| June 2009 | Print Article |
Comparative Biosciences Phone: 408.738.9260 |
Tissue Cross-Reactivity Studies Tissue Cross-Reactivity Studies are key in the development of monoclonal antibodies and other related biologics. The purpose of the Tissue Cross-Reactivity Study is to assure that the experimental antibody does not bind to epitopes other than the target site as this could lead to treatment-related toxicity in human subjects. Secondly, TCR studies assist in identifying potential relevant toxicology species and target organs. Most monoclonal antibodies or other biologics may be extremely specific and identification of relevant toxicology species can be difficult. Initial work with a test article biologic revolves around identifying appropriate positive and negative control tissues or cell types and optimizing the staining methodology. With biologics that are specific for tumor cells, cell pellets are often useful as a starting point, followed by employing actual tumor biopsies from patients. It is often possible at this stage to determine if subtypes of tumors are or are not positive reactors. With highly specific biologics, it is not uncommon to have differences in staining positivity between different individual tumors of the same type. Consequently, identification of strong positive reactor tumors or other tissues is important early on in the optimization process. In the case of identifying positive cell types unique to specific disease entities, this can be more difficult. A second issue in the optimization process concerns nonspecific staining on nontarget tissues. For example, bright clean positive staining may be observed on the positive control tissue, yet diffuse, nonspecific staining may occur under the same conditions on smooth or cardiac muscle. This may be addressed in the optimization process and can usually be controlled by modulating the concentration of the primary, and tweaking protein blocking, endogenous peroxide blocking, and buffer-rinsing procedures. In a typical GLP TCR study at the Phase III, a complete battery of human tissues (about 34 tissues from 3 unrelated humans) is stained with the optimal concentration, a 10x concentration of the primary, no primary, an irrelevant antibody (IgG or IgM), and a positive method control. The positive method control assures that the actual method is functioning properly and generally consists of a stain that would be expected to stain all human tissues. B2Microglobulin is generally used for human tissues, but CD31 is also effective, especially if the study involves additional species such as primates and rodents. Upwards of 1000 cryosections are prepared and evaluated for such a study. A full cross-reactivity study is performed in accordance with the FDA’s recommendation (“Points to Consider in the Manufacture and Testing of Monoclonal Antibody Products for Human Use”, FDA Guidance Document) Investigative TCR studies often involve assessment of multiple species side by side with human or positive control tissues. These studies assist in the identification of target organs, as well as relevant toxicology species. Often, a battery of tissues from human, primate, rat and mouse. Transgenic and knockout mice, or tissues from diseased animals are employed. Diseased conditions for example could include diabetes, obesity, cancer, arthritis, MS, and immune mediated disorders.
Comparative Biosciences, Inc. Histology Laboratory provides complete and comprehensive Tissue Cross-Reactivity Studies to support both research efforts and IND enabling studies for FDA submission.
To learn more about Tissue Cross-Reactivity Studies at Comparative Biosciences, Inc., visit www.compbio.com. Copyright © 2009 Comparative Biosciences, Inc. All rights reserved |
