Labelled chemical probes for demonstrating direct target engagement in living systems

Demonstrating target engagement in living systems can help drive successful drug discovery. Target engagement and occupancy studies in cells confirm direct binding of a ligand to its intended target protein and provide the binding affinity. Combined with biomarkers to measure the functional consequences of target engagement, these experiments can increase confidence in the relationship between in vitro pharmacology and observed biological effects. In this review, we focus on chemically and radioactively labelled probes as key reagents for performing such experiments. Using recent examples, we examine how the labelled probes have been employed in combination with unlabelled ligands to quantify target engagement in cells and in animals. Finally, we consider future developments of this emerging methodology.

Solution NMR assignment of the ARC4 domain of human tankyrase 2

Tankyrases are poly(ADP-ribose)polymerases (PARPs) which recognize their substrates via their ankyrin repeat cluster (ARC) domains. The human tankyrases (TNKS/TNKS2) contain five ARCs in their extensive N-terminal region; of these, four bind peptides present within tankyrase interactors and substrates. These short, linear segments, known as tankyrase-binding motifs (TBMs), contain some highly conserved features: an arginine at position 1, which occupies a predominantly acidic binding site, and a glycine at position 6 that is sandwiched between two aromatic side chains on the surface of the ARC domain. Tankyrases are involved in a multitude of biological functions, amongst them Wnt/β-catenin signaling, the maintenance of telomeres, glucose metabolism, spindle formation, the DNA damage response and Hippo signaling. As many of these are relevant to human disease, tankyrase is an important target candidate for drug development. With the emergence of non-catalytic (scaffolding) functions of tankyrase, it seems attractive to interfere with ARC function rather than the enzymatic activity of tankyrase. To study the mechanism of ARC-dependent recruitment of tankyrase binders and enable protein-observed NMR screening methods, we have as the first step obtained a full backbone and partial side chain assignment of TNKS2 ARC4. The assignment highlights some of the unusual structural features of the ARC domain.

A critical evaluation of the approaches to targeted protein degradation for drug discovery

There is a great deal of excitement around the concept of targeting proteins for degradation as an alternative to conventional inhibitory small molecules and antibodies. Protein degradation can be undertaken by bifunctional molecules that bind the target for ubiquitin mediated degradation by complexing them with Cereblon (CRBN), von Hippel-Lindau or other E-3 ligases. Alternatively, E-3 ligase receptors such as CRBN or DCAF15 can also be used as a 'template' to bind IMiD or sulphonamide like compounds to degrade multiple context specific proteins by the selected E-3 ligases. The 'template approach' results in the degradation of neo-substrates, some of which would be difficult to drug using conventional approaches. The chemical properties necessary for drug discovery, the rules by which neo-substrates are selected by E-3 ligase receptors and defining the optimal components of the ubiquitin proteasome for protein degradation are still to be fully elucidate. Theis review will aim to critically evaluate the different approaches and principles emerging for targted protein degradation.

Binding to an Unusual Inactive Kinase Conformation by Highly Selective Inhibitors of Inositol-Requiring Enzyme 1α Kinase-Endoribonuclease

A series of imidazo[1,2- b]pyridazin-8-amine kinase inhibitors were discovered to allosterically inhibit the endoribonuclease function of the dual kinase-endoribonuclease inositol-requiring enzyme 1α (IRE1α), a key component of the unfolded protein response in mammalian cells and a potential drug target in multiple human diseases. Inhibitor optimization gave compounds with high kinome selectivity that prevented endoplasmic reticulum stress-induced IRE1α oligomerization and phosphorylation, and inhibited endoribonuclease activity in human cells. X-ray crystallography showed the inhibitors to bind to a previously unreported and unusually disordered conformation of the IRE1α kinase domain that would be incompatible with back-to-back dimerization of the IRE1α protein and activation of the endoribonuclease function. These findings increase the repertoire of known IRE1α protein conformations and can guide the discovery of highly selective ligands for the IRE1α kinase site that allosterically inhibit the endoribonuclease.

Tailored NEOadjuvant epirubicin, cyclophosphamide and Nanoparticle Albumin-Bound paclitaxel for breast cancer: The phase II NEONAB trial-Clinical outcomes and molecular determinants of response

BACKGROUND

This study evaluated the feasibility of achieving high response rates in stage II or III breast cancer by tailoring neoadjuvant therapy using clinical and histopathological features and the Oncotype DX Breast Recurrence Score. Genomic determinants of response and resistance were also explored.

PATIENTS AND OUTCOME MEASURES

Fifty-one patients were enrolled. The primary cohort comprised 40 patients: 15 human epidermal growth factor receptor type 2 (HER2)-amplified; 15 triple-negative (TNBC); and ten hormone receptor (HR)-positive, HER2-non-amplified tumours; with recurrence scores ≥25. Patients were treated with epirubicin and cyclophosphamide, followed by nab-paclitaxel, with the addition of trastuzumab if HER2-amplified. The primary endpoint was pathological complete response (pCR) in the breast. Pre- and post-treatment tumour samples underwent variant burden, gene and gene pathway, mutational signature profile and clonal evolution analyses.

RESULTS

The pCR rates were: overall 55% (n = 22), HER2-amplified 80% (n = 12), triple-negative 46% (n = 7) and HR-positive, HER2-non-amplified 30% (n = 3). Grade 3 or 4 adverse events included febrile neutropenia (8%), neutropenia (18%), sensory neuropathy (5%), deranged transaminases (5%), fatigue (2%), diarrhoea (2%), and pneumothorax (2%). Molecular analyses demonstrated strong similarities between residual disease and matched primary tumour. ATM signalling pathway alterations and the presence of a COSMIC Signature 3 implied the majority of tumours contained some form of homologous repair deficiency. ATM pathway alterations were identified in the subset of TNBC patients who did not achieve pCR; Signature 3 was present in both pCR and non-pCR subgroups. Clonal evolution analyses demonstrated both persistence and emergence of chemoresistant clones.

CONCLUSIONS

This treatment regime resulted in a high rate of pCR, demonstrating that tailored neoadjuvant therapy using a genomic recurrence score is feasible and warrants further investigation. Molecular analysis revealed few commonalities between patients. For TNBC future clinical gains will require precision medicine, potentially using DNA sequencing to identify specific targets for individuals with resistant disease.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01830244.

Mapping the EORTC-QLQ-C30 to the EQ-5D-3L: An Assessment of Existing and Newly Developed Algorithms

Objectives. To assess the external validity of mapping algorithms for predicting EQ-5D-3L utility values from EORTC QLQ-C30 responses not previously validated and to assess whether statistical models not previously applied are better suited for mapping the EORTC QLQ-C30 to the EQ-5D-3L. Methods. In total, 3866 observations for 1719 patients from a longitudinal study (Cancer 2015) were used to validate existing algorithms. Predictive accuracy was compared to previously validated algorithms using root mean squared error, mean absolute error across the EQ-5D-3L range, and for 10 tumor-type specific samples as well as using differences between estimated quality-adjusted life years. Thirteen new algorithms were estimated using a subset of the Cancer 2015 data (3203 observations for 1419 patients) applying various linear, response mapping, beta, and mixture models. Validation was performed using 2 data sets composed of patients with varying disease severity not used in the estimation and all available algorithms ranked on their performance. Results. None of the 5 existing algorithms offer an improvement in predictive accuracy over preferred algorithms from previous validation studies. Of the newly estimated algorithms, a 2-part beta model performed the best across the validation criteria and in data sets composed of patients with different levels of disease severity. Validation results did, however, vary widely between the 2 data sets, and the most accurate algorithm appears to depend on health state severity as the distribution of observed EQ-5D-3L values varies. Linear models performed better for patients in relatively good health, whereas beta, mixture, and response mapping models performed better for patients in worse health. Conclusion. The most appropriate mapping algorithm to apply in practice may depend on the disease severity of the patient sample whose utility values are being predicted.

Abstract 2976: Confirmation of in-cell target engagement using the proteolysis targeting chimeras (PROTACs) against pirin

We recently reported the identification of the original bisamide lead compound CCT251236 as an inhibitor of the HSF1 stress pathway with a high affinity for the putative transcription factor co-regulator, pirin (SPR KD=44nM) (Cheeseman et al., J Med Chem, 60; 180-201, 2017). Pirin is a highly conserved non-heme iron-binding regulatory protein that is a member of the functionally diverse cupin superfamily, but has no known enzymatic function or biomarkers of activity. To understand further this poorly characterized protein and to confirm that CCT251236 binds to pirin within living cells, we conceived and optimized a heterobifunctional protein degradation probe using the proteolysis targeting chimeras (PROTACs; CCT367766) comprising a pirin-binding moiety linked to the cereblon-targeting ligand thalidomide. This PROTAC molecule was designed to recruit pirin to the E3 ubiquitin ligase cereblon resulting in the ubiquitylation and degradation of pirin. Negative control probes lacking binding to pirin (CCT367857) or cereblon (CCT367936) were also designed and synthesized. We demonstrated a concentration-dependent depletion of pirin protein from as low as 0.5nM and as early as 2 hr treatment of SKOV3 human ovarian cancer cells with the PROTAC. The negative controls CCT367857 and CCT367936 exhibited no pirin depletion at equimolar concentrations. At higher concentrations of the active probe, a hook effect is observed, consistent with the formation of a ternary complex. Degradation of pirin by the PROTAC was confirmed to be proteasome-dependent by rescue of depletion following pre-incubation with the proteasome inhibitor MG132. In addition, the PROTAC could not induce pirin degradation in CRISPR/cas9 cereblon knockout SKOV3 cells, confirming dependence on cereblon. Pre-treatment with the bisamide compound CCT251236 or free thalidomide abrogated the PROTAC-induced pirin degradation, consistent with pirin and cereblon engagement. Finally, to estimate the cellular selectivity of the PROTAC to pirin in an unbiased manner, we carried out whole proteome mass spectrometry in SKOV3 cells. From 8547 quantifiable proteins identified, only pirin (2.3-fold reduction) displayed a statistically significant (Padj<0.05) difference in protein expression, indicating impressive selectivity. In summary, we have designed a PROTAC as an intracellular probe against a poorly understood molecular target, pirin. This approach has allowed us to confirm in-cell target engagement of our bisamide lead CCT251236 with pirin and validates CCT367766 as a PROTAC tool to further study this largely unexplored protein. Our results also provide a systematic approach for the use of the powerful PROTAC technology to investigate potential and poorly understood cancer drug targets.

Citation Format: Swee Y. Sharp, Nicola E. Chessum, John J. Caldwell, Marissa V. Powers, A Elisa Pasqua, Birgit Wilding, Ian Collins, Bugra Ozer, Martin Rowlands, Mark Stubbs, Rosemary Burke, Rob L. van Montfort, Matthew D. Cheeseman, Paul A. Clarke, Paul Workman, Keith Jones. Confirmation of in-cell target engagement using the proteolysis targeting chimeras (PROTACs) against pirin [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2976.

Objective, Quantitative, Data-Driven Assessment of Chemical Probes

Chemical probes are essential tools for understanding biological systems and for target validation, yet selecting probes for biomedical research is rarely based on objective assessment of all potential compounds. Here, we describe the Probe Miner: Chemical Probes Objective Assessment resource, capitalizing on the plethora of public medicinal chemistry data to empower quantitative, objective, data-driven evaluation of chemical probes. We assess >1.8 million compounds for their suitability as chemical tools against 2,220 human targets and dissect the biases and limitations encountered. Probe Miner represents a valuable resource to aid the identification of potential chemical probes, particularly when used alongside expert curation.

Demonstrating In-Cell Target Engagement Using a Pirin Protein Degradation Probe (CCT367766)

Demonstrating intracellular protein target engagement is an essential step in the development and progression of new chemical probes and potential small molecule therapeutics. However, this can be particularly challenging for poorly studied and noncatalytic proteins, as robust proximal biomarkers are rarely known. To confirm that our recently discovered chemical probe 1 (CCT251236) binds the putative transcription factor regulator pirin in living cells, we developed a heterobifunctional protein degradation probe. Focusing on linker design and physicochemical properties, we generated a highly active probe 16 (CCT367766) in only three iterations, validating our efficient strategy for degradation probe design against nonvalidated protein targets.

Abstract A024: Probe Miner: objective, quantitative, data-driven assessment of chemical probes for target validation

Chemical probes are important, widely used reagents for understanding biologic systems and for target validation. However, selection of chemical probes is largely subjective and prone to historical and commercial biases. Despite many publications discussing the aspirational properties of chemical probes and the proposal of "fitness factors" to be considered when assessing chemical tools, scientists often select probes through web-based searchers or previous literature that are heavily biased towards older and often flawed probes or use vendor catalogues that do not discriminate between probes. Here, we analyze the scope and quality of published bioactive molecules and uncover large biases and limitations of chemical tools in public databases that need to be urgently addressed and should be always considered when using chemical tools. We also provide the online Probe Miner resource (http://probeminer.icr.ac.uk) capitalizing on the plethora of public pharmacologic data to enable quantitative, unbiased, objective, Big Data-driven assessment of chemical probes and complement expert-curated approaches. We assess >1.8m compounds for their suitability as chemical tools against 2,220 human targets, demonstrating that large-scale public data can contribute to improving chemical probe assessment and prioritization to empower researchers in the selection of chemical tools for biomedical research and target validation.

Citation Format: Albert A. Antolin, Joe E. Tym, Angeliki Komianou, Ian Collins, Paul Workman, Bissan Al-Lazikani. Probe Miner: objective, quantitative, data-driven assessment of chemical probes for target validation [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2017 Oct 26-30; Philadelphia, PA. Philadelphia (PA): AACR; Mol Cancer Ther 2018;17(1 Suppl):Abstract nr A024.

Abstract 293: Screening the druggable genome for synthetic lethal interactions with the CHK1 inhibitor PNT737

Check point kinase 1 (CHK1) is a key regulator of the cell cycle, DNA damage repair and DNA replication. CHK1 inhibition sensitises cancer cells to genotoxic agents and recent studies have indicated that CHK1 inhibitors could be used as single agents to treat cancers with high levels of replication stress. We have recently described the discovery of a highly selective and orally bioavailable CHK1 inhibitor, PNT737, that not only has potent antitumour activity in combination with standard-of-care genotoxic agents but also as a single agent in defined tumour types. Here we sought to identify gene products whose loss would be synthetically lethal with CHK1 inhibition, with the aim of identifying patient populations likely to be sensitive to single agent CHK1 inhibition or to novel combinations utilising CHK1 inhibitors. To do this, we performed a large siRNA screen of the druggable genome (~6500 genes) in A549 (NSCLC) and SW620 (colon cancer) cell lines, with and without PNT737 treatment, and determined effects on cell viability by SRB. POLA1, POLE and POLE2 (B-family DNA polymerases) were identified as significant hits causing synthetic lethality with PNT737 in both cancer cell lines. Treatment with additional siRNA sequences subsequently validated these genes in both the original two cell lines and extra NSCLC and colon cancer cell lines. Interestingly, a number of biomarkers for replication stress, pRPA2 and pCHK1, were increased in cells treated with POLA1, POLE and POLE2 siRNA in combination with PNT737, in comparison to cells treated with the siRNA or drug alone. Further studies conducted with PNT737 and the B-family DNA polymerase inhibitor aphidicolin showed that these agents had a synergistic effect on inhibiting cell viability on 8 out of 9 NSCLC and colon cancer cell lines tested. In addition, immunofluorescence analysis revealed that there was an increase in the level of γH2AX, a marker of DNA damage, in 4 out of 5 cell lines that exhibited synergy when treated with a combination of aphidicolin and PNT737, as compared to cells treated with either agent alone. Our data indicate that the combination of a reduction in POLA1, POLE or POLE2 activity (by siRNA transfection or aphidicolin treatment) and CHK1 activity (PNT737 treatment) increases replication stress and DNA damage in NSCLC and colon cancer cells. Encouragingly, our data support the case for the use of the clinically relevant combination of PNT737 and gemcitabine, as gemcitabine is metabolised it is incorporated into DNA, inhibiting the B-family DNA polymerases. Furthermore, it will now be important to establish if subsets of colon and endometrial cancers with mutations in their POLE proofreading domain are sensitive to CHK1 inhibitors.

Citation Format: Rebecca Rogers, Mike I. Walton, Paul Clarke, Ian Collins, Michelle D. Garrett, Paul Workman. Screening the druggable genome for synthetic lethal interactions with the CHK1 inhibitor PNT737 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 293. doi:10.1158/1538-7445.AM2017-293

Chemical approaches to targeted protein degradation through modulation of the ubiquitin-proteasome pathway

Manipulation of the ubiquitin-proteasome system to achieve targeted degradation of proteins within cells using chemical tools and drugs has the potential to transform pharmacological and therapeutic approaches in cancer and other diseases. An increased understanding of the molecular mechanism of thalidomide and its analogues following their clinical use has unlocked small-molecule modulation of the substrate specificity of the E3 ligase cereblon (CRBN), which in turn has resulted in the advancement of new immunomodulatory drugs (IMiDs) into the clinic. The degradation of multiple context-specific proteins by these pleiotropic small molecules provides a means to uncover new cell biology and to generate future drug molecules against currently undruggable targets. In parallel, the development of larger bifunctional molecules that bring together highly specific protein targets in complexes with CRBN, von Hippel-Lindau, or other E3 ligases to promote ubiquitin-dependent degradation has progressed to generate selective chemical compounds with potent effects in cells and in vivo models, providing valuable tools for biological target validation and with future potential for therapeutic use. In this review, we survey recent breakthroughs achieved in these two complementary methods and the discovery of new modes of direct and indirect engagement of target proteins with the proteasome. We discuss the experimental characterisation that validates the use of molecules that promote protein degradation as chemical tools, the preclinical and clinical examples disclosed to date, and the future prospects for this exciting area of chemical biology.

Synthesis of a Ribose-Incorporating Medium Ring Scaffold via a Challenging Ring-Closing Metathesis Reaction

A practical synthesis of a novel oxabicyclo[6.2.1]undecenetriol useful as a medicinal chemistry scaffold has been developed starting from l‐ribose. The sequence involves an oxidation/Grignard addition sequence and a challenging ring‐closing metathesis (RCM) reaction as the ring forming step. Exploration of the RCM substrate protecting groups revealed the key factor for successful nine‐membered medium ring formation to be conformational bias of the reacting alkenes of the RCM substrate by very bulky silyl ether protecting groups. The synthesis also allowed access to an epimeric triol and saturated and unsaturated variants of the nine‐membered ring. The medium ring conformation of the oxabicyclo[6.2.1]undecenetriol was determined by X‐ray crystallography and correlated to the solution state conformation by NMR experiments.

Identifying and Validating Tankyrase Binders and Substrates: A Candidate Approach

The poly(ADP-ribose)polymerase (PARP) enzyme tankyrase (TNKS/ARTD5, TNKS2/ARTD6) uses its ankyrin repeat clusters (ARCs) to recognize degenerate peptide motifs in a wide range of proteins, thereby recruiting such proteins and their complexes for scaffolding and/or poly(ADP-ribosyl)ation. Here, we provide guidance for predicting putative tankyrase-binding motifs, based on the previously delineated peptide sequence rules and existing structural information. We present a general method for the expression and purification of tankyrase ARCs from Escherichia coli and outline a fluorescence polarization assay to quantitatively assess direct ARC-TBM peptide interactions. We provide a basic protocol for evaluating binding and poly(ADP-ribosyl)ation of full-length candidate interacting proteins by full-length tankyrase in mammalian cells.

A fragment-based approach applied to a highly flexible target: Insights and challenges towards the inhibition of HSP70 isoforms

The heat shock protein 70s (HSP70s) are molecular chaperones implicated in many cancers and of significant interest as targets for novel cancer therapies. Several HSP70 inhibitors have been reported, but because the majority have poor physicochemical properties and for many the exact mode of action is poorly understood, more detailed mechanistic and structural insight into ligand-binding to HSP70s is urgently needed. Here we describe the first comprehensive fragment-based inhibitor exploration of an HSP70 enzyme, which yielded an amino-quinazoline fragment that was elaborated to a novel ATP binding site ligand with different physicochemical properties to known adenosine-based HSP70 inhibitors. Crystal structures of amino-quinazoline ligands bound to the different conformational states of the HSP70 nucleotide binding domain highlighted the challenges of a fragment-based approach when applied to this particular flexible enzyme class with an ATP-binding site that changes shape and size during its catalytic cycle. In these studies we showed that Ser275 is a key residue in the selective binding of ATP. Additionally, the structural data revealed a potential functional role for the ATP ribose moiety in priming the protein for the formation of the ATP-bound pre-hydrolysis complex by influencing the conformation of one of the phosphate binding loops.

AMPK-independent inhibition of human macrophage ER stress response by AICAR

Obesity-associated insulin resistance is driven by inflammatory processes in response to metabolic overload. Obesity-associated inflammation can be recapitulated in cell culture by exposing macrophages to saturated fatty acids (SFA), and endoplasmic reticulum (ER) stress responses essentially contribute to pro-inflammatory signalling. AMP-activated protein kinase (AMPK) is a central metabolic regulator with established anti-inflammatory actions. Whether pharmacological AMPK activation suppresses SFA-induced inflammation in a human system is unclear. In a setting of hypoxia-potentiated inflammation induced by SFA palmitate, we found that the AMP-mimetic AMPK activator 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) potently suppressed upregulation of ER stress marker mRNAs and pro-inflammatory cytokines. Furthermore, AICAR inhibited macrophage ER stress responses triggered by ER-stressors thapsigargin or tunicamycin. Surprisingly, AICAR acted independent of AMPK or AICAR conversion to 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranosyl monophosphate (ZMP) while requiring intracellular uptake via the equilibrative nucleoside transporter (ENT) ENT1 or the concentrative nucleoside transporter (CNT) CNT3. AICAR did not affect the initiation of the ER stress response, but inhibited the expression of major ER stress transcriptional effectors. Furthermore, AICAR inhibited autophosphorylation of the ER stress sensor inositol-requiring enzyme 1α (IRE1α), while activating its endoribonuclease activity in vitro. Our results suggest that AMPK-independent inhibition of ER stress responses contributes to anti-inflammatory and anti-diabetic effects of AICAR.

Identification of Novel Keratinocyte Differentiation Modulating Compounds by High-Throughput Screening

The authors have designed high-throughput screens to identify compounds that promote or inhibit terminal differentiation of primary human epidermal keratinocytes. Eleven known inhibitors of signaling pathways and approximately 4000 compounds of diverse structure were screened using an In-Cell Western system based on immunofluorescent staining of the terminal differentiation marker, involucrin. Staurosporine, a nonspecific protein kinase C inhibitor, and H89, a protein kinase A inhibitor, promoted expression of involucrin. Conversely, U0126, a MEK inhibitor, and SAHA or SBHA, 2 histone deacetylase inhibitors, reduced the expression of involucrin during calcium-induced stratification. In addition, the authors found 1 novel compound that induced keratinocyte differentiation and 2 novel compounds that were inhibitory to calcium-induced differentiation. The differentiation-inducing compound also inhibited growth of a human squamous cell carcinoma line by stimulating both differentiation and apoptosis. Because the compound affected the tumor cells at a lower concentration than primary keratinocytes, it may have potential as an antitumor therapy.

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)

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.

Exploiting Protein Conformational Change to Optimize Adenosine-Derived Inhibitors of HSP70

HSP70 is a molecular chaperone and a key component of the heat-shock response. Because of its proposed importance in oncology, this protein has become a popular target for drug discovery, efforts which have as yet brought little success. This study demonstrates that adenosine-derived HSP70 inhibitors potentially bind to the protein with a novel mechanism of action, the stabilization by desolvation of an intramolecular salt-bridge which induces a conformational change in the protein, leading to high affinity ligands. We also demonstrate that through the application of this mechanism, adenosine-derived HSP70 inhibitors can be optimized in a rational manner.

Synthesis and Evaluation of a 2,11-Cembranoid-Inspired Library

The 2,11-cembranoid family of natural products has been used as inspiration for the synthesis of a structurally simplified, functionally diverse library of octahydroisobenzofuran-based compounds designed to augment a typical medicinal chemistry library screen. Ring-closing metathesis, lactonisation and SmI2 -mediated methods were exemplified and applied to the installation of a third ring to mimic the nine-membered ring of the 2,11-cembranoids. The library was assessed for aqueous solubility and permeability, with a chemical-space analysis performed for comparison to the family of cembranoid natural products and a sample set of a screening library. Preliminary investigations in cancer cells showed that the simpler scaffolds could recapitulate the reported anti-migratory activity of the natural products.

A Discrete Choice Experiment to Examine the Preferences of Patients With Cancer and Their Willingness to Pay for Different Types of Health Care Appointments

BACKGROUND

This study sought to understand the preferences of patients with cancer and the trade-offs between appointment attributes using discrete choice experiment (DCE).

METHODS AND STUDY DESIGN

Patients with cancer at 3 hospitals completed a self-administered DCE. Each scenario described 6 attributes: expertise of health care professionals (HCPs), familiarity of doctors with patients' medical history, waiting time, accompaniment by family/friends, travel time, and out-of-pocket costs. Patient preferences were estimated using logistic regression. Willingness to pay (WTP) estimates were derived from regression coefficients.

RESULTS

Of 512 patients contacted, 185 returned the questionnaire. The mean age was 61 years, and 60% of respondents were female. The mean time since cancer diagnosis was 34 months, 90% had received treatment; and 61% had early-stage disease. The most important attributes were expertise and familiarity of doctors with patients' medical history; distance traveled was least likely to influence patient preferences. The WTP analysis estimated that patients were willing to pay $680 (95% CI, 470-891) for an appointment with a specialist, $571 (95% CI, 388-754) for doctors familiar with their history, $422 (95% CI, 262-582) for shorter waiting times, $399 (95% CI, 249-549) to be accompanied by family/friends, and $301 (95% CI, 162-441) for shorter traveling times. Male patients had a stronger preference for accompaniment by family/friends. The expertise of HCP was the most important attribute for patients regardless of geographic remoteness.

CONCLUSIONS

Our study can assist the development of patient-centered health care models that improve patient access to experienced HCPs, support the role of primary care providers during the cancer journey, and educate patients about the roles of non-oncology HCPs to cope with increasing demand for cancer care.

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

CCT245737 is the first orally active, clinical development candidate CHK1 inhibitor to be described. The IC50 was 1.4 nM against CHK1 enzyme and it exhibited>1,000-fold selectivity against CHK2 and CDK1. CCT245737 potently inhibited cellular CHK1 activity (IC50 30-220 nM) 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.

Transitioning to routine breast cancer risk assessment and management in primary care: what can we learn from cardiovascular disease?

To capitalise on advances in breast cancer prevention, all women would need to have their breast cancer risk formally assessed. With ~85% of Australians attending primary care clinics at least once a year, primary care is an opportune location for formal breast cancer risk assessment and management. This study assessed the current practice and needs of primary care clinicians regarding assessment and management of breast cancer risk. Two facilitated focus group discussions were held with 17 primary care clinicians (12 GPs and 5 practice nurses (PNs)) as part of a larger needs assessment. Primary care clinicians viewed assessment and management of cardiovascular risk as an intrinsic, expected part of their role, often triggered by practice software prompts and facilitated by use of an online tool. Conversely, assessment of breast cancer risk was not routine and was generally patient- (not clinician-) initiated, and risk management (apart from routine screening) was considered outside the primary care domain. Clinicians suggested that routine assessment and management of breast cancer risk might be achieved if it were widely endorsed as within the remit of primary care and supported by an online risk-assessment and decision aid tool that was integrated into primary care software. This study identified several key issues that would need to be addressed to facilitate the transition to routine assessment and management of breast cancer risk in primary care, based largely on the model used for cardiovascular disease.

Rho kinase inhibitors block melanoma cell migration and inhibit metastasis

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.