GSK's Hepatitis B 'Functional Cure' Drug Bepirovirsen Granted FDA Priority Review and Breakthrough Therapy Designation

On April 28, 2026, GSK announced that the FDA had accepted the marketing application for its new hepatitis B ASO drug, Bepirovirsen, granting it Priority Review status as well as Breakthrough Therapy Designation (BTD). The PDUFA date is October 26, 2026.

Bepirovirsen Demonstrates Clinically Meaningful Functional Cure Rates in Two Phase III Clinical Trials, B-WELL 1/2; Specific Data to Be Disclosed at This Year’s EASL Conference and Published Simultaneously in an Academic Journal.

GSK predicts that the peak sales of Bepirovirsen will exceed £2 billion.

Provegen Injection(Bepirovirsen Solution for Injection) is a product developed by Ionis.ASO Therapy, with a triple mechanism, can identify and degrade the genetic material (i.e., RNA) of the hepatitis B virus that causes chronic infections, thereby inhibiting the replication of viral DNA in the body, reducing the levels of hepatitis B surface antigen (HBsAg) in the blood, and stimulating the immune system to enhance the chances of a sustained response.

In August 2019, GSK acquired the development and commercialization rights of this product from Ionis for an upfront payment and milestone payments totaling $262 million.

On January 7 this year, GSK announced that BeipruovirBoth pivotal Phase III B-Well 1 and B-Well 2 studies met their primary endpointsThese two studies collectively enrolled more than 1,800 participants across 29 countries.

The results showed that, in the B-Well study,BepravirShowed a functionally curative rate with statistical and clinical significance,and the functional cure rate of combined standard treatment is significantly higher than that of standard treatment alone.

Currently, Bepirovirsen has been submitted for marketing approval in Japan. If approved, this product is expected to become the first six-month finite treatment option for chronic hepatitis B and a cornerstone drug for future sequential therapies.

Globally, multiple hepatitis B clinical cure antisense oligonucleotide (ASO) and small interfering RNA (siRNA) candidate drugs are currently undergoing clinical research.

In addition to bepirovirsen, GSK has multiple small nucleic acid therapies for hepatitis B in development, such asGSK5637608(Original R&D code: JNJ-3989 (ARO-HBV) is currently in Phase II clinical trials. The siRNA drug developed in collaboration by Roche and Dicerna.Xalnesiran, which can target the conserved regions of the hepatitis B virus (HBV) genome to silence multiple HBV transcripts, may be effective for patients with chronic HBV infection, either in combination with or without immunomodulators.

Significant progress has been made in the development of small nucleic acid drugs produced in China, including Brii Biosciences' HBV siRNA candidate drug.BRII-835（Elebsiran）, Ascletis Pharma (ASC22（Envafolimab）、Stellar Biotechnologies' HBV siRNA Candidate DrugHT-101, China Resources Tianqing's HBV siRNA Candidate DrugTQA-3038。

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