A novel tetravalent bispecific TandAb (CD30/CD16A) efficiently recruits NK cells for the lysis of CD30⁺ tumor cells

Abstract

To improve recruitment and activation of natural killer (NK) cells to lyse tumor cells, we isolated a human anti-CD16A antibody with similar affinity for the CD16A 158F/V allotypes, but no binding to the CD16B isoform. Using CD16A-targeting Fv domains, we constructed a tetravalent bispecific CD30/CD16A tandem diabody (TandAb®) consisting solely of Fv domains. This TandAb has two binding sites for CD16A and two for CD30, the antigen identifying Hodgkin lymphoma cells. The binding and cytotoxicity of the TandAb were compared with antibodies with identical anti-CD30 domains: (1) a native IgG, (2) an IgG optimized for binding to Fc receptors, and (3) a bivalent bispecific CD30/CD16A diabody. Due to its CD16A-bivalency and reduced k_off, the TandAb was retained longer on the surface of NK cells than the IgGs or the diabody. This contributed to the higher potency and efficacy of the TandAb relative to those of the other anti-CD30 antibodies. TandAb cytotoxicity was independent of the CD16A allotype, whereas the anti-CD30 IgGs were substantially less cytotoxic when NK cells with low affinity CD16A allotype were employed. TandAb activation of NK cells was strictly dependent on the presence of CD30⁺ target cells. Therefore, the CD30/CD16A TandAb may represent a promising therapeutic for the treatment of Hodgkin’s lymphoma; further, anti-CD16A TandAbs may function as potent immunotherapeutics that specifically recruit NK cells to destroy cancer cells.

Keywords: :

• CD16A
• FcγRIIIA
• Hodgkin’s lymphoma
• NK cells
• bispecific antibodies

10.4161/mabs.28591

Disclosure of Potential Conflicts of Interest

All the authors are or were employees of Affimed Therapeutics.

Financial Disclosures

U.R., C.B., I.F., S.H.J.K., M.L., and E.A.Z. are employees of Affimed Therapeutics AG. F.L.G., M.L.G., and K.H. are former employees of Affimed Therapeutics AG. Otherwise there are no potential conflicts of interest.

Acknowledgments

We thank S. Kiprijanov (Affitech Research, Oslo, Norway) for the contributions to the early stages of the project, G. Moldenhauer (Department of Molecular Immunology, German Cancer Research Center (DKFZ) Heidelberg, Germany) for providing cell lines and antibodies, and O. Mandelboim (The Lautenberg Center for General and Tumor Immunology, The Hebrew University Hadassah Medical School, Jerusalem, Israel) for providing plasmids. The technical assistance of Frank Malischewsky, Andreas Müller, Michael Schott, Alexandra Stolarek, Stefanie Wolff, Helena Mennemann, and Tatjana Zingraf (all Affimed Therapeutics AG, Heidelberg, Germany) was gratefully appreciated.

Footnotes

This work was supported by the BioChancePlus grant no. 0313183 of the Federal Ministry of Education and Research (Germany).

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