REG - GSK PLC - Bepirovirsen priority review US filing acceptance

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RNS Number : 1130C  GSK PLC  28 April 2026

Issued: 28 April 2026, London UK

 

Bepirovirsen accepted for priority review and granted Breakthrough Therapy
Designation by the US FDA

 

·   Regulatory application supported by phase III B-Well trials
demonstrating statistically significant and clinically meaningful functional
cure rates in chronic hepatitis B

·   Breakthrough Therapy Designation added to Fast Track Designation,
recognising potential for substantial improvement over existing treatments

·   Chronic hepatitis B is a leading cause of liver cancer globally 1 
(#_edn1)

·   26 October 2026 assigned by FDA as PDUFA date

 

 

GSK plc (LSE/NYSE: GSK) today announced that the US Food and Drug
Administration (FDA) has accepted for priority review a New Drug Application
(NDA) for bepirovirsen, an investigational antisense oligonucleotide (ASO),
for the treatment of adults with chronic hepatitis B (CHB).

 

Bepirovirsen has also received Breakthrough Therapy Designation (BTD), which
is reserved for investigational medicines where preliminary clinical evidence
indicates the potential for substantial improvement over available therapies.
A BTD enables greater FDA guidance on an asset's development programme.(( 2 
(#_edn2) )) The BTD for bepirovirsen builds on the Fast Track Designation also
provided by the US FDA in February 2024.(( 3  (#_edn3) )) A Fast Track
Designation expedites the review of drugs to treat serious conditions and fill
an unmet medical need.

 

Chronic hepatitis B is a major public health challenge, affecting more than
250 million people worldwide 4  (#_edn4) and an estimated 1.7 million in the
United States. 5  (#_edn5) Current standard of care - typically nucleos(t)ide
analogues - often requires lifelong therapy and functional cure rates remain
low, typically around 1%. 6  (#_edn6) Functional cure occurs when hepatitis B
virus DNA and viral protein - hepatitis B surface antigen (HBsAg) - are
undetectable in the blood for at least 24 weeks after stopping all treatment,
indicating that the disease is controlled by the immune system without
medication. Achieving a functional cure is associated with a significant
reduction in the risk of long-term complications, including liver cancer. 7 
(#_edn7)

 

The regulatory submission and BTD are supported by positive results from the
Phase III B-Well 1 and B-Well 2 trials, where bepirovirsen demonstrated
statistically significant and clinically meaningful functional cure rates.
Functional cure rates were significantly higher with bepirovirsen plus
standard of care compared to standard of care alone across all ranked
endpoints, including in patients with lower baseline HBsAg levels, where an
even greater effect was observed. Bepirovirsen demonstrated an acceptable
safety and tolerability profile consistent with previous studies. Data from
the B-Well 1 and B-Well 2 trials will be presented at the European Association
for the Study of Liver Congress (EASL) and submitted for scientific
peer-reviewed publication in 2026.

 

The FDA has assigned 26 October 2026 as the Prescription Drug User Fee Act
(PDUFA) goal date.

 

About chronic hepatitis B

Hepatitis B is a viral infection that can cause both acute and chronic liver
disease. Chronic hepatitis B occurs when the immune system is unable to clear
the virus, resulting in long-lasting infection that affects more than 250
million people worldwide. The disease causes approximately 1.1 million deaths
each year globally.(4) Many patients often require lifelong antiviral therapy
for viral suppression; making functional cure a critical goal in disease
management.

 

About bepirovirsen

Bepirovirsen is a triple action investigational antisense oligonucleotide
designed to recognise and orchestrate the destruction of the genetic
components (i.e. mRNA and pregenomic RNA) of the hepatitis B virus that can
lead to chronic disease, potentially allowing a person's immune system to
regain control. Bepirovirsen inhibits the replication of the viral genome in
the body, suppresses the level of hepatitis B surface antigen in the blood,
and stimulates the immune system to increase the chances of a durable and
sustained response.

 

Clinical trial programme

B-Well 1 and B-Well 2 trials are global multi-centre, randomised,
double-blind, placebo-controlled trials conducted in 29 countries. They
assessed the efficacy, safety, pharmacokinetic profile, and the durability of
functional cure in nucleos(t)ide analogue-treated participants with chronic
hepatitis B and baseline surface antigen (HBsAg) ≤3000 IU/ml. The primary
endpoint assessed the proportion of participants achieving functional cure in
patients with baseline HBsAg ≤3000 IU/ml. A key ranked secondary endpoint
evaluated functional cure in participants with baseline HBsAg ≤1000 IU/ml.
Functional cure is defined as HBsAg being undetectable in the blood for at
least 24 weeks after stopping all treatment, indicating that the disease is
controlled by the immune system without medication.

 

Bepirovirsen is also being evaluated as a potential backbone therapy for
future sequential treatment strategies aimed at expanding functional cure to
broader patient populations.

 

GSK licensed bepirovirsen from Ionis Pharmaceuticals and collaborated with
them on its development. Bepirovirsen has been recognised by global regulatory
authorities for its innovation and potential to address significant unmet need
in hepatitis B, with Fast Track Designation and Breakthrough Therapy
Designation from the US FDA, Breakthrough Therapy Designation in China and
SENKU Designation in Japan. Bepirovirsen is currently not approved anywhere in
the world.

 

About GSK

GSK is a global biopharma company with a purpose to unite science, technology,
and talent to get ahead of disease together. Find out more at www.gsk.com
(https://www.gsk.com) .

 

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Cautionary statement regarding forward-looking statements

GSK cautions investors that any forward-looking statements or projections made
by GSK, including those made in this announcement, are subject to risks and
uncertainties that may cause actual results to differ materially from those
projected. Such factors include, but are not limited to, those described in
the "Risk Factors" section in GSK's Annual Report on Form 20-F for 2025.

 

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WC1A 1DG

 1  (#_ednref1) Rumgay H et al . Global burden of primary liver cancer in 2020
and predictions to 2040. J Hepatol. 2022;77:1598-1606. doi:
10.1016/j.jhep.2022.08.021

 2  (#_ednref2) US Food and Drug Administration. Breakthrough Therapy.
Available at:
https://www.fda.gov/patients/fast-track-breakthrough-therapy-accelerated-approval-priority-review/breakthrough-therapy
(https://www.fda.gov/patients/fast-track-breakthrough-therapy-accelerated-approval-priority-review/breakthrough-therapy)
(last accessed March 2026)

 3  (#_ednref3) GSK Press Release, available at:
https://www.gsk.com/en-gb/media/press-releases/gsk-receives-us-fda-fast-track-designation-for-bepirovirsen-in-chronic-hepatitis-b/
(https://www.gsk.com/en-gb/media/press-releases/gsk-receives-us-fda-fast-track-designation-for-bepirovirsen-in-chronic-hepatitis-b/)
(last accessed March 2026)

 4  (#_ednref4) WHO. Global hepatitis report 2024. Available at:
https://www.who.int/publications/i/item/9789240091672
(https://www.who.int/publications/i/item/9789240091672) (last accessed: March
2026)

 5  (#_ednref5) Razavi-Shearer D, Gamkrelidze I, Hall S, Cohen C, Gish R, Pham
T, et al. The Current Burden of Hepatitis B in the United States: A State,
Territorial, and County Modelling Analysis. J Viral Hepat. 2026;33(1):e70122

6 Slaets, L. et al. "Systematic review with meta-analysis: hepatitis B surface
antigen decline and seroclearance in chronic hepatitis B patients on
nucleos(t)ide analogues or pegylated interferon therapy" in GastroHep 2,
106-116 (2020)

(#_ednref6) 7 EASL, "Clinical Practice Guidelines on the management of
hepatitis B virus infection" in Journal of Hepatology Volume 83, Issue 2,
August 2025, Pages 502-583. Available at:
https://www.sciencedirect.com/science/article/pii/S0168827825001746 (last
accessed: March 2026).

(#_ednref7)

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