These data suggest that VEGF-R2 phosphorylation is necessary for VEGF-A-mediated increases in microvascular permeability in vivo.

2516 Background: A key metabolic alteration in tumour cells is an increased dependency on the glycolysis, resulting in the production of lactate, which is transported out of cells by MCTs. Inhibition of MCT-1 leads to a profound inhibition of cancer cell growth in preclinical models. AZD3965 is a FIC inhibitor of MCT-1, and we report results from the phase I study of this agent. Methods: Patients with advanced solid tumours were treated with oral (po) AZD3965 at total daily doses of 5-30mg given once (od) and twice daily (bd). Exclusion criteria included a history of retinal or cardiac disease due to preclinical toxicology findings in the eye and heart (which express MCT-1). The primary objectives were to determine the safety, dose limiting toxicities (DLT) and maximum tolerated dose (MTD) of AZD3965. Intensive pharmacokinetic (PK) profiling was performed with subsequent modelling for receptor occupancy. Pharmacodynamic profiling included imaging to detect pH changes and tumour glucose uptake; plasma/urine metabolomics and MCT-1 and MCT-4 tumour expression by immunohistochemistry. Results: 35 patients (20M:15F median age 65) were treated at dose levels 5, 10, 20, and 30mg od and 15 and 10mg bd. AZD3965 was generally well tolerated with nausea and fatigue (CTCAE Gr1-2) the most commonly reported side effects. A single DLT of cardiac troponin rise was observed at 20mg od. Asymptomatic, reversible retinal ERG changes were observed in all but the lowest dose levels, with DLTs observed at doses above 20mg od. PK data indicate exposures in the preclinical efficacy range. Metabolomic changes in urinary lactate and urinary ketones correlate with on-target activity. The increase in urinary ketones is likely to be attributable to the role of MCT1 in physiological ketone transport. Conclusions: The MCT1 inhibitor AZD3965 can be administered to patients at doses which engage the drug target, with a MTD of 20mg od po. DLTs seen were primarily dose dependent, asymptomatic and reversible changes in retinal function, which were an expected on-target effect. Investigation of the activity of AZD3965 is ongoing in tumours known to express MCT1. Clinical trial information: NCT01791595.

Androgen receptor variants (AR-Vs) provide a mechanism of therapy evasion in castrate-resistant prostate cancer (CRPC), yet mechanisms of regulation remain largely unknown. Here we investigate the role of Aurora A kinase on AR-Vs in models of CRPC and show depletion of Aurora A reduces AR-V target gene expression. Importantly, knockdown of Aurora A reconfigures splicing of AR pre-mRNA to discriminately down-regulate synthesis of AR-V transcripts, including AR-V7, without effecting full-length AR mRNA; and as a consequence, AR-V-driven proliferation and survival of CRPC cells is markedly reduced. Critically, these effects are reproduced by Aurora A inhibition. We show that Aurora A levels increase in advanced disease and AURKA is an AR-V target gene demonstrating a positive feedback mechanism of androgenic signalling in CRPC. In all, our data suggests that Aurora A plays a pivotal role in regulation of AR-V7 expression and represents a new therapeutic target in CRPC.

The persistence of androgen receptor (AR) signalling in castrate-resistant prostate cancer (CRPC) highlights the unmet clinical need for the development of more effective AR targeting therapies. A key mechanism of therapy-resistance is by selection of AR mutations that convert anti-androgens to agonists enabling the retention of androgenic signalling in CRPC. To improve our understanding of these receptors in advanced disease we developed a physiologically-relevant model to analyse the global functionality of AR mutants in CRPC. Using the bicalutamideactivated AR W741L/C mutation as proof of concept, we demonstrate that this mutant confers an androgenic-like signalling programme and growth promoting phenotype in the presence of bicalutamide. Transcriptomic profiling of AR W741L highlighted key genes markedly up-regulated by the mutant receptor, including TIPARP, RASD1 and SGK1. Importantly, SGK1 expression was found to be highly expressed in the KUCaP xenograft model and a CRPC patient biopsy sample both of which express the bicalutamide-activated receptor mutant. Using an SGK1 inhibitor, AR W741L transcriptional and growth promoting activity was reduced indicating that exploiting functional distinctions between receptor isoforms in our model may provide new and effective therapies for CRPC patients.

Lometrexol is an antifolate which inhibits glycinamide ribonucleotide formyltransferase (GARFT), an enzyme essential for de novo purine synthesis. Extensive experimental and limited clinical data have shown that lometrexol has activity against tumours which are refractory to other drugs, notably methotrexate. However, the initial clinical development of lometrexol was curtailed because of severe and cumulative antiproliferative toxicities. Preclinical murine studies demonstrated that the toxicity of lometrexol can be prevented by low dose folic acid administration, i.e. for 7 days prior to and 7 days following a single bolus dose. This observation prompted a Phase I clinical study of lometrexol given with folic acid supplementation which has confirmed that the toxicity of lometrexol can be markedly reduced by folic acid supplementation. Thrombocytopenia and mucositis were the major toxicities. There was no clear relationship between clinical toxicity and the extent of plasma folate elevation. Associated studies demonstrated that lometrexol plasma pharmacokinetics were not altered by folic acid administration indicating that supplementation is unlikely to reduce toxicity by enhancing lometrexol plasma clearance. The work described in this report has identified for the first time a clinically acceptable schedule for the administration of a GARFT inhibitor. This information will facilitate the future evaluation of this class of compounds in cancer therapy.