Novel ADC PK Assays Revolutionize Targeted Therapy Analysis

Quality Assay Data for Reliable Optimal Dose and Efficacy Determination

The development and validation of bioanalytical assay methods is a notoriously complex and rigorous process. Assays typically involve time-consuming, specialized steps to quantify the concentration of therapeutics in the body. During clinical development, assay results are used to determine optimal dose, and subsequently, efficacy of a drug substance.

Antibody drug conjugate (ADC) assays, however, pose distinct challenges, including the analysis of multiple drug analytes. Antibody drug conjugates, a type of targeted therapy, are a rapidly growing class of drug molecules. The pharmacokinetic (PK) profiles of ADCs, and its respective analytes, must be characterized as part of the overall process of ensuring therapeutics are safe and effective.

High quality, robust ADC PK assays are therefore invaluable to ADC development. This renders Amador’s recent development of 3 novel ADC PK assays a noteworthy feat.

The collaborative effort by the Amador Bioanalysis & Biomarkers team shed light on efficient and robust methods of generating accurate and reliable ADC PK profiles.

The Design and Fate of Antibody Drug Conjugates

Antibody Drug Conjugates are complex molecules. An ADC is composed of a monoclonal antibody (mAb) chemically linked to a cytotoxic small-molecule drug referred to as the payload.

The antibody component of the ADC is designed to specifically bind to a target antigen in the body. For cancer therapeutics, the target antigen is located on a cancer cell. After antibody-antigen binding, the target cell internalizes the ADC. The payload is then released within the cancer cell leading to destruction of the target cell.

An ADC is designed to remain in a stable form when it is absorbed and circulated until it reaches the intended cell (target) in the body. To accomplish this, numerous factors must be considered for the various ADC components.

Crucial factors include linker stability, payload potency, antibody specificity, and immunogenicity. Quantifying ADC components yields valuable information about how the ADC is absorbed, distributed, metabolized, and eliminated.

Amador ultimately uses PK analysis to inform dose regimens and determine the relationship between exposure and safety/efficacy. However, an ADC's molecular complexity results in unique bioanalytical challenges.

The Basics and Objectives of ADC Assays

The characterization of ADC PK profiles typically includes quantifying intact or antibody-conjugated drug, total antibody, and free warhead. Ligand binding assays (LBA) has traditionally been a reliable method particularly for large molecules.

Liquid chromatography-mass spectrometry (LC-MS) has been used for small molecule analysis. The 2 platforms used in combination are highly desirable for ADC characterization despite significant technical challenges.

One important advantage to using the LCMS method is to enable the determination of drug-to-antibody ratio (DAR), which is valuable for the assessment of ADC stability and potency. As such, the LCMS method is the preferred method for ADC quantification.

Amador’s Development and Optimization of the Total Antibody, Intact ADC, and Free Payload Assays

The validation of ADC assays is essential to ensure high quality of assay performance and assess multiple parameters including sensitivity, accuracy and precision, specificity, stability, and robustness ,etc.

Amador’s team developed and validated 3 specialized assays to be used for quantifying various ADC components, including intact ADC, free payload/warhead, and total antibody, during all phases of clinical development.

Key team members responsible for the method development and validation include Andrea Ngai (Associate Director), Guillaume Diagne (Principal Scientist), Thomas Kralj (Scientist II), Morgan Stickney (Scientist II), and LingShan You (Sr. Associate Scientist). Cross-functional support, including QA, Project Management, and Medical Writing have all been important to the success.

These novel PK assays will be used for sample analysis in support of ADC clinical development and the knowledge gained will apply to other new drug modalities.

Amador's Role in the Growing Need for Reliable ADC Characterization

As ADC therapeutics continue to rise in prominence, the pharmaceutical industry will need to keep pace in determining the relationship between exposure and safety/efficacy, especially as novel ADCs are deployed to fight complex diseases.

Amador’s novel PK assays set the stage for reliable ADC characterization in support of their ongoing clinical development. If you wish to seek support for your ADC projects or employment opportunities with Amador, please send us your information.

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