Abstract 3125: TCX-101, a novel antibody-drug conjugate targeting a tumor-associated carbohydrate antigen for the treatment of solid tumors

Abstract Tumor-associated carbohydrate antigens (TACAs) are short oligosaccharides expressed on the surface of cancer cells and play key roles in cellular communication, immune evasion, apoptosis and metastasis. TACAs are therefore interesting targets for antibody-based therapies in cancer. We have generated an antibody (TCX-101) against a TACA structure with improved binding affinity compared to other monoclonal antibodies (mAbs) against the same target as shown by surface plasmon resonance (~ 10x superior KD), as well as high level of specificity against glycan species related to the target, as accessed by glycan array, flow cytometry, and immunocytochemistry or immunofluorescence. Immunohistochemistry studies on fresh-frozen tissue microarrays showed high expression of the target in various solid tumors (e. g. gastrointestinal, lung, and breast) and only low expression in normal tissues. In vitro, TCX-101 has ~ 4x higher maximum binding, ~ 2x faster binding kinetics, ~ 4x faster cellular internalization and induces ~ 2x higher antibody-dependent cellular cytotoxicity than a reference antibody. Monomethyl auristatin E (MMAE) was used in a drug-antibody ratio (DAR) of 4 to generate an antibody-drug conjugate (ADC). This ADC was effective in in vitro toxicity assays against murine B16 melanoma cells induced to express the target (measurable effect on WT cells), as well as human breast cancer MCF7 WT cells (~ 25x less activity on target-knockout MCF7 cells, Table 1). When tested in vivo, TCX-101 was highly effective in two different xenograft mouse models (B16, MCF7) with more than 95% tumor growth inhibition compared to vehicle, and no signs of toxicity (no weight loss, no histophatological findings). A fully humanized version of TCX-101 with improved binding properties (EC50 6. 27 nM vs. 8. 13 nM) was generated and will be evaluated in further in vivo experiments. In conclusion, TCX-101 is a promising ADC for the treatment of various solid tumors. IC50 nM TCX-101-MMAE 4 DAR B16 KI 7. 64 B16 WT no killing observed MCF7 WT 1. 97 MCF7 KO 45. 97 Citation Format: Fausto G. Gomes, Francesco Muraca, Gustavo M. Schmidt Garcia Moreira, Kathrin Rösch, Maria Bräutigam, Peter Sondermann, Matthias Ocker. TCX-101, a novel antibody-drug conjugate targeting a tumor-associated carbohydrate antigen for the treatment of solid tumors abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3125.