IMFINZI® Plus Tremelimumab Significantly Improves Overall Survival in Advanced Hepatocellular Carcinoma

SUMMARY: The American Cancer Society estimates that for 2022, about 41,260 new cases of primary liver cancer and intrahepatic bile duct cancer will be diagnosed in the US and 30,520 patients will die of their disease. Liver cancer is seen more often in men than in women and the incidence has more than tripled since 1980. This increase has been attributed to the higher rate of Hepatitis C Virus (HCV) infection among baby boomers (born between 1945 through 1965). Obesity and Type II diabetes have also likely contributed to the increasing trend. Other risk factors include alcohol, which increases liver cancer risk by about 10% per drink per day, and tobacco use, which increases liver cancer risk by approximately 50%. HepatoCellular Carcinoma (HCC) is also a leading cause of cancer deaths worldwide, accounting for more than 700,000 deaths each year, and majority of patients typically present at an advanced stage. The prognosis for unresectable HCC remains poor and one year survival rate is less than 50% following diagnosis and only 7% of patients with advanced disease survive five years. NEXAVAR® was approved by the FDA in 2007 for the first line treatment of unresectable HepatoCellular Carcinoma (HCC) and the median Overall Survival was 10.7 months in the NEXAVAR® group and 7.9 months in the placebo group.

Immune checkpoints are cell surface inhibitory proteins/receptors that are expressed on activated T cells. They harness the immune system and prevent uncontrolled immune reactions by switching off the T cells of the immune system. Immune checkpoint proteins/receptors include CTLA-4 (Cytotoxic T-Lymphocyte Antigen 4, also known as CD152) and PD-1(Programmed cell Death 1). Checkpoint inhibitors unleash the T cells resulting in T cell proliferation, activation, and a therapeutic response.

IMFINZI® (Durvalumab) is a human monoclonal antibody that binds to the PD-L1 protein and blocks the interaction of PD-L1 with the PD-1 and CD80 proteins, countering the tumor’s immune-evading tactics and unleashes the T cells. Tremelimumab is a human monoclonal antibody that targets and blocks the activity of CTLA-4, contributing to T-cell activation, priming the immune response to cancer and fostering cancer cell death. In a Phase II study, a single priming dose of Tremelimumab added to IMFINZI® (STRIDE regimen), showed encouraging clinical activity and limited toxicity in patients with unresectable HepatoCellular Carcinoma (HCC), suggesting that a single exposure to Tremelimumab may be sufficient to improve upon activity of IMFINZI®.

HIMALAYA trial is a randomized, open-label, multicentre, global, Phase III study conducted in 190 centres across 16 countries, including in the US, Canada, Europe, South America and Asia. In this study, 1,171 patients with Stage III or IV unresectable hepatocellular carcinoma who had received no prior systemic therapy and were not eligible for locoregional therapy (treatment localized to the liver and surrounding tissue), were randomly assigned to receive either the STRIDE regimen which consisted of a single priming dose of Tremelimumab 300 mg IV added to IMFINZI® (Durvalumab) 1500 mg IV, followed IMFINZI® 1500 mg IV by every 4 weeks (N= 393), IMFINZI® monotherapy given at the same dose and schedule (N = 389) or NEXAVAR® (Sorafenib) 400 mg orally BID (N=389). Enrolled patients had ECOG performance status of 0 or 1 and Child-Pugh A disease and could not have main portal vein thrombosis. Patients were stratified based on macrovascular invasion (Yes versus No), etiology of liver disease (Hepatitis B virus versus Hepatitis C virus versus others), and ECOG Performance Status (0 versus 1). The Primary endpoint was Overall Survival (OS) for STRIDE regimen versus NEXAVAR® and key Secondary endpoints included OS for IMFINZI® monotherapy versus NEXAVAR®, Objective Response Rate and Progression Free Survival (PFS) for STRIDE and IMFINZI® monotherapy.

The Primary objective of this study was met at the time of data cutoff. At a median follow up of 16.1 months of treatment with the STRIDE regimen, there was a 22% reduction in the risk of death for patients who received the STRIDE regimen compared to NEXAVAR® alone (HR=0.78; P=0.0035). The median OS with the STRIDE regimen was 16.4 months, compared with 13.8 months with NEXAVAR®, and the 3 year OS rate was 30.7% versus 20.2 % respectively. The Overall Response Rate for the combination STRIDE regimen was 20.1% compared to 5.1% for NEXAVAR®

IMFINZI® monotherapy met the objective of OS non-Inferiority to NEXAVAR® (HR=0.86; 96% CI, 0.73–1.03) and the median OS after 16.5 months of median follow up was 16.6 months with IMFINZI® monotherapy versus 13.8 months with NEXAVAR®, and the 3 year OS rate was 24.7% versus 20.2 % respectively. The Overall Response Rate with IMFINZI® monotherapy was 17% compared to 5.1% for NEXAVAR®. The Secondary endpoint of PFS was not superior in either investigational study group relative to the NEXAVAR® control arm.

It was concluded that HIMALAYA is the first large Phase III trial to add a novel single priming dose of an anti-CTLA4 antibody Tremelimumab, to another checkpoint inhibitor, IMFINZI®. This combination regimen (STRIDE) demonstrated superior efficacy and a favorable benefit-risk profile when compared with NEXAVAR® and should be considered a novel , first-line standard of care systemic therapy, for patients with unresectable Hepatocellular Carcinoma.

Phase 3 randomized, open-label, multicenter study of tremelimumab (T) and durvalumab (D) as first-line therapy in patients (pts) with unresectable hepatocellular carcinoma (uHCC): HIMALAYA. Abou-Alfa GK, Chan SL, Kudo M, et al. J Clin Oncol. 2022;40(suppl 4):379. doi:10.1200/JCO.2022.40.4_suppl.379