Authors: De Goeij BE[1], Vink T[2], Ten Napel H[2], Breij EC[2], Satijn D[2], Wubbolts R[3], Miao D[4], Parren PW[2][5][6].
Title: Efficient Payload Delivery by a Bispecific Antibody-Drug Conjugate Targeting HER2 and CD63.
Published in: Mol Cancer Ther. 2016 Nov;15(11):2688-2697. Epub 2016 Aug 24.

Keywords: CD63, HER2, bispecific antibody, bsAb, lysosomal membrane protein

Antibody-drug conjugates (ADC) are designed to be stable in circulation and to release potent cytotoxic drugs intracellularly following antigen-specific binding, uptake, and degradation in tumor cells. Efficient internalization and routing to lysosomes where proteolysis can take place is therefore essential.

For many cell surface proteins and carbohydrate structures on tumor cells, however, the magnitude of these processes is insufficient to allow for an effective ADC approach. We hypothesized that we could overcome this limitation by enhancing lysosomal ADC delivery via a bispecific antibody (bsAb) approach, in which one binding domain would provide tumor specificity, whereas the other binding domain would facilitate targeting to the lysosomal compartment.

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We therefore designed a bsAb in which one binding arm specifically targeted CD63, a protein that is described to shuttle between the plasma membrane and intracellular compartments, and combined it in a bsAb with a HER2 binding arm, which was selected as model antigen for tumor-specific binding.

The resulting bsHER2xCD63his demonstrated strong binding, internalization and lysosomal accumulation in HER2-positive tumor cells, and minimal internalization into HER2-negative cells. By conjugating bsHER2xCD63his to the microtubule-disrupting agent duostatin-3, we were able to demonstrate potent cytotoxicity of bsHER2xCD63his-ADC against HER2-positive tumors, which was not observed with monovalent HER2- and CD63-specific ADCs.

Our data demonstrate, for the first time, that intracellular trafficking of ADCs can be improved using a bsAb approach that targets the lysosomal membrane protein CD63 and provide a rationale for the development of novel bsADCs that combine tumor-specific targeting with targeting of rapidly internalizing antigens.

Author affiliation:
[1] Genmab, Utrecht, the Netherlands.
[2] Genmab, Utrecht, the Netherlands.
[3] Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, the Netherlands.
[4] Concortis Biosystems Corp., San Diego, California.
[5] Department of Cancer and Inflammation Research, Institute of Molecular Medicine, University of Southern Denmark, Odense, Denmark.
[6] Department of Immunohematology and Blood Transfusion, Leiden University Medical Center, Leiden, the Netherlands.

Featured Image: Technician in laboratory Feature image Courtesy: © 2016 Fotolia. Used with permission.

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