapid exploration of the hits through straightforward chemistry established structure–activity relationships and a proposed ATP-competitive binding mode which was verified by X-ray crystallography of several analogues bound to CHK2. Variation of the 5-(hetero)aryl substituent identified bicyclic dioxolane and dioxane groups which improved the affinity and the selectivity of the compounds for CHK2 versus CHK1. The 3-(4-carboxamidophenyl) substituent could be successfully replaced by acyclic ?-aminoalkylamides, which made additional polar interactions within the binding site and led to more potent inhibitors of CHK2. Compounds from this series showed activity in cell-based mechanistic assays for inhibition of CHK2.
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