Cabozantinib enhances anti-PD1 efficacy and elicits a neutrophil-based immune response in murine models: implications for human HCC II

Background & Aims: Immune checkpoint inhibitors combined with anti-angiogenic agents produces benefits in the treatment of advanced hepatocellular carcinoma (HCC). We investigated the efficacy and immunomodulatory activity of cabozantinib alone and combined with anti-PD1 in experimental models of HCC, and explored the potential target population that might benefit from this combination. Approach & Results: C57BL/6J mice bearing subcutaneous Hepa1-6 or Hep53.4 tumours received cabozantinib, anti-PD1, their combination or placebo. Tumour and blood samples were analysed by flow cytometry, immunohistochemistry, transcriptome and cytokine profiling. Cabozantinib-related effects were validated in a colorectal cancer PDX model. Transcriptomic data from three human HCC cohorts (Cohort 1: n=167, Cohort 2: n=57, TCGA: n=319) were used to cluster patients according to neutrophil features, and assess their impact on survival. The combination of cabozantinib and anti-PD1 showed increased anti-tumour efficacy compared to monotherapy and placebo (P<0.05). Cabozantinib alone significantly increased neutrophil infiltration and reduced CD8+PD1+ T cell proportions in the tumour, while the combination with anti-PD1 further stimulated both effects and significantly decreased T regulatory cell infiltration (all P<0.05). In blood, cabozantinib and especially combination increased the proportions of overall T cells (P<0.01) and memory/effector T cells (P<0.05), while lowering the neutrophil-to-lymphocyte ratio (P<0.001 for combination). Unsupervised clustering of human HCCs revealed that high tumour enrichment in neutrophil features observed with the treatment combination was linked to less proliferative phenotypes, and well-differentiated HCC with better prognosis. Neutrophil recruitment in both humans and mice was linked to CXCR2 ligands and CXCL12 (P<0.05). Conclusions: Cabozantinib in combination with anti-PD1 enhanced anti-tumour immunity by bringing together innate neutrophil-driven and adaptive immune responses, a mechanism of action which favours this approach for the treatment of HCC. C57BL/6 mice bearing subcutaneous HCC tumours were randomly assigned to receive a) Placebo; b) Cabozantinib; c) Anti-PD1; or d) Combination of cabozantinib with anti-PD1. Animals were culled at day 14 and tumours were extracted and processed for the transcriptomic assessment through a microarray platform.