This new range of recombinant monoclonal anti-idiotypic antibodies is comprised of four inhibitory antibodies that are highly specific for the humanized IgG2/4 kappa monoclonal antibody drug, eculizumab, a biotherapeutic that is used to treat paroxysmal nocturnal hemoglobinuria and atypical hemolytic uremic syndrome. The anti-eculizumab inhibitory antibodies can be used to quantify the level of eculizumab in patient samples and they may also be used in bioanalytical assays for biosimilar development. An antibody pair is suitable for the development of a pharmacokinetic bridging ELISA, and antibodies of high, medium, and low affinity can be used as a positive control or calibrator in an anti-drug antibody assay. The recombinant monoclonal anti-idiotypic 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 recombinant production method also ensures a consistent and secure supply.