Repeated deep-inspiration breath-hold CT scans at planning underestimate the actual motion between breath-holds at treatment for lung cancer and lymphoma patients

PURPOSE/OBJECTIVE

Deep-inspiration breath-hold (DIBH) during radiotherapy may reduce dose to the lungs and heart compared to treatment in free breathing. However, intra-fractional target shifts between several breath-holds may decrease target coverage. We compared target shifts between four DIBHs at the planning-CT session with those measured on CBCT-scans obtained pre- and post-DIBH treatments.

MATERIAL/METHODS

Twenty-nine lung cancer and nine lymphoma patients were treated in DIBH. An external gating block was used as surrogate for the DIBH-level with a window of 2 mm. Four DIBH CT-scans were acquired: one for planning (CTDIBH3) and three additional (CTDIBH1,2,4) to assess the intra-DIBH target shifts at scanning by registration to CTDIBH3. During treatment, pre-treatment (CBCTpre) and post-treatment (CBCTpost) scans were acquired. For each pair of CBCTpre/post, the target intra-DIBH shift was determined. For lung cancer, tumour (GTV-Tlung) and lymph nodes (GTV-Nlung) were analysed separately. Group mean (GM), systematic and random errors, and GM for the absolute maximum shifts (GMmax) were calculated for the shifts between CTDIBH1,2,3,4 and between CBCTpre/post.

RESULTS

For GTV-Tlung, GMmax was larger at CBCT than CT in all directions. GMmax in cranio-caudal direction was 3.3 mm (CT)and 6.1 mm (CBCT). The standard deviations of the shifts in the left-right and cranio-caudal directions were larger at CBCT than CT. For GTV-Nlung and CTVlymphoma, no difference was found in GMmax or SD.

CONCLUSION

Intra-DIBH shifts at planning-CT session are generally smaller than intra-DIBH shifts observed at CBCTpre/post and therefore underestimate the intra-fractional DIBH uncertainty during treatment. Lung tumours show larger intra-fractional variations than lymph nodes and lymphoma targets.

SAT0020 MOMELOTINIB, A JANUS KINASE 1/2 AND ACTIVIN RECEPTOR 1 INHIBITOR, AMELIORATES JOINT INFLAMMATION, SYSTEMIC TH17 DIFFERENTIATION AND ARTHRITIS-LINKED ANEMIA IN PRE-CLINICAL AUTOIMMUNE RA

Background:

Janus kinases (JAKs) serve as signaling hubs orchestrating inflammation, innate and adaptive immunity and erythropoiesis. Unfortunately, some of these agents cause suppression of JAK-dependent erythropoiesis, thereby exacerbating inflammation-associated anemia, leading to potential under-dosing and reduced therapeutic benefit. We previously showed that the JAKi momelotinib (MMB) can correct anemia in a rat model of RA, an effect that has been clinically reproduced in myelofibrosis patients treated with MMB. Subsequently, the molecular basis for MMB’s anemia benefit was determined to be a consequence of its potent inhibition of Activin Receptor Type 1 (ACVR1), resulting in decreased hepcidin and, as a consequence, increased systemic iron availability and improved erythropoiesis.

Objectives:

The goal of the current study was to investigate the effects of MMB on arthritis in pre-clinical RA models.

Methods:

The anti-arthritic activity of daily administration of MMB was assessed in Streptococcus cell wall-induced arthritis in Lewis rats (PG-PS model) and in collagen antibody-induced arthritis (CAIA) in DBA/1 mice. Consecutive assessment of arthritis was performed by joint thickness measurements and paw scoring. Following 3 weeks of treatment, synovial immune cell infiltration and T cell subset differentiation was quantified. Cytokine gene expression was profiled by quantitative rt-PCR. Anemia was assessed by determination of blood hemoglobin and serum, spleen and liver iron levels.

Results:

MMB reduced inflammatory granulocyte and macrophage infiltration in synovial tissue by more than 60% at all tested doses as compared to vehicle treatment in PG-PS animals. Importantly, MMB treatment effectively decreased arthritogenic Th17 cell differentiation and overall CD4+ T cells in the synovia beginning at the lowest tested dose and coincided with complete remission of joint swelling at 25 mg/kg. Anti-arthritic activity of MMB was confirmed with significant reductions in arthritis scoring, which demonstrated non-inferiority versus the TNF-α inhibitor, etanercept, in the CAIA model. Consistent with its inhibitory activity on the ACVR1-hepcidin axis, MMB reduced circulating hepcidin levels and mobilized systemic iron, resulting in substantial improvement of the RA-associated anemia in rats.

Conclusion:

MMB is a highly efficacious anti-arthritic agent that ameliorates local joint inflammation and reduces the systemic differentiation of major arthritogenic effector cell population, Th17 lymphocytes. In accord with our previous report, MMB is distinct from other JAKi due to its ability to inhibit ACVR1 signaling leading to decreased plasma hepcidin, improved iron homeostasis and increased erythropoiesis. The dual anti-inflammatory and anemia-improving pharmacologic activities of MMB position it as a promising and differentiated therapeutic agent for the treatment of RA and other inflammatory diseases with an anemia component.

Disclosure of Interests:

Piotr Tymoszuk: None declared, Verena Petzer: None declared, Malte Asshoff: None declared, Andrea Schroll: None declared, Markus Seifert: None declared, Ryan Hansen Employee of: I’m a former employee of Sierra Oncology, Snezana Milutinovic Employee of: I’m a former employee of Sierra Oncology, Bryan Strouse Employee of: I’m an employee of Sierra Oncology, Christian Hassig Employee of: I am a former employee of Sierra Oncology, Guenter Weiss: None declared, Igor Theurl Grant/research support from: I have received research support from Sierra Oncology, Consultant of: I have consulted for Kymba Ltd.

Comparison of the Petrifilm Dry Rehydratable Film and Conventional Culture Methods for Enumeration of Yeasts and Molds in Foods: Collaborative Study

A collaborative study was performed involving 18 laboratories and 6 food types to compare 3M Petrifilm yeast and mold count plates with the method described in the U.S. Food and Drug Administration’s Bacteriological Analytical Manual. Four species of mold and 2 species of yeast were used to inoculate the following foods: hot dogs, corn meal, ketchup, orange juice, yogurt, and cake mix. Each collaborator received 15 samples of each food type: 5 low-level inoculations, 5 high- level inoculations, and 5 uninoculated samples. There was no significant difference between the means of the 2 methods for any product or inoculation level. The Petrifilm yeast and mold count plate method for enumeration of yeasts and molds in foods has been adopted first action by AOAC INTERNATIONAL.

A dispensable paralog of succinate dehydrogenase subunit C mediates standing resistance towards a subclass of SDHI fungicides in Zymoseptoria tritici

Succinate dehydrogenase inhibitor (SDHI) fungicides are widely used for the control of a broad range of fungal diseases. This has been the most rapidly expanding fungicide group in terms of new molecules discovered and introduced for agricultural use over the past fifteen years. A particular pattern of differential sensitivity (resistance) to the stretched heterocycle amide SDHIs (SHA-SDHIs), a subclass of chemically-related SDHIs, was observed in naïve Zymoseptoria tritici populations not previously exposed to these chemicals. Subclass-specific resistance was confirmed at the enzyme level but did not correlate with the genotypes of the succinate dehydrogenase (SDH) encoding genes. Mapping and characterization of the molecular mechanisms responsible for standing SHA-SDHI resistance in natural field isolates identified a gene paralog of SDHC, termed ZtSDHC3, which encodes for an alternative C subunit of succinate dehydrogenase, named alt-SDHC. Using reverse genetics, we showed that alt-SDHC associates with the three other SDH subunits, leading to a fully functional enzyme and that a unique Qp-site residue within the alt-SDHC protein confers SHA-SDHI resistance. Enzymatic assays, computational modelling and docking simulations for the two SQR enzymes (altC-SQR, WT_SQR) enabled us to describe enzyme-inhibitor interactions at an atomistic level and to propose rational explanations for differential potency and resistance across SHA-SDHIs. European Z. tritici populations displayed a presence (20–30%) / absence polymorphism of ZtSDHC3, as well as differences in ZtSDHC3 expression levels and splicing efficiency. These polymorphisms have a strong impact on SHA-SDHI resistance phenotypes. Characterization of the ZtSDHC3 promoter in European Z. tritici populations suggests that transposon insertions are associated with the strongest resistance phenotypes. These results establish that a dispensable paralogous gene determines SHA-SDHIs fungicide resistance in natural populations of Z. tritici. This study paves the way to an increased awareness of the role of fungicidal target paralogs in resistance to fungicides and demonstrates the paramount importance of population genomics in fungicide discovery.

Zymoseptoria tritici is the causal agent of Septoria tritici leaf blotch (STB) of wheat, the most devastating disease for cereal production in Europe. Multiple succinate dehydrogenase inhibitor (SDHI) fungicides have been developed and introduced for the control of STB. We report the discovery and detailed characterization of a paralog of the C subunit of the SDH enzyme conferring standing resistance towards the SHA-SDHIs, a particular chemical subclass of the SDHIs. The SDHC paralog is characterized by its presence/absence, expression and alternative splicing polymorphisms, which in turn influence resistance levels. The identified mechanisms exemplify the importance of population genomics for the discovery and rational design of the most adapted solutions.

4179Feasibility and validation of routine CMR-based phenotyping for the prediction of heart failure admission or death in patients with systolic dysfunction

Background

Standardized patient phenotyping using cardiovascular magnetic resonance (CMR) imaging has been shown to be of clinical value for prediction of adverse events in patients with heart failure and reduced ejection fraction (HFrEF). Studies have validated the prognostic capacity of function (LV, RV and LA) and replacement fibrosis burden in patients with ischemic and non-ischemic cardiomyopathy. The translation and validation of routine CMR-based phenotyping into clinical practice has yet to be demonstrated in prospective studies.

Purpose

This study was designed to explore feasibility and prognostic value of routine CMR-based patient phenotyping in a high-volume clinical referral center for patients with HFrEF.

Methods

One thousand three hundred and ninety-three consecutive patients with chronic HFrEF were prospectively recruited between January 2015 and June 2018. Chronic HFrEF was defined by LVEF≤50% by CMR, with no recent (within 90 days) acute myocardial infarction or myocarditis diagnosis. Patients with congenital heart disease and those without LGE CMR protocol were excluded. All patients underwent standardized CMR protocols with multi-chamber volumetric analysis and regional myocardial fibrosis coding. Pharmacy, ECG, laboratory and patient reported data was used for statistical modelling. A minimum three-month follow-up was mandated to identify the composite clinical outcome of heart failure hospitalization or death.

Results

The cohort had a median age of 61 years with 23% being female. The median follow-up was 737 days with 146 patients (10.5%) experiencing the composite outcome. Numerous imaging and non-imaging variables were significantly different between patients with and without the composite outcome, including: median LVEF (32% vs 39%, p<0.0001), RVEF (46% vs 51% p<0.0001), LV mass (77g/m2 vs. 65g/m2, p<0.0001), digoxin (19% vs. 9%, p<0.0001) and diuretic (63% vs 41%, p<0.0001) use. Presence of replacement fibrosis (HR=2.09, p=0.001), particularly midwall striae (HR=2.01, p<0.0001), diffuse (HR=3.88, p<0.0001) and RV insertion site fibrosis (HR=1.54, p=0.022) patterns, were significantly associated with the combined endpoint. A stepwise multivariable model was applied using all eligible variables and resulted in robust accuracy for prediction of the combined outcome with a concordance index of 0.751 (Figure 1).

Conclusions

This study demonstrates the feasibility and prognostic value of automated patient phenotyping that captures patient reported data, imaging, and administrative data for risk prediction modelling in HFrEF. The incremental application of machine learning is being explored.

Acknowledgement/Funding

J White: Early Investigator Award (Heart and Stroke Foundation of Alberta), Calgary Health Trust

Abstract 929: Discovery of novel covalent KRASG12C inhibitors that display high potency and selectivity in vitro and in vivo

Activating mutations in KRAS have a high prevalence in human cancer. The codon 12 glycine to cysteine missense mutation (KRASG12C) is among the most common KRAS mutations, present in non-small cell lung adenocarcinoma (~15 %), colorectal adenocarcinoma (~3 %), and pancreatic adenocarcinoma (~1 %). KRASG12C was previously identified as potentially druggable by allele-specific covalent targeting of cysteine 12 near the allosteric switch II pocket (S-IIP). Building on this early work, we recently described the ARS-853 series of S-IIP KRASG12C inhibitors that covalently react with the GDP-bound state of KRASG12C, trapping KRASG12C in this inactive state. In cells, ARS-853 series compounds profoundly deplete the signaling competent GTP-bound state of KRASG12C, thereby inhibiting downstream RAS signaling. However, this series of covalent KRASG12C inhibitors exhibited modest cellular potency and/or poor pharmacokinetic properties, making them unsuitable for further evaluation of covalent KRASG12C inhibition in animal models.

We now describe in further detail the discovery and characterization of a new series of structurally distinct quinazoline based S-IIP KRASG12C inhibitors with substantially improved potency and pharmacologic properties that overcome limitations of the ARS-853 series. Through structure-guided medicinal chemistry optimization we identified compound ARS-1620, a potent, orally bioavailable covalent inhibitor of KRASG12C. The co-crystal structure of ARS-1620 covalently bound to KRASG12C reveals a distinct binding mode and additional interactions, compared to ARS-853. ARS-1620 rapidly engages KRASG12C, depletes KRASG12C-GTP in tumor cell lines, and inhibits downstream RAS signaling in a dose-dependent manner. The compound potently inhibits the growth of cell lines harboring the KRASG12C mutation with little or no effect on control cell lines. ARS-1620 demonstrates robust dose-dependent efficacy with once daily oral administration across a panel of KRASG12C-positive mouse cell line (CDX) and patient-derived (PDX) tumor xenograft models, with no response observed at all doses tested in KRASG12C-negative tumor models. The anti-tumor activity of ARS-1620 correlates with target engagement in the tumors as well as with inhibition of downstream RAS signaling. The in vivo efficacy and mutant selectivity observed with ARS-1620 across a wide range of KRASG12C mouse tumor models provides the first in vivo evidence that the S-IIP targeted approach may be a promising therapeutic strategy for patients with KRASG12C mutant cancers.

Citation Format: Liansheng Li, Matthew R. Janes, Jingchuan Zhang, Rasmus Hansen, Ulf Peters, Xin Guo, Yuching Chen, Anjali Babbar, Sarah J. Firdaus, Jun Feng, Jeffrey H. Chen, Shuangwei Li, Shisheng Li, Carol Thach, Yuan Liu, Ata Zarieh, Jeff M. Kucharski, Tao Wu, Ke Yu, Yi Wang, Yvonne Yao, Xiaohu Deng, Patrick P. Zarrinkar, Dashyant Dhanak, Matthew V. Lorenzi, Dana Hu-Lowe, Pingda Ren, Yi Liu. Discovery of novel covalent KRASG12C inhibitors that display high potency and selectivity in vitro and in vivo [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 929.

Abstract 686: Drugging an undruggable pocket: The biochemical mechanism of covalent KRASG12C inhibitors

We describe the biochemical mechanism of the covalent KRASG12C inhibitors ARS-853 and ARS-1620. Activating mutations in KRAS are among the most common mutations found in cancer. The KRASG12C mutation in particular is observed in approximately 15 % of non-small cell lung adenocarcinoma, 3 % of colorectal adenocarcinoma and 1 % of pancreatic adenocarcinoma. Until recently, KRAS had been considered undruggable due to the lack of clearly defined pockets that might support binding of small molecules, and the difficulty of targeting the nucleotide binding site due to the high affinity of GDP and GTP. However several years ago small molecules were discovered that bind an inducible pocket near the switch II region and covalently target the mutated cysteine in KRASG12C, trapping KRASG12C in a nonproductive GDP-bound state. Subsequent optimization of these compounds yielded the recently described inhibitors ARS-853 and ARS-1620, the first compounds that directly inhibit KRAS with high potency in cells and animals. While the biological activity of the inhibitors has been described, the biochemical mechanism of how the compounds achieve potent inhibition remained incompletely understood. We now show through biochemical kinetics studies that the activity of ARS-853 and ARS-1620 is primarily driven by KRAS-mediated catalysis of the chemical step of covalent bond formation with cysteine 12 in KRASG12C, rather than by high reversible binding affinity. The reversible inhibition constant (Ki) for both ARS-853 and ARS-1620 is well above the highest compound concentration tested (64 µM, to avoid solubility limitations), likely in the hundreds of micromolar range, while the rate of the chemical step (kinact) is fast. We confirm by several independent means that there is no detectable reversible binding affinity of the inhibitors for KRAS up to at least 32 µM, and show that the rapid chemical reaction is not due to high inherent reactivity of cysteine 12 in KRAS, nor to high intrinsic reactivity of the inhibitors. The results imply that the inhibitors do bind reversibly to KRAS to enable bond formation, but that binding is weak and primarily serves to orient the electrophile. The KRAS-dependent activation of covalent bond formation of ARS-853 and ARS-1620 with the mutated cysteine 12 is reminiscent of mechanism-based or suicide covalent enzyme inhibition, and explains both the high selectivity of the inhibitors for this cysteine relative to other cellular cysteines, and their potent overall activity despite exhibiting poor reversible affinity. The mechanism described here therefore resolves how an induced, shallow and dynamic pocket that is not expected to support high affinity binding of small molecules can nevertheless be targeted with potent inhibitors, and may be applicable to other targets conventionally considered undruggable.

Citation Format: Rasmus Hansen, Ulf Peters, Anjali Babbar, Yuching Chen, Jun Feng, Matthew R. Janes, Liansheng Li, Pingda Ren, Yi Liu, Patrick P. Zarrinkar. Drugging an undruggable pocket: The biochemical mechanism of covalent KRASG12C inhibitors [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 686.

Abstract 3885: 11q13 amplification selects for sensitivity to the ERK inhibitor KO-947 in squamous cell carcinomas

The MAPK pathway is a major driver of malignant progression, particularly in cancers arising from mutations in pathway components, and BRAF and MEK inhibitors have been approved for treatment of BRAF-mutant melanoma. ERK1/2 kinases are the final node in the MAPK signaling pathway and offer the possibility of clinical benefit in settings where earlier drugs are ineffective. We have previously reported that KO-947, a potent and selective inhibitor of ERK1/2 with extended target residence time and favorable pharmaceutic properties, displays robust single-agent antitumor activity in PDX models of adenocarcinomas with RAS/RAF mutations, and in squamous cell carcinomas (SCCs) that lack mutations in MAPK pathway components. Here we report the discovery of a novel biomarker that is associated with sensitivity to KO-947 in head and neck SCC and esophageal SCC PDX models. Recurring amplification of chromosome 11 between bands q13.3 and q13.4 is a feature of several tumor types, including ESCC and HNSCC. TCGA reports incidence rates of &gt;50% in ESCC and ~20% in HNSCC, although higher frequencies are seen in some subtypes, such as pharyngeal and HPV-negative SCC. The 11q13 amplicon commonly contains about a dozen genes, including several potential oncogenes with functional linkage to the MAPK pathway, such as CCND1, FADD and the recently described calcium-dependent chloride channel ANO1. PDX campaigns were carried out in 24 ESCC and 18 HNSCC models, including 16 and 7 of each with 11q13 amplification, respectively. Groups of three animals were dosed with KO-947 at 300mg/kg QW, tumor growth was monitored for 3-6 weeks and responses were categorized as progressive disease, stable disease (SD, &gt;80% TGI) or partial/complete response (PR/CR, &gt;30% regression). In ESCC tumor-bearing animals, the overall response rates (ORR = PR+CR) were 33% in the overall population, 51% in the 11q13-amplified (11q-AMP) and 3% in 11q13-WT. The disease control rates (DCR = PR/CR+SD) were 54% overall, 77% in 11q-AMP and 21% in 11q-WT. In HNSCC tumor-bearing animals, the ORRs were 24% in the overall population, 56% in 11q-AMP and 9% in 11q-WT, with DCRs of 40%, 69% and 26% in the three subsets, respectively. 11q-AMP was significantly associated with response to KO-947 in both tumor types. ROC analysis defined the minimum effective copy number as 4 and revealed significant associations between expression levels of several 11q13 amplicon genes and response to KO-947. A key role for ANO1 in driving ERK-dependent tumor growth in 11q-AMP cases was further indicated by the observation that ANO1 expression was silenced in some 11q-AMP models and these tumors failed to respond the ERK inhibition. The results suggest that 11q13 amplification in SCCs can drive tumor growth and survival in a MAPK-dependent manner and that 11q-AMP may be a useful biomarker for predicting clinical response to ERK inhibitors.

Citation Format: Francis J. Burrows, Linda Kessler, Tao Wu, Xin Gao, Jeffrey Chen, Rasmus Hansen, Shuangwei Li, Carol Thach, Shisheng Li, Ke Yu, Jeff Kucharski, Ulf Peters, Jun Feng, Yi Wang, Yvonne Yao, Ata Zarieh, Matt Janes, Jingchuan Zhang, Liansheng Li, Dana Hu-Lowe, Pingda Ren, Yi Liu. 11q13 amplification selects for sensitivity to the ERK inhibitor KO-947 in squamous cell carcinomas [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 3885.

Review article: the gut microbiome in inflammatory bowel disease-avenues for microbial management

BACKGROUND

The concept of an altered collective gut microbiota rather than identification of a single culprit is possibly the most significant development in inflammatory bowel disease research. We have entered the "omics" era, which now allows us to undertake large-scale/high-throughput microbiota analysis which may well define how we approach diagnosis and treatment of inflammatory bowel disease (IBD) in the future, with a strong steer towards personalised therapeutics.

AIM

To assess current epidemiological, experimental and clinical evidence of the current status of knowledge relating to the gut microbiome, and its role in IBD, with emphasis on reviewing the evidence relating to microbial therapeutics and future microbiome modulating therapeutics.

METHODS

A Medline search including items 'intestinal microbiota/microbiome', 'inflammatory bowel disease', 'ulcerative colitis', 'Crohn's disease', 'faecal microbial transplantation', 'dietary manipulation' was performed.

RESULTS

Disease remission and relapse are associated with microbial changes in both mucosal and luminal samples. In particular, a loss of species richness in Crohn's disease has been widely observed. Existing therapeutic approaches broadly fall into 3 categories, namely: accession, reduction or indirect modulation of the microbiome. In terms of microbial therapeutics, faecal microbial transplantation appears to hold the most promise; however, differences in study design/methodology mean it is currently challenging to elegantly translate results into clinical practice.

CONCLUSIONS

Existing approaches to modulate the gut microbiome are relatively unrefined. Looking forward, the future of microbiome-modulating therapeutics looks bright with several novel strategies/technologies on the horizon. Taken collectively, it is clear that ignoring the microbiome in IBD is not an option.

Abstract 5168: KO-947, a potent ERK inhibitor with robust preclinical single agent activity in MAPK pathway dysregulated tumors

The RAS/RAF/MEK pathway is a major driver of malignant progression, particularly in cancers arising from mutations in RAS, BRAF and NF1. Although both BRAF and MEK inhibitors have been approved for treatment of melanoma, their clinical activity is commonly limited by acquired resistance due to reactivation of the pathway downstream of their targets. Since the ERK1/2 kinases are the final node in the MAPK signaling pathway, they are not subject to the feedback reactivation mechanisms that can undermine RAF or MEK blockade, offering the possibility of clinical benefit in settings where earlier drugs are ineffective. Here we describe the characterization of KO-947, a potent and selective inhibitor of ERK1/2 kinases, in biochemical, cellular and in vivo antitumor activity assays. KO-947 was profiled in vitro in biochemical activity assays, competition binding assays, and a probe-based competition binding assay in cell lysates, and subsequently screened in a large panel of human tumor cell lines focused on MAPK-dysregulated tumor types. In vivo studies were carried out in well-characterized xenograft models of BRAF-, KRAS- and NRAS-mutant disease and subsequently extended to a large panel of early-passage patient-derived xenograft (PDX) models representative of a wide range of tumor types and molecular profiles. Biochemical assays reveal that KO-947 is a 10nM inhibitor of ERK with at least 50-fold selectivity against a panel of 450 kinases. KO-947 blocks ERK signaling and proliferation of tumor cells exhibiting dysregulation of MAPK pathway signaling, including mutations in BRAF, NRAS or KRAS, at low nanomolar concentrations. KO-947 is differentiated from other published ERK inhibitors by an extended residence time and high potency in cell engagement that translate into prolonged pathway inhibition in vitro and in vivo. In cell-line derived xenograft studies, the drug profoundly suppresses ERK signaling for up to five days after a single dose and induces regressions in RAS- and RAF-mutant melanoma, NSCLC and pancreatic cancer models on administration schedules ranging from daily to weekly. Intermittent dosing enables comparable antitumor activity at reduced dose-intensity. PDX screening confirms and extends these findings to include RAS and BRAF mutant colorectal, gastric and cervical carcinoma models, and robust activity is also seen on both weekly and Q2D schedules in tumor models lacking BRAF/RAS mutations but with other dysregulation of the MAPK pathway. Thus, the favorable ADME properties of KO-947 enable the achievement of optimal antitumor activity with intermittent dosing, which may provide an opportunity to maximize the therapeutic window with flexible administration routes and schedules. These results demonstrate the potential clinical utility of KO-947 in MAPK pathway dysregulated tumors.

Citation Format: Francis Burrows, Linda Kessler, Jeffrey Chen, Xin Gao, Rasmus Hansen, Shuangwei Li, Carol Thach, Levan Darjania, Yvonne Yao, Yi Wang, Ata Zarieh, Ke Yu, Tao Wu, Jingchuan Zhang, Dana Hu-Lowe, Liansheng Li, Pingda Ren, Yi Liu. KO-947, a potent ERK inhibitor with robust preclinical single agent activity in MAPK pathway dysregulated tumors [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 5168. doi:10.1158/1538-7445.AM2017-5168

The importance of a high rectal pressure on strain in constipated patients: implications for biofeedback therapy

BACKGROUND

A subset of patients with chronic constipation display a relatively high manometric rectal pressure on strain. We hypothesized that these patients represent a unique phenotype of functional defecatory disorder (FDD) and would benefit from undergoing anorectal biofeedback (BF).

METHODS

Of 138 consecutive patients with chronic constipation and symptoms of FDD, 19 were defined as having a high rectal pressure on strain, using a statistically derived cut-off of 78 mm Hg. This subset was compared with remaining patients in regard to baseline clinical profile and physiology, and outcome of BF.

KEY RESULTS

There was a greater representation of males in the high rectal pressure group. Their constipation score, impact of bowel dysfunction on quality of life and satisfaction with bowel habits did not differ from the remaining patients. Eighty-four percent of patients in the high group successfully expelled the rectal balloon and 95% displayed paradoxical anal contraction on strain (P<.05 compared with the remaining patients). Following BF, 89% of patients in the high group reduced their rectal pressure to normal. End of BF treatment outcomes improved significantly, and to a similar degree, in both groups.

CONCLUSIONS & INFERENCES

We have identified a subgroup of patients with dyssynergic symptoms but without a formal Rome III diagnosis of FDD, who were characterized by a high straining rectal pressure. Although these patients displayed some physiological differences to the patients with lower straining rectal pressure, they suffer similarly. Importantly, we have shown that these patients can respond favorably to anorectal BF.

Executive Function Index (EFI) performance in nonclinical individuals with high levels of autistic traits

This study examined the ability of the Executive Function Index (EFI) to detect differences in executive functioning amongst participants with varying levels of subclinical autistic symptoms as quantified by the Autism Spectrum Quotient (ASQ). Participants were a nonclinical college subject sample classified as displaying either Low (0-15 ASQ score, n = 182) ASQ traits or High (16 or higher ASQ score, n = 91) ASQ traits. Participants were given the ASQ (Baron-Cohen et al., 2001) and the EFI (Spinella, 2005 ). High ASQ subjects were significantly impaired (p's < .04) on the Motivation/Drive (EFI-1) and Organization (EFI-4) subscales of the EFI, as compared to the Low ASQ subjects. However, no High/Low ASQ group differences were observed for EFI-2 (Impulse Control), EFI-3 (Empathy), EFI-5 (Planning) subscales or the EFI-Total Score (p's > .12), although these differences were in the predicted direction (High ASQ < Low ASQ). Use of the EFI as a measure of executive function performance in nonclinical ASQ trait individuals requires further study and may not be sensitive enough of an instrument to assess EF in nonclinical populations with autistic traits.

Biochemical Foundations of Health and Energy Conservation in Hibernating Free-ranging Subadult Brown Bear Ursus arctos

Brown bears (Ursus arctos) hibernate for 5-7 months without eating, drinking, urinating, and defecating at a metabolic rate of only 25% of the summer activity rate. Nonetheless, they emerge healthy and alert in spring. We quantified the biochemical adaptations for hibernation by comparing the proteome, metabolome, and hematological features of blood from hibernating and active free-ranging subadult brown bears with a focus on conservation of health and energy. We found that total plasma protein concentration increased during hibernation, even though the concentrations of most individual plasma proteins decreased, as did the white blood cell types. Strikingly, antimicrobial defense proteins increased in concentration. Central functions in hibernation involving the coagulation response and protease inhibition, as well as lipid transport and metabolism, were upheld by increased levels of very few key or broad specificity proteins. The changes in coagulation factor levels matched the changes in activity measurements. A dramatic 45-fold increase in sex hormone-binding globulin levels during hibernation draws, for the first time, attention to its significant but unknown role in maintaining hibernation physiology. We propose that energy for the costly protein synthesis is reduced by three mechanisms as follows: (i) dehydration, which increases protein concentration without de novo synthesis; (ii) reduced protein degradation rates due to a 6 °C reduction in body temperature and decreased protease activity; and (iii) a marked redistribution of energy resources only increasing de novo synthesis of a few key proteins. The comprehensive global data identified novel biochemical strategies for bear adaptations to the extreme condition of hibernation and have implications for our understanding of physiology in general.

Abstract LB-071: Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism

Oncogenic mutations impair the GTPase activity of RAS, causing it to accumulate in the activated, GTP-bound conformation. Here we describe the mechanism of action of a novel compound that binds to KRASG12C to selectively inhibit proliferation and induce apoptosis in cancer cells with this mutation. The inhibitor interacted preferentially with the GDP-bound form of the protein, yet it reduced the level of GTP-bound KRASG12C. This suggested that GTPase activity is required for inhibition, which turned out to be the case. The inhibitor traps GDP-bound KRASG12C and prevents nucleotide exchange to the GTP-bound form. Genetic experiments revealed that mutants completely lacking GTPase activity, and those promoting exchange, reduced the potency of the drug. In contrast, mutants with diminished exchange were more susceptible to inhibition. In agreement with these findings, targeting receptor signaling potentiated KRASG12C inhibition, whereas its activation had the opposite effect. This mechanism reveals that KRASG12C undergoes nucleotide cycle in cancer cells and provides a basis for the development of effective combination therapies to treat KRASG12C-driven cancers.

Citation Format: Piro Lito, Martha Solomon, Rasmus Hansen, Lian-Sheng Li, Neal Rosen. Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism. [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 LB-071.

Bleeding, thrombosis, and anticoagulation in myeloproliferative neoplasms (MPN): analysis from the German SAL-MPN-registry

BACKGROUND

Patients with Ph-negative myeloproliferative neoplasms (MPN), such as polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF), are at increased risk for thrombosis/thromboembolism and major bleeding. Due to the morbidity and mortality of these events, antiplatelet and/or anticoagulant agents are commonly employed as primary and/or secondary prophylaxis. On the other hand, disease-related bleeding complications (i.e., from esophageal varices) are common in patients with MPN. This analysis was performed to define the frequency of such events, identify risk factors, and assess antiplatelet/anticoagulant therapy in a cohort of patients with MPN.

METHODS

The MPN registry of the Study Alliance Leukemia is a non-interventional prospective study including adult patients with an MPN according to WHO criteria (2008). For statistical analysis, descriptive methods and tests for significant differences as well as contingency tables were used to identify the odds of potential risk factors for vascular events.

RESULTS

MPN subgroups significantly differed in sex distribution, age at diagnosis, blood counts, LDH levels, JAK2V617F positivity, and spleen size (length). While most thromboembolic events occurred around the time of MPN diagnosis, one third of these events occurred after that date. Splanchnic vein thrombosis was most frequent in post-PV-MF and MPN-U patients. The chance of developing a thromboembolic event was significantly elevated if patients suffered from post-PV-MF (OR 3.43; 95% CI = 1.39-8.48) and splenomegaly (OR 1.76; 95% CI = 1.15-2.71). Significant odds for major bleeding were previous thromboembolic events (OR = 2.71; 95% CI = 1.36-5.40), splenomegaly (OR = 2.22; 95% CI 1.01-4.89), and the administration of heparin (OR = 5.64; 95% CI = 1.84-17.34). Major bleeding episodes were significantly less frequent in ET patients compared to other MPN subgroups.

CONCLUSIONS

Together, this report on an unselected "real-world" cohort of German MPN patients reveals important data on the prevalence, diagnosis, and treatment of thromboembolic and major bleeding complications of MPN.

Proteomic dataset of the organohalide-respiring bacterium Dehalococcoides mccartyi strain CBDB1 grown on hexachlorobenzene as electron acceptor

The proteome of the anaerobic organohalide-respiring bacterium Dehalococcoides mccartyi strain CBDB1 was analyzed by nano liquid chromatography coupled to mass spectrometry (LC-MS/MS). Two different preparation methods, (i) in-solution and (ii) in-gel proteolytic digestion were assessed to elucidate the core and the functional proteome of bacterial cultures grown in synthetic anaerobic medium with hexachlorobenzene as sole electron acceptor. A detailed analysis of the data presented is available (Schiffmann et al., 2014) [1].

Allele-specific inhibitors inactivate mutant KRAS G12C by a trapping mechanism

It is thought that KRAS oncoproteins are constitutively active because their guanosine triphosphatase (GTPase) activity is disabled. Consequently, drugs targeting the inactive or guanosine 5'-diphosphate-bound conformation are not expected to be effective. We describe a mechanism that enables such drugs to inhibit KRAS(G12C) signaling and cancer cell growth. Inhibition requires intact GTPase activity and occurs because drug-bound KRAS(G12C) is insusceptible to nucleotide exchange factors and thus trapped in its inactive state. Indeed, mutants completely lacking GTPase activity and those promoting exchange reduced the potency of the drug. Suppressing nucleotide exchange activity downstream of various tyrosine kinases enhanced KRAS(G12C) inhibition, whereas its potentiation had the opposite effect. These findings reveal that KRAS(G12C) undergoes nucleotide cycling in cancer cells and provide a basis for developing effective therapies to treat KRAS(G12C)-driven cancers.

Selective Inhibition of Oncogenic KRAS Output with Small Molecules Targeting the Inactive State

KRAS gain-of-function mutations occur in approximately 30% of all human cancers. Despite more than 30 years of KRAS-focused research and development efforts, no targeted therapy has been discovered for cancers with KRAS mutations. Here, we describe ARS-853, a selective, covalent inhibitor of KRAS(G12C) that inhibits mutant KRAS-driven signaling by binding to the GDP-bound oncoprotein and preventing activation. Based on the rates of engagement and inhibition observed for ARS-853, along with a mutant-specific mass spectrometry-based assay for assessing KRAS activation status, we show that the nucleotide state of KRAS(G12C) is in a state of dynamic flux that can be modulated by upstream signaling factors. These studies provide convincing evidence that the KRAS(G12C) mutation generates a "hyperexcitable" rather than a "statically active" state and that targeting the inactive, GDP-bound form is a promising approach for generating novel anti-RAS therapeutics.

SIGNIFICANCE

A cell-active, mutant-specific, covalent inhibitor of KRAS(G12C) is described that targets the GDP-bound, inactive state and prevents subsequent activation. Using this novel compound, we demonstrate that KRAS(G12C) oncoprotein rapidly cycles bound nucleotide and responds to upstream signaling inputs to maintain a highly active state.

The fungal microbiota of de-novo paediatric inflammatory bowel disease

Inflammatory bowel disease (IBD) is characterised by an inappropriate chronic immune response against resident gut microbes. This may be on account of distinct changes in the gut microbiota termed as dysbiosis. The role of fungi in this altered luminal environment has been scarcely reported. We studied the fungal microbiome in de-novo paediatric IBD patients utilising next generation sequencing and compared with adult disease and normal controls. We report a distinct difference in fungal species with Ascomycota predominating in control subjects compared to Basidiomycota dominance in children with IBD, which could be as a result of altered tolerance in these patients.

Comparison of targeted peptide quantification assays for reductive dehalogenases by selective reaction monitoring (SRM) and precursor reaction monitoring (PRM)

Targeted absolute protein quantification yields valuable information about physiological adaptation of organisms and is thereby of high interest. Especially for this purpose, two proteomic mass spectrometry-based techniques namely selective reaction monitoring (SRM) and precursor reaction monitoring (PRM) are commonly applied. The objective of this study was to establish an optimal quantification assay for proteins with the focus on those involved in housekeeping functions and putative reductive dehalogenase proteins from the strictly anaerobic bacterium Dehalococcoides mccartyi strain CBDB1. This microbe is small and slow-growing; hence, it provides little biomass for comprehensive proteomic analysis. We therefore compared SRM and PRM techniques. Eleven peptides were successfully quantified by both methods. In addition, six peptides were solely quantified by SRM and four by PRM, respectively. Peptides were spiked into a background of Escherichia coli lysate and the majority of peptides were quantifiable down to 500 amol absolute on column by both methods. Peptide quantification in CBDB1 lysate resulted in the detection of 15 peptides using SRM and 14 peptides with the PRM assay. Resulting quantification of five dehalogenases revealed copy numbers of <10 to 115 protein molecules per cell indicating clear differences in abundance of RdhA proteins during growth on hexachlorobenzene. Our results indicated that both methods show comparable sensitivity and that the combination of the mass spectrometry assays resulted in higher peptide coverage and thus more reliable protein quantification.