Abstract 2646: Screening the membrane proteome to determine antibody specificity and de-risk CAR-T cell development

Abstract

Abstract Rigorous specificity analysis is critical for the development of antibody-based therapies, as even minimal off-target binding can lead to toxicity and clinical failures. Long believed to be exquisitely specific, recent preclinical data and our own work indicate that monoclonal antibodies (MAbs) frequently (~25%) display cross-reactivity. In many cases, off-target interactions occur with unrelated proteins that cannot be predicted by protein sequence homology. Cross-reactivity can lead to serious or even life-threatening consequences especially when MAbs are configured as bispecifics, antibody-drug conjugates (ADC) or CAR-T cell therapies, and IND applications for biotherapeutics require cross-reactivity assessment to prevent adverse events. Tissue cross-reactivity (TCR) studies have traditionally been used to screen for off-target binding, however, with poor predictive value for in vivo safety and toxicity. We developed the Membrane Proteome Array (MPA) platform to de-risk MAb-based therapeutics by testing for specificity across 6,000 human membrane proteins expressed in live cells. In contrast to TCR studies, proteins in the MPA exist in their native conformations and are not altered by fixation. The MPA assesses binding interactions by high-throughput flow cytometry allowing for high sensitivity detection and rapid analysis. We will discuss the importance of early-stage specificity testing to expose possible toxicities and present case studies for antibody and cell therapy profiling. MPA data have been used in numerous successful regulatory applications and may be used to replace or complement other cross-reactivity studies. In particular, MPA profiling has been used in IND applications for CAR-T and cell-therapies where conventional immunohistochemical binding assays did not suffice. Citation Format: Joseph Rucker, Rachel H. Fong, Tabb Sullivan, Carmen Navia, Brad Screnci, Rona Wilf, Benjamin J. Doranz. Screening the membrane proteome to determine antibody specificity and de-risk CAR-T cell development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2646.