Quantitative Cell-Based Bioassays For Therapeutic Development Targeting Immune Checkpoint And Co-Stimulatory Receptors

Immunotherapy harnesses the immune system to fight cancer and has proven to be a very promising therapeutic strategy. Drug targets in cancer immunotherapy include both inhibitory and co-stimulatory immune receptors on T cells or NK cells, in particular. Current approaches to assay immunotherapy biologics rely on primary cells, are highly variable, and are not suitable for a quality control environment during drug development. We have developed a panel of cell-based assays using a bioluminescent reporter platform that can quantitatively determine the potencies of antibodies and ligand proteins targeting immune checkpoint receptors and co-stimulatory receptors including PD-1, CTLA-4, LAG-3, GITR, 4-1BB, OX40 and CD40. For each target, a stable cell line was generated in an immune cell background to stably express an immune checkpoint or co-stimulatory receptor and a luciferase reporter driven by a response element specifically responding to signaling induced by TCR or directly from the immune receptor. These bioassays reflect biological mode-of-action for each class of drug candidate and are able to determine the potencies for on-market biologic drugs including PD-1 antibodies pembrolizumab and nivolumab, and CTLA-4 antibody ipilimumab. The assay signals are robust, specific, and have good repeatability and linearity. Therefore they can serve as valuable tools for drug screening, QC lot release and stability studies in immunotherapy drug development. Citation Format: Jamison Grailer, Pete Stecha, Jun Wang, Jim Hartnett, Frank Fan, Mei Cong, Zhi-jie Jey Cheng. Quantitative cell-based bioassays for therapeutic development targeting immune checkpoint and co-stimulatory receptors. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4878.