Recent Developments in ADA Titer Assay Technology: Implications for Drug Development

Anti-drug antibodies induced by large molecules and biologics can influence the clinical efficacy and pharmacokinetics/pharmacodynamics properties of a drug product. Hence, anti-drug antibody testing is crucial to assess the immunogenicity risk profile of biotherapeutics and their ability to generate neutralizing and non-neutralizing antibodies, especially during ADA sample analysis in clinical trials. ADA immunogenicity testing involves different assays to detect anti-drug antibodies, including radioimmunoassay, ELISA, electrochemiluminescence-based methodologies, and surface plasmon resonance. The current article focuses on ADA studies and advancements in ADA titer assay. However, ADA assay development and validation remain crucial for generating reliable and reproducible results.

Developments in anti-drug antibody assays and their significance in advancing immunogenicity testing

The gyrolab platform incorporating partial automation and microfluidics has been widely employed in ligand binding assays. Today, scientists have validated bioanalytical assays such as bridging ADA assays on the gyrolab platform to quantify drug compounds and determine their pharmacokinetic profile and affinity towards protein interaction. Due to the microfluidics system, minimum use of sample volume and critical reagents are the primary advantages of the gyrolab platform. 

Interference caused by circulating drugs is a significant challenge observed during ADA testing methodologies. Today approaches such as ADA enrichment and acid dissociation have helped improve drug tolerance. Besides, sample collection after washout is also commonly practiced. Another approach to increase drug tolerance is incorporating large sample dilution to minimize drug concentration in the study sample. Techniques such as immune PCR can effectively work with diluted samples and offer higher sensitivity for detecting anti-drug antibodies. However, one should consider the fact that immune PCR depends on proprietary reagents, and hence, may be challenging to develop in-house. 

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Additionally, anti-drug antibody characterization may need bioanalytical assays for isotyping the detected anti-drug antibody. The SquidLite platform offers the alternative of isotyping and detecting anti-drug antibodies in the same well. This feature eliminates the requirement for multiple assays and reduces the required sample volume. Researchers have reported increased drug tolerance and sensitivity while using SquidLite compared to ECL or ELISA platforms. The advantage of this platform is the automation process that can increase throughput while offering multiplexing capacities for ADA isotyping. 

Another platform enabling simultaneous isotyping and detection of anti-drug antibodies is the Genalyte Maverick. This platform uses photonic biosensor surfaces and streptavidin-coated beads to capture and evaluate anti-drug antibodies. The Maverick system can detect all immunoglobulin isotypes. It requires acid dissociation followed by affinity capture of anti-drug antibodies. The Genalyte Maverick system has label-free ADA detection, allowing real-time analysis of assay kinetics. 

LC-MS systems are increasingly becoming integral to drug development. They are rapidly applied for quantifying biotherapeutics and endogenous protein biomarkers in different biological matrices. Today, scientists have successfully employed a generic LC-MS method for measuring human monoclonal antibodies or FC fusion proteins during PK bioanalysis. However, successful implementation of LC-MS assays requires in-depth expertise and method development capabilities, which may not necessarily be available in smaller bioanalytical laboratories. Besides, the LC-MS application requires testing in clinical settings.