A Novel Combination Therapeutic Strategy Aiming to Functional Cure for Chronic Hepatitis B Virus Infection (Sustained HBsAg Loss) (A)

Hepatitis B virus (HBV) infection is a major public health threat in China. At present, a functional cure, also known as clinical cure or sustained Hepatitis B surface antigen (HBsAg) loss, is recommended as the ideal endpoint of HBV treatment. However, HBsAg loss can be achieved in less than 10% of chronic hepatitis B (CHB) patients treated with current available antiviral drug interferon (IFNα) or nucleos(t)ide analogues (NAs) monotherapy. With the support of the national major special funding for infectious diseases from "11th Five-Year Plan" to "13th Five-Year Plan", we have implemented a pioneer clinical study of sequential combination of IFNα therapy on NAs to treat NAs-treated CHB patients (ie. New Switch Study). This is the world's first clinical trial aiming to functional cure, which increased the rate of HBsAg loss to 15% in the overall population in our study, and to 30-50% among those with lower baseline HBsAg levels. How to further improve the HBsAg loss rate is an urgent issue for us. The key point of achieving functional cure is to reverse the HBV-specific T cell exhaustion and establish the long-term immune control against HBV infection. Programmed death-1 (PD-1)/ programmed death-ligand 1 (PD-L1) axis blockade has been demonstrated to reinvigorate exhausted CD8+ T cells, and would be a potential strategy to treat chronic HBV infection. In this study, a large multicenter prospective study will be performed to explore the safety and efficacy of a novel combination strategy involving immune checkpoint inhibitor (anti-PD-1 antibody) in CHB patients, observe the HBsAg loss rate in NA-treated CHB patients receiving this combination strategy, evaluate the potential of breaking immune tolerance by this strategy, and further assess its efficacy to further improve the clinical cure rate on the basis of New Switch Study. Based on New Switch Study, this study further attempts to reverse T cell exhaustion in CHB patients, explore a novel platform of combination therapy development for clinical cure, and ultimately increase the HBsAg loss rate to higher than 50% in overall patients. The implementation of the project is expected to reduce the burden of HBV infection in China and contribute to the goal of global elimination of hepatitis B and C by 2030 (WHO 2030).