Intracellular Trafficking and Degradation of Antibody Drug Conjugates

Intracellular Trafficking and Degradation of Antibody Drug Conjugates

Katie Maass, K. Dane Wittrup

Chemotherapeutics used for cancer treatment are commonly limited in dose due to systemic toxicity. A new class of cancer therapeutics known as Antibody Drug Conjugates (ADCs) has shown promise in effectively killing cancer cells while reducing systemic toxicity. ADCs are comprised of a small-molecule cytotoxic drug conjugated to an antibody that targets an antigen specific to cancer cells. Ideally, the cytotoxic drug remains conjugated to the antibody until it is internalized within a cancer cell and then released to have its cytotoxic effect. However, there are numerous steps before the active drug component reaches its target in the cell, and the impact of ADC design parameters on these processing steps is poorly characterized. Increased understanding of their cellular processing may facilitate more rational design of ADCs.

In this work, we develop a kinetic model that describes the internalization and degradation of ADCs on a cellular level. Using flow cytometry and a novel gel imaging assay, we measure surface association and disassociation, internalization, and intracellular degradation and exocytosis rates for model fluorophore-labeled ADCs. Thus, we present a generalizable method to determine kinetic parameters, which can be used in a basic model for cellular processing of ADCs and can be incorporated into larger scale pharmacokinetic/pharmacodynamic models.