Abstract 4953: Differential expression of ICOS on circulating immune cells and tumor infiltrating lymphocytes in patient with solid tumors

Background: The Inducible T-cell costimulator (ICOS/CD278) is upregulated during T cell activation and is an important regulator of the immune response against pathogens and cancer cells. When engaged by its ligand, the activation of ICOS signaling improves the survival of ICOS+ effector (TEff) and regulatory T cells (TReg). In addition, depending on the T cell subtypes expressing ICOS, activation of the signaling pathway induces the expression and secretion of either pro- (by TEff) or anti-inflammatory (by TReg) cytokines. ICOS has been reported to be upregulated in the tumor microenvironment (TME) of most tumor indications. However, the variability in ICOS expression levels on ICOS expressing T cells (TEff and TReg) and their relative abundance in different tumor types is still poorly understood. The aim of this study was to take advantage of multiple analytical platforms to assess the expression of ICOS on immune cells in the periphery and on tumor infiltrating lymphocytes (TILs) from cancers known to express high levels of ICOS, based on previous TCGA analyses.

Methods: We analysed ICOS expression on peripheral blood mononuclear cell (PBMCs) and TILs by FACS, ChipcytometryTM and by single cell RNAseq. The analysis aimed to compare the expression of ICOS on different immune T cell subtypes. This comparison was performed on samples isolated from treatment naive non-small cell lung cancer (NSCLC) patients. In parallel, we established dual immunohistochemistry staining protocols supplemented by digital pathology to quantify and compare the expression of ICOS in the context of either FOXP3 or CD8 positive cells in NSCLC, gastric, esophageal, cervical, bladder and head and neck tumor samples.

Results and conclusion: Using these approaches, we confirmed high ICOS expression in several solid tumor types. ICOS expression was also shown to be higher on immune cells in the TME compared to the periphery. Finally, ICOS expression was found to be more abundant on the surface of intratumoral TReg than on CD8+ T effector cells, confirming the data obtained in preclinical syngeneic tumor models (AACR2018 abstract #2792). Importantly, this work highlighted variability in the abundance and ratio of the different ICOS+ T cells subtypes (TEff and TReg) between different ICOSHigh tumors. Altogether, the variability in the intratumoral ratio of ICOS positive T cells observed in different tumor types could differentially affect their response to antibodies targeting ICOS. This work suggests that understanding the expression of ICOS in the context of different immune T cell subtypes may improve selection of patients with higher potential to respond to anti-ICOS therapies such as KY1044.

Citation Format: Richard C. Sainson, Miha Kosmac, Rachael Kimber, Joana Carvalho, Gwenoline Bohris, Anil Thotakura, David Melvin, Matthew McCourt. Differential expression of ICOS on circulating immune cells and tumor infiltrating lymphocytes in patient with solid tumors [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 4953.

A first-in-human study of KY1044, a fully human anti-ICOS IgG1 antibody as monotherapy and in combination with atezolizumab in patients with selected advanced malignancies

TPS2644

Background: The Inducible T-cell costimulator (ICOS/CD278) is related to the CD28 superfamily and is induced upon T cell activation. There is a hierarchical order of ICOS expression level, in which highly immunosuppressive TReg (CD4+Foxp3+) present in the tumor microenvironment (TME) are at the top level of expression and CD8 TEff cells are at the bottom level. In addition, ICOS expression on TRegs is higher in the TME than in the blood or spleen. Methods: KY1044, a fully human anti-ICOS IgG1 kappa monoclonal antibody, selectively binds to ICOS with high affinity (which is maintained at intratumoral acidic pH) and has a dual mechanism of action: it promotes the preferential depletion of intratumoral ICOSHigh TRegs resulting in an increase in the TEff:TReg ratio in the TME; and it stimulates ICOSLow TEff cells. Preclinical data demonstrate that KY1044 monotherapy or in combination with anti-PD-L1 is associated with immune cell activation and anti-tumor response. In order to validate the dual mechanism of action in vivo, studies in mice and cynomolgus monkeys were conducted. Firstly, KY1044 injected i.v. at doses up to 100 mg/kg weekly were well tolerated in non-human primates. In addition, pharmacodynamic studies in mice and cynomolgus monkey confirm preferential depletion of ICOSHigh cells. KY1044-CT01 is an open-labelled first in human Phase I/II study assessing the safety, tolerability, PK, PD and anti-tumor activity of KY1044 administered every 3 weeks (Q3W) as an i.v. single agent infusion and in combination with atezolizumab (1200 mg, Q3W IV) in adult patients with advanced/metastatic malignancies. The primary endpoint of the Phase I dose escalations, designed as sequential but overlapping arms of KY1044 monotherapy and combination with atezolizumab, is safety and tolerability. Secondary endpoints are the characterization of pharmacokinetic, pharmacodynamic and efficacy profiles in all patients. In the Phase II part, the primary endpoint is overall response rate (ORR), and the measure of clinical efficacy will be confirmed as per RECIST 1.1. and immune-related (ir)RECIST. An intensive biomarker plan is integral to the study design to underpin the phenotypic and molecular changes in both peripheral blood and tumor. Clinical trial information: NCT03829501.

Abstract 2792: The combination of immune checkpoint blockers with the anti-ICOS KY1044 antibody results in a strong tumor response

The last few years have shown a strong paradigm shift in cancer therapies with the approval of antibodies targeting immune checkpoints (CTLA-4, PD-1 and PD-L1). These immune checkpoint blockers (ICBs) are associated with a strong and long-lasting response in patients suffering from different malignancies. However, there is still a high proportion of patients showing intrinsic or acquired resistance to ICBs. Although the mechanisms associated with the lack of immune response are multiple, the presence of highly anti-inflammatory regulatory T cells (TRegs) in the tumour microenvironment (TME) is known to negatively affect the response to these therapies. Similarly, high TReg levels in the TME have been associated with poor prognosis in several cancers. Together, this highlights the potential of targeting and depleting TRegs to enhance anti-tumour responses.

The Inducible T-cell costimulator (ICOS/CD278) is related to the CD28 superfamily and is induced when T cells get activated. ICOS expression levels vary in different immune cell subtypes and in different tissues. In preclinical mouse tumour models, TRegs (CD4+/FOXP3+) constitutively express ICOS on their surface and the expression of ICOS on TRegs is significantly higher than that on effector T cells (TEffs). In addition, ICOS expression on TRegs is higher in the TME than in the blood or spleen, which makes it a strong candidate for preferential depletion of TRegs in tumours. By immunizing Kymice™ in which the endogenous Icos gene has been knocked out, we identified a novel, fully human antibody called KY1044 that cross-reacts with mouse ICOS. KY1044 is an anti-ICOS subclass G1 kappa monoclonal antibody that selectively binds to dimeric ICOS (Fc fusion) with an affinity of less than 2nM. Using in vitro and in vivo approaches we demonstrate that KY1044 has a dual mechanism of action: (1) it promotes the preferential depletion of intratumoural ICOShigh TRegs resulting in an increase in the TEff:TReg ratio in the TME; and (2) it stimulates ICOSLow TEff cells. Using the mouse effector enabled version of KY1044 (mIgG2a) we confirm, using syngeneic models, a strong anti-tumour efficacy as monotherapy or in combination with surrogates of ICBs. We also demonstrated a tumour antigen specific immunity, as highlighted by the rejection of the original tumour cells in animals cured of the disease and re-challenged by the same cell line. Noteworthy, Pharmacodynamic studies demonstrate long-term depletion of TRegs and a significant increase in the TEff:TReg ratio in response to KY1044. In summary, our data demonstrate that targeting ICOS with KY1044 is a valid approach for manipulating the immune system and for inducing a strong anti-tumour response in several indications. The data presented here also warrant the assessment of KY1044 in cancer patients in a clinical trial.

Citation Format: Richard C. Sainson, Matthew McCourt, Anil Thotakura, Nahida Parveen, Miha Kismac, Gwenoline Borhis, Joana Carvalho, Tracey Myers, Robert Rowlands, Hanif Ali, Hannah Craig, Vivian Wong, Qi Liang, Volker Germaschewski. The combination of immune checkpoint blockers with the anti-ICOS KY1044 antibody results in a strong tumor response [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 2792.

Structure of FKBP12.6 in complex with rapamycin

FKBP12.6 is a novel isoform of FKBP12, which selectively binds to the cardiac ryanodine receptor (RyR2). The crystal structure of FKBP12.6 in complex with rapamycin has now been determined at 2.0 A resolution. The structures of FKBP12.6 and FKBP12 are nearly identical, except for a displacement observed in the helical region of FKBP12.6 toward the hydrophobic pocket. This displacement was not predicted by homology modeling studies. Analyses of the residues that are likely to confer the RyR2-binding specificity are presented.