A Simple & Powerful Cell-Based Assay to Quantify Specific Target Cell Death by Antibody-Dependent Cellular Phagocytosis (ADCP)

A Simple & Powerful Cell-Based Assay to Quantify Specific Target Cell Death by Antibody-Dependent Cellular Phagocytosis (ADCP)
Version:
21297

File Name/Number:
KILR ADCP Application Note

Year:
2023

 

With the increasing industry focus on antibody drugs, there is an ever-greater need for functional bioassays that interrogate the therapeutic antibody's mechanisms-of-action (MOA). Typical formats for antibody therapeutics contains two antigen-binding Fab arms and an Fc region. The Fc domain can be comprised of different isotypes (IgG1, IgG2, IgG3 or IgG4) which have varying affinities for binding to Fcγ receptors expressed on immune effector cells. Engagement of Fcγ receptors mediates target cell death by various mechanisms such as Complement-Dependent Cytotoxicity (CDC), Antibody-Dependent Cell-Mediated Cytotoxicity (ADCC), and Antibody-Dependent Cell-Mediated Phagocytosis (ADCP). Regulatory authorities now commonly require data on the impact of each of these Fc-mediated effector mechanisms for the submitted antibody therapeutic. There are several methods available to measure these Fc-mediated effector MOAs; however, getting a reproducible true measure of ADCP, in particular, has been quite challenging.

Antibody-Dependent Cell-Mediated Phagocytosis

ADCP is a physiologically important MOA of therapeutic antibodies that can be mediated by various immune effector cells, namely: monocytes, macrophages, dendritic cells, and neutrophils through multiple FcγRs. The Fab region of the antibody binds to a specific antigen on the surface of target cells. In contrast, the Fc region of the antibody binds and activates various Fcγ receptors on immune effector cells. Activation of specific Fcγ receptors, like FcγRIIa, FcγRI, and FcγRIIIa, leads to the continued activation of a complex pathway that triggers phagocytosis and destruction of the target cells within the lysosomes of different effector cells.