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

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. Upon patients' consent, we obtained human HCC and non-tumour adjacent tissue samples from 57 resected patients with preserved liver function (Child-Pugh A). Transcriptomic data obtained from Human Genome U219 Array (Affymetrix) was used to cluster samples according to enrichment in active neutrophil profiles in those tissues and to identify key molecular features associated with the tumour biology among the groups that were generated.