Abstract 605: MoA-based potency bioassays for immunotherapy programs targeting the TIGIT/CD112R/CD226 axis
Authors: Grailer Jamison , Garvin Denise , Hartnett Jim , Fan Frank , Cong Mei , Cheng Zhi-Jie Jey 
Published: June 2022

Immune checkpoint (IC) receptors play critical roles in maintaining immune homeostasis and have emerged as proven drug targets for the treatment of various cancers and autoimmune disorders. Monoclonal antibodies (mAb) designed to block immune inhibitory receptors PD-1 and CTLA-4 have been approved and show unprecedented efficacy in cancer treatment. This led to rapid expansion of drug development to many more IC receptors including members of the T cell immunoreceptor with Ig and ITIM domains (TIGIT) - CD112R (PVRIG) - CD226 Axis. TIGIT binds to its ligands CD155 (PVR) and CD112 (PVRL2) while CD112R binds to CD112. Binding of TIGIT or CD112R to CD155/CD112 inhibits the co-stimulatory activity of the paired receptor CD226. Thus, therapeutic targeting of this axis can modulate T cell and NK cell activation and unleash anti-cancer immunity. One of the bottlenecks of immunotherapy drug development is the lack of quantitative and reproducible functional assays for mAb potency determination. Existing methods rely heavily on primary immune cells which is 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 mAbs targeting TIGIT/CD155, TIGIT/CD112, and CD112R/CD112. Owing to positive clinical trial results of TIGIT blockade in combination with PD-1/PD-L1 blockade, we further developed a potency bioassay for bispecific antibodies simultaneously targeting TIGIT and PD-1/PD-L1. 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 lines also express a luciferase reporter driven by a promoter specifically responding to TCR activation which can be inhibited by signaling from the IC receptors. Additionally, we developed bioassays that can measure potencies of agonist or antagonist mAbs targeting CD226. 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. Most 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 valuable tools for early drug discovery, potency determination and stability studies throughout the development of mAbs targeting the TIGIT/CD112R/CD226 axis.

Citation Format: Jamison Grailer, Denise Garvin, Jim Hartnett, Frank Fan, Mei Cong, Zhi-Jie Jey Cheng. MoA-based potency bioassays for immunotherapy programs targeting the TIGIT/CD112R/CD226 axis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 605.