GSK’s Bepirovirsen under EMA review for chronic hepatitis B

UK—GSK plc has announced that the European Medicines Agency (EMA) has accepted for review its marketing authorisation application (MAA) for bepirovirsen, an investigational drug being developed to treat adults with chronic hepatitis B (CHB).

The move marks a significant regulatory milestone in the decades-long search for a functional cure for a disease that continues to burden millions of people across Europe and around the world.

Chronic hepatitis B affects an estimated 3.2 million people in Europe alone and more than 250 million people globally.

Unlike acute infections that the body can clear on its own, chronic hepatitis B develops when the immune system fails to eliminate the virus, resulting in a long-lasting infection that progressively damages the liver.

The disease causes approximately 1.1 million deaths each year worldwide, including around 15,000 in Europe, and accounts for roughly 56% of liver cancer cases globally.

The current standard of care—a class of drugs called nucleos (t) ide analogues — can suppress the virus effectively, but patients typically need to take them for life.

Functional cure rates with existing treatments remain as low as 1%, making the development of a more definitive solution an urgent priority.

The European Association for the Study of the Liver (EASL) identifies functional cure as the ultimate goal of hepatitis B treatment.

What makes Bepirovirsen different

Bepirovirsen works differently from existing therapies. It belongs to a class of drugs called antisense oligonucleotides (ASOs), which are designed to target the genetic machinery of the hepatitis B virus directly.

Bepirovirsen acts by blocking the virus from replicating inside the body, reduces the levels of hepatitis B surface antigen (HBsAg), which is a key viral protein in the blood.

It also stimulates the patient’s immune system to mount a more sustained response against the infection.

This triple mechanism aims to give the immune system a fighting chance to control the disease on its own, without the need for ongoing medication.

In clinical terms, functional cure means that both hepatitis B virus DNA and HBsAg become undetectable in the blood for at least 24 weeks after completing a finite course of treatment, indicating that the immune system has regained control.

Promising phase III trial results

GSK’s regulatory submission to the EMA draws on results from two large Phase III clinical trials—B-Well 1 and B-Well 2—conducted across 29 countries.

Both trials met their primary endpoints, demonstrating statistically significant and clinically meaningful functional cure rates with bepirovirsen added to standard of care, compared with standard of care alone.

The drug performed consistently across all ranked endpoints, with an even stronger effect observed in patients who had lower baseline levels of HBsAg (≤1,000 IU/ml).

The trials also showed an acceptable safety and tolerability profile consistent with earlier studies.

GSK plans to present the full data at a medical congress and submit findings to a peer-reviewed journal in 2026.

Development background and broader ambitions

GSK originally licensed bepirovirsen from Ionis Pharmaceuticals and collaborated with Ionis throughout its development.

The drug has not yet received regulatory approval in any country.

Beyond the current application, GSK is also exploring bepirovirsen as a potential foundation for future combination treatment strategies, with the aim of extending functional cure to a broader population of patients with chronic hepatitis B.