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3115 Background: Tumours rely on lactate transporters (MCT1-4) to maintain glycolytic flux and avoid intracellular acidification. In haematological tumours the MCT1 transporter acts as a lactate and pyruvate exporter. AZD3965 is a potent and specific inhibitor of MCT1 causing intracellular lactate accumulation. In vivo efficacy was observed in xenografts of DLBCL and BL, expressing high levels of MCT1 and no or low levels of MCT4. In the AZD3965 phase I (NCT01791595) dose-escalation an oral recommended phase 2 dose (RP2D) of 10mg twice-daily (bd) was determined. Pharmacokinetic (PK) showed exposure estimated to produce a minimum MCT1 occupancy of 90% (based on modelling). DLTs were primarily on-target dose-dependent, reversible, asymptomatic alterations in retinal function seen on ERG. Methods: This expansion cohort enrolled patients with relapsed/refractory DLBCL and BL. Expression of MCT1/MCT4 was assessed by immunohistochemistry. Pharmacokinetic (PK) sampling was performed and pharmacodynamic assessments included [18F]FDG-PET/CT imaging and plasma/urine metabolomics. Results: 11 DLBCL patients were treated with AZD3965 10mg bd. PK showed exposure to be broadly in line with the escalation cohort. No significant ERG changes were observed. One patient experienced a dose-limiting SUSAR of Troponin I increase. MCT1 is expressed in erythrocytes, however no serious events of anaemia were seen, with one non-clinically significant episode of grade 3 anaemia reported. Urine analysis showed increased excretion of lactate and ketone bodies post AZD3965 treatment consistent with renal target engagement. No alteration was detected in plasma. Ongoing stable disease at cycle 5 was observed in one patient and an additional patient had a confirmed complete response (CR) lasting 15 months, with no significant toxicity. In the patient showing CR a reduction in tumour FDG uptake was observed on day 3 of cycle 1. The other four patients who consented to research imaging did not have a clinical response and no changes were observed on FDG-PET. Conclusions: AZD3965 can be safely administered at 10mg bd. In one DLBCL patient monotherapy activity was observed with changes in FDG-PET providing evidence indicative of proof of mechanism. These changes in FDG uptake as early as on day 3 in the responding patient warrant further investigation of FDG-PET as a predictive biomarker. Further biomarker analysis and preclinical studies are ongoing to understand the biology and explore effective combinations with other agents targeting tumour cell metabolism 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.

We investigated the cellular response to two MDM2-p53 antagonists (RG7388 and Cpd 1) in a panel of 19 tumor cell lines and in patient-derived chronic lymphocytic leukemia (CLL) cells. RG7388 (Idasanutlin) is an MDM2-p53 antagonist developed by Roche and Cpd1 a novel potent and selective MDM2-p53 antagonist developed as part of an ongoing Alliance between Newcastle University, Cancer Research UK and Astex Pharmaceuticals. RG7388 and Cpd1 potently inhibited the proliferation of many cell lines, with MDM2-amplified SJSA-1 osteosarcoma cells and cells from haematological malignancies being the most sensitive (e.g. GI50 values in the acute myeloid leukemia cell line MOLM13 were 33 + 16 nM for RG7388 and 8 + 1 nM for Cpd 1). We also examined induction of apoptosis by measuring caspase 3/7 activation (24 h treatment). SJSA-1 cells showed a 20-fold increase in caspase activation and Molm13 cells a 6-fold increase (measured at 300nM with RG7388). However, cell lines from solid tumours such as the colorectal carcinoma HCT116 or the hepatocellular carcinoma HepG2 did not show any induction of apoptosis, even at concentrations up to 1µM RG3788. In primary CLL cells, Cpd 1 reduced cell viability (48 h) with an average LC50 of 131 + 46 nM (n = 4), compared to 400 + 55 nM for RG7388 (n =23). We also quantified mRNA levels in 25 primary CLL samples and found that RG7388 induced a predominantly pro-apoptotic gene signature: following 6h treatment, 1µM RG7388 resulted in an average 8-fold induction of PUMA and 3.5-fold increase in BAX compared to a 1.6-fold induction of CDKN1A (p21). Our data confirm that targeting the MDM2-p53 interaction is an effective strategy to inhibit growth and viability of tumor cells, and that some cells, including those expressing high levels of MDM2 or those derived from hematological malignancies, display a striking apoptotic response. Citation Format: Elaine Willmore, Yan Zhao, Carmela Ciardullo, Laura Woodhouse, Huw D. Thomas, Maria Ahn, Lynsey Fazal, Martin E. Noble, Ian Hardcastle, Steven Howard, Gianni Chessari, John Lunec, Steve Wedge. The anti-proliferative and pro-apoptotic effect of MDM2-p53 antagonists evaluated in human tumor cells lines and chronic lymphocytic leukemia patient samples [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 1870.