Abstract
Mimotope peptides selected from combinatorial peptide libraries can be used as capture reagents for immunoassay detection of therapeutic monoclonal antibodies (mAbs). We report the use of phage display libraries to identify peptide ligands (Veritopes(TM)) that bind natalizumab, a therapeutic mAb indicated for use in multiple sclerosis. PKNPSKF is identified as a novel natalizumab-binding motif, and peptides containing this motif demonstrated utility as capture reagents in enzyme-linked immunosorbent assays (ELISAs). A peptide containing the identified motif was shown to be competitive with the natural ligand (α4-integrin) and a neutralizing anti-idiotype antibody for natalizumab binding, indicating that Veritopes(TM) act as surrogate ligands that bind the antigen binding site of natalizumab. Affinity maturation further confirmed the motif sequence and yielded peptides with greater apparent affinity by ELISA. Veritopes(TM) are promising assay reagents for therapeutic drug level monitoring.