Abstract 3053: Development of novel cell-based bioassays for the development of biologics targeting LAG-3 and PD-1xLAG-3

Abstract

Abstract Programmed cell death protein 1 (PD-1) and Lymphocyte-activation gene 3 (LAG-3) are immune checkpoint receptors that bind to PD-L1/PD-L2 or MHCII, respectively, on antigen presenting cells or tumor cells. PD-1 or LAG-3 activation results in the inhibition of T cell receptor (TCR) signaling and reduced T cell activation. However, co-blockade of PD-1 and LAG-3 leads to a synergistic enhancement in T cell responses, suggesting functionally divergent inhibitory signaling mechanisms between the two receptors. Preclinical studies suggest that blocking LAG-3 re-activates the immune system to kill cancer cells, and co-blockade of both PD-1 and LAG-3 lead to a synergistic increase in tumor control and survival in preclinical models. Current methods for measuring the potency of LAG-3 and PD-1xLAG-3 blocking antibodies measure cytokine production from human PBMCs upon Staphylococcal Enterotoxin B (SEB) superantigen stimulation. These protocols are tedious, highly variable, and require the use of highly toxic superantigen. Herein, we describe the development of reporter-based bioassays for the development of LAG-3 and PD-1xLAG-3 combination-targeted biologics. Engineered T effector cell lines expressing LAG-3 alone or in combination with PD-1 are activated in an antigen-dependent manner by APC cell lines. The assays are specific for LAG-3 or PD-1xLAG-3-targeted biologics and are robust as demonstrated by Design of Experiments analyses. In addition, the assays can be used to measure the relative potencies of test samples compared with reference sample in a detection range of 50% to 200% and show appropriate precision, accuracy and linearity. The assays can detect potency changes for heat-stressed samples, and are tolerant to human serum, demonstrating the potential to be further developed into neutralizing antibody (NAb) assays. Therefore, these bioassays can serve as valuable tools for the development of biologics targeting LAG-3 and PD-1xLAG-3. Citation Format: Jamison Grailer, Denise Garvin, Jim Hartnett, Frank Fan, Mei Cong, Zhi-jie Jey Cheng. Development of novel cell-based bioassays for the development of biologics targeting LAG-3 and PD-1xLAG-3 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3053.