Abstract 5593: Inhibition of A2AR induces anti-tumor immunity alone and in combination with anti-PD-L1 in preclinical and clinical studies

Abstract

Abstract Adenosine signaling via A2A receptor (A2AR) on immune cells suppresses anti-tumor immunity and limits the efficacy of immunotherapy, chemotherapy, CAR-T, and vaccines. CPI-444 is a potent and selective oral A2AR antagonist. Daily treatment of mice with CPI-444 led to dose-dependent inhibition of tumor growth in multiple syngeneic tumor models. Combining CPI-444 with anti-PD-L1 treatment synergistically eliminated tumors in up to 90% of treated mice, including restoration of immune responses in models that are poorly responsive to anti-PD-1 or anti-PD-L1 monotherapy. We have initiated a Phase 1/1b clinical trial to examine safety, tolerability, biomarkers, and preliminary efficacy of CPI-444 as a single agent and in combination with the anti-PD-L1 antibody, atezolizumab, in patients with non-small cell lung, melanoma, renal, triple negative breast, and other (bladder, prostate, head and neck, colorectal) tumors. Step 1 of the trial focused on determining the optimal dose and schedule for CPI-444; Step 2 is currently evaluating the efficacy of optimal CPI-444 dosing alone and with atezolizumab. In 48 patients treated in Step 1, CPI-444 was well tolerated with 1 Grade 3 or 4 treatment related adverse events. Preliminary evidence of clinical activity was observed in patients treated with single agent CPI-444, including patients who previously failed anti-PD-1 therapy. A pCREB-based pharmacodyamic assay showed that 100 mg, BID dose of CPI-444 resulted in a complete, sustained inhibition of A2AR on circulating immune cells. CPI-444 treatment alone or in combination with atezolizumab resulted in increased frequency of circulating CD8+PD-1+ cells and memory/effector subsets of CD4+ and CD8+ T cells. Substantial changes in TCR repertoire (Morisita Index <0.9) were observed in both anti-PD-1 native and refractory patients and correlated to patient responses. CD73 expression, CD8+ infiltration, TREG distribution, and gene expression signatures are currently being evaluated in serial tumor biopsy specimens and will be presented. In total, this shows that CPI-444 is well tolerated in cancer patients, exhibits functional inhibition of adenosine signaling, and treatment is associated with activation of anti-tumor immunity and clinical activity. Citation Format: Stephen Willingham, Andrew Hotson, Po Ho, Carmen Choy, Kim Walter, Erik Yusko, Sharon Benzeno, Ginna Laport, Richard Miller, Ian McCaffery. Inhibition of A2AR induces anti-tumor immunity alone and in combination with anti-PD-L1 in preclinical and clinical studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5593. doi:10.1158/1538-7445.AM2017-5593