ESTRO 2020 Abstract Book

S38 ESTRO 2020

OC-0082 TNFα-mediated crosstalk between regulatory T cells and monocytes limits radiotherapy efficacy M. Mondini 1 , P. Hamon 1 , P. Loyher 2 , M. Gerbé de Thoré 1 , C. Clemenson 1 , M. Laviron 2 , K. Berthelot 1 , B.L. Salomon 2 , C. Combadière 2 , A. Boissonnas 2 , E. Deutsch 3 1 Gustave Roussy, Inserm U1030, Villejuif, France ; 2 Sorbonné Université - Inserm, CIMI Paris, Paris, France ; 3 Gustave Roussy, Inserm U1030 and Departement of Radiotherapy, Villejuif, France Purpose or Objective Beyond the expected direct effects of radiation therapy (RT ) on tumor cells, several evidence support the importance of an immune response to radiotherapy. These observations foster the use of combination of immunomodulators with RT to enhance its therapeutic index. Several efforts have been put to investigate the induction of an antitumor-immunity by RT. Nevertheless, RT can also induce or amplify tumor immunosuppressive mechanisms. The balance between RT-mediated immunogenic and immunosuppressive activities deserves more attention. Infiltration of monocytes/macrophages and regulatory T cells (Tregs) into the tumor is a known factor limiting the antitumor immune response. Among the many cytokines secreted by tumor cells, CCL2 is involved in monocyte recruitment from bone marrow to the inflammatory site, as well as a subset of Tregs. We thus speculated that the CCL2/CCR2 axis might be implicated in the co-recruitment of TAMs and Tregs following RT, favoring immunosuppression. Material and Methods We used orthotopic models of oral and lung cancer in immunocompetent mice to evaluate the effects of irradiation on monocytes and Tregs recruitments to tumors. Flow cytometry and histological analysis were performed. Cytokine profiling and ELISA analyses were performed on tumor tissues and blood samples. Transgenic mice bearing fluorescent reporters allowed us to identify target cells by confocal and intravital biphoton microscopy. Mice knockout (KO) for CCL2 or CCR2 were used to investigate the respective role of the chemokine pathway in the response to radiotherapy, as well as mice selectively depleted of Tregs (Foxp3-DTR mice) to analyze their contribution to the resistance to RT. Results Radiotherapy strongly upregulated CCL2 chemokine production in tumor cells. This resulted in an accumulation of monocytes and of a subset of CCR2-positive Tregs in the tumor bed of voth oral and lung tumors, and a dynamic physical interaction between these cells was identified. CCR2-KO mice and mice conditionally depleted of Tregs had an improved response to radiotherapy. Recruited monocytes produced TNFα, which contributed to the activation of Tregs. In agreement with this observation, anti-TNFα treatment increased the efficacy of RT. Conclusion We propose that reducing radiation-induced monocyte and Trges recruitment may yield improved results in the treatment of head and neck and lung carcinomas by radiotherapy. We thus indicate CCL2/CCR2 and TNFα as potential clinical candidates to counteract the radioprotective action of monocyte-derived cells and Tregs, paving the way for effective combined immunoradiotherapies. As modulators of CCL2, CCR2 and TNFα are already being tested in clinical settings, the results from this study can be transferred into the clinic. Immunologically-augmented radiotherapy could also allow the reduction of the delivered radiation dose, thus minimizing the risk of treatment sequelae while maintaining optimal tumor control. OC-0083 Abolition of metastases of mouse triple negative breast cancer by alpha-radiation and immunotherapy

Abstract withdrawn from presentation

OC-0084 Combining RT with L19-IL2 and aPDL1: from preclinical results towards a phase II trial (ImmunoSABR). R. Lieverse 1 , E. Van Limbergen 2 , V. Olivo Pimentol 1 , C. Oberije 1 , D. Neri 3 , A. Yaromina 1 , L.J. Dubois 1 , P. Lambin 1 1 MUMC/UM, Precision Medicine - The D-lab and The M- lab, Maastricht, The Netherlands ; 2 Maastro-clinic, Radiotherapy, Maastricht, The Netherlands ; 3 Pharmaceutical Sciences, Chemistry and Applied Biosciences, Zurich, Switzerland Purpose or Objective At initial diagnosis 47% of NSCLC patients already have stage IV metastatic disease with limited treatment options and 1-5% 5-year overall survival (OS) rates. Current therapies emphasize the necessity for combinatorial treatment approaches. Interleukin-2 (IL2) plays an essential role in the activation phase of both specific and innate immune responses. To avoid IL2 induced systemic toxicity we have evaluated a more targeted approach using an immunocytokine consisting of the anti-EDB scFv L19 antibody coupled to IL2. Combination with radiotherapy (RT) in tumour models expressing high EDB resulted in long-term primary tumour responses, abscopal effects distant from the irradiated site, and an immunological memory. Aim of the current study was to evaluate preclinically and in a phase 2 clinical trial the combination of precise SABR with the well-tolerated tumour selective immunocytokine L19-IL2 and the immune checkpoint inhibitor (ICI) aPDL1 in an intermediate EDB expressing, immune cold LLC model. Material and Methods Upon an average LLC tumour volume of 200mm 3 , C57BL/6 mice were randomised into following treatment groups: RT (10Gy) + vehicle/L19-IL2 + IgG or RT + vehicle/L19-IL2 + aPDL1/aCTLA4. Vehicle/L19-IL2 (1mg/kg), aCTLA4 (10mg/kg) and IgG (10mg/kg) were given i.v. on day 1, 3 and 5 after RT; aPDL1 (10mg/kg) and IgG were given i.p. 1, 3, 5, 7 and 9 days after RT, Figure 1. Tumour response was quantified as time to reach 4x initial tumour volume (T4xIV). This triple therapy is implemented as 1 st , 2 nd , or 3 rd line in the phase 2 trial, to treat WHO PS 0-1, advanced stage IV NSCLC patients. The main objective is improved PFS at 1.5 years. The secondary objectives will be OS, QoLQ, and abscopal response. The exploratory objectives will be biomarker studies, immune cell subsets, mutational burden, and stool collection will be performed.

Results L19-IL2 and aCTLA4 (p<0.05), but not aPDL1, enhanced the therapeutic effect of RT. Furthermore, RT + L19-IL2 efficacy was better compared to RT + ICIs, especially for RT + aPDL1 (p<0.05). Adding aCTLA4 to RT + L19-IL2 did not improve outcome compared to RT + L19-IL2. However, RT + L19-IL2+aPDL1 enhanced therapeutic efficacy compared to RT + L19-IL2 (p<0.05) and RT + aPDL1 (p<0.001), resulting in 38% long-term tumour remission, Figure 2.