IMMUNOGENICITY TESTING USING FLOW CYTOMETRY - Flow Cytometry in Drug Discovery and Development - page 199

10

IMMUNOGENICITY TESTING USING
FLOW CYTOMETRY

D ENISE M. O'H ARA AND V ALERIE T HEOBALD

10.1 INTRODUCTION

It is widely recognized that clinical administration of biotherapeutic molecules in
human subjects has the potential to elicit unwanted immune responses to the
biotherapeutic product. Consequently, a fundamental component of the development
and commercialization of biotherapeutics is to have the capability to monitor patients
for the development of antidrug antibody (ADA) responses. Following detection of
antibodies to the biotherapeutic, the ADA responses are characterized, for example, in
terms of both specificity and neutralizing capacity and the outcomes are correlated
to any clinical sequelae. Typically, immunogenicity testing utilizes bioanalytical
methods specifically designed to detect antidrug binding and neutralizing antibodies.
Flow cytometric cell-based immunogenicity assays can be employed when testing for
neutralizing activity of antibody positive samples and included in a tiered design
approach to detect and characterize specific antibody responses in clinical (and
sometimes nonclinical) samples [1, 2].
The analytical power of the flow cytometer instrument lies in its ability to
simultaneously quantify the intensity of fluorescent dyes on the surface of cells or
intracellularly in addition to measuring light-scatter signals indexing cell size and
granularity. These measurements are used to determine cell characteristics that define
a cell's activation status, cell lineage, or subset identity. Flow cytometry offers the
advantage of simultaneous multiparameter analysis of mixed cell populations without