Uncovering the cellular and molecular drivers of biotherapeutic immunogenicity 9397

Abstract Description Immunogenicity to biologic drugs manifests as the generation of anti-drug antibodies (ADAs), which can significantly impact the safety, efficacy, pharmacokinetics, and pharmacodynamics of biotherapeutic products, potentially rendering them ineffective. Understanding the causes of immunogenicity is necessary to mitigate the risks associated with drug candidates. To characterize the cellular and molecular processes initiated during an immune response to human biologics, we performed single-cell transcriptome and surface proteome analysis of over 150,000 peripheral blood mononuclear cells, treated with biotherapeutics exhibiting varying degrees of clinical immunogenicity. Our findings highlight CD14+ monocytes as the primary cells initiating an immune response against a biotherapeutic. These cells preferentially internalize immunogenic biotherapeutics at higher rates leading to activation and secretion of key pro-inflammatory mediators. Furthermore, we identified a biomarker of immunogenicity, RNASE 1. The expression of this enzyme is suppressed during an immunogenic response in vitro, as well as in vivo in clinical ADA+ patients. Perturbation of the extracellular availability of RNASE 1 also regulated therapeutic protein-dependent T cell activation. This study provides critical insights into antigen processing mechanisms by CD14+ monocytes, emphasizing their role in biologic immunogenicity and highlighting a potential biomarker for predicting immunogenicity. Topic Categories Antigen and Dendritic Cell Processing, Presentation, and Biology (AGDC)