Combination immunotherapy for hepatocellular carcinoma

Single-agent immune checkpoint inhibitors (ICIs) have been tested in patients with advanced hepatocellular carcinoma (HCC), leading to objective response rates of 15-20%, mostly without a significant overall survival (OS) benefit. Furthermore, approximately 30% of HCC exhibits intrinsic resistance to ICIs. In the absence of predictive biomarkers to identify patients likely to benefit most from immunotherapy, research has moved to exploring combinations with potential activity in broader patient populations. Basket trials, including cohorts of patients with HCC, and early phase studies tested the combination of ICIs with anti-angiogenic agents as well as the combination of two different ICIs. The promising results that were achieved provided the rationale for the following phase III trials, which tested the combination of anti-PD-1/PD-L1 antibodies with bevacizumab, or tyrosine kinase inhibitors, or anti-CTLA-4 antibodies. Positive results from the IMbrave150 trial led to the practice-changing approval of atezolizumab-bevacizumab, the first regimen to demonstrate improved survival in the front-line setting since the approval of sorafenib. More recently, the HIMALAYA trial demonstrated the superiority of durvalumab-tremelimumab (STRIDE regimen) over sorafenib, establishing a new first-line option. In contrast, inconsistent results have been achieved with combinations of ICIs and tyrosine kinase inhibitors, with only one phase III trial showing an OS benefit. The rapid evolution of the therapeutic landscape for patients with advanced HCC has left many unanswered questions that will need to be addressed by future research. These include the choice and sequencing of treatments, identification of biomarkers, combinations with locoregional therapies, and development of new immunotherapy agents. This review summarises the scientific rationale and available clinical data for combination immunotherapy in advanced HCC.