Bepirovirsen (the study drug) is an experimental new drug for treating chronic hepatitis B (CHB) and is not yet approved for use in people living with CHB. CHB is caused by the hepatitis B virus (HBV), which infects the liver and can cause damage. Most people who become infected as an adult with the virus are able to clear it from their body without any problems. People who become infected as a child may be more likely to develop a chronic infection. In some people, the immune system (which helps your body protect you from getting sick) is unable to remove of the hepatitis B virus from the body and this results in lifelong infection that can cause serious liver disease.

There are other medicines available to treat CHB. A commonly used type of medicine are   nucleotide/nucleoside analogues (NAs).  NAs work by stopping the virus from multiplying. NAs are usually a lifelong treatment as the body is not able to fully control the infection by itself.

Bepirovirsen, the study drug being tested works in a different way. It stops the virus from making substances that we think prevents the immune system from fighting it. We hope that by stopping the virus from making these substances, the study drug will allow the body to gain full control over the infection and remove the need for further CHB treatments.

This research study is being done to learn more about CHB and if bepirovirsen can improve the treatment of CHB. Bepirovirsen has been given to people living with CHB for up to 24 weeks in previous studies and showed a decrease in viral substances (for example Hepatitis B surface antigen [HBsAg]).

In this study, we will investigate treatment with the study drug (up to 24 weeks) to see if this can improve the removal of viral substances in the body and prevent them from returning.

We also would like to answer the following questions with this study:

• Is bepirovirsen safe to take for up to 24 weeks?
• How well does bepirovirsen work to treat people living with CHB?
• Does bepirovirsen help clear the virus substances from the blood, even after treatment stops?

This study will test Bepirovirsen, which has not yet been approved by the national health agency in the UK. Bepirovirsen is currently only given to people who participate in clinical trials.

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