FDA grants GSK (NYSE: GSK) bepirovirsen priority review and breakthrough status

Rhea-AI Filing Summary

GSK reports that the US FDA has accepted for priority review a New Drug Application for bepirovirsen, an investigational antisense oligonucleotide for adults with chronic hepatitis B. The FDA has also granted Breakthrough Therapy Designation, adding to the Fast Track Designation awarded in February 2024.

The submission is backed by phase III B-Well 1 and B-Well 2 trials, where bepirovirsen plus standard of care achieved statistically significant, clinically meaningful functional cure rates versus standard of care alone, with an acceptable safety profile. Chronic hepatitis B affects more than 250 million people worldwide, and current standard therapies usually require lifelong treatment with low functional cure rates around 1%. The FDA has assigned 26 October 2026 as the PDUFA goal date.

Positive

• Regulatory momentum in a large disease area: Bepirovirsen has received FDA priority review, Breakthrough Therapy Designation, and earlier Fast Track Designation for chronic hepatitis B, a condition affecting more than 250 million people worldwide with low existing functional cure rates.
• Supportive phase III data: The NDA and designations are backed by phase III B-Well 1 and B-Well 2 trials, where bepirovirsen plus standard of care achieved statistically significant and clinically meaningful functional cure rates with an acceptable safety profile.

Negative

• None.

Insights

Biopharma regulatory analyst

Priority review and Breakthrough status highlight bepirovirsen’s potential in chronic hepatitis B.

The FDA’s priority review of bepirovirsen’s New Drug Application, combined with Breakthrough Therapy and prior Fast Track designations, underscores regulators’ view that this drug candidate may offer substantial improvement over existing chronic hepatitis B treatments that typically deliver about 1% functional cure rates.

Phase III B-Well 1 and B-Well 2 data showed statistically significant and clinically meaningful functional cure rates for bepirovirsen plus standard of care versus standard of care alone, with an acceptable safety and tolerability profile. These late-stage results form the backbone of the US submission and upcoming scientific presentations.

The PDUFA goal date of 26 October 2026 provides a clear timeline for a potential FDA decision on bepirovirsen. Data presentations at the European Association for the Study of the Liver Congress and peer-reviewed publications planned for 2026 will add important detail on efficacy, safety, and durability of functional cure.

Key Figures

PDUFA goal date: 26 October 2026 Global chronic hepatitis B prevalence: More than 250 million people US chronic hepatitis B prevalence: Approximately 1.7 million people +2 more

5 metrics

PDUFA goal date 26 October 2026 FDA review timeline for bepirovirsen NDA

Global chronic hepatitis B prevalence More than 250 million people Worldwide CHB population affected

US chronic hepatitis B prevalence Approximately 1.7 million people Estimated CHB population in the United States

Annual global hepatitis B deaths Approximately 1.1 million Deaths each year from hepatitis B–related disease

Typical functional cure rate on current care Around 1% Functional cure with existing nucleos(t)ide analogue therapy

Key Terms

Breakthrough Therapy Designation, Fast Track Designation, antisense oligonucleotide, functional cure, +2 more

6 terms

Breakthrough Therapy Designation regulatory

"Bepirovirsen has also received Breakthrough Therapy Designation (BTD), which is reserved for investigational medicines..."

A breakthrough therapy designation is a regulatory fast-track given to a drug or treatment that shows early signs of providing a major improvement over existing options for a serious condition. Think of it as a VIP lane that can speed up development and more intensive guidance from regulators, which matters to investors because it can shorten time to market, reduce development risk and potentially increase a company’s value — though it does not guarantee approval.

Fast Track Designation regulatory

"The BTD for bepirovirsen builds on the Fast Track Designation also provided by the US FDA in February 2024."

A "fast track designation" is a process that speeds up the review and approval of a product or project, allowing it to reach the market or be completed more quickly than usual. For investors, it can signal that a product may become available sooner, potentially leading to earlier revenue or benefits, and indicating a priority status that might influence company performance and market opportunities.

antisense oligonucleotide medical

"bepirovirsen, an investigational antisense oligonucleotide (ASO), for the treatment of adults with chronic hepatitis B"

An antisense oligonucleotide is a small piece of synthetic genetic material designed to attach to specific molecules in the body’s cells, effectively blocking or modifying how genes are expressed. This technology is important because it can be used to develop targeted treatments for certain diseases, which may influence the value of biotech companies and the broader healthcare sector. Its development reflects advances in personalized medicine and gene-based therapies.

functional cure medical

"demonstrating statistically significant and clinically meaningful functional cure rates in chronic hepatitis B"

A functional cure is a medical outcome in which a chronic disease is controlled so effectively that symptoms and progression are halted without completely removing the underlying cause; think of silencing a smoke alarm and removing the visible fire while some embers remain. For investors, a functional cure can change a treatment’s commercial value and market demand by reducing the need for continuous therapy, altering pricing, reimbursement and long-term revenue expectations for companies developing or selling the therapy.

PDUFA goal date regulatory

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

The PDUFA goal date is the target deadline set by the U.S. Food and Drug Administration for completing its review of a new drug or biologic application. Investors watch it like a court date for a product: the outcome (approval, rejection, or request for more information) can sharply change a company’s revenue prospects and stock price, and the date gives a predictable event around which markets and planning can focus.

priority review regulatory

"the US Food and Drug Administration (FDA) has accepted for priority review a New Drug Application (NDA) for bepirovirsen"

Priority review is a regulatory fast-track that shortens the time an agency spends evaluating a drug, vaccine or medical device application so a decision comes sooner than normal. For investors, it matters because a faster review is like an express lane to market: it can speed revenue potential and reduce regulatory uncertainty, but it does not guarantee approval and still requires the product to meet safety and effectiveness standards.

Form 6-K: How Foreign Companies Report to the SEC →

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 6-K

REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR 15d-16

UNDER THE SECURITIES EXCHANGE ACT OF 1934

For the month of April 2026

Commission File Number 001-15170

GSK plc

(Translation of registrant's name into English)

79 New Oxford Street, London, WC1A 1DG

(Address of principal executive office)

Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F.

Form 20-F . . . .X. . . . Form 40-F . . . . . . . .

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]

●    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] The BTD for bepirovirsen builds on the Fast Track Designation also provided by the US FDA in February 2024.[3] 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] and an estimated 1.7 million in the United States.[5] Current standard of care - typically nucleos(t)ide analogues - often requires lifelong therapy and functional cure rates remain low, typically around 1%.[6] 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]

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.

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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.

Registered in England & Wales:

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

[3] 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/ (last accessed March 2026)

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

[5]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)

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).

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorised.

GSK plc

(Registrant)

Date: April 28, 2026

By:/s/ VICTORIA WHYTE

--------------------------

Victoria Whyte

Authorised Signatory for and on

behalf of GSK plc

FAQ

What did GSK (GSK) announce about bepirovirsen in this 6-K filing?

GSK announced that the US FDA accepted a New Drug Application for bepirovirsen with priority review and granted Breakthrough Therapy Designation. The submission targets adults with chronic hepatitis B and is supported by phase III B-Well trials showing statistically significant, clinically meaningful functional cure rates.

What FDA designations has GSK’s bepirovirsen received for chronic hepatitis B?

Bepirovirsen has received Breakthrough Therapy Designation and priority review from the FDA, building on Fast Track Designation granted in February 2024. Breakthrough and Fast Track designations highlight the medicine’s potential to improve outcomes in serious conditions with significant unmet medical need.

When is the FDA’s PDUFA decision date for GSK’s bepirovirsen NDA?

The FDA has set 26 October 2026 as the Prescription Drug User Fee Act (PDUFA) goal date for GSK’s bepirovirsen New Drug Application. This date marks the agency’s target for completing its review of the application for treating adults with chronic hepatitis B.

What clinical data support GSK’s bepirovirsen filing for chronic hepatitis B?

The filing is supported by phase III B-Well 1 and B-Well 2 trials, where bepirovirsen plus standard of care achieved statistically significant, clinically meaningful functional cure rates versus standard of care alone. The trials also showed an acceptable safety and tolerability profile consistent with earlier studies.

How large is the chronic hepatitis B population targeted by GSK’s bepirovirsen?

Chronic hepatitis B affects more than 250 million people worldwide and about 1.7 million in the United States. Many patients require lifelong antiviral therapy, and existing standard treatments typically achieve functional cure rates around 1%, highlighting a significant unmet medical need.

What is meant by a functional cure in GSK’s bepirovirsen studies?

Functional cure is defined as hepatitis B surface antigen being undetectable in blood for at least 24 weeks after stopping all treatment. This indicates the immune system controls the disease without medication and is associated with reduced risk of long-term complications such as liver cancer.