Abstract 1827: Efficacy and characterization of a specific and potent monoclonal antibody, LYT-210, against immunosuppressive gd1 T cell in cancer (2021)

Abstract Background: Targeting and engineering γδ T cells has emerged as an orthogonal therapeutic approach in oncology with capacity to modulate both innate and adaptive immunity. Solid tumors (e.g. pancreatic ductal adenocarcinoma (PDAC), melanoma, glioblastoma, ovarian-, breast- cancer etc.), can be enriched for γδ1T cells, where they mediate a robust, multi-faceted immunosuppression. We verified the phenotypic and functional features, and the immunosuppressive potential of cancer patient γδ1T cells and have developed a therapeutic antibody (mAb), LYT-210, for selective depletion of these immune evasion culprits. LYT-210 is highly specific, fully human, species cross-reactive IgG1 antibody, aimed for IND enabling studies and clinical development. Methods: γδ1T cells were profiled and studied from blood of healthy and cancer donors, and from surgically excised primary or metastatic tumors. A proprietary, synthetic Fab-phage library was used to generate LYT-210, a fully human IgG1 mAb. Functional assays (ADCC/ADCP) confirmed an expected and desired, Fcγ-dependent LYT-210 mode of action. We used healthy and patient PBMCs to assess the dynamics, dose dependence and specificity of γδ1 T cell killing with LYT-210. Patient tumor organoids were used for ex vivo efficacy studies. Purified proteins and engineered cell lines served to determine specificity and affinity of LYT-210. Retrogenix protein array (&gt;5500 cell surface and secreted proteins) was used to identify possible off-target binding of LYT-210. Results: Anti-δ1antibody was used to treat patient tumor organoids (n = 29) and showed potent intra-tumoral T cell activation across tumor types (e.g. colorectal and liver cancer). Additionally, LYT-210 exerted potent ADCP and ADCC on: i) stable cell lines expressing γδ1TCRs and ii) γδ1T cells from patient PBMCs and did so by sparing αβ T cells and γδ2 T cells. Furthermore, LYT-210 induced ADCP and ADCC were Fcγ receptor dependent, confirming LYT-210-specific and effector cell dependent mode of action. LYT-210 induced γδ1 T cell-specific death rapidly, i.e. within 30 minutes of treatment with an EC50 of 26 pM and with the effect sustained over 70 hours of culture. Cell surface proteomics microarray analysis showed very weak cross reaction of LYT-210 with CEACAM5 (a known human cancer cell surface antigen), but in confirmatory assays had minimal binding to CEACAM5 expressed onto HEK293 cells (~200 nM) and no binding at all to purified CEACAM5. The Retrogenix array and additional assays therefore confirm the profound specificity of LYT-210 to γδ1T cells. Conclusions: We have developed a novel, therapeutic immuno-oncology strategy specifically targeting imunosuppressive γδ1cells. Our data support that this therapeutic approach may have the potential to be transformative for the treatment of cancers where γδ1T cells drive a pro-tumorigenic, immunosuppressive environment. Citation Format: Tatyana Panchenko, Wei Wang, Eric Denbaum, Akiko Koide, Takamitsu Hattori, Aleksandra Filipovic, George Miller, Shohei Koide. Efficacy and characterization of a specific and potent monoclonal antibody, LYT-210, against immunosuppressive gd1 T cell in cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1827.