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J. Lowe, E. Wakshull, V. Quarmby, M. Maia; Development of Immunogenicity Assays for Detection and Characterization of Anti-Ranibizumab Antibodies in Human Sera. Invest. Ophthalmol. Vis. Sci. 2008;49(13):5565.
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© ARVO (1962-2015); The Authors (2016-present)
To develop a comprehensive immunogenicity testing algorithm to support ranibizumab (LUCENTIS®) clinical trials. A multi-tier suite of assays was developed to detect, confirm and titer antibody (Ab) responses to ranibizumab in patients. Confirmed-positive samples are further characterized for the presence of neutralizing anti-ranibizumab antibodies (NAbs). Circulating vascular endothelial growth factor (VEGF) interferes in both assay formats, giving false positive results. We developed a novel approach for blocking or removing high-levels of circulating VEGF molecules.
Serum anti-ranibizumab Abs are detected using a bridging electrochemiluminescence assay (ECLA), forming a trimeric complex with BV-TAG®-ranibizumab and biotin-ranibizumab. These complexes are captured by streptavidin-coated paramagnetic beads (SA-beads), and are detected with a BioVeris® analyzer. In the confirmatory assay, VEGF interference is blocked using murine anti-VEGF MAb with a different CDR-amino acid sequence from ranibizumab. To detect NAbs, we developed a ligand-based ECLA in which the binding of BV-TAG®-ranibizumab to biotin-VEGF is blocked by the presence of NAbs. In the absence of NAbs, the immune complexes are captured and detected as described above. In the NAb assay, VEGF is removed from samples prior to testing. For that, samples are treated with a different biotin-anti-VEGF MAb, followed by capture with SA-beads and bead removal.
The sensitivity of the screening and confirmatory assays was 100 ng/mL. Addition of murine anti-VEGF MAb in the confirmatory assay effectively blocked up to 1 µg/mL of VEGF. The NAb assay sensitivity was 315 ng/mL and we demonstrated that it can tolerate at least up to 100 ng/mL of VEGF. All 3 assays performed well with serum samples from age-related macular degeneration patients.
The sensitivity and specificity of Ab assays can be compromised by serum interfering factors. The assays reported herein used a novel approach to effectively rule out and prevent false-positive results caused by high-levels of VEGF: blocking, with high-affinity murine MAbs that lack CDR-amino acid sequence homology to the drug.
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