Cross-reactivity studies monoclonal antibodies

Tissue cross-reactivity studies for monoclonal antibody products were originally intended to explore off-target tissue binding. Studies have thus been used to screen candidates to avoid off-target binding. As stated in ICH S6, an animal species that does not express the desired epitope may be of some relevance for assessing toxicity if comparable unintentional tissue cross-reactivity to... 

An example of results from a tissue cross-reactivity study comparing binding of a monoclonal antibody therapeutic to human, cynomolgus monkey, and mouse tissues is shown in Table 9.2. A cell line that did not express the target was used as negative control tissue the same cell line transfected with the... 

TABLE 9.2 Cross-species tissue cross-reactivity study of a monoclonal antibody... 

Tissue Cross-Reactivity Studies for Monoclonal Antibodies Predictive Value and Use for Selection of Relevant Animal Species for Toxicity Testing... 

TISSUE CROSS-REACTIVITY STUDIES FOR MONOCLONAL ANTIBODIES... 

Several types of hypersensitivity reactions can occur in the host receiving monoclonal antibody therapy, and the tissue cross-reactivity study might be predictive of some of these hypersensitivity reactions. Theoretically, adverse reactions result in tissue destruction because of the activation of complement or release... 

Tissue cross-reactivity studies, although burdensome, provide a rational in vitro assay to determine the range and intensity of distribution of potential epitopes reactive with a monoclonal antibody test article prior to its administration to humans. In addition, cross-reactivity studies provide a useful tool to identify animal species for safety assessment. The cross-reactivity profiles of different species can be compared to the profiles obtained in human tissues. The predictive value of the assay lies in incorporating the characteristics of the monoclonal antibody (isotype, subtype, and other molecular modifications) with the biological activity of the molecule itself, and the potential in vivo distribution of it. 

Tissue cross-reactivity studies are required by FDA for monoclonal antibody products to determine if the product binds to target and/or nontarget tissues. They are also performed for nonmonoclonal biopharmaceuticals if warranted. For example, ARANESP was tested in a human tissue panel ex vivo to determine if it bound to nontarget tissues or cross-reacted with related cytokine receptors. These studies are also used to explore known or potential clinical adverse safety events (i.e., mechanism of toxicity). For example, one patient in a Raptiva study developed unilateral hearing loss. This finding was further evaluated by cross-reactivity studies with human optic chiasm, acoustic nerve, and inner ear tissues. 

For monoclonal antibodies, the immunological properties of the antibody should be described in detail, including its antigenic specificity, complement binding, and any unintentional reactivity and/or cytotoxicity towards human tissues distinct from the intended target. Such cross-reactivity studies should be carried out by appropriate immunohistochemical procedures using a range of human tissues. 

A wide selection of monoclonal and polyclonal anti-Ca -ATPase antibodies have become available in recent years. Studies with these antibodies defined the localization of Ca " -ATPase in the sarcoplasmic reticulum of developing and mature skeletal muscles [60,262-270] and established a pattern of cross reactivity with various Ca -ATPase isoenzymes in the sarco(endo)plasmic reticulum [270-286] and in the plasma membrane [284,287-290] of skeletal, cardiac and smooth muscles. Antibodies have also proved useful in the quantitation of Ca -ATPase, both in muscles of diverse fiber types [291-294] and in COS-1 cells transfected with Ca -ATPase cDNA [97,103,126,127,129,215],... 

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