Lymphoid neogenesis, or the development of lymphoid structures in nonlymphoid organs, is frequently observed in chronically inflamed tissues, during the course of autoimmune, infectious, and chronic graft rejection diseases, in which a sustained lymphocyte activation occurs in the presence of persistent antigenic stimuli. The presence of such ectopic lymphoid structures has also been reported in primary lung, breast, and germline cancers, but not yet in melanoma. In this study, we observed ectopic lymphoid structures, defined as lymphoid follicles comprising clusters of B lymphocytes and follicular dendritic cells (DC), associated with high endothelial venules (HEV) and clusters of T cells and mature DCs, in 7 of 29 cutaneous metastases from melanoma patients. Some follicles contained germinal centers. In contrast to metastatic lesions, primary melanomas did not host follicles, but many contained HEVs, suggesting an incomplete lymphoid neogenesis. Analysis of the repertoire of rearranged immunoglobulin genes in the B cells of microdissected follicles revealed clonal amplification, somatic mutation and isotype switching, indicating a local antigen-driven B-cell response. Surprisingly, IgA responses were observed despite the nonmucosal location of the follicles. Taken together, our findings show the existence of lymphoid neogenesis in melanoma and suggest that the presence of functional ectopic lymphoid structures in direct contact with the tumor makes the local development of antimelanoma B-and T-cell responses possible.

Melanoma is not only one of the most immunogenic cancers but also one of the most effective cancers at subverting host immunity. The role of T lymphocytes in tumor immunity has been extensively studied in melanoma, whereas less is known about the importance of B lymphocytes. The effects of plasma cells (PCs), in particular, are still obscure. The aim of this study was to characterize pathological features and clinical outcome of primary cutaneous melanomas associated with PCs. Moreover, we investigated the origins of the melanoma-associated PCs. Finally, we studied the outcome of patients with primary melanomas with PCs. We reviewed 710 melanomas to correlate the presence of PCs with histological prognostic markers. Immunohistochemistry for CD138 and heavy and light chains was performed in primary melanomas (PM) and in loco-regional lymph nodes (LN), both metastatic and not metastatic. In three PM and nine LN with frozen material, VDJ-rearrangement was analyzed by Gene Scan Analysis. Survival analysis was performed on a group of 85 primary melanomas 42 mm in thickness. Forty-one cases (3.7%) showed clusters/sheets of PCs. PC-rich melanomas occurred at an older age and were thicker, more often ulcerated and more mitotically active (Po 0.05). PCs were polyclonal and often expressed IgA in addition to IgG. In LN, clusters/sheets of IgA+ PCs were found both in the sinuses and subcapsular areas. Analysis of VDJ-rearrangements showed the IgA to be oligoclonal. Melanomas with clusters/sheets of PCs had a significantly worse survival compared with melanomas without PCs while, interestingly, melanomas with sparse PCs were associated with a better clinical outcome (P = 0.002). In conclusion, melanomas with sheets/clusters of PCs are associated with worse prognosis. IgG and IgA are the isotypes predominantly produced by these PCs. IgA oligoclonality suggests an antigen-driven response that facilitates melanoma progression by a hitherto unknown mechanism.

TIGIT is an immune checkpoint inhibitor expressed by effector CD4 + and CD8 + T, NK cells and regulatory T-cells. Inhibition of TIGIT-ligand binding using antagonistic anti-TIGIT monoclonal antibodies (mAbs) has shown in vitro potential to restore T-cell functions and therapeutic efficacy in murine tumor models when combined with an anti-PD(L)-1 antibody. Here, we demonstrate for the first time, broader TIGIT expression than previously reported in healthy donors and cancer patients: being observed on  T-cells, particularly in CMVseropositive donors and on tumor cells from hematological malignancies such as cutaneous T -cell lymphoma. Quantification of TIGIT density revealed tumor-infiltrating Treg as the population expressing the highest receptor density. Consequently, the therapeutic potential of anti-TIGIT mAbs might be broader than the previously described anti-PD(L)-1 like restoration of  T-cell function. In addition to  T-cell re-invigoration, CD155 also mediated inhibition in  T-cells, an immune population not previously described to be sensitive to TIGIT inhibition, and could be fully prevented via use of an antagonistic anti-TIGIT mAb (EOS884448). In PBMC from cancer patients, as well as TILs from mice, the higher TIGIT expression in Treg correlated with strong antibody-dependent killing and preferential depletion of this highly immunosuppressive population. Accordingly, ADCCenabling anti-TIGIT mAb had superior antitumor activity, that was depending on Fc receptor engagement. In addition, we induced direct killing of TIGIT-expressing tumor cells both in human patient material and animal models, demonstrating strong rational for therapeutic intervention in heme malignancies. These findings reveal broad therapeutic opportunities for anti-TIGIT mAbs in cancer therapeutics.

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T cell Immunoreceptor with Ig and ITIM domains (TIGIT) is a co-inhibitory receptor expressed by lymphocytes, preferentially CD8+ T cells, NK, as well as by regulatory T cells (Treg). CD226 (DNAM-1), a co-stimulatory receptor also expressed on NK and T cells competes with TIGIT for PVR binding but with a lower affinity. Co-expression of TIGIT and CD226 receptors on T and NK effector cells suggests a role of these molecules in the fine control of cell activation. In cancer, TIGIT expression is upregulated on conventional and even more on regulatory T cells and co-expression with exhaustion markers such as PD-1 is frequent, giving a strong rationale for blocking TIGIT as a therapeutic approach to reverse T or NK cell dysfunction linked with cancer progression. Antagonistic anti-TIGIT antibodies were selected using a synthetic yeast display library of fully human antibodies and characterized for their binding and functional properties. EOS884448 anti-TIGIT mAb displays a strong affinity for recombinant and native TIGIT expressed on human primary T cells. It competes with CD155 for binding to human TIGIT and restores cytokine production when human primary T cells are suppressed in presence of CD155. To further explore its potency, EOS884448 was produced in a mammalian system on different human isotypes with different Fc effector functions. In the hIgG1 format, EOS884448 demonstrated preferential depletion of Treg cells in vitro when spiked in PBMC from healthy volunteers. Interestingly, the preferential depletion of Treg was also observed in PBMCs from cancer patients that harbour higher level of expression of TIGIT on Tregs but also on conventional CD4+ and CD8+ T cell populations. In vivo, two different isotypes of surrogate mouse anti-TIGIT mAb were used to evaluate the anti-tumor efficacy in the CT26 syngeneic murine model. Interestingly, only the ADCC enabling mIgG2a isotype was able to induce strong antitumor efficacy in monotherapy and in combination with an anti-PD1, resulting in a complete regression of pre-established tumors in the majority of animals. Anti-tumor efficacy was associated with an increased activity of conventional CD8+ and CD4+ T cells but also with Treg depletion within the tumor microenvironment, reaffirming the in vitro data generated on human PBMCs. The importance of depleting Treg using an a-TIGIT Ab isotype with effector functions was further confirmed in CT26 tumor bearing mice where the a-TIGIT mIgG1 isotype only shows efficacy when Treg are previously depleted using an anti-CD4 antibody. In summary, in vitro and in vivo data demonstrate for the first time the potential for a-TIGIT mAb EOS884448 to promote antitumor immunity by preferential depletion of Treg cells and activation of conventional T cells, which supports the rationale for its clinical evaluation. Citation Format: XAVIER LEROY, Catherine Hoofd, Julia Cuende, Sofie Denies, Virginie Rabolli, Julie Preillon, Florence Lambolez, Shruthi Prasad, Marjorie Mercier, Florence Nyawouame, Véronique Bodo, Noémie Wald, Grégory Driessens, Michel Detheux. a-TIGIT antagonist antibody EOS884448 shows dual mechanism of action by restoration of T cell effector functions and preferential depletion of Treg [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr LB-114.

Adenosine is a potent immunosuppressive metabolite that is often found elevated in the extracellular tumor microenvironment (TME). We determined concentrations of extracellular adenosine in different patient-derived xenografts (PDX) from 7 different histological types, in which extracellular median adenosine concentrations were shown to range from 0.5 to 45 µM, with the overall median adenosine concentration being about 4.5 µM. Adenosine concentration in the non-tumorous subcutaneous space in mice was measured at about 0.5 µM. Adenosine in the TME is generated mainly by the concerted action of the ectonucleotidases CD39 and CD73. The expression of these enzymes across various cancer types was evaluated by flow cytometry in dissociated human tumor biopsies. CD73 and CD39 were strongly expressed by multiple tumor-infiltrating T cell types. Tumor-associated myeloid cells mostly expressed CD39 and high frequencies of EpCAM+ tumor cells strongly expressed CD73. These data strongly suggest that adenosine levels could be further increased compared to non-immune-infiltrated PDX.Adenosine activates 4 G protein-coupled receptor subtypes, of which the adenosine A2A receptor in particular suppresses innate and adaptive immune cell responses leading to suppression of anti-tumor immunity. Among the 4 adenosine receptors, we confirmed the A2A receptor as the main adenosine receptor expressed in CD4+ and CD8+ T cells, natural killer cells, monocytes, and dendritic cells. Stimulation of these immune cell subsets further increased A2A receptor expression. A2B receptor was expressed at very low levels in stimulated CD4+ and CD8+ T cells and in monocytes and immature DCs. A1 and A3 receptors were hardly detected in these subsets of immune cells. EOS100850, a highly potent and selective A2A receptor antagonist, was characterized in various in vitro functional assays. A2A receptor activation by a selective agonist suppressed priming of mouse OVA-specific OT1 T cells and subsequent antigen-specific CD8+ T cell cytotoxicity in a co-culture assay of effector CD8+ T cells and target cancer cells. This A2A receptor-mediated immune suppression was potently and dose-dependently reversed by EOS100850. In a mixed lymphocyte reaction between human dendritic cells and T cells, EOS100850 blocked the adenosine-dependent inhibition of T cell proliferation and secretion of IFNg, TNFa and IL-2 in a dose-dependent manner. In conclusion, extracellular adenosine as well as adenosine pathway components were strongly present across multiple tumor types, and across multiple tumor-associated cell types. In addition, EOS100850, a highly potent A2A receptor antagonist, reversed A2A receptor-mediated suppression of T cell priming, cytotoxicity, cytokine production and proliferation. Citation Format: Erica Houthuys, Paola Basilico, Veronique Bodo, Margreet Brouwer, Michel Detheux, Gregory Driessens, Bruno Gomes, Annelise Hermant, Catherine Hoofd, Florence Lambolez, Xavier Leroy, Reece Marillier, Chiara Martinoli, Marjorie Mercier, Florence Nyawouame, Shruthi Prasad, Ariane Scoumanne, Stefano Crosignani. EOS100850 potently restores adenosine A2Areceptor-dependent suppression of T cell function in the adenosine rich tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3278.

TIGIT is a T cell co-inhibitory receptor recently described as a key checkpoint driving tumor cell immunosuppression. It is predominantly expressed on CD4+ Tregs, CD8+ T cells and NK cells from healthy individuals but further upregulated in cancer patients where it frequently co-expresses with exhaustion markers such as PD-1. TIGIT cognate receptors are members of the poliovirus receptors, among which CD155 has the highest affinity for TIGIT. They are expressed on antigen presenting cells but also on tumor cells which provides a strong rationale for blocking TIGIT as a therapeutic approach to reverse T or NK cell dysfunction linked with cancer progression. To substantiate the importance of TIGIT as an immunotherapy target, we used flow cytometry and immunohistochemistry (IHC) to extensively characterize TIGIT and CD155 expression in both healthy donors and cancer patients. We initially confirmed TIGIT expression on multiple immune subsets from healthy donors. Similar flow cytometry analysis performed on matched circulating and tumor-infiltrating immune populations from 15 cancer patients highlighted the global overexpression of TIGIT associated with cancer. Interestingly, ex vivo polyfunctional analysis of cytokine release strongly supported the immunosuppressed character of infiltrated TIGIT positive CD4+ and CD8+ T cells. Finally, combining receptor density with frequency of positive cells led to the interesting observation that tumor-infiltrating Tregs represents the population with the highest TIGIT expression, confirming the opportunity to preferentially target that suppressive population within the tumor microenvironment. These findings on Tregs were further confirmed by IHC. TIGIT was expressed in 10 out of the 11 lung adenocarcinoma tissues analysed. Both Tregs and CD8+ T cells express TIGIT, with Tregs showing a higher proportion of TIGIT+ cells. Finally, direct expression of TIGIT on tumor cells was also found on several haematological malignancies, opening the door for anti-TIGIT therapies to act directly on tumor cells besides revigoration of the immune system. The presence of TIGIT ligands within the tumor microenvironment was also assessed and confirmed using both flow cytometry and IHC. CD155 expression was analysed by IHC in both normal individuals (n=90) and cancer patient tissues from 9 different cancer indications (n=284). In cancer tissues, CD155 is mostly expressed by tumor cells, ranging from a median percentage of 50 % for pancreatic cancer to 2 % for cervix cancer. Cancer samples with the highest CD155 expression are pancreatic, prostate, kidney, gastric and colon cancers. CD155 expression is always lower in normal tissues compared to their cancer counterparts except for lung. Together, these data strongly support the relevance of targeting TIGIT in immuno-oncology and pave the way to select the ideal indications where patients could benefit from such a therapy. Citation Format: Noémie Wald, Marjorie Mercier, Julia Cuende, Florence Nyawouame, Shruthi Prasad, Margreet Brouwer, Erica Houthuys, Anne Marie-Cardine, Martine Bagot, Grégory Driessens, Véronique Bodo, Catherine Hoofd. TIGIT pathway phenotyping sheds light on promising strategies to restore anti-tumor immunity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 4969.

T cell Immunoreceptor with Ig and ITIM domains (TIGIT) is a co-inhibitory receptor expressed by lymphocytes, preferentially CD8+, NK, as well as by regulatory T cells (Treg). CD226 (DNAM-1), a co-stimulatory receptor also expressed on NK and T cells, competes with TIGIT for their common ligand, CD155, binding but with a lower affinity. Co-expression of TIGIT and CD226 receptors on T and NK effector cells suggests a role of these molecules in the fine control of cell activation. In cancer, TIGIT expression is upregulated on conventional and even more on regulatory T cells and co-expression with exhaustion markers such as PD-1 is frequent, giving a strong rationale for blocking TIGIT as a therapeutic approach to reverse T or NK cell dysfunction linked with cancer progression. We have developed EOS884448, a fully human antagonist anti-TIGIT antibody that demonstrates strong potential in vitro to compete with TIGIT natural ligands and to prevent CD155-mediated inhibition of T cells from healthy volunteers and cancer patients. In addition, EOS884448 preferentially depletes Treg via an ADCC-triggered mechanism. In vivo, in mouse tumor models, a surrogate a-TIGIT antibody has shown potent antitumor activity through a combination of its antagonistic properties and its effector function through Fc gamma receptor engagement. EOS884448 was tested in a non-human primate GLP toxicology study and demonstrated a safe profile at all tested doses (≤10mg/kg) after repeated injection for up to 4 weeks at weekly intervals (5 doses in total). Pharmacokinetic data showed dose-dependent increase of EOS884448 concentration in the blood that correlated with gradual increased in TIGIT receptor occupancy measured on NK and T cells and that reached saturation in Cynomolgus monkeys dosed at 1mg/kg. In anticipation of the first-in-human (FIH) study of EOS884448, assays to measure PK, ADA and receptor occupancy in human blood samples were developed. In addition, to support the clinical strategy, multiple cancer indications were tested for expression of members of the TIGIT pathway. The frequency of TIGIT-expressing immune cells, analysed by FACS, was increased in PBMCs from cancer patients as compared to healthy donors. Further increase in TIGIT expression (both in proportion and density) was measured on TILs, and particularly on Treg cells that had the highest expression. CD155 expression analysed by IHC in solid cancers (n=284) was higher in tumor and seen in the nine tested indications, with close to 50% of CD155high tumor cells measured in indications including pancreatic, prostate, kidney, gastric and colon cancers. CD226 expression was confirmed by IHC on immune infiltrate in solid tumor samples (n=307). Altogether, preclinical, toxicology and translational medicine data support the initiation of a FIH study of a-TIGIT mAb EOS884448 in cancer patients. Citation Format: Thi Lien-Anh Nguyen, Julia Cuende, Julie Preillon, Lucile Garnero, Virginie Rabolli, Noémie Wald, Catherine Hoofd, Patricia Chevron, Marjorie Mercier, Olivier De Henau, Véronique Bodo, Gregory Driessens. Preparation of aclinical trial with a-TIGIT antagonist antibody EOS884448, which demonstrates potent preclinical activity and safe toxicology profile [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3161.