Antibodies for bioanalytical and patient monitoring assays for vedolizumab and biosimilar products Recombinant monoclonal anti-idiotypic antibodies, highly specific for the humanized IgG1 kappa antibody drug vedolizumab (Entyvio) Anti-Vedolizumab Inhibitory Antibodies These antibodies inhibit the binding of the drug vedolizumab to its target, Α4Β7 integrin, and therefore detect free drug. A pair of these antibodies is ideal for the development of a pharmacokinetic (PK) bridging ELISA. Three antibodies of high, medium or low affinity are suitable as a reference standard for an anti-drug antibody (ADA) assay. Our recombinant, monoclonal antibodies are generated using the Human Combinatorial Antibody Library (HuCAL®) and CysDisplay®, a proprietary method of phage display, with guided selection methods to obtain highly targeted reagents. The result is highly specific and high affinity antibodies, ideal for development of PK assays. These fully human antibodies are also suitable as controls or calibrators for ADA assays. The in vitro production of recombinant antibodies results in a consistent, secure supply of these critical reagents throughout preclinical development and clinical trials.