The ATR inhibitor ceralasertib potentiates cancer checkpoint immunotherapy by regulating the tumor microenvironment

The Ataxia telangiectasia and Rad3-related (ATR) inhibitor ceralasertib in combination with the PD-L1 antibody durvalumab demonstrated encouraging clinical benefit in melanoma and lung cancer patients who progressed on immunotherapy. Here we show that modelling of intermittent ceralasertib treatment in mouse tumor models reveals CD8+ T-cell dependent antitumor activity, which is separate from the effects on tumor cells. Ceralasertib suppresses proliferating CD8+ T-cells on treatment which is rapidly reversed off-treatment. Ceralasertib causes up-regulation of type I interferon (IFNI) pathway in cancer patients and in tumor-bearing mice. IFNI is experimentally found to be a major mediator of antitumor activity of ceralasertib in combination with PD-L1 antibody. Improvement of T-cell function after ceralasertib treatment is linked to changes in myeloid cells in the tumor microenvironment. IFNI also promotes anti-proliferative effects of ceralasertib on tumor cells. Here, we report that broad immunomodulatory changes following intermittent ATR inhibition underpins the clinical therapeutic benefit and indicates its wider impact on antitumor immunity.

Relevance of ATM Status in Driving Sensitivity to DNA Damage Response Inhibitors in Patient-Derived Xenograft Models

Ataxia-telangiectasia mutated gene (ATM) is a key component of the DNA damage response (DDR) and double-strand break repair pathway. The functional loss of ATM (ATM deficiency) is hypothesised to enhance sensitivity to DDR inhibitors (DDRi). Whole-exome sequencing (WES), immunohistochemistry (IHC), and Western blotting (WB) were used to characterise the baseline ATM status across a panel of ATM mutated patient-derived xenograft (PDX) models from a range of tumour types. Antitumour efficacy was assessed with poly(ADP-ribose)polymerase (PARP, olaparib), ataxia- telangiectasia and rad3-related protein (ATR, AZD6738), and DNA-dependent protein kinase (DNA-PK, AZD7648) inhibitors as a monotherapy or in combination to associate responses with ATM status. Biallelic truncation/frameshift ATM mutations were linked to ATM protein loss while monoallelic or missense mutations, including the clinically relevant recurrent R3008H mutation, did not confer ATM protein loss by IHC. DDRi agents showed a mixed response across the PDX's but with a general trend toward greater activity, particularly in combination in models with biallelic ATM mutation and protein loss. A PDX with an ATM splice-site mutation, 2127T > C, with a high relative baseline ATM expression and KAP1 phosphorylation responded to all DDRi treatments. These data highlight the heterogeneity and complexity in describing targetable ATM-deficiencies and the fact that current patient selection biomarker methods remain imperfect; although, complete ATM loss was best able to enrich for DDRi sensitivity.

Identification of a Molecularly-Defined Subset of Breast and Ovarian Cancer Models that Respond to WEE1 or ATR Inhibition, Overcoming PARP Inhibitor Resistance

PURPOSE

PARP inhibitors (PARPi) induce synthetic lethality in homologous recombination repair (HRR)-deficient tumors and are used to treat breast, ovarian, pancreatic, and prostate cancers. Multiple PARPi resistance mechanisms exist, most resulting in restoration of HRR and protection of stalled replication forks. ATR inhibition was highlighted as a unique approach to reverse both aspects of resistance. Recently, however, a PARPi/WEE1 inhibitor (WEE1i) combination demonstrated enhanced antitumor activity associated with the induction of replication stress, suggesting another approach to tackling PARPi resistance.

EXPERIMENTAL DESIGN

We analyzed breast and ovarian patient-derived xenoimplant models resistant to PARPi to quantify WEE1i and ATR inhibitor (ATRi) responses as single agents and in combination with PARPi. Biomarker analysis was conducted at the genetic and protein level. Metabolite analysis by mass spectrometry and nucleoside rescue experiments ex vivo were also conducted in patient-derived models.

RESULTS

Although WEE1i response was linked to markers of replication stress, including STK11/RB1 and phospho-RPA, ATRi response associated with ATM mutation. When combined with olaparib, WEE1i could be differentiated from the ATRi/olaparib combination, providing distinct therapeutic strategies to overcome PARPi resistance by targeting the replication stress response. Mechanistically, WEE1i sensitivity was associated with shortage of the dNTP pool and a concomitant increase in replication stress.

CONCLUSIONS

Targeting the replication stress response is a valid therapeutic option to overcome PARPi resistance including tumors without an underlying HRR deficiency. These preclinical insights are now being tested in several clinical trials where the PARPi is administered with either the WEE1i or the ATRi.

PARP inhibition is a modulator of anti-tumor immune response in BRCA-deficient tumors

PARP inhibitors are synthetically lethal with BRCA1/2 mutations, and in this setting, accumulation of DNA damage leads to cell death. Because increased DNA damage and subsequent immune activation can prime an anti-tumor immune response, we studied the impact of olaparib ± immune checkpoint blockade (ICB) on anti-tumor activity and the immune microenvironment. Concurrent combination of olaparib, at clinically relevant exposures, with ICB gave durable and deeper anti-tumor activity in the Brca1m BR5 model vs. monotherapies. Olaparib and combination treatment modulated the immune microenvironment, including increases in CD8+ T cells and NK cells, and upregulation of immune pathways, including type I IFN and STING signaling. Olaparib also induced a dose-dependent upregulation of immune pathways, including JAK/STAT, STING and type I IFN, in the tumor cell compartment of a BRCA1m (HBCx-10) but not a BRCA WT (HBCx-9) breast PDX model. In vitro, olaparib induced BRCAm tumor cell–specific dendritic cell transactivation. Relevance to human disease was assessed using patient samples from the MEDIOLA (NCT02734004) trial, which showed increased type I IFN, STING, and JAK/STAT pathway expression following olaparib treatment, in line with preclinical findings. These data together provide evidence for a mechanism and schedule underpinning potential benefit of ICB combination with olaparib.

Abstract 1142: Activity and tolerability of combination of trastuzumab deruxtecan with the next generation PARP1-selective inhibitor AZD5305 in preclinical models

Background: Trastuzumab deruxtecan (T-DXd) is an antibody-drug conjugate composed of an anti-HER2 antibody, a cleavable tetrapeptide-based linker, and a cytotoxic topoisomerase I inhibitor, approved for HER2+ metastatic breast cancer. Clinically, T-DXd has demonstrated antitumor activity in both HER2+ and HER2-low cancers. Due to the role of PARP1 in resolution of DNA damage induced by topoisomerase I trapping, we tested the combination of the next generation PARP1-selective inhibitor AZD5305 with T-DXd.

Methods: We evaluated the antiproliferative ability of the combination of T-DXd with AZD5305 in a panel of 27 breast cancer cell lines in an in vitro 7-day viability assay. The combination was also evaluated in vivo in two non-HRD HER2+ models, KPL4 (Breast) and NCI-N87 (Gastric) at doses of 3mg/kg and 10mg/kg Q3W for T-DXd combined with 0.01, 0.1, and 1 mg/kg QD of AZD5305. To evaluate the specificity of the combination activity in tumor cells (vs normal tissue), we further evaluated the combination in a human 2D in vitro bone marrow progenitor assay.

Results: We found that the combination had enhanced in vitro cell killing activity over single agents in 8/27 of the models tested. The benefit was present in both Homologous Recombination Deficient (HRD) as well as Homologous Recombination proficient, suggesting it does not depend on HRD (as defined by mutations in DNA damage repair genes). Mechanistically, T-DXd activated PARP and the combination of T-DXd with AZD5305 abrogated PARP1 auto-parylation, leading to enhanced DNA damage (gH2AX, pRPA-S4/8) and cell death (cCasp3). In vivo, the combination was well tolerated and more active than monotherapy of either compound in both KPL4 (at 30 days the growth inhibition was 95% at 10mg/kg T-DXd, 10% at 1mg/kg AZD5305, and 100% TGI with 97% regression with T-DXd + AZD5305) and NCI-N87 (at 41 days TGI of 74% with 10mg/kg T-DXd, 47% with 1mg/kg AZD5305, and 100% TGI with 40% regression for T-DXd + AZD5305; p<0.0001). In an in vitro human bone marrow assay, the combination demonstrated modest enhancement over monotherapy activity (average Loewe Synergy Score of 3.1). We tested alternative doses and schedules of the combination in KPL4 in vivo. We found that reducing the dose of AZD5305 as low as 0.01mg/kg resulted in combination benefit (100% TGI with 78% regression for combination versus 0% TGI for monotherapy on day 30). Further, 7-day delay of 0.01mg/kg AZD5305 in combination with 10mg/kg T-DXd also provided greater activity (>100% TGI with 72% regression on day 30) vs. monotherapy T-DXd alone (95% TGI).

Conclusions: These results suggest that T-DXd combined with the next generation PARP1 inhibitor AZD5305 is a potentially active combination, with preclinical activity demonstrated in HRD and HR proficient models. Further, the dose and scheduling may warrant exploration clinically to optimize therapeutic index.

Citation Format: Yann Wallez, Theresa Proia, Elisabetta Leo, Laura Bradshaw, Zena Wilson, Joe’l Owusu, Azadeh Cheraghchi-Bashi-Astaneh, Anna Staniszewska, Mark O’Connor, Sabina Cosulich, Jerome Mettetal. Activity and tolerability of combination of trastuzumab deruxtecan with the next generation PARP1-selective inhibitor AZD5305 in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1142.

ATR Inhibitor AZD6738 (Ceralasertib) Exerts Antitumor Activity as a Monotherapy and in Combination with Chemotherapy and the PARP Inhibitor Olaparib

AZD6738 (ceralasertib) is a potent and selective orally bioavailable inhibitor of ataxia telangiectasia and Rad3-related (ATR) kinase. ATR is activated in response to stalled DNA replication forks to promote G2-M cell-cycle checkpoints and fork restart. Here, we found AZD6738 modulated CHK1 phosphorylation and induced ATM-dependent signaling (pRAD50) and the DNA damage marker γH2AX. AZD6738 inhibited break-induced replication and homologous recombination repair. In vitro sensitivity to AZD6738 was elevated in, but not exclusive to, cells with defects in the ATM pathway or that harbor putative drivers of replication stress such as CCNE1 amplification. This translated to in vivo antitumor activity, with tumor control requiring continuous dosing and free plasma exposures, which correlated with induction of pCHK1, pRAD50, and γH2AX. AZD6738 showed combinatorial efficacy with agents associated with replication fork stalling and collapse such as carboplatin and irinotecan and the PARP inhibitor olaparib. These combinations required optimization of dose and schedules in vivo and showed superior antitumor activity at lower doses compared with that required for monotherapy. Tumor regressions required at least 2 days of daily dosing of AZD6738 concurrent with carboplatin, while twice daily dosing was required following irinotecan. In a BRCA2-mutant patient-derived triple-negative breast cancer (TNBC) xenograft model, complete tumor regression was achieved with 3 to5 days of daily AZD6738 per week concurrent with olaparib. Increasing olaparib dosage or AZD6738 dosing to twice daily allowed complete tumor regression even in a BRCA wild-type TNBC xenograft model. These preclinical data provide rationale for clinical evaluation of AZD6738 as a monotherapy or combinatorial agent.

SIGNIFICANCE

This detailed preclinical investigation, including pharmacokinetics/pharmacodynamics and dose-schedule optimizations, of AZD6738/ceralasertib alone and in combination with chemotherapy or PARP inhibitors can inform ongoing clinical efforts to treat cancer with ATR inhibitors.

Abstract LB-104: Quantification of the preclinical and clinical relationship between pRAD50 and efficacy after treatment with the ATR inhibitor ceralasertib (AZD6738)

Ceralasertib is a potent and selective ATP competitive inhibitor of ataxia telangiectasia and Rad3 related (ATR) in clinical development as monotherapy and in combination with olaparib (Lynparza) and durvalumab (Imfinzi) in patients with advanced solid tumors. Paired pre- and on-treatment tumour samples from seven patients during ceralasertib monotherapy in Phase 1 studies (NCT02223923, NCT02264678), all ATM expressing, showed increases in pRAD50 on treatment. This study aimed to robustly understand the relationship between ceralasertib pharmacokinetics, pRAD50 (pSer635) induction by immunohistochemistry and anti-tumor efficacy, in mouse xenografted models; to enable interpretation of paired clinical tumour samples. First, in vivo data were generated in a range of xenografted models (HBCx9 [TNBC, Xentech], HCC1806 [BC], OCI-Ly19 [DLBCL] and OE21 [HNSCC]) and NSCLC and HNSCC PDX models at Champions). Mouse ceralasertib doses (6.25 - 25mg/kg BID and 50mg/kg QD) reflected the observed free drug exposure achieved at clinical doses. In pharmacodynamic studies, animals were dosed continuously for 5 days, with PKPD endpoints being assessed on the 5th day. In anti-tumor studies, animals were randomized and treated for at least 28 days continuously. Increases in pRAD50 on treatment, versus control, were both dose and time dependent. There was a wide range of baseline pRAD50 expression (H-Scores ranging from 2 to 48) but the fold increase was consistent; a 3-fold increase being seen at the highest dose. Similarly, the anti-tumor activity was dose dependent with a range of sensitivities being observed across the models; the OCI-Ly19 model was most sensitive with %TGI ranging 43% to 104%. Mathematical modelling confirmed a consistent PKPD relationship for the fold increase of pRAD50. The effect was not saturated at the tested drug exposures and the slope relating drug in plasma to fold pRAD50 increases was estimated to be 0.75 uM-1. Modelling also demonstrated a relationship between pRAD50 and the observed anti-tumor activity, across all models. Of note, the fold induction required for efficacy increased with the baseline pRAD50 The hypothesis for this observation is that the baseline pRAD50 H-score is a functional measure of DDR signaling and so low pRAD50 may be indicative of impaired signaling and thus sensitivity to inhibition of DDR signaling. The results demonstrate the utility of generating PKPD-Efficacy relationships across a range of patient relevant xenografts and PDXs. Here, a marker of ATR inhibitor pharmacology, pRAD50, has been related to anti-tumor activity increasing our understanding of predictive markers of drug sensitivity. Clinical translation of these findings is being tested in a Phase I study, where patients provide paired tumour biopsies pre-treatment and following ceralasertib monotherapy dosing (NCT02264678).

Citation Format: James William Thomas Yates, Zena Wilson, Gemma N. Jones, Kevin Harrington, Matthew Krebs, Magnus Dillon, Andrew J. Pierce, Emma Dean, Alan Lau. Quantification of the preclinical and clinical relationship between pRAD50 and efficacy after treatment with the ATR inhibitor ceralasertib (AZD6738) [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr LB-104.

Abstract 626: Mechanistic differentiation of targeted DDR agent combinations

The DNA damage response (DDR) safeguards genome stability and promotes cellular survival by counteracting deleterious consequences of DNA damage. Deficiencies in DDR pathways contribute to genome instability, a hallmark of cancer development, and targeting the DDR is a promising anti-cancer therapy strategy. We describe here in vitro and in vivo studies allowing mechanistic understanding of the benefit of combining our DDR kinase inhibitors (DDRi) targeting ATM (AZD0156), ATR (AZD6738) and DNA-PK (AZD7648) with the PARP inhibitor, olaparib, in homologous recombination-deficient backgrounds. Using the break-induced replication (BIR) assay, which measures homologous-recombination repair (HRR) of DNA double-strand breaks resembling broken replication forks, we observed that ATRi decreases this type of homologous recombination repair by up to 50%, while inhibiting DNA-PK or ATM showed no effect. This provides a mechanistic rationale for combining ATRi with compounds that cause replication-fork collapse, such as PARPi. Indeed, combination of olaparib with the ATRi in BRCA1 mutant UWB1.289 cells enhanced olaparib sensitivity a thousand-fold (GI50 from 590 nM to 0.6 nM). This correlates with the complete tumour growth inhibitions (TGI) observed for the ATRi + olaparib combination in the BRCA2 mutant HBCx-10 triple negative breast cancer PDX model and is consistent with a synergistic increase of genome instability measured by metaphase spread analysis (total aberrations: olaparib; 11, ATRi; 8, combination; 35). DNA-PKi, however, did not synergise with olaparib, showing little enhancement of olaparib single-agent treatment (GI50 from 0.59 μM to 0.33 μM) and no significant impact on the total amount of chromosomal aberrations (total aberrations: olaparib; 11, DNA-PKi ; 3, combination; 14), suggesting that DNA-PKi alone or in combination with olaparib have little impact on BRCA1 mutated tumours. In ATM KO FaDu xenografts, ATRi or DNA-PKi single-agent treatment resulted in TGI, with complete tumour regressions when combined. Focusing on the olaparib combination, metaphase spread analysis of ATRi-treated FaDu ATM KO cells showed an enhancement of DNA replication-dependent chromatid breaks (1.3 vs 0.2 breaks/spread in ATM WT), while DNA-PKi treatment predominantly caused chromosome breaks (1.7 vs 0.2 breaks/spread in ATM WT) that are not dependent on replication. When combined with olaparib, ATRi acted synergistically and in a manner similar to that observed in the BRCA1 mutant cells, while the DNA-PKi + olaparib combination was additive. These data suggest that enhanced olaparib sensitisation of ATM KO cells by ATRi or DNA-PKi combinations occurs through different mechanisms. Together, these findings provide mechanistic differentiation of our DDRi in specific genetic backgrounds. This work informs how to clinically position these agents to benefit the right patients not only as single-agent treatments, but also in combination.

Citation Format: Josep V. Forment, Paul Wijnhoven, Antonio Ramos-Montoya, Jacqueline Fok, Valeria Follia, Mercedes Vazquez-Chantada, Rajesh Oderda, Zena Wilson, Alan Lau, Elisabetta Leo, Stephen Durant, Elaine Cadogan, Mark J. O'Connor. Mechanistic differentiation of targeted DDR agent combinations [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 626.

Abstract 967: Anti-tumor and immune effects of olaparib +/- anti-PD-L1 in preclinical BRCA1mut tumor models

PARP inhibitor treatments are synthetically lethal with BRCA1/2 mutations and, in this setting, accumulation of DNA damage leads ultimately to cell death. Increases in DNA damage are also associated with increased levels of cytosolic DNA and consequently signalling through the cGAS-STING pathway, which can lead to increased inflammatory gene expression and Type I interferon response.

We sought to evaluate the benefit of combining the PARP inhibitor olaparib with immune checkpoint blockade (ICB) in a mouse syngeneic ovarian model, BR5, which lacks BRCA1. We show that olaparib combination with anti-PD-L1 prolonged duration of anti-tumor response vs. either monotherapy. The combination increased durable complete responses (CRs) with 6/10 animals tumor free at 77 days, compared with 1/9 and 2/9 tumor-free animals for olaparib and anti-PD-L1 monotherapies, respectively. Similar results were observed for combination of olaparib with anti-CTLA-4. Furthermore, mice treated with olaparib + ICB demonstrated immunological memory, with 100% of mice with CRs successfully rejecting tumor growth upon rechallenge with BR5. Olaparib treatment of human T cells in vitro and mouse T cells in vitro and in vivo did not show inhibition of T cell activation or proliferation. Moreover, olaparib treatment led to changes in tumor immune infiltrate in the BR5 tumors, including approximately 2-fold increased CD8 T cells and 1.5-fold increased NK cells relative to vehicle.

Differential gene expression analysis of olaparib or anti-PD-L1treated BR5 tumors revealed broad upregulation of immune pathways. Interestingly, type I IFN and STING pathways showed a more pronounced upregulation with Olaparib than with anti-PD-L1 treatment. Moreover, a dose-dependent upregulation of immune pathways, including JAK-STAT, STING and type I IFN was observed in a tumor cell-centric analysis from a BRCA1mut breast PDX model treated with olaparib. In contrast, no significant upregulation of STING or type I IFN pathways is observed in response to olaparib in a BRCAwt breast PDX model.

In vitro mechanistic studies demonstrated that co-culture of olaparib-treated human BRCA1mut MDA-MB-436 tumor cells with human dendritic cells (DC) resulted in an approximately 2-fold upregulation of CD86 expression on DCs. Comparison of isogenic DLD-1 tumor cells showed CD86 upregulation on DCs only following co-culture with olaparib-treated BRCA2-/- DLD-1 cells, but not wt DLD-1 cells. Similarly, increased PD-L1 expression was only observed in BRCA2-/- DLD-1 cells treated with olaparib and following co-culture with DC. These observations suggest a basis for increased immune priming following olaparib treatment of BRCAmut tumors, which can be consolidated with ICB, such as anti-PD-L1, treatment.

Citation Format: Anna Staniszewska, Joshua Armenia, Matthew King, Chrysiis Michaloglou, Maneesh Singh, Maryann San Martin, Zena Wilson, Theresa Proia, Oona Delpuech, Mark O'Connor, Elisabetta Leo, Viia Valge-Archer. Anti-tumor and immune effects of olaparib +/- anti-PD-L1 in preclinical BRCA1mut tumor models [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 967.

Combined PARP and ATR inhibition potentiates genome instability and cell death in ATM-deficient cancer cells

The poly (ADP-ribose) polymerase (PARP) inhibitor olaparib is FDA approved for the treatment of BRCA-mutated breast, ovarian and pancreatic cancers. Olaparib inhibits PARP1/2 enzymatic activity and traps PARP1 on DNA at single-strand breaks, leading to replication-induced DNA damage that requires BRCA1/2-dependent homologous recombination repair. Moreover, DNA damage response pathways mediated by the ataxia-telangiectasia mutated (ATM) and ataxia-telangiectasia mutated and Rad3-related (ATR) kinases are hypothesised to be important survival pathways in response to PARP-inhibitor treatment. Here, we show that olaparib combines synergistically with the ATR-inhibitor AZD6738 (ceralasertib), in vitro, leading to selective cell death in ATM-deficient cells. We observe that 24 h olaparib treatment causes cells to accumulate in G2-M of the cell cycle, however, co-administration with AZD6738 releases the olaparib-treated cells from G2 arrest. Selectively in ATM-knockout cells, we show that combined olaparib/AZD6738 treatment induces more chromosomal aberrations and achieves this at lower concentrations and earlier treatment time-points than either monotherapy. Furthermore, single-agent olaparib efficacy in vitro requires PARP inhibition throughout multiple rounds of replication. Here, we demonstrate in several ATM-deficient cell lines that the olaparib and AZD6738 combination induces cell death within 1-2 cell divisions, suggesting that combined treatment could circumvent the need for prolonged drug exposure. Finally, we demonstrate in vivo combination activity of olaparib and AZD6738 in xenograft and PDX mouse models with complete ATM loss. Collectively, these data provide a mechanistic understanding of combined PARP and ATR inhibition in ATM-deficient models, and support the clinical development of AZD6738 in combination with olaparib.

A multi-batch design to deliver robust estimates of efficacy and reduce animal use - a syngeneic tumour case study

Phenotypic plasticity, the ability of a living organism to respond to the environment, can lead to conclusions from experiments that are idiosyncratic to a particular environment. The level of environmental responsiveness can result in difficulties in reproducing studies from the same institute with the same standardised environment. Here we present a multi-batch approach to in-vivo studies to improve replicability of the results for a defined environment. These multi-batch experiments consist of small independent mini-experiments where the data are combined in an integrated data analysis to appropriately assess the treatment effect after accounting for the structure in the data. We demonstrate the method on two case studies with syngeneic tumour models which are challenging due to high variability both within and between studies. Through simulations and discussions, we explore several data analysis options and the optimum design that balances practical constraints of working with animals versus sensitivity and replicability. Through the increased confidence from the multi-batch design, we reduce the need to replicate the experiment, which can reduce the total number of animals used.

Identifying strategies to target the metabolic flexibility of tumours

Plasticity of cancer metabolism can be a major obstacle to efficient targeting of tumour-specific metabolic vulnerabilities. Here, we identify the compensatory mechanisms following the inhibition of major pathways of central carbon metabolism in c-MYC-induced liver tumours. We find that, while inhibition of both glutaminase isoforms (Gls1 and Gls2) in tumours considerably delays tumourigenesis, glutamine catabolism continues, owing to the action of amidotransferases. Synergistic inhibition of both glutaminases and compensatory amidotransferases is required to block glutamine catabolism and proliferation of mouse and human tumour cells in vitro and in vivo. Gls1 deletion is also compensated for by glycolysis. Thus, co-inhibition of Gls1 and hexokinase 2 significantly affects Krebs cycle activity and tumour formation. Finally, the inhibition of biosynthesis of either serine (Psat1-KO) or fatty acid (Fasn-KO) is compensated for by uptake of circulating nutrients, and dietary restriction of both serine and glycine or fatty acids synergistically suppresses tumourigenesis. These results highlight the high flexibility of tumour metabolism and demonstrate that either pharmacological or dietary targeting of metabolic compensatory mechanisms can improve therapeutic outcomes.

An innovative non-invasive technique for subcutaneous tumour measurements

Introduction

In oncological drug development, animal studies continue to play a central role in which the volume of subcutaneous tumours is monitored to assess the efficacy of new drugs. The tumour volume is estimated by taking the volume to be that of a regular spheroid with the same dimensions. However, this method is subjective, insufficiently traceable, and is subject to error in the accuracy of volume estimates as tumours are frequently irregular.

Methods & results

This paper reviews the standard technique for tumour volume assessment, calliper measurements, by conducting a statistical review of a large dataset consisting of 2,500 tumour volume measurements from 1,600 mice by multiple operators across 6 mouse strains and 20 tumour models. Additionally, we explore the impact of six different tumour morphologies on volume estimation and the detection of treatment effects using a computational tumour growth model. Finally, we propose an alternative method to callipers for estimating volume–BioVolume^TM, a 3D scanning technique. BioVolume simultaneously captures both stereo RGB (Red, Green and Blue) images from different light sources and infrared thermal images of the tumour in under a second. It then detects the tumour region automatically and estimates the tumour volume in under a minute. Furthermore, images can be processed in parallel within the cloud and so the time required to process multiple images is similar to that required for a single image. We present data of a pre-production unit test consisting of 297 scans from over 120 mice collected by four different operators.

Conclusion

This work demonstrates that it is possible to record tumour measurements in a rapid minimally invasive, morphology-independent way, and with less human-bias compared to callipers, whilst also improving data traceability. Furthermore, the images collected by BioVolume may be useful, for example, as a source of biomarkers for animal welfare and secondary drug toxicity / efficacy.

Discovery and Characterization of AZD6738, a Potent Inhibitor of Ataxia Telangiectasia Mutated and Rad3 Related (ATR) Kinase with Application as an Anticancer Agent

The kinase ataxia telangiectasia mutated and rad3 related (ATR) is a key regulator of the DNA-damage response and the apical kinase which orchestrates the cellular processes that repair stalled replication forks (replication stress) and associated DNA double-strand breaks. Inhibition of repair pathways mediated by ATR in a context where alternative pathways are less active is expected to aid clinical response by increasing replication stress. Here we describe the development of the clinical candidate 2 (AZD6738), a potent and selective sulfoximine morpholinopyrimidine ATR inhibitor with excellent preclinical physicochemical and pharmacokinetic (PK) characteristics. Compound 2 was developed improving aqueous solubility and eliminating CYP3A4 time-dependent inhibition starting from the earlier described inhibitor 1 (AZ20). The clinical candidate 2 has favorable human PK suitable for once or twice daily dosing and achieves biologically effective exposure at moderate doses. Compound 2 is currently being tested in multiple phase I/II trials as an anticancer agent.

Abstract 2826: Differential activity of ATR and WEE1 inhibitors in DLBCL subtypes is linked to replication stress and differences in mode of action

The checkpoint kinases ATR and WEE1 protect cells from replication stress (RS), a hallmark of cancer that has potential to be exploited for cancer treatment. ATR and WEE1 inhibitors are in early clinical trials. Here we report selective anti-tumour activity of inhibitors to ATR (AZD6738) and WEE1 (AZD1775) in a subset of diffuse large B-cell lymphoma (DLBCL) cell lines. Using the cell-of-origin (COO) gene expression scoring system, we found enhanced sensitivity to AZD6738 in the activated B-cell like (ABC, n=6) and unclassified cell lines (n=6) with a combined median GI50 of 0.372 µM, compared to germinal centre B-cell like (GCB, n=7) cell lines, with median GI50 of 1.554 µM. Grouping the cells into AZD6738 sensitive (GI50 ≤ 0.5 µM) or insensitive (≥ 1 µM), we show that the ABC/unclassified COO score, together with high c-MYC protein or CDKN2A/B deletion identified 7/8 sensitive cell lines and 0/7 insensitive cell lines. Furthermore, markers of RS correlated with cell line sensitivity. Treatment of cells with 0.5 µM AZD6738 increased the quantity of 53BP1 nuclear bodies by 3-6 fold across the sensitive cell lines compared to only 2 fold across the insensitive cell lines. DNA fibre analysis also showed that sensitive cells lines had slower rates of replication fork progression (0.80 - 1.12 kbmin-1) compared to insensitive cell lines (1.22 - 1.41 kbmin-1). Across the same DLBCL cell line panel sensitivity to the WEE1 inhibitor AZD1775 was positively correlated with AZD6738 sensitivity, although at lower concentrations. However, using OCI-LY19 and DB cells to reflect high and low replication stress respectively, we show that AZD6738 and AZD1775 differ mechanistically in the extent of DNA damage and apoptosis induced within cell cycle phases. Treatment with 1 µM AZD1775 induced S-phase arrest and increased γH2AX+ cells in S/G2 from 4% to 20% in both cell lines at 8 h, indicating replication-associated DNA damage. However, earlier onset of cell death was observed in the OCI-LY19 cells, with 30% γH2AX+ cells undergoing apoptosis at 24 h compared to 25% γH2AX+ DB cells at 72 h. In contrast, AZD6738 only caused G1 arrest in OCI-LY19 daughter cells, with 20% apoptosis at 72 h. These findings are reflected in the anti-tumour activity of the inhibitors in xenograft DLBCL models in vivo. Once-daily, oral dosing of 50 mg/kg/day AZD6738 or 120 mg/kg/day AZD1775 in OCI-LY19 xenograft model showed efficacy with mean % tumour growth inhibition (%TGI) at day 8 of 104.1% (n=10) and 114.3% (n=10) respectively. In addition, the combination of AZD1775 (60 mg/kg/day; monotherapy %TGI=88.7, n=10) and AZD6738 (25 mg/kg/day; monotherapy %TGI=89.8%, n=10) dosed using a 5 day on, 9 day off dosing schedule was tolerated in mice and resulted in tumour regressions (combination %TGI=108.4%, n=8). These data suggest potential for both single agent and combination opportunities for ATR and WEE1 inhibitors in the DLBCL ABC subtype.

Citation Format: Lucy A. Young, Lenka Oplustil O'Connor, Zena Wilson, Corinne Reimer, Alan Lau, Jiri Bartek, Mark J. O'Connor. Differential activity of ATR and WEE1 inhibitors in DLBCL subtypes is linked to replication stress and differences in mode of action [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 2826.

Abstract LB-263: Preclinical efficacy of the ATR inhibitor AZD6738 in combination with the BTK inhibitor acalabrutinib in ABC-DLBCL models

Bruton tyrosine kinase (BTK) is an essential kinase in the B-cell receptor (BCR) signalling pathway. Acalabrutinib is a potent and highly selective irreversible BTK inhibitor that received accelerated approval by FDA for the treatment of Relapsed/Refractory Mantle Cell Lymphoma. It is proposed to be combined with the Ataxia telangiectasia and Rad3-related (ATR) kinase inhibitor AZD6738, in a Phase I/II proof of concept clinical trial to assess safety and efficacy in patients with B-cell malignancies. ATR is a key regulator of DNA replication, repair and cell cycle checkpoints. The Activated B-Cell (ABC) subtype of Diffuse Large B-Cell Lymphoma (DLBCL) is associated with chronic active BCR signalling, and given our previous identification of sensitivity to AZD6738 in ABC-DLBCL cell lines, we hypothesised that combination with acalabrutinib may have additional therapeutic benefit. Here we report preliminary data to support combination efficacy in models of ABC-type DLBCL. The growth inhibitory and cell kill effect of AZD6738 and acalabrutinib in combination was assessed in 3 ABC and 4 GCB DLBCL cell lines. Combination activity and cell kill was detected specifically in the ABC-type TMD8 cell line. Using flow cytometry, we show that the cell kill effects of the drug combination were dependent on dose and schedule. Single agent treatment with 5 nM acalabrutinib or 0.5 µM AZD6738 for 72 h, caused cell death in 12% and 17% of cells respectively. The equivalent doses given in combination for 72 h induced cell death in 39% of cells, indicative of a greater than additive effect. Cell killing was increased with longer co-exposure to the combination, shown by an increase in cell death from 18% at 24 h, to 30% at 48 h. Acalabrutinib is dosed on a BID schedule, thus we tested whether its activity in combination with AZD6738 was affected by pre- or post-addition of acalabrutinib. A 24 h pre-treatment of cells with acalabrutinib, followed by the combination of AZD6738 and acalabrutinib for 48 h resulted in 20% cell death, whereas 48 h combination treatment followed by 24 h acalabrutinib monotherapy caused a similar 27% increase in death, suggesting that combination efficacy is not dependent on sequence of drug administration. Furthermore, the mRNA expression of BTK target genes in ABC-DLBCL cell lines was modulated by acalabrutinib, however there was no additional modulation to this pathway by the combination with AZD6738, suggesting the two agents kill cells through different mechanisms of action. In the TMD8 xenograft mouse model, daily dosing of AZD6738 (25 mg/kg) with twice daily dosing of acalabrutinib (20 mg/kg) was well tolerated and resulted in complete and durable tumor regressions (8/8 tumors), whereas single agent treatments resulted in tumor growth delay. Collectively, our preliminary data support a rationale for combining BTK and ATR inhibitors for an effective and alternative treatment option in ABC-DLBCL.

Citation Format: Lucy A. Young, Oona Delpuech, Brandon Willis, Alexandra Bussey, Zena Wilson, Michelle Dupont, Carlos Grajales, Andrew Bloecher, Todd Covey, Kate Wills, Alan Lau, Simon J. Hollingsworth. Preclinical efficacy of the ATR inhibitor AZD6738 in combination with the BTK inhibitor acalabrutinib in ABC-DLBCL models [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 LB-263.

Abstract 2494: ATR inhibitor AZD6738 as monotherapy and in combination with olaparib or chemotherapy: defining pre-clinical dose-schedules and efficacy modelling

Introduction: AZD6738 is a potent and selective oral inhibitor of the ataxia telangiectasia and rad3 related (ATR) protein kinase. ATR has a key role in the DNA replication stress response (RSR) pathway of DNA repairby facilitating the recovery and repair of potentially cytotoxic persistent, stalled DNA replication forks. Inhibition of ATR leads to the inability to resolve replication associated damage and the accumulation of DNA strand breaks, which if remains unrepaired leads to cell death. AZD6738 is currently in Phase I/II clinical trials being evaluated as a monotherapy and in combination with novel agents olaparib / Lynparza (PARP DNA damage response inhibitor), durvalumab (PD-L1 immune checkpoint inhibitor) and DNA-damaging agents such as carboplatin and ionising radiation. Critical in helping to guide the clinical usage of AZD6738 and maximise patient benefit, pre-clinical studies were performed to determine optimal doses and schedules as monotherapy and in combination with olaparib and carboplatin.

Experimental procedures: Human cancer cell lines, xenograft and patient-derived explant (PDX) models of non-small cell lung cancer (NSCLC), head & neck squamous cell carcinoma (HNSCC), and triple-negative breast cancer (TNBC) were tested comparing once daily versus twice daily dosing, the number of consecutive days dosing (3 days/week, 5 days/week, continuous) and co-dosing versus sequential or intermittent dosing with AZD6738 alone or in combination with olaparib or carboplatin. The magnitude and duration of anti-tumour responses were then compared with AZD6738 mouse pharmacokinetic (PK), pharmacodynamic (PD) and in vitro target (IC) / growth inhibition (GI) profiles.

Results: A mathematical model was derived which adequately described the AZD6738 PK/PD-efficacy relationship. This modelling confirms that duration of cover (time) above cellular ATR target inhibition thresholds (IC90 pCHK1 / GI90) per day, rather than Cmax or exposures per se, is the major determinant of anti-tumour responses. As monotherapy, in sensitive ATM-deficient models, it is necessary to inhibit ATR continuously to give tumour stabilisation, which can be achieved through repeat daily of AZD6738 over several weeks. Co-dosing AZD6738 in combination with olaparib or carboplatin gives best efficacy compared to sequential dosing and PK cover over the first 48-72 hours is necessary to give tumour regressions. The models predict that extending the duration of ATR cover, achieved through repeat daily dosing, further increases efficacy. These pre-clinical dose-schedules were compared to human free plasma AZD6738 PK data and predicted efficacious exposures found to be clinically achievable.

Conclusions: Together these data further support the clinical evaluation of AZD6738 and suggest optimal dosing schedules for ATR inhibitors.

Citation Format: Alan Y. Lau, James Yates, Zena Wilson, Lucy A. Young, Adina M. Hughes, Alienor Berges, Amy Cheung, Rajesh Odedra, Elaine Brown, Mark J. O'Connor, Simon Hollingsworth. ATR inhibitor AZD6738 as monotherapy and in combination with olaparib or chemotherapy: defining pre-clinical dose-schedules and efficacy modelling [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 2494. doi:10.1158/1538-7445.AM2017-2494

Abstract 1828: Are callipers obsolute? A novel 3D scanning technology to measure subcutaneous tumor volume

Most preclinical oncology studies (xenograft, PDX, GEMMS) involve monitoring tumour growth rates, measuring them with callipers, and calculating the volume. Volume is calculated from the width and the length to estimate a 3D volume and is directly used to assess treatment efficacy. Although this technique is useful, it is unable to accurately assess non-uniformly shaped or very small tumours and introduces a systematic bias by assuming that tumours present with spheroid shape. Furthermore callipers do not inform of the tumour condition, which is dependent upon a visual estimation.

Here we describe the development and validation of a 3D scanner as an alternative method to callipers to monitor tumour progression in rodents. The resulting 3D scanner solution made up of hardware and software, has the potential to impact on the 3Rs guiding principles underpinning the humane use of animals in oncology research. The 3Rs benefits identified are primarily through reduction of animals via improved data accuracy allowing reduction in group sizes or the ability to include irregularly shaped tumours to test. In addition the scanner system described will make it possible to record tumour measurements in a rapid, minimally invasive, morphology-independent, and human-bias-free way, removing interoperator variability. This photo-based technique captures external symptoms of redness, paleness, ulceration of tumours, etc., which could ultimately be used to detect early toxicities of compounds or determine scales of animal welfare.

We describe the development and early validation of the scanner system within our laboratories. Using the 3D scanner alongside tumour callipers to monitor tumour growth of Oncology tumour studies we demonstrated that we can accurately measure tumour size parameters (length, width and volume) in multiple mouse strains and across a range of tumour models. 3D scanning tumour data is comparable to tumour measures generated from tumour callipers If successful the introduction of this system to replace tumour callipers could have a large impact for groups running oncology in-vivo tumour studies.

Citation Format: Zena Wilson, Juan Delgado, Michael Davies, Rebecca Whiteley, Jennifer Hare, Amar Rahi, Stephen Marshall, Andrew Smith, Stephen Atkinson, Jarno Ralli, Adeala Zabair, Adeala Zabair, Jane Kendrew. Are callipers obsolute? A novel 3D scanning technology to measure subcutaneous tumor volume [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 1828. doi:10.1158/1538-7445.AM2017-1828

CXCR2 Inhibition Profoundly Suppresses Metastases and Augments Immunotherapy in Pancreatic Ductal Adenocarcinoma

CXCR2 has been suggested to have both tumor-promoting and tumor-suppressive properties. Here we show that CXCR2 signaling is upregulated in human pancreatic cancer, predominantly in neutrophil/myeloid-derived suppressor cells, but rarely in tumor cells. Genetic ablation or inhibition of CXCR2 abrogated metastasis, but only inhibition slowed tumorigenesis. Depletion of neutrophils/myeloid-derived suppressor cells also suppressed metastasis suggesting a key role for CXCR2 in establishing and maintaining the metastatic niche. Importantly, loss or inhibition of CXCR2 improved T cell entry, and combined inhibition of CXCR2 and PD1 in mice with established disease significantly extended survival. We show that CXCR2 signaling in the myeloid compartment can promote pancreatic tumorigenesis and is required for pancreatic cancer metastasis, making it an excellent therapeutic target.

AZD9496: An Oral Estrogen Receptor Inhibitor That Blocks the Growth of ER-Positive and ESR1-Mutant Breast Tumors in Preclinical Models

Fulvestrant is an estrogen receptor (ER) antagonist administered to breast cancer patients by monthly intramuscular injection. Given its present limitations of dosing and route of administration, a more flexible orally available compound has been sought to pursue the potential benefits of this drug in patients with advanced metastatic disease. Here we report the identification and characterization of AZD9496, a nonsteroidal small-molecule inhibitor of ERα, which is a potent and selective antagonist and downregulator of ERα in vitro and in vivo in ER-positive models of breast cancer. Significant tumor growth inhibition was observed as low as 0.5 mg/kg dose in the estrogen-dependent MCF-7 xenograft model, where this effect was accompanied by a dose-dependent decrease in PR protein levels, demonstrating potent antagonist activity. Combining AZD9496 with PI3K pathway and CDK4/6 inhibitors led to further growth-inhibitory effects compared with monotherapy alone. Tumor regressions were also seen in a long-term estrogen-deprived breast model, where significant downregulation of ERα protein was observed. AZD9496 bound and downregulated clinically relevant ESR1 mutants in vitro and inhibited tumor growth in an ESR1-mutant patient-derived xenograft model that included a D538G mutation. Collectively, the pharmacologic evidence showed that AZD9496 is an oral, nonsteroidal, selective estrogen receptor antagonist and downregulator in ER(+) breast cells that could provide meaningful benefit to ER(+) breast cancer patients. AZD9496 is currently being evaluated in a phase I clinical trial. Cancer Res; 76(11); 3307-18. ©2016 AACR.

PDGFR Inhibition Results in Pericyte Depletion and Hemorrhage into the Corpus Luteum of the Rat Ovary

The growth plate, ovary, adrenal gland, and rodent incisor tooth are sentinel organs for antiangiogenic effects since they respond reliably, quantitatively, and sensitively to inhibition of the vascular endothelial growth factor receptor (VEGFR). Here we report that treatment of rats with platelet-derived growth factor receptor beta (PDGFRβ) inhibitors that target pericytes results in severe ovarian hemorrhage with degeneration and eventual rupture of the corpus luteum. Evaluation of the growth plate, adrenal gland, and incisor tooth that are typical target organs for antiangiogenic treatment in the rodent revealed no abnormalities. Histologically, the changes in the ovary were characterized by sinusoidal dilatation, increased vessel fragility, and hemorrhage into the corpus luteum. Immunocytochemical staining of vessels with alpha smooth muscle actin and CD31 that recognize pericytes and vascular endothelium, respectively, demonstrated that this effect was due to selective pericyte deficiency within corpora lutea. Further experiments in which rats were treated concurrently with both PDGFRβ and VEGFR inhibitors ablated the hemorrhagic response, resulting instead in corpus luteum necrosis. These changes are consistent with the notion that selective pericyte loss in the primitive capillary network resulted in increased vessel fragility and hemorrhage, whereas concomitant VEGFR inhibition resulted in vessel regression and reduced vascular perfusion that restricted development of the hemorrhagic vessels. These results also highlight the utility of the rodent ovary to respond differentially to VEGFR and PDGFR inhibitors, which may provide useful information during routine safety assessment for determining target organ toxicity.

Optimization of a Novel Binding Motif to (E)-3-(3,5-Difluoro-4-((1R,3R)-2-(2-fluoro-2-methylpropyl)-3-methyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-yl)phenyl)acrylic Acid (AZD9496), a Potent and Orally Bioavailable Selective Estrogen Receptor Downregulator and Antagonist

The discovery of an orally bioavailable selective estrogen receptor downregulator (SERD) with equivalent potency and preclinical pharmacology to the intramuscular SERD fulvestrant is described. A directed screen identified the 1-aryl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole motif as a novel, druglike ER ligand. Aided by crystal structures of novel ligands bound to an ER construct, medicinal chemistry iterations led to (E)-3-(3,5-difluoro-4-((1R,3R)-2-(2-fluoro-2-methylpropyl)-3-methyl-2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indol-1-yl)phenyl)acrylic acid (30b, AZD9496), a clinical candidate with high oral bioavailability across preclinical species that is currently being evaluated in phase I clinical trials for the treatment of advanced estrogen receptor (ER) positive breast cancer.

Abstract DDT01-03: Discovery and pre-clinical pharmacology of AZD9496: An oral, selective estrogen receptor down-regulator (SERD)

With over 70% of breast cancers expressing estrogen receptor alpha protein (ERα), treatment with either anti-hormonal therapies that directly block ERα function (e.g. tamoxifen) or therapies that block the production of estrogen itself (e.g. anastrozole) have proven to be effective treatments for the disease. Following the discovery of the ERα antagonist tamoxifen in the 1960s, identification of the selective estrogen receptor down-regulator (SERD) fulvestrant represented a further step forward in the treatment of advanced ER+ breast cancer, especially in the endocrine resistance setting where ERα appears to be activated by a ligand independent route through other growth factor signaling pathways. In addition, fulvestrant has also shown significant overall survival (OS) results in the FIRST trial comparing 500 mg fulvestrant with anastrozole in first line advanced ER+ve patients where the majority of patients had not received prior endocrine therapy. Given fulvestrant's low bioavailability following intramuscular injection and the levels of ERα protein in clinical samples after treatment, the question remains as to whether an agent that could achieve higher steady state levels of drug more rapidly and drive further decreases in ERα levels would give enhanced clinical benefit. We have identified a novel, potent, non-steroidal SERD that can be administered orally and could yield improved exposure and clinical benefit. This presentation will describe the discovery and pre-clinical pharmacology of AZD9496, a small molecule that can antagonise ERα and induce receptor degradation in breast cancer cell lines at picomolar concentrations. The good oral pharmacokinetic properties of the compound in pre-clinical species led to significant tumor growth inhibition in an endocrine sensitive MCF-7 xenograft model at a dose of 5 mg/kg and >90% reduction in ER-regulated, progesterone receptor (PR) levels. Tumor regressions were seen in a long term estrogen deprived (LTED) in vivo model, representing the aromatase resistant setting, and corresponded with significant reductions in ERα protein levels, >90% at 5 mg/kg dose. AZD9496 also showed antagonist and down-regulation activity against ERα mutant protein both in vitro and in vivo. These findings strongly supported selection of AZD9496 as a clinical candidate for the treatment of ER+ve breast cancer and the drug is now under evaluation in a Phase 1 clinical trial.

Citation Format: Hazel Weir, Mandy Lawson, Rowena Callis, Michael Hulse, Michael Tonge, Gareth Davies, Graeme Walker, Rachel Rowlinson, Jon Curwen, Zena Wilson, Steve Powell, Robert Bradbury, Alfred Rabow, Craig Donald, David Buttar, Richard Norman, Camila de Almeida, Peter Ballard, Gordon Currie, David Andrews, Graham Richmond, Anne Marie Mazzola, Ermira Pazolli, Brendon Ladd, Celina D'Cruz, Chris De Savi. Discovery and pre-clinical pharmacology of AZD9496: An oral, selective estrogen receptor down-regulator (SERD). [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 DDT01-03. doi:10.1158/1538-7445.AM2015-DDT01-03

Explanatory models of mental disorders and treatment practices among traditional healers in Mpumulanga, South Africa

OBJECTIVE

In many traditional belief systems in Africa, including South Africa, mental health problems may be attributed to the influence of ancestors or to bewitchment. Traditional healers are viewed as having the expertise to address these causes. However, there is limited information on their explanatory models and consequent treatment practices. The present study examines traditional healers' explanatory models (EMs) and treatment practices for psychotic and non-psychotic mental illnesses.

METHOD

4 focus group discussions (8 healers in each group) and 18 in-depth interviews were conducted. Four vignettes were presented (schizophrenia, depression, panic and somatisation) and traditional healers' views on the nature of the problem, cause, consequence, treatment and patient expectations were elicited.

RESULTS

Traditional healers held multiple explanatory models for psychotic and non-psychotic disorders. Psychotic illnesses appear to be the main exemplar of mental illness and were treated with traditional medicine, while nonpsychotic illnesses were not viewed as a mental illness at all. Additionally, traditional healers do not only use herbs and substances solely from "traditional" sources but rather have incorporated into their treatment practices modern ingredients that are potentially toxic.

CONCLUSION

Interventions aimed at increasing the mental health literacy of traditional healers are essential. In addition, investigations of the effectiveness of traditional healer treatment for psychiatric disorders should be conducted.

Schizophrenia-Window-of-Hope.com: Development of a psycho-educational Internet resource for the South African setting

Psycho-educational programmes for families of persons with schizophrenia have been shown to reduce relapse rates, subsequently reducing the burden on the family as well as health care systems. Although various South African helplines and psycho-educational websites exist, none of these focused specifically on schizophrenia. The South African Depression and Anxiety Group SADAG was approached for assistance to enable us to develop a piggy-back schizophrenia service on their already established helpline. A multidisciplinary mental health team compiled a manual for use by SADAG helpline operators, but owing to the huge amount of information it was realised that the resource would be more efficient if both a helpline and an Internet resource could be created. The website (www.schizophrenia-window-of-hope.com) was then developed with the help of an IT professional. This site represents the first attempt to create an internet-based schizophrenia-specific educational resource for the South African setting. The next step will be to obtain formal feedback from helpline and website users in order to inform the ongoing development of the site.

Distribution of radioactivity and metabolite profiling in tumour and plasma following intravenous administration of a colchicine derivative (14C-ZD6126) to tumour-bearing mice

The main aim of the study was to investigate the distribution of radioactivity in the tissues and tumours using quantitative whole-body autoradiography (QWBA), together with a more detailed investigation of plasma and tumour samples, following administration of a single intravenous dose at 200 mg kg(-1) of 14C-ZD6126 to mice bearing subcutaneous Hras5 tumour xenografts. The study also included an assessment of tumour necrosis following administration of a single intravenous dose of non-labelled ZD6126 at 200 mgkg(-1). QWBA analysis showed that drug-related material was widely distributed to the tissues and tumour. In the majority of tissues, concentrations of radioactivity were highest at 15 min and declined rapidly thereafter. The tumour-to-plasma ratio was 0.6:1 at 0.25 h and increased to 6:1 at 48 h, indicating that drug-related material persisted in the tumour longer than in plasma. ZD6126, a phosphate ester, is rapidly hydrolysed to ZD6126 phenol, the active metabolite. The major metabolite in plasma (36% of the sample radioactivity) and all tumour samples (58-83% of the sample radioactivity) was confirmed as ZD6126 phenol. Extensive tumour necrosis was noted by 24h, which was still evident at 48 h, although there was some evidence of tumour regrowth.

Correlation of MRI biomarkers with tumor necrosis in Hras5 tumor xenograft in athymic rats

Magnetic resonance imaging (MRI) can measure the effects of therapies targeting the tumor vasculature and has demonstrated that vascular-damaging agents (VDA) induce acute vascular shutdown in tumors in human and animal models. However, at subtherapeutic doses, blood flow may recover before the induction of significant levels of necrosis. We present the relationship between changes in MRI biomarkers and tumor necrosis. Multiple MRI measurements were taken at 4.7 T in athymic rats (n = 24) bearing 1.94 +/- 0.2-cm3 subcutaneous Hras5 tumors (ATCC 41000) before and 24 hours after clinically relevant doses of the VDA, ZD6126 (0-10 mg/kg, i.v.). We measured effective transverse relaxation rate (R2*), initial area under the gadolinium concentration-time curve (IAUGC(60/150)), equivalent enhancing fractions (EHF(60/150)), time constant (K(trans)), proportion of hypoperfused voxels as estimated from fit failures in K(trans) analysis, and signal intensity (SI) in T2-weighted MRI (T(2)W). ZD6126 treatment induced > 90% dose-dependent tumor necrosis at 10 mg/kg; correspondingly, SI changes were evident from T2W MRI. Although R2* did not correlate, other MRI biomarkers significantly correlated with necrosis at doses of > or = 5 mg/kg ZD6126. These data on Hras5 tumors suggest that the quantification of hypoperfused voxels might provide a useful biomarker of tumor necrosis.

Barriers to treatment among members of a mental health advocacy group in South Africa

BACKGROUND

As part of an international survey of mental health advocacy groups, information pertinent to patients' concerns regarding their diagnosis and treatment was gathered from South African members of a depression and anxiety support group (n = 404).

METHODS

Questionnaires developed by GAMIAN, an international consortium of advocacy groups, were mailed along with explanatory letters and self-addressed envelopes to South African members and members in nine other countries, for completion. Of 1,000 questionnaires mailed in South Africa, 40.4 % were returned.

RESULTS

The sample comprised patient members with anxiety-only (39 %), depression-only (8 %), mixed anxiety-depression (26 %), and other diagnoses (27 %). While one-third of respondents reported onset of symptoms before the age of 20, most waited 3-5 years before seeking help. After making contact with the health system, respondents experienced further delays in obtaining a correct diagnosis. In many instances, respondents were poorly informed of diagnosis and treatment (25 %), and nearly half of all respondents discontinued treatment on account of side-effects.

CONCLUSIONS

Attempts to improve awareness of mental illness, and better communication between physicians and their patients, might help to break down some of the barriers patients encounter when seeking help.

Toothbrushing forces in children with fixed orthodontic appliances

The aim of this investigation was to determine whether toothbrushing forces are influenced by wearing fixed orthodontic appliances. Thirty children, (10 males, 20 females) with planned fixed appliance therapy and aged 10-15 years, were recruited to the study. No subject had previously worn an orthodontic appliance. At baseline, each subject brushed their teeth in their usual way, unsupervised. The toothbrush used was a purpose-designed electronic instrument that measured the force applied to the brush and transmitted force data by radio to a remote PC. After toothbrushing, subjects had orthodontic brackets fitted. Toothbrushing was repeated at 2 and 14 weeks after baseline, and brushing forces recorded. There were no significant differences between the measurements made at baseline and those made at 2 and 14 weeks. There were no differences between males and females in the forces used at any time point. It was concluded that toothbrushing forces are unaffected by placing fixed orthodontic appliances in children. The brushing forces recorded were comparable with those previously found by other investigators.

Comparative study of electric and manual toothbrushes in patients with fixed orthodontic appliances

The objective of this three treatment, three period, single blind, cross-over trial was to evaluate the efficacy of three toothbrushes in a cohort of children undergoing fixed appliance orthodontic therapy. The brushes used were: (1) Dental Logic HP550 with regular brush head HP5924 (Philips, U.K.); (2) Braun Oral B Plaque Remover (D7) with dedicated orthodontic brush head OD5-1 (Braun AG, Germany); and (3) a manual dedicated orthodontic toothbrush (P35, Oral B Laboratories, Calif.). Sixty orthodontic patients, aged 10 to 16 years and wearing upper and lower fixed appliances, were screened and recruited with parental consent. After an oral soft tissue examination at baseline, the percentage of plaque-covered tooth surfaces and gingival bleeding sites were recorded using visible plaque and gingival bleeding indexes. Each subject was randomly allocated to one of three groups (n = 20) with brushing sequences 1-2-3, 2-1-3, 3-2-1. The first brush was given 2 weeks after baseline (visit 1). The time interval for using each brush was 4 weeks at the end of which visible plaque and gingival bleeding indexes were recorded and a further prophylaxis given. Statistical analysis was undertaken with analysis of variance. Data were analyzed on a site-specific basis; buccal smooth and interproximal surfaces, lingual smooth and interproximal surfaces. At baseline the mean visible plaque index for all subjects were; buccal smooth, 52.5% (+/- 22.5%); buccal interproximal, 70.5% (+/- 18.5%); lingual smooth, 68.5% (+/- 21%); lingual interproximal, 76% (+/- 16%). At visit 1, the plaque scores at all surfaces had reduced significantly compared to baseline, but there had been no active treatment. This was attributed to a Hawthorne effect. Subsequently, there were no significant effects on visible plaque (or gingival bleeding) indexes with any toothbrush at any tooth surfaces. This suggests that the new HP550 is equally effective as specifically designed orthodontic toothbrushes in removing plaque from patients with fixed orthodontic appliances.

Drug analysis in fly larvae

We reared larvae of Calliphora vicina on human skeletal muscle obtained from cases of suicidal overdose with co-proxamol (propoxyphene and acetaminophen) and amitriptyline. After 4 days, third-instar larvae were either transferred to drug-free muscle or continued to feed on drug-laden muscle for a further 2 days prior to harvesting. Amitriptyline and nortriptyline were detected in both groups of larvae, but propoxyphene was only in those fed continuously on drug-laden muscle, and acetaminophen was in neither. Drug concentrations in muscle food source were amitriptyline 0.48 microgram/g, nortriptyline 0.38 microgram/g, propoxyphene 0.99 microgram/g, and acetaminophen 14.13 micrograms/g. For triplicate rearings, the mean ratios of drug concentrations in larvae to food source were amitriptyline, 0.56; nortriptyline, 0.5; and propoxyphene, 0.06. In triplicate rearings, no drug or metabolite was detected in puparia, puparial cases, or imagos. We conclude that the absence of a drug in maggots is not necessarily an indication that the drug was not present in significant concentrations in the food source. The malpighian tubules and the "nephrocytes" of fly larvae appear capable of eliminating different drugs with varying efficiency.