Discovery of a first-in-class reversible DNMT1-selective inhibitor with improved tolerability and efficacy in acute myeloid leukemia

DNA methylation, a key epigenetic driver of transcriptional silencing, is universally dysregulated in cancer. Reversal of DNA methylation by hypomethylating agents, such as the cytidine analogs decitabine or azacytidine, has demonstrated clinical benefit in hematologic malignancies. These nucleoside analogs are incorporated into replicating DNA where they inhibit DNA cytosine methyltransferases DNMT1, DNMT3A and DNMT3B through irreversible covalent interactions. These agents induce notable toxicity to normal blood cells thus limiting their clinical doses. Herein we report the discovery of GSK3685032, a potent first-in-class DNMT1-selective inhibitor that was shown via crystallographic studies to compete with the active-site loop of DNMT1 for penetration into hemi-methylated DNA between two CpG base pairs. GSK3685032 induces robust loss of DNA methylation, transcriptional activation and cancer cell growth inhibition in vitro. Due to improved in vivo tolerability compared with decitabine, GSK3685032 yields superior tumor regression and survival mouse models of acute myeloid leukemia.

In vitro and in vivo induction of fetal hemoglobin with a reversible and selective DNMT1 inhibitor

Pharmacological induction of fetal hemoglobin (HbF) expression is an effective therapeutic strategy for the management of beta-hemoglobinopathies such as sickle cell disease. DNA methyltransferase (DNMT) inhibitors 5-azacytidine (5-aza) and 5-aza-2'-deoxycytidine (decitabine) have been shown to induce fetal hemoglobin expression in both preclinical models and clinical studies, but are not currently approved for the management of hemoglobinopathies. We report here the discovery of a novel class of orally bioavailable DNMT1-selective inhibitors as exemplified by GSK3482364. This molecule potently inhibits the methyltransferase activity of DNMT1, but not DNMT family members DNMT3A or DNMT3B. In contrast with cytidine analog DNMT inhibitors, the DNMT1 inhibitory mechanism of GSK3482364 does not require DNA incorporation and is reversible. In cultured human erythroid progenitor cells (EPCs), GSK3482364 decreased overall DNA methylation resulting in de-repression of the gamma globin genes HBG1 and HBG2 and increased HbF expression. In a transgenic mouse model of sickle cell disease, orally administered GSK3482364 caused significant increases in both HbF levels and in the percentage HbF-expressing erythrocytes, with good overall tolerability. We conclude that in these preclinical models, selective, reversible inhibition of DNMT1 is sufficient for the induction of HbF, and is well-tolerated. We anticipate that GSK3482364 will be a useful tool molecule for the further study of selective DNMT1 inhibition both in vitro and in vivo.

Decision-making for active living infrastructure in new communities: a qualitative study in England

BACKGROUND

Urban design can influence population levels of physical activity and subsequent health impacts. This qualitative study investigates local level decision-making for 'active living' infrastructure (ALI)-walking and cycling infrastructure and open spaces in new communities.

METHODS

Thirty-five semi-structured interviews with stakeholders, and limited ethnographic observations, were conducted with local government and private sector stakeholders including urban and transport planners, public health practitioners, elected councillors and developers. Interview transcripts were coded and analysed thematically.

RESULTS

Public health practitioners in local government could act as knowledge brokers and leaders to motivate non-health stakeholders such as urban and transport planners to consider health when designing and building new communities. They needed to engage at the earliest stages and be adequately resourced to build relationships across sectors, supporting non-health outcomes such as tackling congestion, which often had greater political traction. 'Evidence' for decision-making identified problems (going beyond health), informed solutions, and also justified decisions post hoc, although case study examples were not always convincing if not considered contextually relevant.

CONCLUSION

We have developed a conceptual model with three factors needed to bridge the gap between evidence and ALI being built: influential public health practitioners; supportive policies in non-health sectors; and adequate resources.

Regulation of ALT-associated homology-directed repair by polyADP-ribosylation

The synthesis of poly(ADP-ribose) (PAR) reconfigures the local chromatin environment and recruits DNA-repair complexes to damaged chromatin. PAR degradation by poly(ADP-ribose) glycohydrolase (PARG) is essential for progression and completion of DNA repair. Here, we show that inhibition of PARG disrupts homology-directed repair (HDR) mechanisms that underpin alternative lengthening of telomeres (ALT). Proteomic analyses uncover a new role for poly(ADP-ribosyl)ation (PARylation) in regulating the chromatin-assembly factor HIRA in ALT cancer cells. We show that HIRA is enriched at telomeres during the G2 phase and is required for histone H3.3 deposition and telomere DNA synthesis. Depletion of HIRA elicits systemic death of ALT cancer cells that is mitigated by re-expression of ATRX, a protein that is frequently inactivated in ALT tumors. We propose that PARylation enables HIRA to fulfill its essential role in the adaptive response to ATRX deficiency that pervades ALT cancers.

Discovery and Optimization of wt-RET/KDR-Selective Inhibitors of RETV804M Kinase

A combination of focused library and virtual screening, hit expansion, and rational design has resulted in the development of a series of inhibitors of RETV804M kinase, the anticipated drug-resistant mutant of RET kinase. These agents do not inhibit the wild type (wt) isoforms of RET or KDR and therefore offer a potential adjunct to RET inhibitors currently undergoing clinical evaluation.

Poly (ADP) Ribose Glycohydrolase Can Be Effectively Targeted in Pancreatic Cancer

Patients with metastatic pancreatic ductal adenocarcinoma (PDAC) have an average survival of less than 1 year, underscoring the importance of evaluating novel targets with matched targeted agents. We recently identified that poly (ADP) ribose glycohydrolase (PARG) is a strong candidate target due to its dependence on the pro-oncogenic mRNA stability factor HuR (ELAVL1). Here, we evaluated PARG as a target in PDAC models using both genetic silencing of PARG and established small-molecule PARG inhibitors (PARGi), PDDX-01/04. Homologous repair-deficient cells compared with homologous repair-proficient cells were more sensitive to PARGi in vitro. In vivo, silencing of PARG significantly decreased tumor growth. PARGi synergized with DNA-damaging agents (i.e., oxaliplatin and 5-fluorouracil), but not with PARPi therapy. Mechanistically, combined PARGi and oxaliplatin treatment led to persistence of detrimental PARylation, increased expression of cleaved caspase-3, and increased γH2AX foci. In summary, these data validate PARG as a relevant target in PDAC and establish current therapies that synergize with PARGi. SIGNIFICANCE: PARG is a potential target in pancreatic cancer as a single-agent anticancer therapy or in combination with current standard of care.

Abstract A123: Delivery of a potent, selective, and efficacious RET inhibitor for the treatment of RET-driven lung adenocarcinoma

Background: Constitutive activation of RET kinase activity following mutation or rearrangement can lead to the development of cancers such as medullary thyroid carcinoma and lung adenocarcinoma. The currently approved therapeutics for these diseases are significantly compromised due to dose-limiting toxicities associated with off-target activity vs KDR (VEGFR2) and lack of potency vs anticipated secondary resistance (e.g., gatekeeper) mutations. Consequently there is considerable interest in the development of highly selective inhibitors targeting diverse RET alterations including the putative resistance mutation, V804M. Methods: We have established a robust screening cascade complemented by structure-enabled drug design and effective medicinal chemistry. Biochemical activity vs RET, KDR, and RETV804M protein was assessed using a HTRF assay. Cellular activity was quantified in BaF3 cells dependent on activity of RET, KDR, or RETV804M for proliferation. Tumor growth inhibition and supporting PK/PD studies were carried out in a number of disease-relevant models including a KIF5B-RET lung cancer patient-derived xenograft (PDX) model, a medullary thyroid carcinoma (MZ-CRC-1) xenograft model, and a lung cancer control (Calu-6) xenograft model. Results: Using this optimized, robust platform, we have identified a number of selective compounds offering a range of interesting biochemical and cellular profiles, targeting either, or both, RET and the gatekeeper mutant, RETV804M. We believe certain examples of these compounds offer the first cell-active RETV804M-selective derivatives. More importantly perhaps, we have also delivered a highly selective preclinical candidate compound demonstrating potency vs both RET fusion and RETV804M. This compound is well tolerated in vivo after oral dosing at up to 80mg/kg bid and, in a KIF5B-RET lung cancer PDX model, demonstrates efficacy at much lower doses: 50% tumor regression at 20mg/kg bid and 92% tumor growth inhibition at 10mg/kg bid. Importantly, this agent shows no efficacy in the (non-RET driven) Calu-6 xenograft model, demonstrating selective inhibition of the RET kinase domain. Conclusions: We believe that the identification of well-tolerated, selective RET inhibitors with potent activity against diverse RET alterations (including the anticipated resistance mutation, V804M) offers a clear therapeutic advantage over the present clinically approved compounds. Our most advanced compound fulfills all of these challenging criteria and has now entered preclinical development.

Citation Format: Mandy Watson, Rebecca Newton, Ben Acton, Helen Small, Habiba Begum, Samantha Hitchin, Paul Kelly, Donald Ogilvie, Ian Waddell, Allan Jordan. Delivery of a potent, selective, and efficacious RET inhibitor for the treatment of RET-driven lung adenocarcinoma [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 A123.

Development of (4-Cyanophenyl)glycine Derivatives as Reversible Inhibitors of Lysine Specific Demethylase 1

Inhibition of lysine specific demethylase 1 (LSD1) has been shown to induce the differentiation of leukemia stem cells in acute myeloid leukemia (AML). Irreversible inhibitors developed from the nonspecific inhibitor tranylcypromine have entered clinical trials; however, the development of effective reversible inhibitors has proved more challenging. Herein, we describe our efforts to identify reversible inhibitors of LSD1 from a high throughput screen and subsequent in silico modeling approaches. From a single hit (12) validated by biochemical and biophysical assays, we describe our efforts to develop acyclic scaffold-hops from GSK-690 (1). A further scaffold modification to a (4-cyanophenyl)glycinamide (e.g., 29a) led to the development of compound 32, with a Kd value of 32 nM and an EC50 value of 0.67 μM in a surrogate cellular biomarker assay. Moreover, this derivative does not display the same level of hERG liability as observed with 1 and represents a promising lead for further development.

Development of 5-hydroxypyrazole derivatives as reversible inhibitors of lysine specific demethylase 1

A series of reversible inhibitors of lysine specific demethylase 1 (LSD1) with a 5-hydroxypyrazole scaffold have been developed from compound 7, which was identified from the patent literature. Surface plasmon resonance (SPR) and biochemical analysis showed it to be a reversible LSD1 inhibitor with an IC50 value of 0.23µM. Optimisation of this compound by rational design afforded compounds with Kd values of <10nM. In human THP-1 cells, these compounds were found to upregulate the expression of the surrogate cellular biomarker CD86. Compound 11p was found to have moderate oral bioavailability in mice suggesting its potential for use as an in vivo tool compound.

Abstract 2092: A potent and selective RET inhibitor with efficacy in RET-driven mouse models of medullary thyroid carcinoma and lung adenocarcinoma

Background: The aim of this CRUK-MI Drug Discovery project is to deliver a RET-selective inhibitor for the treatment of cancers with RET activating mutations, which include 1-2% of lung adenocarcinomas and medullary thyroid cancers (MTC). Recent data supports the hypothesis that the efficacy of vandetanib and cabozantinib, clinically approved multi-kinase inhibitors, is limited by toxicities associated with potent activity against KDR. Therefore, a RET-selective inhibitor would represent a best-in-class agent for the treatment of these cancers.

Methods: We have established a robust screening cascade to develop a potent, selective RET inhibitor and developed several in vivo models to evaluate compound PKPD and antitumor efficacy. Tumor growth inhibition and PKPD studies were carried out in BaF3 mouse allograft models overexpressing KIF5B-RET or RETV804M and other disease relevant models, including an MTC xenograft (MZ-CRC-1), a KIF5B-RET lung cancer patient derived xenograft (PDX) model (CTG-0838, Champions Oncology) and a lung cancer control xenograft (Calu-6).

Results: Two orally bioavailable compounds displaying nanomolar RET potency and &gt;10 fold selectivity over KDR in cellular assays were selected from the lead series and further evaluated in our in vivo PD and efficacy models. Both compounds demonstrated efficacy in the BaF3 KIF5B-RET driven model (71% and 103% tumor growth inhibition (TGI), respectively), accompanied by reduced levels of pRET in the tumor tissue. Following further lead optimisation; a compound displaying an improved DMPK profile and additional nanomolar potency versus the gatekeeper mutation (RETV804M) was identified and accelerated through our DMPK/in vivo cascade. We consider this additional activity versus RETV804M beneficial since mutations at the gatekeeper residue in other tyrosine kinases (e.g. EGFR) have been shown to mediate acquired drug resistance in the clinic. This compound demonstrated significant TGI of 58% and 82% respectively in the BaF3 KIF5B-RET and BaF3 RETV804M allograft models. Moreover, tumor growth in the lung cancer PDX model was strongly inhibited (95% TGI) and tumor regression induced in the MTC xenograft model (109% TGI). As expected, this potent and selective RET inhibitor was not active in the Calu-6 model, which is sensitive to KDR inhibition, whereas vandetanib, a potent KDR inhibitor, significantly inhibited tumor growth (84% TGI). Additional in vitro and in vivo DMPK analyses further support the nomination of this compound as a preclinical candidate.

Conclusions: The identification of selective RET inhibitors with significant in vivo activity and minimal toxicity may overcome the limitations of the currently available clinical compounds. We have made considerable progress towards this goal and show here the compelling data supporting our nomination of a preclinical development compound.

Citation Format: Mandy Watson, Helen Small, Ben Acton, Habiba Begum, Samantha Hitchin, Allan Jordan, Paul Kelly, Rebecca Newton, Ian Waddell, Gina Paris, Donald Ogilvie. A potent and selective RET inhibitor with efficacy in RET-driven mouse models of medullary thyroid carcinoma and lung adenocarcinoma [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 2092. doi:10.1158/1538-7445.AM2017-2092

Abstract 3236: Delivering selective and cell-active inhibitors of V804M mutant RET kinase through structure-guided drug discovery

Activating gene fusions in the RET receptor tyrosine kinase have been found to drive 1-2% of lung adenocarcinomas and therefore offer an attractive target for targeted therapy. Whilst non-selective tyrosine kinase inhibitors with RET activity are efficacious in this setting, their use is generally limited by dose limiting toxicity associated with their more potent activity versus other targets, specifically KDR (VEGFR2) in the case of cabozantinib and vandetanib. Given this limitation, there is considerable interest in developing more selective inhibitors of RET kinase. Tyrosine kinase inhibitors are prone to early clinical failure due to mutations in the kinase ATPase binding domain, which render the kinase catalytically active but no longer sensitive to drug treatment. Such mutations often occur in the so-called “gatekeeper” region and in this specific case, resistance is predicted to arise from a Val-Met or Val-Leu mutation at residue 804. Through a combination of computational methods, structural biology and drug design, we have identified and further optimized a series of inhibitors of the V804M mutant RET kinase which show sub-micromolar cellular activity in cells driven by V804M RET. Moreover, these agents show excellent selectivity against the wtRET kinase and KDR. As such, these agents may offer valuable start-points for second-generation RET inhibitors for use in patents who relapse after treatment with first generation selective RET inhibitors.

Citation Format: Allan M. Jordan, Rebecca Newton, Bohdan Waszkowycz, Richard Bayliss, Habiba Begum, Daniel Burschowsky, Aude Echalier, Samantha Hitchin, Colin Hutton, Shaun Johns, Stuart Jones, Li-Ying Lin, Mark Richards, Chitra Seewooruthun, Alex Stowell, Ian Waddell, Mandy Watson, Donald Ogilvie. Delivering selective and cell-active inhibitors of V804M mutant RET kinase through structure-guided drug discovery [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 3236. doi:10.1158/1538-7445.AM2017-3236

Discovery and Optimization of Allosteric Inhibitors of Mutant Isocitrate Dehydrogenase 1 (R132H IDH1) Displaying Activity in Human Acute Myeloid Leukemia Cells

A collaborative high throughput screen of 1.35 million compounds against mutant (R132H) isocitrate dehydrogenase IDH1 led to the identification of a novel series of inhibitors. Elucidation of the bound ligand crystal structure showed that the inhibitors exhibited a novel binding mode in a previously identified allosteric site of IDH1 (R132H). This information guided the optimization of the series yielding submicromolar enzyme inhibitors with promising cellular activity. Encouragingly, one compound from this series was found to induce myeloid differentiation in primary human IDH1 R132H AML cells in vitro.

Abstract 3715: Benzimidazolone sulphonamides - potent, selective and drug-like inhibitors of poly(ADP Ribose) Glycohydrolase (PARG)

In recent years, many proteins involved in DNA repair, such as ATR, ATM and PARP, have received considerable attention as potential points of therapeutic intervention in cancer. Indeed, these efforts have recently delivered several agents into clinical evaluation or FDA regulatory approval. However, the DNA repair protein poly(ADP ribose) glycohydrolase (PARG), which plays an equally critical role in DNA single stand break repair, to successful drug discovery efforts.

Through our innovative collaboration with AstraZeneca, we have discovered a novel PARG-binding pharmacophore and have employed this information to discover drug-like chemotypes, facilitating the development of potent and selective inhibitors.

This poster will describe our emerging results in this area, where a novel benzimidazolone sulphonamide scaffold has been shown potently to inhibit PARG in both biochemical and cellular assays with potencies of 40 nM and 60 nM respectively. Moreover, these agents display pharmacology consistent with the anticipated mode of action, appropriate drug-like properties and are selective against PARP1 and the close glycohydrolase homologue ARH3. The medicinal chemistry optimisation of this scaffold will be described, alongside the recent biological results obtained. Ultimately, this work has helped deliver tool compounds which may help to elucidate the true pharmacology and roles of PARG in cancer and other disease settings.

Citation Format: Allan Jordan, Ben Acton, Nicola Hamilton, James Hitchin, Colin Hutton, Dominic James, Cliff Jones, Stuart Jones, Alison McGonagle, Helen Small, Kate Smith, Alex Stowell, Julie Tucker, Ian Waddell, Bohdan Waszkowycz, Donald Ogilvie. Benzimidazolone sulphonamides - potent, selective and drug-like inhibitors of poly(ADP Ribose) Glycohydrolase (PARG). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3715.

Abstract 4352: Discovery of the first cell-active inhibitors of poly(ADP Ribose) glycohydrolase through high-throughput screening and computational approaches

DNA repair is a critical process for the survival and normal proliferation of healthy cells. However, given the enhanced levels of cellular stress and genomic instability, these repair processes are even more critical to the survival of malignant cells, where rates of DNA damage are considerably increased. Given this, inhibitors of DNA damage repair have seen a resurgence of interest in recent years in an effort to exploit tumour cell vulnerabilities. One such example of this approach has resulted in the recent approval of the PARP inhibitor olaparib (Lynparza™) for women with advanced ovarian cancer associated with defective BRCA genes.

Olaparib acts against the poly(ADP-ribose)polymerase (PARP) enzymes, more recently re-defined as the ARTD (Diphtheria toxin-like human ADP-ribosyltransferase) enzyme class. Whilst PARP is widely known to play critical and well-understood roles in DNA repair, poly(ADP ribose) glycohydrolase (PARG) is less well known but equally essential for effective DNA repair, degrading PAR chains and facilitating effective DNA repair. However, its inhibition may offer several key advantages over PARP inhibition. Most critically, whilst there are 18 isoforms, there exists only a single PARG protein, offering a specific point of therapeutic intervention. However, due to the open nature of the PARG binding cleft and the nature of the binding site, this protein has been considered to be difficult to inhibit with small, drug-like small molecules, particularly in the cellular context.

This poster will describe our efforts to overcome these challenges against this challenging target and report our early successes achieved through innovative computational chemistry strategies. These efforts have delivered several credible, drug-like startpoints for further medicinal chemistry optimisation.

Citation Format: Bohdan Waszkowycz, Dominic James, Steven Durant, Nicola Hamilton, Cliff Jones, Stuart Jones, Allan Jordan, Alan Lau, Alison MGonagle, Mark O’Connor, Kate Smith, Alex Stowell, Julie Tucker, Ian Waddell, Donald Ogilvie. Discovery of the first cell-active inhibitors of poly(ADP Ribose) glycohydrolase through high-throughput screening and computational approaches. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4352.

Abstract A176: RET inhibition: Development of novel compounds and a personalized medicine strategy in lung adenocarcinoma

Background:RET is a receptor tyrosine kinase (RTK) and forms part of a macromolecular receptor complex containing dimerised RET receptor, two co-receptors and a bound ligand. Signalling networks downstream of RET play an important role in regulating cell survival, differentiation, proliferation, migration and chemotaxis. Activating mutations in RET (e.g. C634W and M918T) are known drivers in medullary thyroid carcinomas (MTC). More recently, oncogenic RET fusions (e.g. CCDC6-RET and KIF5B-RET) have been identified in 1-2% of lung adenocarcinoma patients. We are currently developing novel, selective inhibitors of RET, and at the same time, investigating a number of biomarker approaches for the stratification of RET fusion-positive lung cancer patients who might benefit from such therapy.

Methods: We have undertaken collaborative studies using established techniques including immunohistochemistry (IHC) and FISH (DNA break apart and RNA). In addition, we have investigated hybrid capture DNA sequencing of both biopsy material and circulating tumour DNA in the blood. Here we, compare and contrast the benefits of each biomarker assay evaluated and consider how these approaches could be translated for use in Phase I clinical trials at The Christie.

Conclusion: Our data supports the successful implementation of predictive biomarkers to identify patients who might benefit from treatment with selective RET inhibitors.

Acknowledgements:This work was funded by Cancer Research UK (Grant numbers C480/A1141 and C5759/A17098).

Citation Format: Mandy Watson, Helen Small, Phil Chapman, Gemma Hopkins, Habiba Begum, Ian D. Waddell, Garry Ashton, Caron Abbey, Jade Harris, Mahmood Ayub, Sumitra Mohan, Dominic Rothwell, Ged Brady, Caroline Dive, Allan Jordan, Donald Ogilvie. RET inhibition: Development of novel compounds and a personalized medicine strategy in lung adenocarcinoma. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A176.

Abstract C39: First-in-class inhibitors of the putatively undruggable DNA repair target Poly(ADP-ribose) glycohydrolase (PARG)

Poly(ADP-ribose) glycohydrolase (PARG) is the only enzyme known to catalyse hydrolysis of the O-glycosidic linkages of ADP-ribose polymers, thereby reversing the effects of poly(ADP-ribose) polymerases (PARPs). PARG depletion, using RNAi, results in several effects such as PAR chain persistence, progression of single- to double-strand DNA lesions and NAD+ depletion. Given these findings, inhibition of PARG with a small molecule agent offers a potential opportunity to interfere with DNA repair mechanisms and induce cell death in those cells with increased susceptibility to DNA damage, such as tumour cells.

Previous efforts to develop small molecule inhibitors of PARG activity have generally been hampered by poor physicochemical properties, off-target pharmacology and a lack of cell permeability, leading some to suggest that PARG may be undruggable.

In contrast, we have now developed a series of first-in-class PARG inhibitors which display drug-like properties and attractive pharmacokinetic parameters. These compounds have proved to be useful biological tool compounds.

Moreover, displaying selective activity in both biochemical and, more importantly, cellular assays of PARG function, these derivatives have allowed an exploration of the phenotypes resulting from reversible, pharmacological PARG inhibition in both in vitro cell panels and in vivo models. Furthermore, our initial bioinformatic analysis suggests that deficiency of a known tumour suppressor confers sensitivity to PARG inhibition, suggesting patient populations that will potentially benefit from PARGi therapies.

Citation Format: Bohdan Waszkowycz, Dominic James, Ben Acton, Emma Fairweather, Sam Fritzl, Niall Hamilton, Nicola Hamilton, Sarah Holt, James Hitchen, Colin Hutton, Stuart Jones, Allan Jordan, Alison McGonagle, Daniel Mould, Helen Small, Kate Smith, Alexandra Stowell, Ian D. Waddell, Donald Ogilvie. First-in-class inhibitors of the putatively undruggable DNA repair target Poly(ADP-ribose) glycohydrolase (PARG). [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr C39.

Abstract 5429: Inhibition of SMARCA2: a novel target for SMARCA4-deficient lung adenocarcinoma

Aim: With the decreasing costs of genomics technologies, ever more data is being put into the public domain. Scientific papers only highlight a fraction of the information in the data, consequently further mining can answer drug discovery relevant questions and identify new targets. In this work we developed a bioinformatics pipeline, based on the collateral vulnerability hypothesis, to integrate several sources of public data and identify novel targets to form the basis of a new drug discovery project.

Methods: Genomic data from TCGA was integrated with phenotypic data extracted from Mousemine, Flymine and Wormbase to identify loss-of-function aberrations in genes from families with essential predicted function. Follow-up experiments investigated the effect of siRNA knockdown of paralogs of genes of interest on various cellular phenotypes including proliferation, survival and senescence in gene deficient cell lines. A fragment screen was used to assess drugability of genes of interest.

Results: The pipeline has been applied to several cancer types, and as a result a drug discovery project has been initiated against SMARCA2 in SMARCA4-deficient lung adenocarcinoma. SMARCA4 is a bromodomain-containing transcriptional co-activator within the multi-subunit SWF/SNF complex, which also possesses helicase and ATPase activities and functions to alter chromatin structure. SMARCA4-deficient cell lines harbour abrogating mutations, and previous studies have demonstrated that knockdown of SMARCA2, its functional paralog, in SMARCA4-deficient cell lines results in reduced cellular proliferation and survival. Moreover, SMARCA2 has been shown to be inactivated by epigenetic silencing in a proportion of human tumours. The collateral vulnerability hypothesis was tested in a panel of lung adenocarcinoma cell lines with SMARCA2- and/or SMARCA4-deficiencies. Experiments investigating the effect of siRNA knockdown confirmed both our hypothesis and the published data. A fragment screen against the bromodomain of SMARCA2 generated a high ‘ligandability’ index, suggesting that this target is druggable.

Conclusion: SMARCA2 has been validated by our work and others as a target in SMARCA4 deficient lung adenocarcinoma. Future work will focus on elucidating the role of the bromodomain and the ATPase domain in SMARCA2/4 activity, and we are actively pursuing the identification of small molecule inhibitors of SMARCA2. An HTS has been undertaken against a library of &gt;700 million compounds in a DNA-encoded library to identify novel hit matter that may ultimately be developed for therapeutic value.

Citation Format: Phil Chapman, Nikki March, Graeme Thomson, Emma Fairweather, Samantha Fritzl, James Hitchin, Nicola Hamilton, Allan Jordan, Ian Waddell, Donald Ogilvie. Inhibition of SMARCA2: a novel target for SMARCA4-deficient lung adenocarcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5429. doi:10.1158/1538-7445.AM2015-5429

Abstract 778: The identification and structure-guided optimisation of potent and selective inhibitors of oncogenes in medullary thyroid carcinoma and lung adenocarcinoma

RET (REarranged during Transfection) is a receptor tyrosine kinase (TK), which plays pivotal roles in regulating cell survival, differentiation, proliferation, migration and chemotaxis. Activating mutations in RET (C634W and M918T) have been identified in both familial and sporadic forms of medullary thyroid carcinoma (MTC) and correlate with aggressive disease progression, validating RET as a classical oncogene. Furthermore the recent identification of RET fusions (CCDC6-RET and KIF5B-RET) present in ∼1% of lung adenocarcinoma (LAD) patients has renewed interest in the identification and development of more selective RET inhibitors lacking the toxicities associated with the current treatments.

At present, there are no known specific RET inhibitors in clinical development, although many potent inhibitors of RET have been identified opportunistically through selectivity profiling of compounds initially designed to target other TKs. Such “secondary RET inhibitors” include the clinical agents Vandetanib and Cabozantinib, both approved for use in MTC, but additional pharmacological activities (most notably inhibition of KDR) lead to dose-limiting toxicity.

Using a robust screening cascade developed in house, we have measured RET and KDR inhibitory activity in vitro and in relevant cell line models to assess compound potency and selectivity. Anti-proliferative activity and off-target toxicity of these agents have also been measured. Although these competitor compounds displayed reasonable RET potency in cellular assays and this translated into anti-proliferative effects in our MTC and LAD disease models, as expected none met our target candidate criteria, clearly highlighting the need for therapeutic agents with improved selectivity.

Guided by structure-based drug design, we have identified and optimised a novel series of potent and selective inhibitors of the RET kinase domain. These agents met our stringent criteria for enzyme and cell selectivity and, whilst potent in a RET-driven cell line, display little overt toxicity in a matched non-RET driven cell line. Herein, we describe the chemical optimisation of these agents and, using structural information, rationalise their improved selectivity.

Citation Format: Roger J. Butlin, Rebecca Newton, Mandy Watson, Gemma Hopkins, Ben Acton, Kate Bowler, Samantha Fritzl, Kristin Goldberg, Niall Hamilton, Sarah Holt, Stuart Jones, Allan Jordan, Nikki March, Daniel Mould, Helen Small, Alexandra Stowell, Ian Waddell, Bohdan Waszkowycz, Donald Ogilvie. The identification and structure-guided optimisation of potent and selective inhibitors of oncogenes in medullary thyroid carcinoma and lung adenocarcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 778. doi:10.1158/1538-7445.AM2015-778

Abstract 3656: PARG inhibition: development of novel compounds and a biomarker strategy to determine cell line sensitivity in breast cancer

Background: DNA single strand breaks (SSBs) are the most common type of damage occurring in cells. Poly (ADP ribose) polymerase (PARP) binds to SSBs and auto-ribosylates itself using NAD+ as a substrate. PARG is the only enzyme known to efficiently catalyse the hydrolysis of O-glycosidic linkages of ADP-ribose polymers and exists (unlike PARP) as a single gene. We have developed novel inhibitors of PARG and here we describe our efforts to understand their sensitivity against a range of cell lines

Methods: A robust and detailed screening cascade for small molecule inhibition of PARG has been developed. Active compounds are tested in cells for PAR chain persistence and for cytotoxicity using a 3-day HeLa assay. In addition, suitable compounds were then evaluated for their physico-chemical properties and their in vivo PK profiles determined. Compounds with the desired PK properties are subsequently profiled in tumour bearing mice to determine their pharmacodynamic effect before progressing to efficacy studies.

Results: We have developed nM PARG inhibitors that are highly selective against ARH3 and PARP1and these derivatives show potent activity in cells. We have designed a breast cancer cell panel against which our compounds have been tested. Our initial bioinformatics analysis suggests that deficiency of a known tumour suppressor confers sensitivity to PARG inhibition.

Conclusions: We have developed two drug-like series of PARG inhibitors that block the breakdown of PAR chains in cells after exogenous DNA damage by methylating agents. These tool compounds are potent, selective and have pharmacokinetic and pharmacodynamics properties that have allowed us to explore their anti-tumour potential. The discovery of a tumour suppressor profile indicating cell line sensitivity will aid the about identification of patient populations that will potentially benefit from PARGi therapies.

Citation Format: Ian D. Waddell, Dominic James, Kate Smith, Sarah Holt, Ben Acton, Emma Fairweather, Niall Hamilton, Nicola Hamilton, James Hitchen, Colin Huttom, Allan Jordan, Alison McGonagle, Helen Small, Alex Stowell, Bohdan Waszkowycz, Donald Ogilvie. PARG inhibition: development of novel compounds and a biomarker strategy to determine cell line sensitivity in breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3656. doi:10.1158/1538-7445.AM2015-3656

Inhibition of PI3Kβ signaling with AZD8186 inhibits growth of PTEN-deficient breast and prostate tumors alone and in combination with docetaxel

Loss of PTEN protein results in upregulation of the PI3K/AKT pathway, which appears dependent on the PI3Kβ isoform. Inhibitors of PI3Kβ have potential to reduce growth of tumors in which loss of PTEN drives tumor progression. We have developed a small-molecule inhibitor of PI3Kβ and PI3Kδ (AZD8186) and assessed its antitumor activity across a panel of cell lines. We have then explored the antitumor effects as single agent and in combination with docetaxel in triple-negative breast (TNBC) and prostate cancer models. In vitro, AZD8186 inhibited growth of a range of cell lines. Sensitivity was associated with inhibition of the AKT pathway. Cells sensitive to AZD8186 (GI50 < 1 μmol/L) are enriched for, but not exclusively associated with, PTEN deficiency. In vivo, AZD8186 inhibits PI3K pathway biomarkers in prostate and TNBC tumors. Scheduling treatment with AZD8186 shows antitumor activity required only intermittent exposure, and that increased tumor control is achieved when AZD8186 is used in combination with docetaxel. AZD8186 is a potent inhibitor of PI3Kβ with activity against PI3Kδ signaling, and has potential to reduce growth of tumors dependent on dysregulated PTEN for growth. Moreover, AZD8186 can be combined with docetaxel, a chemotherapy commonly used to treat advanced TBNC and prostate tumors. The ability to schedule AZD8186 and maintain efficacy offers opportunity to combine AZD8186 more effectively with other drugs.

Abstract B98: Development and evaluation of selective, reversible LSD1 inhibitors from fragment startpoints

There is currently considerable interest in lysine-specific histone demethylase 1 (LSD1) as a therapeutic target in human malignancies. Specifically LSD1 has been demonstrated to be an essential regulator of leukaemia stem cell potential, inhibiting differentiation and apoptosis in the MLL-AML setting. There are a variety of potent irreversible LSD1 inhibitors available but here we present two series of reversible aminothiazole inhibitors obtained through the expansion of hits derived from a high concentration biochemical screen of a fragment library. The potency of the initial fragment hits was increased 32-fold through synthesis, with one series of compounds showing clear structure activity relationships (SAR) and inhibitory activities in the range of 7 to 187 µM in a biochemical assay. This series also showed selectivity against the homologous amine oxidase enzyme monoamine oxidase A (MAO-A).

This work represents one of the first reported examples of a reversible small molecule inhibitor of LSD1 with clear SAR and selectivity against MAO-A, and could provide a platform for the development of more potent reversible inhibitors. We also report the first Proof of Mechanism (POM) cell based assay utilizing CD86 expression as a surrogate marker of LSD1 activity in THP1 cells and its use to evaluate both our compounds and some recently reported reversible LSD1 inhibitors.

Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B98.

Citation Format: Alex Stowell, Niall Hamilton, James Hitchin, Julian Blagg, Rosemary Burke, Samantha Burns, Mark J. Cockerill, Emma Fairweather, Colin Hutton, Allan Jordan, Daniel Mould, Graeme Thomson, Ian Waddell, Donald Ogilvie. Development and evaluation of selective, reversible LSD1 inhibitors from fragment startpoints. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B98.

Discovery of AZD8931, an Equipotent, Reversible Inhibitor of Signaling by EGFR, HER2, and HER3 Receptors

Deregulation of HER family signaling promotes proliferation and tumor cell survival and has been described in many human cancers. Simultaneous, equipotent inhibition of EGFR-, HER2-, and HER3-mediated signaling may be of clinical utility in cancer settings where the selective EGFR or HER2 therapeutic agents are ineffective or only modestly active. We describe the discovery of AZD8931 (2), an equipotent, reversible inhibitor of EGFR-, HER2-, and HER3-mediated signaling and the structure-activity relationships within this series. Docking studies based on a model of the HER2 kinase domain helped rationalize the increased HER2 activity seen with the methyl acetamide side chain present in AZD8931. AZD8931 exhibited good pharmacokinetics in preclinical species and showed superior activity in the LoVo tumor growth efficacy model compared to close analogues. AZD8931 is currently being evaluated in human clinical trials for the treatment of cancer.

Abstract 3324: The discovery and optimisation of small-molecule inhibitors of human 5’-tyrosyl DNA phosphodiesterase (Tdp2)

Topoisomerases (topo) regulate DNA topology by the transient cleavage and re-ligation of DNA during transcription and replication. Topo II poisons such as etoposide can induce abortive DNA strand breaks in which topo II remains covalently bound to a 5’ DNA strand terminus via a phosphotyrosyl linker. Tyrosyl DNA phosphodiesterase 2 (Tdp2, TTRAP, EAPII) is a recently discovered human 5’-tyrosyl DNA phosphodiesterase which repairs this topo-mediated DNA damage, therefore playing a central role in maintaining normal DNA topology in cells. Cellular depletion of Tdp2 has been shown to result in an increased susceptibility and sensitivity to topo II-induced DNA double strand breaks. It has therefore been proposed that selective pharmacological inhibition of Tdp2 may be a novel approach to overcome intrinsic or acquired resistance to topo II targeted drug therapy.

To date, no known drug-like inhibitors of Tdp2 have been identified. We have recently reported a robust ‘mix and read’ HTS compatible assay and this was used to screen a diverse chemical library of approximately 92,000 compounds. From this endeavour, 2 distinct hit series have been identified. Following further chemical exploration of the original hit compounds, small molecule inhibitors of Tdp2 with sub-100nM potencies have been identified. This poster will describe our biological and chemical progress in this area, detailing SAR and some lessons learnt during investigation of this target.

Citation Format: Allan M. Jordan, Paul Depledge, Nicola Hamilton, James Hitchin, Gemma Hopkins, Laura Maguire, Alison McGonagle, Daniel Mould, Ali Raoof, Mathew Rushbrooke, James Smith, Kate Smilth, Graeme Thomson, Fabrice Turlais, Ian Waddell, Mandy Watson, Donald Ogilvie. The discovery and optimisation of small-molecule inhibitors of human 5’-tyrosyl DNA phosphodiesterase (Tdp2). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3324. doi:10.1158/1538-7445.AM2013-3324

Generation of assays and antibodies to facilitate the study of human 5'-tyrosyl DNA phosphodiesterase

Topoisomerases regulate DNA topology by the transient cleavage and religation of DNA during transcription and replication. Topoisomerase II (Topo II) poisons such as etoposide can induce abortive DNA strand breaks in which Topo II remains covalently bound to a 5' DNA strand terminus via a phosphotyrosyl linker. Tyrosyl DNA phosphodiesterase 2 (Tdp2) is a recently discovered human 5'-tyrosyl DNA phosphodiesterase that repairs this topoisomerase-mediated DNA damage, thereby playing a central role in maintaining normal DNA topology in cells. Cellular depletion of Tdp2 has been shown to result in increased susceptibility and sensitivity to Topo II-induced DNA double-strand breaks, thereby revealing Tdp2 as a potentially attractive anticancer target. No drug-like inhibitors of Tdp2 have been identified to date, and assays suitable for high-throughput screening (HTS) have not been widely reported. Here we have identified a new and effective chromogenic substrate for Tdp2 and developed a homogeneous and robust HTS assay. A second novel Tdp2 assay was also developed to cross-validate hit matter identified from an HTS. In addition, a new and specific Tdp2 antibody is described. Together, these new tools will aid in the identification of novel Tdp2 inhibitors and the investigation of the role of Tdp2 in cancer.

Towards a differentiated understanding of active travel behaviour: using social theory to explore everyday commuting

Fostering physical activity is an established public health priority for the primary prevention of a variety of chronic diseases. One promising population approach is to seek to embed physical activity in everyday lives by promoting walking and cycling to and from work (‘active commuting’) as an alternative to driving. Predominantly quantitative epidemiological studies have investigated travel behaviours, their determinants and how they may be changed towards more active choices. This study aimed to depart from narrow behavioural approaches to travel and investigate the social context of commuting with qualitative social research methods. Within a social practice theory framework, we explored how people describe their commuting experiences and make commuting decisions, and how travel behaviour is embedded in and shaped by commuters' complex social worlds. Forty-nine semi-structured interviews and eighteen photo-elicitation interviews with accompanying field notes were conducted with a subset of the Commuting and Health in Cambridge study cohort, based in the UK. The findings are discussed in terms of three particularly pertinent facets of the commuting experience. Firstly, choice and decisions are shaped by the constantly changing and fluid nature of commuters' social worlds. Secondly, participants express ambiguities in relation to their reasoning, ambitions and identities as commuters. Finally, commuting needs to be understood as an embodied and emotional practice. With this in mind, we suggest that everyday decision-making in commuting requires the tactical negotiation of these complexities. This study can help to explain the limitations of more quantitative and static models and frameworks in predicting travel behaviour and identify future research directions.

A community prevention model to prevent children from inhaling and ingesting harmful legal products

Children's misuse of harmful legal products (HLPs), including inhaling or ingesting everyday household products, prescription drugs, and over-the-counter drugs, constitutes a serious health problem for American society. This article presents a community prevention model (CPM) focusing on this problem among pre and early adolescents. The model, consisting of a community mobilization strategy and environmental strategies targeting homes, schools, and retail outlets, is designed to increase community readiness and reduce the availability of HLPs, which is hypothesized to reduce HLPs use among children. The CPM is being tested in Alaskan rural communities as part of an inprogress eight-year National Institute on Drug Abuse randomized-controlled trial. This paper presents the CPM conceptual framework, describes the model, and highlights community participation, challenges, and lessons learned from implementation of the model over a 21-month period.

Preclinical pharmacology of AZD5363, an inhibitor of AKT: pharmacodynamics, antitumor activity, and correlation of monotherapy activity with genetic background

AKT is a key node in the most frequently deregulated signaling network in human cancer. AZD5363, a novel pyrrolopyrimidine-derived compound, inhibited all AKT isoforms with a potency of 10 nmol/L or less and inhibited phosphorylation of AKT substrates in cells with a potency of approximately 0.3 to 0.8 μmol/L. AZD5363 monotherapy inhibited the proliferation of 41 of 182 solid and hematologic tumor cell lines with a potency of 3 μmol/L or less. Cell lines derived from breast cancers showed the highest frequency of sensitivity. There was a significant relationship between the presence of PIK3CA and/or PTEN mutations and sensitivity to AZD5363 and between RAS mutations and resistance. Oral dosing of AZD5363 to nude mice caused dose- and time-dependent reduction of PRAS40, GSK3β, and S6 phosphorylation in BT474c xenografts (PRAS40 phosphorylation EC(50) ~ 0.1 μmol/L total plasma exposure), reversible increases in blood glucose concentrations, and dose-dependent decreases in 2[18F]fluoro-2-deoxy-D-glucose ((18)F-FDG) uptake in U87-MG xenografts. Chronic oral dosing of AZD5363 caused dose-dependent growth inhibition of xenografts derived from various tumor types, including HER2(+) breast cancer models that are resistant to trastuzumab. AZD5363 also significantly enhanced the antitumor activity of docetaxel, lapatinib, and trastuzumab in breast cancer xenografts. It is concluded that AZD5363 is a potent inhibitor of AKT with pharmacodynamic activity in vivo, has potential to treat a range of solid and hematologic tumors as monotherapy or a combinatorial agent, and has potential for personalized medicine based on the genetic status of PIK3CA, PTEN, and RAS. AZD5363 is currently in phase I clinical trials.

AZD8931, an equipotent, reversible inhibitor of signaling by epidermal growth factor receptor, ERBB2 (HER2), and ERBB3: a unique agent for simultaneous ERBB receptor blockade in cancer

PURPOSE

To test the hypothesis that simultaneous, equipotent inhibition of epidermal growth factor receptor (EGFR; erbB1), erbB2 (human epidermal growth factor receptor 2), and erbB3 receptor signaling, using the novel small-molecule inhibitor AZD8931, will deliver broad antitumor activity in vitro and in vivo.

EXPERIMENTAL DESIGN

A range of assays was used to model erbB family receptor signaling in homodimers and heterodimers, including in vitro evaluation of erbB kinase activity, erbB receptor phosphorylation, proliferation in cells, and in vivo testing in a human tumor xenograft panel, with ex vivo evaluation of erbB phosphorylation and downstream biomarkers. Gefitinib and lapatinib were used to compare the pharmacological profile of AZD8931 with other erbB family inhibitors.

RESULTS

In vitro, AZD8931 showed equipotent, reversible inhibition of EGFR (IC(50), 4 nmol/L), erbB2 (IC(50), 3 nmol/L), and erbB3 (IC(50), 4 nmol/L) phosphorylation in cells. In proliferation assays, AZD8931 was significantly more potent than gefitinib or lapatinib in specific squamous cell carcinoma of the head and neck and non-small cell lung carcinoma cell lines. In vivo, AZD8931 inhibited xenograft growth in a range of models while significantly affecting EGFR, erbB2, and erbB3 phosphorylation and downstream signaling pathways, apoptosis, and proliferation.

CONCLUSIONS

AZD8931 has a unique pharmacologic profile providing equipotent inhibition of EGFR, erbB2, and erbB3 signaling and showing greater antitumor activity than agents with a narrower spectrum of erbB receptor inhibition in specific preclinical models. AZD8931 provides the opportunity to investigate whether simultaneous inhibition of erbB receptor signaling could be of utility in the clinic, particularly in the majority of solid tumors that do not overexpress erbB2.

Evaluation of AZD8931, an Equipotent Inhibitor of erbB1, erbB2, and erbB3 Receptor Signaling, on Ligand Stimulated Breast Cancer Cell Lines with Differing Levels of erbB2 Expression

Background: Further treatment options for patients whose breast cancers do not overexpress erbB2 are required. AZD8931, an equipotent, reversible inhibitor of erbB1 (HER1, EGFR), erbB2 (HER2), and erbB3 (HER3) receptor signaling may be useful in this setting and may lead to inhibition of tumor cell proliferation, invasion, metastasis, angiogenesis and tumor cell survival.Objectives: To compare the activity of AZD8931 with other erbB inhibitors (gefitinib [G] and lapatinib [L]) in breast cancer cell lines stimulated with erbB ligands.Methods: A panel of 9 breast cancer cell lines with differing erbB2 expression levels were used: erbB2+/ER+ (BT474c; MDA-MB-361); erbB2+/ER- (MDA-MB-453; SKBR-3); erbB2-/ER+ (MCF7; T47D; ZR75-1); or erbB2-/ER- (MDA-MB-231; MDA-MB-468). Following overnight serum starvation, cells were incubated with AZD8931, G or L (0-10 µM) for 90 min and then stimulated with erbB ligands (50 ng/ml; EGF, TGFα, amphiregulin, epiregulin, betacellulin, neuregulin1, or HBEGF) for 5 min before lysis. Levels of phosphorylated erbB1, erbB2, and erbB3 were analyzed by ELISA. For IC50 determination, mean basal phosphorylation was subtracted. Geometric mean IC50s were calculated from triplicate assays and 2-sided unequal variance t-tests compared logIC50s.Results: AZD8931 demonstrated potent inhibitory activity (IC50s ≤10610 nM) when phosphorylation of erbB1, erbB2 or erbB3 receptors was driven by any erbB ligand. G demonstrated potent inhibitory activity (IC50s ≤20 nM) when the phosphorylation of erbB1 and erbB2 was driven by any erbB ligand. L more strongly inhibited the phosphorylation of erbB2 (IC50s ≤10 nM) than erbB1 (IC50s &lt;400 nM) and showed a ligand and cell-dependant range of activities against erbB3 phosphorylation. AZD8931 was particularly differentiated from G and L in the inhibition of neuregulin1-driven erbB3 phosphorylation: IC50s were lower for AZD8931 (1-5 nM) than for G (1-120 nM) or L (20-80 nM) in the majority of the cell lines tested. Inhibition of erbB1 phosphorylation driven by EGF (IC50s ≤ vs &gt;20 nM), TGFα (≤5 vs &gt;20 nM), HB-EGF (≤ vs &gt;25 nM), or betacellulin (≤6 vs 10-118 nM) also indicated more potent inhibitory activity for AZD8931 over L in cell lines that respond to ligand stimulation. No phosphorylation response to amphiregulin was seen in any of the cell lines.Conclusion: This study demonstrates that in a range of breast cell lines with varying levels of erbB2 expression, AZD8931 is a potent and balanced inhibitor of erbB1, erbB2, and erbB3 signaling. The pharmacological profile of AZD8931 is thus distinct from G and L and suggests that AZD8931 offers an agent to test the hypothesis that combined, balanced inhibition of erbB signaling could provide clinical benefit. AZD8931 may be particularly useful in the treatment of solid tumors that do not overexpress erbB2 including trastuzumab-ineligible breast cancer, an area of unmet medical need. AZD8931 is being evaluated in a Phase I clinical trial.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 5059.