Abstract 1650: MoA-based reporter bioassays enable quantitative potency determination for therapeutic biologics targeting co-stimulatory and co-inhibitory immune checkpoint receptors

Abstract

Abstract Immune checkpoint (IC) receptors play critical roles in maintaining immune homeostasis and are emerged as promising drug targets for the treatment of various cancers and autoimmune disorders. Monoclonal antibodies designed to block immune inhibitory receptors PD-1 and CTLA-4 have been approved and showed unprecedented efficacy in cancer treatment. This led to rapid expansion of drug development to many more IC receptors targeted individually or in combination. However, due to the novelty and fast speed, one of the bottleneck during immunotherapy drug development is the lack of quantitative and reproducible functional assays for potency determination when existing methods heavily rely on primary immune cells and the process are labor intensive and highly variable. To address this need, we developed a panel of cell-based reporter bioassays that can quantitatively measure the potencies of biologics targeting individual IC receptor (e.g. PD-1, LAG-3, BTLA, CTLA-4, TIGIT, TIM-3, ICOS, 4-1BB, CD40), or bispecific molecules targeting two IC receptors spontaneously (e.g. PD-1xTIGIT, PD-1xLAG-3, PD-1xCTLA-4, PD1x4-1BB). These bioassays each consist of an engineered T effector cell line that expresses T cell receptors and IC receptors of interest, and an engineered artificial antigen presenting cells (aAPC) expressing the corresponding ligands for the IC receptors. The T effector cell line also expresses a luciferase reporter driven by response elements/promoter specifically responding to TCR activation which can be co-stimulated or inhibited by the signal from the IC receptors. These bioassays are designed to reflect the mechanisms of action for the drug candidates designed for each IC receptor and the assay signals are specific. They are prequalified according to ICH guidelines and show the precision, accuracy and linearity required for relative potency determination and product stability study under cGMP environments. Therefore, these MoA-based bioassays can serve as value tools for early drug discovery, potency determination and stability study throughout immunotherapy drug development. Citation Format: Jamison Grailer, Julia Gilden, Pete Stecha, Denise Garvin, Jun Wang, michael Beck, Jim Hartnett, Frank Fan, mei cong, Zhi-Jie Jey Cheng. MoA-based reporter bioassays enable quantitative potency determination for therapeutic biologics targeting co-stimulatory and co-inhibitory immune checkpoint receptors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1650.