Background and purposeCombining inhibitors of vascular endothelial growth factor and the programmed cell death protein 1 (PD1) pathway has shown efficacy in multiple cancers, but the disease-specific and agent-specific mechanisms of benefit remain unclear. We examined the efficacy and defined the mechanisms of benefit when combining regorafenib (a multikinase antivascular endothelial growth factor receptor inhibitor) with PD1 blockade in murine hepatocellular carcinoma (HCC) models.Basic proceduresWe used orthotopic models of HCC in mice with liver damage to test the effects of regorafenib—dosed orally at 5, 10 or 20 mg/kg daily—combined with anti-PD1 antibodies (10 mg/kg intraperitoneally thrice weekly). We evaluated the effects of therapy on tumor vasculature and immune microenvironment using immunofluorescence, flow cytometry, RNA-sequencing, ELISA and pharmacokinetic/pharmacodynamic studies in mice and in tissue and blood samples from patients with cancer.Main findingsRegorafenib/anti-PD1 combination therapy increased survival compared with regofarenib or anti-PD1 alone in a regorafenib dose-dependent manner. Combination therapy increased regorafenib uptake into the tumor tissues by normalizing the HCC vasculature and increasing CD8 T-cell infiltration and activation at an intermediate regorafenib dose. The efficacy of regorafenib/anti-PD1 therapy was compromised in mice lacking functional T cells (Rag1-deficient mice). Regorafenib treatment increased the transcription and protein expression of CXCL10—a ligand for CXCR3 expressed on tumor-infiltrating lymphocytes—in murine HCC and in blood of patients with HCC. Using Cxcr3-deficient mice, we demonstrate that CXCR3 mediated the increased intratumoral CD8 T-cell infiltration and the added survival benefit when regorafenib was combined with anti-PD1 therapy.Principal conclusionsJudicious regorafenib/anti-PD1 combination therapy can inhibit tumor growth and increase survival by normalizing tumor vasculature and increasing intratumoral CXCR3+CD8 T-cell infiltration through elevated CXCL10 expression in HCC cells.
Immune checkpoint blockade combined with anti-angiogenic therapy induces vascular normalization and anti-tumor immunity and is efficacious in hepatocellular carcinoma (HCC). But whether and how initial immunotherapy affects the efficacy of subsequent anti-angiogenic therapy is unknown. We evaluated a cohort of HCC patients (n = 25) who received the pan-VEGF receptor multi-kinase inhibitor sorafenib after initial therapy with an anti-programmed cell death protein (PD)-1 antibody and found superior outcomes in these patients (12% overall response rate to sorafenib and a median OS of 12.1 months). To understand mechanisms of this benefit, we examined the impact of an anti-PD-1 antibody on response to subsequent sorafenib treatment in orthotopic models of murine HCC. Prior anti-PD-1 antibody treatment amplified HCC response to sorafenib therapy and increased survival (n = 8–9 mice per group, HR = 0.28, 95% CI: 0.09–0.91; p = .04). Anti-PD-1 therapy showed angio-protective effects on HCC vessels to subsequent sorafenib treatment, which enhanced the benefit of this therapy sequence in a CD8+ T-cell-dependent manner. This priming approach using immunotherapy provides an immediately translatable strategy for effective HCC treatment while reducing drug exposure.
Hepatocellular carcinoma (HCC) remains as one of the major causes of cancer‐related mortality, despite the recent development of new therapeutic options. Regorafenib, an oral multikinase inhibitor, is the first systemic therapy that has a survival benefit for patients with advanced HCC that have a poor response to sorafenib. Even though regorafenib has been approved by the FDA, the clinical trial for regorafenib treatment does not show significant improvement in overall survival. The impaired efficacy of regorafenib caused by various resistance mechanisms, including epithelial–mesenchymal transitions, inflammation, angiogenesis, hypoxia, oxidative stress, fibrosis and autophagy, still needs to be resolved. In this review, we provide insight on regorafenib microenvironmental, molecular and cellular mechanisms and interactions in HCC treatment. The aim of this review is to help physicians select patients that would obtain the maximal benefits from regorafenib in HCC therapy.
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