Inhibition of A(2A)R by AZD4635 induces anti-tumor immunity alone and in combination with anti-PD-L1 in preclinical models

Adenosine signaling through the high affinity adenosine 2A receptor (A 2A R) on immune cells elicits a range of immunosuppressive effects which can promote tumor growth and limit the efficacy of immune checkpoint inhibitors. AZD4635 (HTL-1071) is a potent and selective oral A 2A R antagonist, currently in a Phase 1 clinical trial as a single agent and in combination with durvalumab (anti-PD-L1 Ab) in patients with solid malignancies. In functional in vitro assays, the IC 50 of AZD4635 for inhibition of A 2A R signaling is dependent on adenosine concentrations and ranges from 1, 10.0, 143 nM in the presence of 0.1, 1, 10 μM adenosine, respectively. However, full understanding of the impact of adenosine on AZD4635 mediated anti-tumor responses requires characterization of intratumoral adenosine concentration and spatial heterogeneity. Using a novel LC/MS based method, measurement of intratumoral adenosine concentrations in a panel of syngeneic tumor models demonstrated a wide range of adenosine levels (5-122 μM). Additionally, measurement of intratumoral adenosine by desorption electrospray ionisation - mass spectroscopy (DESI-MS) demonstrated that adenosine levels are spatially heterogeneous, with levels varying up to 50-fold among regions of a single tumor. High intratumoral adenosine concentrations were correlated with decreased intratumoral CD8 infiltration in vivo. The therapeutic benefit of A 2A R blockade alone and in combination with anti-PD-L1 was evaluated in a panel of syngeneic mouse tumor models with varying adenosine concentrations. In sensitive models, inhibition of A 2A R signaling with AZD4635 led to a dose dependent reduction in tumor growth alone and in combination with checkpoint inhibitors. Tumors harvested from the treated mice exhibited increases in the functional activity of T cell and myeloid subsets. These results demonstrate that AZD4635 is a potent and selective A 2A R inhibitor, that blockade of A 2A R signaling with an inhibitor such as AZD4635 can reduce tumor burden and enhance antitumor immunity. Citation Format: Alexandra Borodovsky, Yanjun Wang, Minwei Ye, Joseph C. Shaw, Kris Sachsenmeier, Nanhua Deng, Kelly Goodwin, James D. Clarke, Richard Goodwin, Nicole Strittmatter, Carl Hay, Vasu Sah, Lawson Deborah, Corinne Reimer, Miles Congreve, Jonathan Mason, Fiona Marshall, Paul Lyne, Richard Woessner. Inhibition of A 2A R by AZD4635 induces anti-tumor immunity alone and in combination with anti-PD-L1 in preclinical models [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 3751.