ABSTRACT:Prostate cancer (PCa) is a multifaceted, heterogeneous disease (with 7 molecular subtypes), which can metastasize to common sites, such as bone, lymph nodes, liver, and lungs. However, with PSMA PET imaging, rare sites of metastasis are increasingly discovered. We report 5 cases of unusual metastases in patients with castrate-sensitive PCa: solitary right inguinal nodal metastasis, solitary abdominal wall metastasis, penile shaft metastases, solitary perineum metastasis, and pleural metastases. These cases further support the use of PSMA-PET imaging in PCa monitoring, with the ability to detect solitary, small volume, and rare sites of metastases, which may not be apparent on conventional imaging.

Metabolic syndrome (MetS) is a pathological condition characterized by abdominal obesity, insulin resistance, hypertension, and hyperlipidemia. Sirtuin 1 (SIRT1), a highly conserved histone deacetylase, is characterized as a key metabolic regulator and protector against aging-associated pathologies, including MetS. In this study, we investigate the therapeutic potential of activating SIRT1 using small activating RNAs (saRNA), thereby reducing inflammatory-like responses and re-establishing normal lipid metabolism. SIRT1 saRNA significantly increased SIRT1 messenger RNA (mRNA) and protein levels in both lipopolysaccharide-stimulated and nonstimulated macrophages. SIRT1 saRNA significantly decreased inflammatory-like responses, by reducing mRNA levels of key inflammatory cytokines, such as Tumor Necrosis Factor alpha, Interleukin 1 beta (IL-1β), Interleukin 6 (IL-6), and chemokines Monocyte Chemoattractant Protein-1 and keratinocyte chemoattractant. SIRT1 overexpression also significantly reduced phosphorylation of nuclear factor-κB and c-Jun N-terminal kinase, both key signaling molecules for the inflammatory pathway. To investigate the therapeutic effect of SIRT1 upregulation, we treated a high-fat diet model with SIRT1 saRNA conjugated to a transferrin receptor aptamer for delivery to the liver and cellular internalization. Animals in the SIRT1 saRNA treatment arm demonstrated significantly decreased weight gain with a significant reduction in white adipose tissue, triglycerides, fasting glucose levels, and intracellular lipid accumulation. These suggest treatment-induced changes to lipid and glucose metabolism in the animals. The results of this study demonstrate that targeted activation of SIRT1 by saRNAs is a potential strategy to reverse MetS.

4601 Background: MTL-CEBPA is the first small activating RNA to enter clinical trials and upregulates C/EBPα, a master regulator of myeloid cell differentiation. We previously reported a favourable safety profile of MTL-CEBPA as a single agent in HCC (Sarker D et al, ASCO 2018). After discontinuation of MTL-CEBPA, 3 out of 5 patients (pts) treated with sorafenib off study had a complete response (CR) of 7-18 months duration; 2 pts of which demonstrated resolution of lung metastases for > 1 year. Here we provide new data on pts prospectively treated with MTL-CEBPA + sorafenib. Methods: Primary objective was to assess safety and tolerability of MTL-CEBPA 90-130mg/m 2 QW or BIW in combination with sorafenib 400mg BD administered to HCC patients either concomitantly or sequentially, in cohorts either tyrosine kinase inhibitor (TKI) naive or resistant. Secondary objectives included preliminary assessment of activity by response rate (RECIST v1.1) and immune landscape analysis. Results: As at the cut off date of 1 Feb 2020, 12 pts have been treated with MTL-CEBPA co-administered with sorafenib and 14 pts with MTL-CEBPA followed by sorafenib (23M/3F, median age 65.5years, range 44-83, ECOG PS 0/1: 18/8). The most common treatment-related AEs (all grades/grade 3-4) in these groups include facial flushing (4/0), raised AST (4/2) raised ALT (2/1), fatigue (5/0), raised ALP (2/0), and anaemia (2/2), diarrhoea (3/0), rash (2/0) and anorexia (1/0). Of 14 evaluable pts in the TKI naive cohorts, 2 pts had CR, 3 pts had partial response and 7 had stable disease. 9/10 pts in the TKI resistant cohorts evaluable for efficacy had stable disease. Flow cytometry demonstrated statistically significant decreases in frequency of immature CD66 + CD10 − neutrophils and myeloid derived suppressor cells. IHC demonstrated significant reduction in M2 macrophages in tumour biopsies. Conclusions: MTL-CEBPA + sorafenib is well tolerated with an acceptable safety profile. This study has confirmed signals of objective response to the combination treatment in TKI naïve HCC patients with viral aetiology, warranting expanded development in these patients. Updated efficacy and safety data will be presented. Clinical trial information: NCT02716012. [Table: see text]

Targeted delivery of oligonucleotides to liver hepatocytes using N-acetylgalactosamine (GalNAc) conjugates that bind to the asialoglycoprotein receptor has become a breakthrough approach in the therapeutic oligonucleotide field. This technol-ogy has led to the approval of givosiran for the treatment of acute hepatic porphyria, and there are another seven conju-gates in registrational review or phase 3 trials and at least another 21 conjugates at earlier stages of clinical development. This review highlights some of the recent chemical and preclin-ical advances in this space, leading to a large number of clinical candidates against a diverse range of targets in liver hepato-cytes. The review focuses on the use of this delivery system for small interfering RNAs (siRNAs) and antisense molecules that cause downregulation of target mRNA and protein. A number of other approaches such as anti-microRNAs and small activating RNAs are starting to exploit the technology, broad-ening the potential of this approach for therapeutic oligonucle-otide intervention.

554 Background: MTL-CEBPA is the first saRNA to enter clinical trials and targets the transcription factor C/EBPα, a master regulator of myeloid cell differentiation. We have previously reported a favourable safety profile of MTL-CEBPA given as a single agent QWx3 every 28 days, in patients with HCC (Sarker D et al, ASCO 2018). After discontinuation of MTL-CEBPA, three out of five patients treated with sorafenib off study have had maintained complete radiological response (CR) of 7-18 months duration; 2 patients demonstrated resolution of lung metastases > 1 year. Here we provide updated data on phase 1 patients treated with sorafenib off study as well as subsequent combination cohorts. Methods: MTL-CEBPA 130mg/m 2 QWx3 or BIW and sorafenib 400mg bd were administered to patients with HCC using combination or sequential dosing regimens, in cohorts either tyrosine kinase inhibitor naive or resistant. On treatment liver biopsies evaluated changes in M2 macrophages (CD163). Flow cytometry of peripheral blood determined changes in myeloid cell populations. Results: 12 patients have been treated with MTL-CEBPA co-administered with sorafenib and 14 patients treated with MTL-CEBPA followed by sorafenib (23M/3F, median age 65.5years, range 44-83, ECOG PS 0/1: 18/8). The most common treatment-related AEs (all grades/grade 3) in this group include facial flushing (4/0), raised AST (3/1) raised ALT (2/1), fatigue (5/0), raised ALP (2/0), and anaemia (2/2), diarrhoea (3/0), rash (2/0) and anorexia (1/0). 1 TKI naïve patient in the co-administration cohort has maintained CR at 7 months and two patients have SD (ongoing at 3 & 4 months both in sequential cohort). IHC in the patient with CR has demonstrated 95% reduction in M2 macrophages with significant decrease in frequency of immature CD10- neutrophils (-85.7%; p = 0.0078), PMN-MDSCs (-49.3%; p = 0.00145) and M-MDSCs (-18.4%; P = 0.0072). All responding patients have underlying HBV or HCV. Conclusions: MTL-CEBPA is a novel saRNA targeting myeloid cells which may result in a significantly enhanced oncological response in HCC of viral aetiology. Updated safety and efficacy data will be presented. Clinical trial information: NCT02716012.

The transcription factor CEBPA (CCAAT/enhancer-binding protein alpha) is recognised for its antiproliferative effects. MTL-CEBPA is a small activating RNA drug which upregulates gene expression of CEBPA and amongst other effects causes and immunomodulatory effect on peripheral granulocytes. Radiofrequency ablation (RFA) is standard treatment for some tumour types such as liver cancer and induces modulation of both innate and adaptive immune systems. To investigate any synergistic effect of MTL-CEBPA with RFA and immune checkpoint inhibition we initiated a reverse translation experiment, where syngeneic BNL hepatocellular carcinoma tumour cells were injected in the two opposite flanks of immunocompetent BALB/c mice (n=8 in each group). Treatments for hepatoma bearing mice included: 1) RFA on one flank (day 0), 2) Anti-PD-1 inhibition immunotherapy (RMP1-14 antibody, BioXCell, West Lebanon, NH, USA at 200 μg IV/mouse/dose on days 0, 2 & 5) and 3) MTL-CEBPA (3mg/kg IV/mouse/dose on days 0, 2 & 5) as well as combinations of all 3 interventions. We found that tumour control on the opposite flank was augmented by addition of RFA and most significant in the triple combination group (RFA + anti-PD1 + MTL-CEBPA) in which 2/8 animals showed a complete response and 5/8 a partial response. This was also the only group that showed a statistically significant increase in CD8+ (Cytotoxic) as well as CD49b+/CD45+ (Natural Killer) tumour infiltrating lymphocytes. These data suggest a clinical role for combination treatment with checkpoint blockade, RFA and MTL-CEBPA through synergistic priming of the immune tumour response, enabling RFA to have a pronounced anti-tumour abscopal effect. Citation Format: Mikael H. Sodergren, Kai-Wen Huang, Vikash Reebye, Cheng-Ean Chee, Dimitris Zacharoulis, Robert Habib, David Blakey, John Rossi, Nagy Habib. MTL-CEBPA combined with radiofrequency ablation and immunotherapy enhances immunological anti-tumour response in an HCC mouse model [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 3211.

INTRODUCTION:Cancer Australia guidelines recommend that hypofractionation should be considered for women over the age of 50 years with early breast cancer. GenesisCare is the largest provider of radiation therapy services in Australia. This study aimed to investigate variation in hypofractionation across 4 states encompassing the period when the most recent guidelines had been released.METHODS:Patients with T1 N0 and T2 N0 breast cancer who received radiation therapy as adjuvant therapy after breast conservation surgery between 2014 and 2016 were reviewed. Patient, treatment and disease-related variables were included in the univariate and multivariate models together with other potential explanatory variables such as the state, in which the patient was treated, radiation oncologist and distance from the treatment centre.RESULTS:Of 3374 patients included, 44% received a hypofractionated schedule. There was an increase in the use of hypofractionation from 32% in 2014 to 56% in 2016. Older patients were more likely to receive a hypofractionated treatment schedule - 75% for patients 80 years and over. Multivariate modelling revealed older age, year of treatment, higher T stage and grade, chemotherapy and the individual radiation oncologist (and state) as independent predictors of the use of hypofractionation. There was no difference in hypofractionation based on laterality.CONCLUSIONS:Guidelines from Cancer Australia may impact clinician behaviour. The influence of the individual radiation oncologist remains paramount, and their practice is affected by their immediate colleagues. Subsequent analysis of hypofractionation rates after presentation of these data has resulted in a significant increase in its use.

Small activating RNAs (saRNAs) are short double-stranded oligonucleotides that selectively increase gene transcription. Here, we describe the development of an saRNA that upregulates the transcription factor CCATT/enhancer binding protein alpha (CEBPA), investigate its mode of action, and describe its development into a clinical candidate. A bioinformatically directed nucleotide walk around the CEBPA gene identified an saRNA sequence that upregulates CEBPA mRNA 2.5-fold in human hepatocellular carcinoma cells. A nuclear run-on assay confirmed that this upregulation is a transcriptionally driven process. Mechanistic experiments demonstrate that Argonaute-2 (Ago2) is required for saRNA activity, with the guide strand of the saRNA shown to be associated with Ago2 and localized at the CEBPA genomic locus using RNA chromatin immunoprecipitation (ChIP) assays. The data support a sequence-specific on-target saRNA activity that leads to enhanced CEBPA mRNA transcription. Chemical modifications were introduced in the saRNA duplex to prevent activation of the innate immunity. This modified saRNA retains activation of CEBPA mRNA and downstream targets and inhibits growth of liver cancer cell lines in vitro. This novel drug has been encapsulated in a liposomal formulation for liver delivery, is currently in a phase I clinical trial for patients with liver cancer, and represents the first human study of an saRNA therapeutic.

Autotaxin (ATX) is a secreted phosphodiesterase that cleaves lysophosphatidylcholine (LPC) in serum to produce lysophosphatidic acid (LPA). LPA can signal through a family of GPCR receptors to mediate cell proliferation, migration and survival in cancer cells. Blocking the enzymatic activity of ATX is proposed to have anti-tumour activity by reducing levels of LPA and preventing signaling through the LPA receptor family. A number of synthetic inhibitors have been developed to understand the role in ATX in driving carcinogenesis and these encompass lipid substrate mimetics as well as inhibitors identified from small molecule library screens. Some of these compounds demonstrate low nM activity in vitro and a subset have shown some in vivo activity although none have progressed into the clinic. We sought to identify novel selective ATX antibodies with low nM affinity, which fully inhibited ATX enzyme activity of human, cyno and mouse ATX protein. Using an ATX enzyme inhibition assay we identified and characterised two ATX antibodies, 9E10 and 18B7 which, interestingly, had different binding mechanisms of inhibition and showed potent cross-species inhibition of ATX in vitro. We measured human and mouse ATX expression levels across of panel of xenograft models and verified ATX activity by measuring cleavage of an ATX substrate using conditioned media from these cells. 9E10 and 18B7 antibodies were shown to inhibit the activity of secreted ATX and prevent cleavage of an ATX substrate. 9E10 and 18B7 showed significant inhibition of LPC stimulated cell growth and IL-8 secretion in a range of ATX and/or LPA responsive tumour cell lines. In ex vivo plasma ATX activity assays, treatment of mouse or human plasma with the ATX antibodies inhibited the increase in LPA levels that are observed over time when serum samples are incubated at 37°C. In summary we have identified highly selective ATX antibody inhibitors which will be useful tools to explore the role of ATX in tumour growth and invasion. Citation Format: Sarah Ross, Scott Collins, Jelena Jovanovic, Jane Kendrew, Simon Barry, Swami Rathanaswami, Blakey David, Hazel Weir. Novel autotaxin inhibitory antibodies block lysophosphatidic acid production in plasma and tumour cell proliferation in vitro. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr A152.

Platelet-derived growth factor receptor α (PDGFRα) is a receptor tyrosine kinase that promotes cell survival and is expressed in both the tumor and the stromal components of human cancers. We have developed a fully human monoclonal antibody, MEDI-575, that selectively binds to human PDGFRα with high affinity, with no observable affinity for murine PDGFRα. To more fully characterize the role of PDGFRα in the regulation of tumor stroma, we evaluated the in vivo antitumor effects of MEDI-575 in tumor-bearing severe combined immunodeficient (SCID) mice and in genetically altered SCID mice expressing human PDGFRα in place of murine PDGFRα. We used the Calu-6 non-small cell lung cancer model because it lacks an in vitro proliferative response to PDGFRα activation. Antitumor activity was observed when the study was performed in mice expressing the human receptor, but no activity was observed in the mice expressing the murine receptor. Immunohistologic analysis of the tumors from mice expressing human PDGFRα showed a highly significant reduction in stromal fibroblast content and only minor changes in tumor proliferative index in tumors exposed to MEDI-575 compared with the results seen in vehicle-treated tumors or in tumors from mice expressing murine PDGFRα. Additional in vitro studies indicated that exposure of primary cancer-associated fibroblasts to MEDI-575 can directly affect proliferation and key signaling pathways in these cells. These results highlight the potential for observing antitumor activity with MEDI-575 through modulation of the stromal component of tumors and confirm that the PDGFRα pathway can play a role in maintaining a tumor microenvironment conducive to tumor growth.

Neutrophils are important innate immune cells that are involved in microbial clearance at sites of infection and in wound healing. The microenvironment of tumors often resembles that of chronic inflammation and increased numbers of neutrophils have been observed in several tumors and, in some cases, these positively correlate with poor prognosis. Neutrophil recruitment into tumors appears to be dependent on chemokines that bind to CXCR1 and CXCR2 expressed by neutrophils. In our study, we used lung adenocarcinoma A549 multicellular tumor spheroids and A549 tumor xenografts along with a CXCR2-specific small molecule inhibitor (AZ10397767) to investigate the recruitment and function of human neutrophils in tumors. We found that A549 spheroids constitutively secrete high levels of CXCL chemokines and that neutrophil recruitment into A549 tumors in vitro and in vivo is largely dependent on CXCR2 activation. AZ10397767 significantly reduced the numbers of infiltrating neutrophils into both in vitro and in vivo tumor models, which was associated with slower growing tumors. Neutrophil infiltration into A549 tumor spheroids increased their size compared to noninfiltrated spheroids and neutrophil-derived factors increased the proliferation of A549 tumor cells and induced endothelial cell tubule formation in vitro. In contrast, we saw no reduction in microvascular density in AZ10397767-treated A549 tumors or in tumors grown in CXCR2(-/-) mice, suggesting that angiogenesis in these tumors is CXCR2-independent. Our data show that neutrophils can contribute to lung tumor growth and that CXCR2 antagonists may be a useful therapeutic agent in the treatment of lung carcinomas.

Antibody 3.19.3 is a novel human antibody that binds to the angiogenic ligand ANG-2 leading to inhibition of Tie-2 receptor phosphoryation in vitro and significant anti-tumor activity as a single agent in preclinical tumor models. In these studies the ability of antibody 3.19.3 to enhance the activity of both small molecule and antibody VEGF pathway inhibitors has been investigated. Human colorectal tumour cells (LoVo, HT29, SW620) were implanted subcutaneously in athymic nude mice and once tumors had reached ~ 100-150 mm3 treatment with either 3.19.3 antibody alone (10 mg/kg twice weekly), VEGF inhibitor alone (Vandetanib-50mg/kg daily, Cediranib- 1.5 mg/kg daily or DC101 murine KDR antibody - 15 mg/kg twice weekly) or a combination of the two agents was initiated. The results of these studies are summarized in Table 1. In all 3 tumor models both the 3.19.3 antibody and the VEGF pathway inhibitor demonstrated significant anti-tumor activity that was enhanced by combining both agents. The combination arm gave significantly (P $$table_{EBEA0BC8-25DC-487B-A178-CFADB600BA2B}$$ > Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 127.

In spite of the widespread use of Rituximab, a chimeric monoclonal antibody with demonstrated efficacy in the treatment of non-Hodgkin's lymphomas, there is a recognized need to develop fully human antibodies with improved efficacy. Towards this end, using XenoMouse™ technology, a fully human IgG1 monoclonal antibody specific to human CD20 was generated. This antibody, denoted mAb 1.5.3, evoked enhanced pro-apoptotic activity in vitro, as compared to Rituximab, in the Ramos human lymphoma cell line. In addition, mAb 1.5.3 was active in mediating complement dependent cytotoxicity (CDC) and elicited improved antibody-dependent cellular cytotoxicity (ADCC) relative to Rituximab in Ramos, Raji, and Daudi human B-lymphoma lines. To recapitulate various aspects of acquired resistance to Rituximab, as observed in a subpopulation of patients, Rituximab-resistant clones were established from lymphoma lines. Interestingly, mAb 1.5.3 demonstrated superior cytolytic activity against engineered Rituximab-refractory lymphoma clones, as well as across multiple human B-lymphoma and chronic B-cell leukemia lines in an in vitro whole blood assay. Furthermore, mAb 1.5.3 exhibited enhanced anti-tumor activity in Rituximab-sensitive cell lines and -refractory engineered lymphoma clones in vivo. Lastly, mAb 1.5.3 produced a superior B-cell depletion profile in lymph node organs and bone marrow as compared to Rituximab in a primate PD model. In contrast to Rituximab, mAb 1.5.3 is a fully human antibody and is thus anticipated to exhibit a longer serum half-life with minimal immunogenicity following repeated administration. In sum, these results demonstrate the superior anti-tumor activity of mAb 1.5.3 relative to Rituximab and its potential for improved clinical activity in the treatment of B-cell malignancies.

Carboxypeptidase G2 (CPG2) is a powerful prodrug-converting enzyme. Without a requirement for endogenous enzymes or cofactors, it can directly activate mustard alkylating prodrugs to cytotoxic species, killing both quiescent and dividing cells. This paper provides the first report of its use in the context of a clinically relevant delivery vehicle using adenovirus vectors. To strengthen the efficacy of the prodrug-activating system, the enzyme has been engineered to be secreted or glycosylphosphatidylinositol (GPI) anchored to the extracellular membrane of tumor cells, resulting in an enhanced bystander effect by facilitating diffusion of the active drug through extracellular, rather than intracellular, activation. Using the vectors, we have achieved expression of functional secreted or GPI-anchored CPG2 in a panel of tumor cell lines demonstrating no loss in efficacy as a result of GPI anchor retention. Despite variable transduction efficiencies inherent to these vectors, greater than 50% cell kill was achievable in all of the cell lines tested following only a single exposure to the prodrug ZD2767P. Even in cell lines refractive to infection with the vectors, substantial cell death was recorded, indicative of the enhanced bystander effect generated following extracellular prodrug activation. A direct evaluation of the efficacy of our system has been made against adenoviral delivery of herpes simples virus thymidine kinase plus ganciclovir (GCV), a suicide gene therapy approach already in the clinic. In a short-term human glioma culture (IN1760) resistant to the clinical chemotherapeutic drug CCNU (1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea), thymidine kinase/GCV effected no cell killing compared to 70% cell killing with our system.