Abstract 1654: Pre-clinical activity of the Wnt/Beta-catenin pathway inhibitor RXC004 in models of biliary tract cancer

Background: RXC004 is a potent and selective inhibitor of the Wnt pathway regulator Porcupine, and is currently being investigated in phase 2 studies in patients with advanced cancers, including Biliary Tract Cancers (BTCs) +/- Pembrolizumab (NCT04907851 and NCT04907539). Whilst genetically-defined ‘upstream’ Wnt pathway alterations, including loss-of-function RNF43 mutations and RSPO gene fusions, sensitise Gastrointestinal (GI) cancers to RXC004, other non-genetic factors remain to be determined. Wnt pathway mutations are rare in BTCs, however these tumors have been shown to overexpress various Wnt ligands, with evidence that this high expression is associated with worse prognosis.

Methods: RXC004 was evaluated as a monotherapy against a panel of patient-derived xenograft (PDX) models of Biliary Tract Cancer for efficacy and pharmacodynamic (PD) activity. RXC004 was dosed at 5mg/kg QD and efficacy was measured by tumor volume, tumor weight and survival endpoint, whilst tumor pharmacodynamic (PD) effects were measured by quantitative Real-Time PCR (qPCR) for gene expression and histological staining methods. Baseline transcriptome characteristics of the PDX models were determined against the PanCancer Pathways and PanCancer IO360 codesets using Nanostring nCounter analysis.

Results: RXC004 monotherapy was efficacious in multiple PDX models of Biliary Tract Cancer, significantly reducing tumor volume and tumor weight (range p<0.05 to p<0.0001). Tumor PD effects of RXC004 treatment on gene expression by qPCR included Wnt pathway genes (AXIN2, cMYC), differentiation genes (MUC2, MUC4, MUC5AC) and secreted Wnt pathway regulators (sFRPs, DKKs), and on histology included Ki67 and Mucin (periodic acid-Schiff’s (PAS)/Alcian blue staining). Hierarchical clustering of the PDX models was performed based on the expression of Wnt signalling genes in the Nanostring analysis. Furthermore, the gene expression profiles were used to predict whether models were likely to be RXC004 sensitive using Random Forest machine learning algorithms.

Conclusion: These data demonstrate that (1) RXC004 is efficacious in pre-clinical PDX models of BTC, (2) RXC004 induces multiple PD effects in BTC models at the level of gene expression, cell proliferation and cell differentiation, and (3) PDX models of BTC can be clustered based on baseline transcriptomic profiles of Wnt signalling genes and predict RXC004 sensitivity.

Citation Format: Simon A. Woodcock, Dorottya Keppel, Catherine Eagle, Inder Bhamra, Eleanor Platt, Lucy Frost, Kevin Randall, Richard Armer, Jane Robertson, Gayle Marshall, Caroline Phillips. Pre-clinical activity of the Wnt/Beta-catenin pathway inhibitor RXC004 in models of biliary tract cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 1654.

Targeting ligand-dependent wnt pathway dysregulation in gastrointestinal cancers through porcupine inhibition

Gastrointestinal cancers are responsible for more cancer deaths than any other system of the body. This review summarises how Wnt pathway dysregulation contributes to the development of the most common gastrointestinal cancers, with a particular focus on the nature and frequency of upstream pathway aberrations. Tumors with upstream aberrations maintain a dependency on the presence of functional Wnt ligand, and are predicted to be tractable to inhibitors of Porcupine, an enzyme that plays a key role in Wnt secretion. We summarise available pre-clinical efficacy data from Porcupine inhibitors in vitro and in vivo, as well as potential toxicities and the data from early phase clinical trials. We appraise the rationale for biomarker-defined targeted approaches, as well as outlining future opportunities for combination with other therapeutics.

The Wnt Pathway Inhibitor RXC004 Blocks Tumor Growth and Reverses Immune Evasion in Wnt Ligand-dependent Cancer Models

Wnt signaling is implicated in the etiology of gastrointestinal tract cancers. Targeting Wnt signaling is challenging due to on-target toxicity concerns and lack of druggable pathway components. We describe the discovery and characterization of RXC004, a potent and selective inhibitor of the membrane-bound o-acyl transferase Porcupine, essential for Wnt ligand secretion. Absorption, distribution, metabolism, and excretion and safety pharmacology studies were conducted with RXC004 in vitro, and pharmacokinetic exposure assessed in vivo. RXC004 effects on proliferation and tumor metabolism were explored in genetically defined colorectal and pancreatic cancer models in vitro and in vivo. RXC004 effects on immune evasion were assessed in B16F10 immune "cold" and CT26 immune "hot" murine syngeneic models, and in human cell cocultures. RXC004 showed a promising pharmacokinetic profile, inhibited Wnt ligand palmitoylation, secretion, and pathway activation, and demonstrated potent antiproliferative effects in Wnt ligand-dependent (RNF43-mutant or RSPO3-fusion) colorectal and pancreatic cell lines. Reduced tumor growth and increased cancer cell differentiation were observed in SNU-1411 (RSPO3-fusion), AsPC1 and HPAF-II (both RNF43-mutant) xenograft models, with a therapeutic window versus Wnt homeostatic functions. Additional effects of RXC004 on tumor cell metabolism were confirmed in vitro and in vivo by glucose uptake and ¹⁸fluorodeoxyglucose-PET, respectively. RXC004 stimulated host tumor immunity; reducing resident myeloid-derived suppressor cells within B16F10 tumors and synergizing with anti-programmed cell death protein-1 (PD-1) to increase CD8⁺/regulatory T cell ratios within CT26 tumors. Moreover, RXC004 reversed the immunosuppressive effects of HPAF-II cells cocultured with human peripheral blood mononuclear cells, confirming the multiple anticancer mechanisms of this compound, which has progressed into phase II clinical trials.

Significance

Wnt pathway dysregulation drives many gastrointestinal cancers; however, there are no approved therapies that target the pathway. RXC004 has demonstrated the potential to block both tumor growth and tumor immune evasion in a genetically defined, clinically actionable subpopulation of Wnt ligand-dependent gastrointestinal cancers. The clinical utility of RXC004, and other Porcupine inhibitors, in such Wnt ligand-dependent cancers is currently being assessed in patient trials.

Manganese Carbonyl Complexes as Selective Electrocatalysts for CO2 Reduction in Water and Organic Solvents

The electrochemical reduction of CO₂ provides a way to sustainably generate carbon-based fuels and feedstocks. Molecular CO₂ reduction electrocatalysts provide tunable reaction centers offering an approach to control the selectivity of catalysis. Manganese carbonyl complexes, based on [Mn(bpy)(CO)₃Br] and its derivatives (bpy = 2,2′-bipyridine), are particularly interesting due to their ease of synthesis and the use of a first-row earth-abundant transition metal. [Mn(bpy)(CO)₃Br] was first shown to be an active and selective catalyst for reducing CO₂ to CO in organic solvents in 2011. Since then, manganese carbonyl catalysts have been widely studied with numerous reports of their use as electrocatalysts and photocatalysts and studies of their mechanism.

This class of Mn catalysts only shows CO₂ reduction activity with the addition of weak Brønsted acids. Perhaps surprisingly, early reports showed increased turnover frequencies as the acid strength is increased without a loss in selectivity toward CO evolution. It may have been expected that the competing hydrogen evolution reaction could have led to lower selectivity. Inspired by these works we began to explore if the catalyst would work in protic solvents, namely, water, and to explore the pH range over which it can operate. Here we describe the early studies from our laboratory that first demonstrated the use of manganese carbonyl complexes in water and then go on to discuss wider developments on the use of these catalysts in water, highlighting their potential as catalysts for use in aqueous CO₂ electrolyzers.

Key to the excellent selectivity of these catalysts in the presence of Brønsted acids is a proton-assisted CO₂ binding mechanism, where for the acids widely studied, lower pK_a values actually favor CO₂ binding over Mn–H formation, a precursor to H₂ evolution. Here we discuss the wider literature before focusing on our own contributions in validating this previously proposed mechanism through the use of vibrational sum frequency generation (VSFG) spectroelectrochemistry. This allowed us to study [Mn(bpy)(CO)₃Br] while it is at, or near, the electrode surface, which provided a way to identify new catalytic intermediates and also confirm that proton-assisted CO₂ binding operates in both the “dimer” and primary (via [Mn(bpy)(CO)₃]⁻) pathways. Understanding the mechanism of how these highly selective catalysts operate is important as we propose that the Mn complexes will be valuable models to guide the development of new proton/acid tolerant CO₂ reduction catalysts.

Abstract 3874: Efficacy of the Wnt/Beta-Catenin pathway inhibitor RXC004 in genetically-defined models of cancer

Background: RXC004, a potent and selective inhibitor of the Wnt/β-Catenin pathway regulator porcupine, is being investigated in a safety and tolerability study in cancer patients with solid tumours (NCT03447470). Wnt pathway alterations, including loss-of-function RNF43 mutations and RSPO gene fusions, result in higher levels of the Wnt receptor Fzd on the cell surface, increasing Wnt-ligand dependent signalling. These alterations are implicated in colorectal, gastric, pancreatic and biliary cancer. We present pre-clinical data on the direct tumour-targeting effects of RXC004 in genetically-defined models of cancer.

Methods: RXC004 in vitro effects on sensitive (RNF43 mutant or RSPO fusion) or insensitive (APC/β-Catenin mutant) colorectal and pancreatic tumour cells lines were assessed against a panel of potential Wnt target genes measured using qPCR. To test if these effects translated in vivo, RXC004 was evaluated in several RNF43 mutant or RSPO fusion tumour line efficacy, PK and PD studies. A range of oral doses and schedules of RXC004 were tested for either 7 or 26 days, for PK/PD or efficacy measurements respectively. Efficacy was measured by tumour volume/weight, RXC004 PK was measured in plasma and tumour, and PD effects were measured by tumour qPCR and histological methods.

Results: In sensitive cell lines, RXC004 inhibited expression of the Wnt pathway negative feedback genes Axin2 and RNF43. Decreases in c-Myc correlated with the anti-proliferative effects of RXC004. Additionally, MMP7 and CD44 were downregulated, whilst Mucin gene expression increased. In contrast, RXC004 had no anti-proliferative effects on APC mutant colorectal cancer cells in vitro, and no modulation of these Wnt target genes. In vivo, RXC004 demonstrated significant efficacy and PD effects in multiple RNF43 mutant and RSPO fusion xenograft models. Focusing on an RSPO fusion model, RXC004 reduced tumour volume in a dose-dependent manner at 1.5 and 5 mg/kg QD, and 1.5mg/kg BID. In addition, 1.5mg/kg BID of RXC004 scheduled 5 days on, 2 days off also gave significant efficacy. PK analysis was consistent with the predicted dose response, showing excellent absorption and tumour distribution. PD analysis confirmed the RXC004-induced Wnt target gene changes identified in vitro translated in vivo, whilst histology showed a clear reduction in the proliferation marker Ki67 and concomitant increase in the staining of Mucins, indicative of mucinous differentiation of the tumour cells.

Conclusion: Taken together, these data demonstrate that RXC004 monotherapy has the potential to benefit patients with tumours bearing RNF43 mutations or RSPO fusions, supporting a genetically-defined patient selection strategy for ongoing RXC004 clinical studies.

Citation Format: Simon Woodcock, Inder Bhamra, Cliff Jones, Alicia Edmenson Cook, Catherine Eagle, Caroline Phillips. Efficacy of the Wnt/Beta-Catenin pathway inhibitor RXC004 in genetically-defined models of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3874.

Abstract 3764: Porcupine inhibitor RXC004 enhances immune response in pre-clinical models of cancer

Background: RXC004, a potent and selective porcupine (PORCN) inhibitor, is being investigated in a safety and tolerability study in cancer patients with solid tumours (CT 2017-000720-98). In addition to the tumour targeting role of RXC004 and other Wnt pathway inhibitors, we present pre-clinical data which suggests further potential for RXC004 in modulating the immune system of the tumour microenvironment. Materials and Methods: To evaluate the potential of a novel porcupine inhibitor, RXC004, as an immunomodulatory anti-cancer agent, sub cutaneous B16F10 melanoma (C57BL/6 mice) and CT26 colorectal (BALB/c mice) murine tumour models were utilised. Mice in both models were treated with RXC004 alone or in combination with mouse anti-PD-1 antibody. Flow cytometry analysis was utilised to measure key immune cell populations in the tumour microenvironment. To probe the underlying mechanism of immune modulation in these models and to provide a link to the emerging clinical data suggesting a role for Wnt pathway activation in immune escape, human monocytic cells were isolated from PBMCs and human dendritic cells were derived in vitro. The Wnt pathway was induced in derived Dendritic cells and expression of IDO was measured. Results: In the murine CT26 model, RXC004 treatment reduced tumour size when dosed in combination with anti-PD-1 antibody, causing regression and cures in some animals. Furthermore, flow cytometry showed RXC004 in combination with anti-PD-1 antibody increased the proportion of CD8+ cytotoxic T cells as well as decreasing FoxP3+ regulatory T cells when compared to the monotherapy anti-PD-1 arm. In a syngeneic murine melanoma B16F10 model, RXC004 monotherapy at a dose of 5mg/kg QD orally significantly inhibited tumour growth, as did RXC004 combined with anti-PD-1. RXC004 had no effect on the proliferation of B16F10 cells in vitro, suggesting this was not caused by the compound directly affecting B16 cell proliferation. Flow cytometry analysis of the B16 tumours showed significant immune modulatory effects in the tumour microenvironment. In addition to mouse model data, Wnt pathway activation in human dendritic cells was shown to increase IDO expression. Conclusion: Taken together, data from murine syngeneic mouse models corroborate literature data suggesting that inhibiting the Wnt pathway may promote the immune response against human cancers.

Citation Format: Inder Bhamra, Richard Armer, Matilda Bingham, Catherine Eagle, Alicia Edmenson Cook, Caroline Phillips, Simon Woodcock. Porcupine inhibitor RXC004 enhances immune response in pre-clinical models of cancer [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 3764.

Application of composted pig bedding litter on a Vertosol and Sodosol soil. 1. Effect on crop growth and soil water

Trials were undertaken at two sites with contrasting soil types in the Wimmera region of Victoria: a well-structured grey cracking clay soil (Vertosol) at Traynors Lagoon and a poorly structured sodic clay soil (Sodosol) at Gre Gre. The effect of a once-off application of three different types of bedding litter (wheat straw and two types of rice hulls) applied at three rates (20, 30 and 40 t/ha) was compared with that of a control (no amelioration), nitrogen fertiliser (46 kg N/ha) applied to each crop, or nitrogen plus a once-off application of gypsum (2.5 t/ha). The growth of three subsequent crops and soil water was examined. Pig bedding litter (rice hulls 1, rice hulls 2 or wheat straw) produced marked improvements in the dry matter production and grain yield of the first crop (wheat) in 1997 and a following canola crop in 1998. In 1999, bedding litter significantly improved the growth of an oats crop at Gre Gre, but had no effect on a crop of field peas at Traynors Lagoon. The beneficial effects of bedding litter on grain yields, however, were matched by small but significant reductions in grain quality resulting from soil water limitations for the yield potential. Although crop growth was improved by the addition of nitrogen fertiliser each year or both nitrogen plus gypsum, the effect was usually small compared with that of adding litter and provided minimal residual value in the following year. There was a general trend for gravimetric soil water to be higher at sowing where bedding litter had been applied, especially at Gre Gre. In contrast, soil water tended to be lower at grain maturity at Traynors Lagoon, where bedding litter or nitrogen fertiliser had been applied, reflecting the enhanced crop growth in these treatments compared with the control. There was no consistent effect of treatments on soil water at maturity in either 1998 or 1999 at Gre Gre.

Genotyping fetal DNA by non-invasive means: extraction from maternal plasma

BACKGROUND AND OBJECTIVES

Identification of fetal DNA in maternal plasma may allow genetic analysis without the use of invasive techniques. The aim of this study was to extract DNA from maternal plasma, identify fetal material through the presence of SRY or RHD gene sequences and assess the reliability of these results.

MATERIALS AND METHODS

A polymerase chain reaction (PCR) method of a commercial kit was used with primers for SRY or exon 10 of the RHD gene sequence.

RESULTS

Multiple plasma samples were collected from 60 women who were evaluable for either SRY or RHD, or both, fetally derived DNA sequences. Fetal DNA was present in the plasma throughout the pregnancies and for some hours or days after delivery.

CONCLUSION

Fetal DNA can be reliably detected in maternal plasma from early in pregnancy and normally is cleared within days of delivery.

Anaesthetic management of a parturient with severe muscular dystrophy, lumbar lordosis and a difficult airway

PURPOSE

This case describes the management of a 19-yr-old wheelchair bound primigravida with severe muscular dystrophy who presented for Caesarean section after spontaneous rupture of membranes. Anaesthesia was influenced by several features of her systemic disease which were impediments to both neuraxial and general anaesthesia.

CLINICAL FEATURES

Other than for a prenatal record and the history obtainable from the patient, little additional medical information was available. Physical examination showed diffuse muscular weakness and an anatomically abnormal airway. Examination of the spine showed slight 10-15 degrees thoracolumbar scoliosis and > 45 degrees lumbar lordosis. Fetal assessment was normal. Echocardiography revealed mildly decreased left ventricular function and was consistent with pulmonary hypertension. After discussion with the patient and her obstetrician, elective Caesarean delivery was deemed the best management. Neuroaxial anaesthesia was at an increased risk of failure due to the profound lumbar lordosis. A plan for awake intubation and general anaesthesia was described to the patient in case regional anaesthesia could not be initiated. A fibreoptic bronchoscope and difficult intubation kit were made available. General anaesthesia was expected to have increased risk of postoperative pulmonary complications, hence epidural anaesthesia was attempted. After difficult catheter insertion, a sensory block was titrated to a T4 level. This was well tolerated by both mother and fetus. A healthy baby was delivered with Apgar scores of 9 and 9. Postoperatively the mother was transferred to the intensive care unit. After 72 hr, the patients respiratory status allowed transfer to the word.

CONCLUSION

This case illustrates the use of epidural anaesthesia in the successful management of a severely compromised patient with limb-girdle muscular dystrophy undergoing elective Caesarean section.

Developing a "clinical presentation" curriculum at the University of Calgary

Currently, medical curricula are structured according to disciplines, body systems, or clinical problems. Beginning in 1988, the faculty of the University of Calgary Faculty of Medicine (U of C) carefully evaluated the advantages and disadvantages of each of these models in seeking to revise their school's curriculum. However, all three models fell short of a curricular structure based on current knowledge and principles of adult learning, clinical problem solving, community demands, and curriculum management. By 1991, the U of C had formulated a strategic plan for a revised curriculum structure based on the way patients present to physicians, and implementation of this plan has begun. In creating the new curriculum, 120 clinical presentations (e.g., "loss of consciousness/syncope") were defined and each was assigned to an individual or small group of faculty for development based on faculty expertise and interest. Terminal objectives (i.e., "what to do") were defined for each presentation to describe the appropriate clinical behaviors of a graduating physician. Experts developed schemes that outlined how they differentiated one cause (i.e., disease category) from another. The underlying enabling objectives (i.e., knowledge, skills, and attitudes) for reaching the terminal objectives for each clinical presentation were assigned as departmental responsibilities. A new administrative structure evolved in which there is a partnership between a centralized multidisciplinary curriculum committee and the departments. This new competency-based, clinical presentation curriculum is expected to significantly enhance students' development of clinical problem-solving skills and affirms the premise that prudent, continuous updating is essential for improving the quality of medical education.

Anaesthetic management of a patient with a descending thoracic aortic aneurysm and severe bilateral bullous pulmonary parenchymal disease

The anaesthetic management of the surgical repair of a descending aortic aneurysm in a patient with large, bilateral, pulmonary bullae is described. Anaesthesia for descending aortic surgery normally involves unilateral, positive-pressure ventilation, an option which poses some risk of barotrauma in the presence of bilateral bullae. Patients with bullous disease commonly have severe lung disease and thorough preoperative assessment and preparation are necessary. Intraoperatively, bilateral rupture of the bullae could be catastrophic and preparations should be made for this possibility. In order to diminish this risk, a surgical technique including preemptive collapse of the bulla by minithoracotomy and tube drainage, with use of a bronchial blocker to the affected part of the lung may be used. If rupture occurs, then high frequency jet ventilation may be effective. Use of a double lumen endobronchial tube may be advantageous for patients with either unilateral and bilateral bullae. Anaesthesia for patients with bullae should avoid positive-pressure ventilation and nitrous oxide in order to limit the risk of barotrauma from a ball valve mechanism. In this case, the risk of barotrauma was reduced by performing an inhalational induction of anaesthesia and limiting peak inflation pressures during thoracotomy. It was elected to use positive-pressure ventilation through a double lumen endobronchial tube following chest incision. A high frequency jet ventilator was available but not employed. Anaesthetic management was complicated by the presence of pleural adhesions, surgical approach directly through a bulla, and the requirement for one lung ventilation.

Anaesthesia and education

A literature review was undertaken to document the status of anaesthetic education in both the peer-reviewed anaesthesia and medical education literature. A search was performed using Silver Platter for the period 1983-91, and the most widely circulated medical education and anaesthesia journals in North America were reviewed in detail. Although anaesthetists are involved in many educational activities, the literature is oriented towards postgraduate training. Common issues include the assessment and selection of residents. Newer methods of evaluation, for example, daily assessment by preceptors, have been described, but work continues to be needed on these and older methods, such as oral examinations. Selection processes may be improved by incorporating psychological and psychomotor measures in the assessment process. A limited number of teaching methods, especially simulators, have been the focus of much interest, while other methods, such as bedside teaching, have received little attention. Programs of recertification or maintenance of competence, which have been announced by certifying bodies, may place new emphasis on the study of the design, effectiveness, and outcome of continuing medical education. In conclusion, the review revealed that there are many opportunities for anaesthetists to conduct educational research into many traditional and new areas of medical education.

Caesarean section in a patient with Cushing's syndrome

Pregnancy is rarely associated with Cushing's syndrome. This case report describes the successful management of a Caesarean section under epidural anaesthesia in a patient with Cushing's syndrome. Maternal and fetal complications are reviewed from an anaesthetic perspective and alternative anaesthetic techniques discussed.