The LBA has been the primary analysis platform used for ADC bioanalysis because of its many advantages, including the ability
to measure the test article in matrix without further sample extraction, its high-throughput nature, the broad dynamic range
and high sensitivity that can be achieved, and the requirement of minimal sample volume. However, the availability of critical
reagents is a key component to the development of highly specific and sensitive LBA methods. Much time and effort is usually
taken to create anti-idiotype antibodies against the carrier antibody or the cytotoxic drug. Because of the low immunogenic
nature of cytotoxic drugs, conjugation with keyhole limpet hemocyanin (KLH) or an adjuvant may be required for antibody creation.
The tight timelines for most IND-enabling studies necessitate early planning during the design of bioanalytical assays that
factors in the timelines for generation of critical reagents. These critical reagents are either prepared in-house or subcontracted
to third parties, and at least six months lead time is typically required. Antibody screening, assay format testing, and reagent
purification are all steps that are part of the reagent-generation process that will add even more time, cost, and risk to
projects. In some instances, the anticarrier antibodies and targeted antigens may be commercially available. In these cases,
it is crucial to secure sufficient quantities of the lot so that the reagent inventory can cover the entire study. Communication
and establishing a good relationship with the reagent vendors are important and should be a key consideration. Should different
reagent lots be used throughout the study, an appropriate way of assessing and bridging the different reagent lots must be
established and implemented.
As ADC technology has become increasingly prevalent, it is imperative that new and reliable methods are developed to better
characterize different ADCs both in vitro and in vivo. Because of the complexity of ADCs, many LBA formats are available for the same bioanalytical purpose. Therefore, caution
has to be taken during assay development and validation to ensure that the selected method is the best fit for a given compound.
The critical reagents are crucial factors for LBAs; therefore, sufficient lead time and effort must be factored into meeting
Yi Qun Xiao, PhD, is director of immunology, Andreea Halford is senior manager of ligand binding assay development, and Roger N. Hayes, PhD, is vice-president and general manager of laboratory sciences, all at MPI Research, 54943 North Main Street, Mattawan, MI,
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