Rosato and Pasupuleti et al. used a lectin domain that recognized Gb3, a tumor-associated carbohydrate antigen overexpressed on Burkitt’s lymphoma and several solid tumors, to create a novel class of T cell engagers (“lectibody”). Structural modeling identified K9 on the pentameric Shigella-derived lectin and E129 on OKT3 (anti-CD3), which could be modified with a non-conventional amino acid and used to join the molecules in an effective, multivalent configuration. The Gb3 lectibody showed high specificity for Gb3 and CD3, and high lytic capability at low concentrations when targeting Gb3-expressing liquid and solid tumors in vitro with human PBMCs.

Contributed by Ed Fritsch

BACKGROUND: Aberrant glycosylation patterns play a crucial role in the development of cancer cells as they promote tumor growth and aggressiveness. Lectins recognize carbohydrate antigens attached to proteins and lipids on cell surfaces and represent potential tools for application in cancer diagnostics and therapy. Among the emerging cancer therapies, immunotherapy has become a promising treatment modality for various hematological and solid malignancies. Here we present an approach to redirect the immune system into fighting cancer by targeting altered glycans at the surface of malignant cells. We developed a so-called "lectibody", a bispecific construct composed of a lectin linked to an antibody fragment. This lectibody is inspired by bispecific T cell engager (BiTEs) antibodies that recruit cytotoxic T lymphocytes (CTLs) while simultaneously binding to tumor-associated antigens (TAAs) on cancer cells. The tumor-related glycosphingolipid globotriaosylceramide (Gb3) represents the target of this proof-of-concept study. It is recognized with high selectivity by the B-subunit of the pathogen-derived Shiga toxin, presenting opportunities for clinical development. METHODS: The lectibody was realized by conjugating an anti-CD3 single-chain antibody fragment to the B-subunit of Shiga toxin to target Gb3(+) cancer cells. The reactive non-canonical amino acid azidolysine (AzK) was inserted at predefined single positions in both proteins. The azido groups were functionalized by bioorthogonal conjugation with individual linkers that facilitated selective coupling via an alternative bioorthogonal click chemistry reaction. In vitro cell-based assays were conducted to evaluate the antitumoral activity of the lectibody. CTLs, Burkitt«s lymphoma-derived cells and colorectal adenocarcinoma cell lines were screened in flow cytometry and cytotoxicity assays for activation and lysis, respectively. RESULTS: This proof-of-concept study demonstrates that the lectibody activates T cells for their cytotoxic signaling, redirecting CTLs« cytotoxicity in a highly selective manner and resulting in nearly complete tumor cell lysis-up to 93%-of Gb3(+) tumor cells in vitro. CONCLUSIONS: This research highlights the potential of lectins in targeting certain tumors, with an opportunity for new cancer treatments. When considering a combinatorial strategy, lectin-based platforms of this type offer the possibility to target glycan epitopes on tumor cells and boost the efficacy of current therapies, providing an additional strategy for tumor eradication and improving patient outcomes.

Author Info: (1) Faculty of Biology, University of Freiburg, Freiburg, Germany. Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany. (2) ACIB - The Austrian C

Author Info: (1) Faculty of Biology, University of Freiburg, Freiburg, Germany. Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany. (2) ACIB - The Austrian Centre of Industrial Biotechnology, Graz, Austria. Institute of Molecular Biotechnology, Graz University of Technology, Graz, Austria. (3) Faculty of Biology, University of Freiburg, Freiburg, Germany. Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany. (4) Faculty of Biology, University of Freiburg, Freiburg, Germany. Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany. Spemann Graduate School of Biology and Medicine, University of Freiburg, Freiburg, Germany. (5) ACIB - The Austrian Centre of Industrial Biotechnology, Graz, Austria. Institute of Molecular Biotechnology, Graz University of Technology, Graz, Austria. (6) Faculty of Biology, University of Freiburg, Freiburg, Germany. Kazan Institute for Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, Kazan, Russian Federation. (7) ACIB - The Austrian Centre of Industrial Biotechnology, Graz, Austria. birgit.wiltschi@acib.at. Institute of Molecular Biotechnology, Graz University of Technology, Graz, Austria. birgit.wiltschi@acib.at. Institute of Bioprocess Science and Engineering, University of Natural Resources and Life Sciences, Vienna, Austria. birgit.wiltschi@acib.at. (8) Faculty of Biology, University of Freiburg, Freiburg, Germany. winfried.roemer@bioss.uni-freiburg.de. Signalling Research Centres BIOSS and CIBSS, University of Freiburg, Freiburg, Germany. winfried.roemer@bioss.uni-freiburg.de. Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany. winfried.roemer@bioss.uni-freiburg.de.