In vitro activity: Imaradenant (AZD4635; HTL-1071) is a novel, potent, selective, orally bioavailable small molecule inhibitor of the adenosine A2A receptor (A2AR) with Ki of 1.7 nM. It binds to human A2AR with a Ki of 1.7 nM and with> 30-fold selectivity over other adenosine receptors. The blockade of A2aR signaling with an inhibitor such as AZD4635 can reduce tumor burden and enhance antitumor immunity. AZD4635 is 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. Accumulation of extracellular adenosine within the microenvironment is a strategy exploited by tumors to escape immunosurveillance. Adenosine signaling through the high affinity adenosine 2A receptor (A2AR) on immune cells elicits a range of immunosuppressive effects which can promote tumor growth and limit the efficacy of immune checkpoint inhibitors such as anti-PD-1 or anti-PD-L1 Abs.

Kinase Assay: It binds to human A2AR with a Ki of 1.7 nM and with> 30-fold selectivity over other adenosine receptors.

Cell Assay: CHO cells stably expressing human A2AR were incubated with concentrations of adenosine ranging from 0.1 to 10 μM. In the presence of 0.1, 1 and 10 μM adenosine, the IC50 of AZD4635 for inhibition of cAMP production was 0.79, 10.0 and 142.9 nM, respectively. In an ex vivo CD8+ T cell assay, AZD4635 reversed suppression and restored IFNγ secretion in cells incubated with 5’-N-ethylcarboxamidoadenosine (NECA), a stable analog of adenosine.