Background Immunotherapies, like immune checkpoint inhibition and tumor infiltrating lymphocytes, have had remarkable success in treating melanoma. However, many patients do still not respond or relapse with therapy-resistant disease. To overcome said limitations, we propose a controlled adoptive cell therapy approach, where T cells are armed with EGFRvIII synthetic agonistic receptors (E3 SAR) that are selectively activated by a cross-linking bispecific antibody (BiAb) specific for both SAR T cell and melanoma-associated antigens.

Materials and Methods Murine as well as human SAR constructs were generated and T cells were retrovirally transduced to stably express the SAR constructs. We validated our approach in murine, human and patient-derived cancer models expressing the melanoma-associated target antigens TYRP1 and MCSP. SAR T cells were functionally characterised by proving specific activation and proliferation of SAR T cells, as well as their tumor-directed cytotoxicity, in vitro and in vivo.

Results Both on a mRNA and protein level, MCSP and TYRP1 were shown to be differentially expressed in treatment-naive as well as treatment-resistant melanoma patients compared to samples from healthy donors. Crosslinking anti-TYRP1 x anti-E3 and anti-MCSP x anti-E3 BiAb mediated conditional antigen-dependent activation, proliferation of SAR-T cells and lead to tumor cell lysis in all models tested. In vivo, anti-tumoral activity and tumor-free survival was mediated by the co-administration of SAR T cells and BiAb in a syngeneic tumor model and was further confirmed in several xenograft models.

Conclusions Here, we apply the SAR x BiAb approach in an effortto deliver specific and conditional activation of SAR transduced T cells, and targeted tumor cell lysis in melanoma models. The modularity of our approach is key for targeting melanoma and is essential towards personalised immunotherapies addressing cancer heterogeneity. Due to variations of antigen expression in primary melanoma tissues, we propose that a dual-targeting approach, either simultaneous or sequential, could mitigate issues of heterogeneity and deliver therapeutic benefit to patients.

Disclosure Information M. Benmebarek: A. Employment (full or part-time); Significant; Klinikum der Universität München. F. Märkl: A. Employment (full or part-time); Significant; Klinikum der Universität München. J. Keyl: None. B. Cadilha: A. Employment (full or part-time); Significant; Klinikum der Universität München. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Pantent in the immuno-oncology field. M. Geiger: A. Employment (full or part-time); Significant; Roche. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Stocks and patents with Roche. C. Karches: A. Employment (full or part-time); Significant; Klinikum der Universität München. H. Obeck: None. M. Schwerdtfeger: A. Employment (full or part-time); Significant; Klinikum der Universität München. D. Briukhovetska: A. Employment (full or part-time); Significant; Klinikum der Universität München. J. Jobst: None. P.J. Müller: None. M. Seifert: None. R. Grünmeier: None. M. Thomas: A. Employment (full or part-time); Significant; Helmholtz München. C. Marr: A. Employment (full or part-time); Significant; Helmholtz München. B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Significant; European Research Council. M. Levesque: A. Employment (full or part-time); Significant; University Hospital Zurich. M. Heppt: A. Employment (full or part-time); Significant; Universitätsklinikum Erlangen. S. Endres: A. Employment (full or part-time); Significant; Klinikum der Universität München. B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Significant; Elite Network of Bavaria, LMU Munich’s Institutional Strategy LMUexcellent. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Patents in the field of immuno-oncology. C. Klein: A. Employment (full or part-time); Significant; Roche. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Stocks and patents with Roche. S. Kobold: A. Employment (full or part-time); Significant; Klinikum der Universität München. B. Research Grant (principal investigator, collaborator or consultant and pending grants as well as grants already received); Significant; Volkswagen Foundation, European Research Council, Hector Foundation, Elite Network of Bavaria, Melanoma Research Alliance, Else Kröner-Fresenius-Stiftung, German Cancer Aid, Ernst-Jung-Sfiftung, LMU Munich’s Institutional Strategy LMUexcellent, Bundesministerium für Bildung und Forschung, European Research Council Grant, Fritz-Bender Foundation, José-Carreras Foundation. C. Other Research Support (supplies, equipment, receipt of drugs or other in-kind support); Significant; German Research Foundation. D. Speakers Bureau/Honoraria (speakers bureau, symposia, and expert witness); Significant; TTCR2 Inc, Novartis, BMS, GSK. E. Ownership Interest (stock, stock options, patent or other intellectual property); Significant; Patents in the field of immuno-oncology.