A tetravalent bispecific TandAb (CD19/CD3), AFM11, efficiently recruits T cells for the potent lysis of CD19⁺ tumor cells

Abstract

To harness the potent tumor-killing capacity of T cells for the treatment of CD19⁺ malignancies, we constructed AFM11, a humanized tetravalent bispecific CD19/CD3 tandem diabody (TandAb) consisting solely of Fv domains. The molecule exhibits good manufacturability and stability properties. AFM11 has 2 binding sites for CD3 and 2 for CD19, an antigen that is expressed from early B cell development through differentiation into plasma cells, and is an attractive alternative to CD20 as a target for the development of therapeutic antibodies to treat B cell malignancies. Comparison of the binding and cytotoxicity of AFM11 with those of a tandem scFv bispecific T cell engager (BiTE) molecule targeting the same antigens revealed that AFM11 elicited more potent in vitro B cell lysis. Though possessing high affinity to CD3, the TandAb mediates serial-killing of CD19⁺ cells with little dependence of potency or efficacy upon effector:target ratio, unlike the BiTE. The advantage of the TandAb over the BiTE was most pronounced at lower effector:target ratios. AFM11 mediated strictly target-dependent T cell activation evidenced by CD25 and CD69 induction, proliferation, and cytokine release, notwithstanding bivalent CD3 engagement. In a NOD/scid xenograft model, AFM11 induced dose-dependent growth inhibition of Raji tumors in vivo, and radiolabeled TandAb exhibited excellent localization to tumor but not to normal tissue. After intravenous administration in mice, half-life ranged from 18.4 to 22.9 h. In a human ex vivo B-cell chronic lymphocytic leukemia study, AFM11 exhibited substantial cytotoxic activity in an autologous setting. Thus, AFM11 may represent a promising therapeutic for treatment of CD19⁺ malignancies with an advantageous safety risk profile and anticipated dosing regimen.

Keywords:

• CD3
• T cells
• bispecific antibodies
• Non-Hodgkin lymphoma
• ALL

Disclosure of Potential Conflicts of Interest

UR, KE, CH, SHJK, IF, and EAZ are employees of Affimed Therapeutics AG.

ME, FM, and FLG are former employees of Affimed Therapeutics AG.

Acknowledgments

We thank G. Moldenhauer (Department of Molecular Immunology, German Cancer Research Center (DKFZ) Heidelberg, Germany) for providing cell lines. We thank B. Stockmeyer (University of Erlangen, Germany) for providing pcDNA3.1(+) plasmid DNA encoding human CD19. We also thank R. Morse for assistance in preparing the manuscript and helpful discussions. The technical assistance of Frank Malischewsky, Sonja Hennemann, Sarah Flößer, Carolin Böhm, Jürgen Weik, Ute Schniegler-Mattox, Thomas Müller, Andreas Müller, Raphael Bleiler, Alexandra Stolarek, Stefanie Wolff, and Tatjana Zingraf (all Affimed Therapeutics AG, Heidelberg, Germany) was gratefully appreciated.

Supplementary Material

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