Immunogenicity and Biomarkers: Bioanalytical Challenges and Considerations

A human receptor occupancy assay to measure anti‐PD‐1 binding in patients with prior anti‐PD‐1

“…This is an advantage since idiotype‐specific detection mAbs do not allow to distinguish between different drugs of the same idiotype. Further restrictions of this approach include anti‐drug antibodies (ADAs) which may bind to idiotypic therapeutic mAbs; this phenomenon can interfere with the readout [ 5 ]. We show that anti‐PGLALA‐PE specifically detects IgG 1 ‐PGLALA bound to immune cells.…”

“…We show that anti‐PGLALA‐PE specifically detects IgG 1 ‐PGLALA bound to immune cells. Consequently, we propose that this would also be of advantage in situations where ADAs against therapeutic mAbs are formed [ 5 , 41 , 42 , 43 ]. Currently, a number of IgG 1 ‐PGLALA based bispecific antibodies, immunocytokines and antibody fusion proteins are in pre‐clinical or clinical development [ 24 , 44 , 45 , 46 , 47 , 48 , 49 ] requiring custom tailored PD biomarker assays.…”

“…However, when therapeutic mAbs of IgG 1 or IgG 4 isotype are applied, their differentiation from natural antibodies is challenging as typically no specific reagents for the therapeutic mAb exist, apart from anti‐idiotype antibodies. These, however, may interfere with the target binding of the therapeutic mAb and may result in extra challenges in the presence of idiotypic anti‐drug antibodies (ADA) [ 5 ]. Determining the degree of RO is particularly important in DE studies with immune‐cell activating mAbs (such as superagonists), given that low doses are usually administered.…”

Innate Immunity Modulating Impurities and the Immunotoxicity of Nanobiotechnology-Based Drug Products

“…Therefore, any of the product- or host-related impurities previously discussed, as well as raw materials used during the product’s manufacture and purification, can technically be considered a potential biomarker [ 85 ]. During method development, quantitative assays must be validated using appropriate controls and quantification must employ a standard curve of known analyte concentrations to determine the range of conditions under which appropriate levels of confidence can be attributed to the reproducibility and accuracy of the data [ 84 , 96 ]. Further, the validated assay must then demonstrate both sensitivity and specificity for the biomarker [ 84 ], such that the biomarker is correctly identified (i.e., true positive, sensitivity) at clinically relevant (ng/mL to pg/mL) concentrations [ 96 ] without also reacting to residual therapeutics or other impurities likely to be present within the therapeutic formulation (i.e., true negative, specificity).…”

“…During method development, quantitative assays must be validated using appropriate controls and quantification must employ a standard curve of known analyte concentrations to determine the range of conditions under which appropriate levels of confidence can be attributed to the reproducibility and accuracy of the data [ 84 , 96 ]. Further, the validated assay must then demonstrate both sensitivity and specificity for the biomarker [ 84 ], such that the biomarker is correctly identified (i.e., true positive, sensitivity) at clinically relevant (ng/mL to pg/mL) concentrations [ 96 ] without also reacting to residual therapeutics or other impurities likely to be present within the therapeutic formulation (i.e., true negative, specificity). Reduced sensitivity can result in mistakenly missing the presence of IIMIs in a formulation (i.e., false negative) resulting in possible dangerous clinical manifestations and immunogenicity, while reduced specificity can result in misidentification of inert compounds as IIMI (i.e., false positive) leading to incorrect quantification and product disposal rather than administration to patients.…”