Abstract B30: Discovery and functional characterization of novel anti-PD-1 antibodies using ex vivo cell-based assays, single-cell immunoprofiling, and in vivo studies in humanized mice

Abstract Given recent approvals of anti-PD-1 inhibitors Keytruda (pembrolizumab) and Opdivo (nivolumab) for treatment of metastatic melanoma and non-small cell lung cancer NSCLC, we asked whether additional anti-PD-1 inhibitors with different epitopes or potentially differentiated mechanisms of action can provide clinical benefit beyond the two marketed therapies. Using Enumeral's proprietary single cell technology, we generated more than 300 anti-PD-1 monoclonal antibodies from primary B cells. Bioinformatics analysis of sequences show these antibodies comprise 26 distinct clades, or families, that bind to PD-1. Results from binding studies further indicate we have discovered a family of novel antibodies that do not appear to compete with currently marketed antibodies for binding to PD-1, nor do they appear to compete with PD-L1, suggesting a differentiated mechanism of action. We have humanized two lead antibodies for preclinical testing and in preparation for clinical studies. Here we describe functional characterization of the two lead antibodies using cell-based ex vivo assays, patient-derived tumor profiling assays using our single-cell platform, and in vivo studies in humanized NSG mice. Results show that the two lead anti-PD-1 antibodies exhibit a higher level of T cell activation in mixed lymphocyte reaction (MLR) assays using primary human immune cells. Second, these antibodies also demonstrated dose-dependent increases in T cell CD25 expression. Next, to test the effect of the two lead anti-PD-1 antibodies on tumor growth, we are conducting a study using a patient-derived tumor (PDX) model on humanized NSG mice. NSG mice reconstitute a full human immune system including a functional T, B cell repertoire, enabling the direct, in vivo evaluation of our human anti-PD-1 antibodies. Effects of drug treatment on tumor growth, transcriptome (RNA seq) and protein expression (IHC) will be described. Finally, results from ex vivo tumor profiling comparing the immmunomodulatory effects of our anti-PD-1 antibodies on tumor-infiltrating lymphocyte function will also be presented. Citation Format: Felix Scheuplein, Sheila Ranganath, Thomas McQuade, Lei Wang, Vikki Spaulding, Sri Vadde, Jennifer Watkins-Yoon, Bin Feng, Shanu Mehta, Maria Isabel Chiu, Cokey Nguyen. Discovery and functional characterization of novel anti-PD-1 antibodies using ex vivo cell-based assays, single-cell immunoprofiling, and in vivo studies in humanized mice. [abstract]. In: Proceedings of the AACR Special Conference: Function of Tumor Microenvironment in Cancer Progression; 2016 Jan 7–10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2016;76(15 Suppl):Abstract nr B30.