A double antigen bridging immunogenicity ELISA for the detection of antibodies to polyethylene glycol polymers

INTRODUCTION: Polyethylene glycol (PEG) polymers attached to biotherapeutic molecules enhance in vivo delivery and stability of these large molecular weight drugs. However, these polymers may by themselves be immunogenic and elicit antibodies that can reduce the efficacy of the drug and contribute to potential patient morbidity. A double antigen bridging ELISA immunogenicity assay for the detection of anti-drug antibodies (ADAs) specific to PEG polymers of various sizes has been developed. METHODS: Hapten-labeled conjugate of 40kDa PEG polymer was synthesized and used in a double antigen bridging ELISA. The hapten-labeled PEG is incubated with the patient sample, then this mixture is added to a 96-well microplate precoated with 40kDa PEG, allowing PEG-specific ADA to form a bridge complex with the PEG conjugate and the PEG coated on the microplate. After incubation, the reaction mixture is removed and replaced by horseradish peroxidase (HRP)-labeled anti-hapten antibody. After sufficient incubation, the plate is washed and substrate reagent is added. Enzyme color development, directly proportional to ADA, is stopped after 20min with 2N sulfuric acid and the absorbance in each well is measured at 450/630nm. Dose response, drug tolerance, matrix effects, reproducibility, specificity/free drug depletion experiments and screening cut-point determination of 350 naïve normal human sera were performed. RESULTS: Using an anti-PEG mouse monoclonal IgM as a positive control, a reproducible dose response curve was demonstrated for the PEG Immunogenicity ELISA. Pre-existing PEG-specific antibodies which were proven to be highly specific to the PEG polymer structure were found in 15 human serum samples in a total population of 350 naïve donors. The assay exhibited no significant matrix effects and was shown to be highly reproducible. DISCUSSION: A double antigen bridging immunogenicity assay for the detection of antibodies to PEG in the typical polymer size ranges used in biotherapeutics has been successfully developed in ELISA format. The antibodies detected in positive samples displayed a diverse spectrum of specificities for different PEG polymer lengths and linking functional groups. The discovery of 15 confirmed positive samples among 350 naïve patient samples calls into focus the need for testing PEG-specific immunogenicity of PEGylated biotherapeutics.