Abstract 4549: Pemetrexed enhances anti-tumor efficacy of PD1 pathway blockade by promoting intra tumor immune response via immunogenic tumor cell death and T cell intrinsic mechanisms
Authors: Novosiadly Ruslan , Schaer David , Amaladas Nelusha , Rasmussen Erik , Lu Zhao Hai , Sonyi Andreas , Carpenito Carmine , Li Yanxia , Luo Shuang , Capen Andrew , Meyer Catalina , Huang Xiaodong , Manro Jason , Donoho Gregory , Doman Thompson , Hall Gerald , Geeganage Sandaruwan , Kalos Michael 
Published: August 2018

Abstract
Background: Recently, pemetrexed and carboplatin in combination with PD–1 antibody (pembrolizumab) demonstrated markedly improved clinical outcome in NSCLC patients (KEYNOTE–021G trial) suggesting a positive interaction between pemetrexed–based chemotherapy and immunotherapy. However, the role of pemetrexed in modulating antitumor immune response is largely unknown. The objective of this study was to characterize the effects of pemetrexed on intra–tumor immune response in monotherapy and combination with carboplatin or PD–1 pathway blockade in preclinical models.
Methods: Mice bearing syngeneic MC38 or Colon26 tumors were treated with pemetrexed with or without carboplatin or anti–mouse PD–L1 antibody (178G7). Immune cell subsets and immune–related changes in mouse tumor tissue and T cells were assessed by flow cytometry and gene expression analysis (Quantigene Plex and nanoString nCounter assays). Effects of pemetrexed on immunogenic cell death in tumor cells and mitochondrial respiration in T cells were evaluated by HMGB1 ELISA and Agilent Seahorse XF analysis, respectively.
Results: In MC38 tumors, pemetrexed monotherapy demonstrated a trend towards an increased frequency of intratumoral leukocytes and total and cycling (Ki67+) T cells accompanied by immune–related gene expression changes indicative of enhanced antigen presentation, T cell infiltration and/or activation and down–modulation of the myeloid cell compartment. Immune gene expression signature induced by pemetrexed was largely unaffected by carboplatin. In both MC38 and Colon26 tumor cells, in vitro treatment with pemetrexed induced a robust release of HMGB1 indicative of immunogenic cell death. Proliferation of primary human T cells stimulated with CD3/CD28 was inhibited by pemetrexed in a dose–dependent manner. At clinically relevant concentrations pemetrexed also enhanced T cell activation phenotype exemplified by an increased frequency of CD137+, GITR+ and PD–L1+ T cells as well as upregulation of multiple interferon gamma–induced genes, and increased mitochondrial respiration. In both MC38 and Colon26 models, treatment with pemetrexed and 178G7 demonstrated a combination benefit compared to either monotherapy, and nCounter profiling of Colon26 tumors followed by Ingenuity Pathway Analysis revealed that improved antigen presentation, enhanced T cell and cytokine signaling and an engagement of CD4+ T cell–mediated immunity might underlie this combination effect.
Conclusions: Pemetrexed promotes intra–tumor T cell–mediated immune response through immunogenic tumor cell death and increased activation and metabolic fitness of T cells leading to an enhanced anti–tumor efficacy in combination with PD–L1 antibody.
Citation Format: Ruslan Novosiadly, David Schaer, Nelusha Amaladas, Erik Rasmussen, Zhao Hai Lu, Andreas Sonyi, Carmine Carpenito, Yanxia Li, Shuang Luo, Andrew Capen, Catalina Meyer, Xiaodong Huang, Jason Manro, Gregory Donoho, Thompson Doman, Gerald Hall, Sandaruwan Geeganage, Michael Kalos. Pemetrexed enhances anti-tumor efficacy of PD1 pathway blockade by promoting intra tumor immune response via immunogenic tumor cell death and T cell intrinsic mechanisms [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 4549.