Ibalizumab is a humanized monoclonal antibody that binds human CD4—a key receptor for HIV—and blocks HIV-1 infection. However, HIV-1 strains with mutations resulting in loss of an N-linked glycan from the V5 loop of the envelope glycoprotein gp120 are resistant to ibalizumab. Previous structural analysis suggests that this glycan fills a void between the gp120 V5 loop and the ibalizumab light chain, perhaps causing steric hindrance that disrupts viral entry. If this void contributes to HIV-1 resistance to ibalizumab, we reasoned that 'refilling' it by engineering an N-linked glycan into the ibalizumab light chain at a position spatially proximal to gp120 V5 may restore susceptibility to ibalizumab. Indeed, one such ibalizumab variant neutralized 100% of 118 diverse HIV-1 strains tested in vitro, including 10 strains resistant to parental ibalizumab. These findings demonstrate that the strategic placement of a glycan in the variable region of a monoclonal antibody can substantially enhance its activity.
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The authors thank N. Padte for project management; Y. Huang, M. Tsuji, M.-W. Chen, C. Andrews, M. Sun and J. Yu for helpful discussions; and M.C. Nussenzweig for reagents. We also thank T.-L. Hsu, P.-C. Chen and the MS Core Facility at the Genomics Research Center, Academia Sinica (Taiwan), for glycoform profiling. Funding support for this study was provided by the Bill and Melinda Gates Foundation (OPP50714 and OPP1040731) via the Collaboration for AIDS Vaccine Discovery. Additional funding support was provided by the US National Institutes of Health grant number 1DP1DA033263-01.
D.D.H. is the scientific founder of TaiMed Biologics, Inc., which owns the commercial rights to ibalizumab. In this capacity, D.D.H. has equity in the company. R.S. and D.D.H. are inventors on a patent describing glycan-modified anti-CD4 antibodies for HIV prevention and therapy.
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Song, R., Oren, D., Franco, D. et al. Strategic addition of an N-linked glycan to a monoclonal antibody improves its HIV-1–neutralizing activity. Nat Biotechnol 31, 1047–1052 (2013). https://doi.org/10.1038/nbt.2677
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