title: A novel bioactivity assay for monoclonal antibodies directed against IgE.
abstract: A novel bioactivity assay has been developed to quantitate the biological activity of a humanized, monoclonal anti-IgE antibody (rhuMAbE25) in human whole blood. Heparinized blood specimens from prescreened healthy donors were sensitized for 2 h with a constant amount of human plasma containing IgE specific for ragweed and then challenged with ragweed allergen. Histamine was released in a dose-dependent fashion and reached plateau levels after 30 min. As expected, the release of histamine by ragweed allergen was time, temperature and Ca2+ dependent, and could be enhanced by the presence of 33% deuterium oxide. Allergen-triggered release could be inhibited by rhuMAbE25 with an effective dose range from 0.1 to 1 microgram/ml. Preincubation with other humanized MAbs, which exhibit 95% homology to rhuMAbE25 but differ in epitope specificity, failed to inhibit the ragweed-induced histamine release. Overall, this bioactivity assay has a low interassay variability (%CV) of 17% (n = 23) and can be readily modified to determine if rhuMAbE25 or other anti-allergy therapeutics are capable of blocking histamine release elicited by other allergens. Moreover, the assay can be used to confirm IgE-mediated allergic responses and to provide early information regarding safety and potential efficacy of therapeutics aimed at blocking IgE dependent responses.
authors.affiliation: Department of Bioanalytical Technology, Genentech, Inc., South San Francisco, CA 94080.
authors.forename: D T
authors.initials: DT
authors.lastname: Fei
authors.forename: J
authors.initials: J
authors.lastname: Lowe
authors.forename: P
authors.initials: P
authors.lastname: Jardieu
mesh_terms: D000328:Adult; D000485:Allergens; D000888:Antibodies, Anti-Idiotypic / Q000097:blood* / Q000378:metabolism / Q000494:pharmacology; D000911:Antibodies, Monoclonal / Q000097:blood* / Q000378:metabolism / Q000494:pharmacology; D000918:Antibody Specificity; D001491:Basophils / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D017666:Deuterium Oxide; D005260:Female; D006636:Histamine Release / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D011058:Pollen
chemical_list: D000485:Allergens; D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; C026408:anti-IgE antibodies; D017666:Deuterium Oxide