FDA Grants Accelerated Approval to Gilead's Hepcludex® (bulevirtide-gmod), the First and Only Approved Treatment for Chronic Hepatitis Delta Virus (HDV)

– Chronic HDV is considered the most severe form of viral hepatitis due to rapid disease progression towards liver failure and liver-related death –

– Approval introduces the first FDA-approved therapy for this disease with limited treatment options and high unmet need –

Gilead Sciences, Inc. (NASDAQ:GILD) today announced that the U.S. Food and Drug Administration (FDA) has granted accelerated approval for Hepcludex^® (bulevirtide-gmod) 8.5 mg for the treatment of adults living with chronic hepatitis delta virus (HDV) infection, making it the first and only approved treatment for HDV in the United States.

The FDA granted accelerated approval to Hepcludex based on reductions in HDV RNA and normalization of alanine aminotransferase (ALT), supported primarily by data from the pivotal, controlled Phase 3 MYR301 study. At Week 48, the study demonstrated a statistically significant improvement versus the control (delayed treatment) group in a combined virologic and biochemical response. Improvement in disease-related clinical outcomes has not been established. Continued approval for the approved indication may be contingent on verification and description of clinical benefit in a confirmatory trial.

Chronic HDV is considered the most severe form of viral hepatitis and is associated with a markedly higher risk of rapid disease progression, liver failure, and mortality compared with HBV alone. In the United States, studies in general populations have estimated that HDV affects between 2% and 4% of individuals who have chronic hepatitis B virus (HBV), representing ~40,000-80,000 people.

"Hepatitis delta virus is associated with rapid progression of liver disease and a high risk of serious or even life-threatening liver-related complications," said Dr. Ira Jacobson, MD, Department of Medicine at NYU Grossman School of Medicine. "For patients, an HDV diagnosis means managing two distinct viral liver diseases—hepatitis B and hepatitis D—each contributing to disease progression, monitoring demands, and treatment complexities. The approval of Hepcludex for chronic HDV represents a critical advancement, introducing a long-awaited option that begins to address a significant unmet medical need and has the potential to meaningfully alter the course of this devastating disease for people living with HDV in the United States."

MYR301 (NCT03852719) evaluated the efficacy and safety of Hepcludex in adults with chronic HDV, with treatment administered for up to 144 weeks followed by 96 weeks of off-treatment follow-up. Hepcludex met its primary endpoint at Week 48, with continued treatment, demonstrated sustained efficacy and was generally well tolerated through up to 144 weeks of on-treatment exposure.

"The approval of Hepcludex represents a historic milestone for people living with HDV in the United States, marking the first FDA-approved treatment for HDV," said Dietmar Berger, MD, PhD, Chief Medical Officer at Gilead Sciences. "This reflects years of close engagement with the FDA and the application of rigorous science to address a serious disease with long-standing unmet need. With Hepcludex, we now have the opportunity to deliver a meaningful clinical advancement that has the potential to change the trajectory of HDV for patients in the U.S."

U.S. Access and Hepcludex Approval Across Markets

The Gilead Support Path^® Program offers information and resources to help patients diagnosed with chronic HBV, HDV and hepatitis C virus (HCV) and primary biliary cholangitis (PBC), as well as healthcare professionals, understand coverage and financial options for prescribed Gilead treatments.

Bulevirtide 2 mg is also approved for use in the European Economic Area (EEA) and other countries globally to treat people living with chronic HDV.

Please see below for U.S. Indication and Important Safety Information for Hepcludex.

U.S. Indication for Hepcludex

Hepcludex (bulevirtide-gmod) 8.5 mg for injection is indicated for the treatment of chronic hepatitis delta virus infection in adults without cirrhosis or with compensated cirrhosis.

This indication is approved under accelerated approval based on a decrease in HDV RNA and alanine aminotransferase (ALT) normalization. An improvement in disease-related clinical outcomes has not been established. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s).

U.S. Important Safety Information for Hepcludex

IMPORTANT SAFETY INFORMATION

BOXED WARNING: POSTTREATMENT SEVERE ACUTE EXACERBATION OF HEPATITIS D and B

Severe acute exacerbations of hepatitis D and hepatitis B may occur after HEPCLUDEX is discontinued, especially in patients with cirrhosis, who may be at increased risk of more severe flares or progression to hepatic decompensation. Monitor hepatic function closely with both clinical and laboratory follow-up, including hepatitis B virus (HBV) DNA and hepatitis delta virus (HDV) RNA viral load, for at least six months in patients who discontinue HEPCLUDEX. Resumption of antiviral therapy may be warranted.

Warnings and Precautions

Hypersensitivity reactions including anaphylaxis: Hypersensitivity reactions, including anaphylaxis, have been reported with HEPCLUDEX. If signs or symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, immediately discontinue HEPCLUDEX and initiate appropriate treatment.

Adverse Reactions

Most common adverse reactions (incidence ≥10%; all grades) in HEPCLUDEX clinical trials were injection site reactions, headache, abdominal pain, fatigue and pruritus.

Dosage and Administration

• Dosage in adults: 8.5 mg once daily administered by subcutaneous injection
• HEPCLUDEX should be continued as long as it is associated with a response to treatment. The optimal treatment duration is unknown.
• In all patients, manage the underlying HBV infection as clinically appropriate.

Pregnancy and Lactation

• Pregnancy: There are insufficient data from human pregnancies exposed to HEPCLUDEX to allow an assessment of a drug-associated risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes.
• Lactation: There are no data on the presence of HEPCLUDEX in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother's clinical need for HEPCLUDEX and any potential adverse effects on the breastfed child from HEPCLUDEX or from the underlying maternal condition.

About Hepcludex (bulevirtide)

Hepcludex (bulevirtide) is a first-in-class entry inhibitor for the treatment of adults living with chronic hepatitis delta virus (HDV) infection. Chronic HDV infection is a serious liver disease that occurs only as a co-infection in individuals with chronic HBV and is associated with rapid disease progression, liver failure, and increased mortality.

Hepcludex is supplied as a vial for once-daily subcutaneous injection. Each vial contains an 8.5 mg dose when prepared according to the Instructions for Use within FDA-approved labeling.

Hepcludex works by blocking the entry of both HDV and HBV into liver cells, addressing a key step in the viral lifecycle. The FDA's accelerated approval of Hepcludex is supported by data from the Phase 3 MYR301 study demonstrating that Hepcludex was an effective and generally well-tolerated treatment option, with durable efficacy observed through long-term treatment of up to 144 weeks.

Hepcludex is supplied as a once-daily injectable therapy and represents the first and only treatment option for people living with HDV that received FDA accelerated approval in the United States, addressing a long-standing unmet medical need for this historically underserved patient community.

As part of the FDA accelerated approval, Gilead has committed to a confirmatory long-term outcomes study, which has already been initiated in people living with chronic HDV. Continued approval may be contingent upon verification of clinical benefit.

About HDV

Chronic HDV is the most severe form of viral hepatitis and can have mortality rates as high as 50% within five years in cirrhotic patients. HDV occurs only as a co-infection in individuals who have HBV. It is estimated that at least 12 million people worldwide are currently co-infected with HDV and HBV. HDV co-infection is associated with a faster progression to liver fibrosis, cirrhosis and hepatic decompensation and an increased risk of liver cancer and death. In the U.S., it is estimated that there are ~40,000-80,000 people living with HDV.

About Gilead Sciences in Liver Disease

For decades, Gilead has pioneered the way forward to improve the lives of people living with liver disease around the world. We have helped to transform hepatitis C from a chronic condition into one that can be cured for millions of people. For people living with hepatitis B or D, our focus on advancing our medicines drives hope that today's research will turn into tomorrow's cures. Beyond viral hepatitis, we're working to deliver advanced treatments for people living with PBC. But our commitment doesn't stop there. Through our ground-breaking science and collaborative partnerships, we strive to create healthier futures for everyone living with liver disease. We are committed to a future without liver disease.

About Gilead Sciences

Gilead Sciences, Inc. is a biopharmaceutical company that has pursued and achieved breakthroughs in medicine for more than three decades, with the goal of creating a healthier world for all people. The company is committed to advancing innovative medicines to prevent and treat life-threatening diseases, including HIV, viral hepatitis, COVID-19, cancer and inflammation. Gilead operates in more than 35 countries worldwide, with headquarters in Foster City, California.

Forward-Looking Statements

This press release includes forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that are subject to risks, uncertainties and other factors, including Gilead's ability to initiate, progress or complete clinical trials or studies within currently anticipated timelines or at all, and the possibility of unfavorable results from ongoing or additional clinical trials or studies, including those involving bulevirtide; uncertainties relating to regulatory applications and related filing and approval timelines, including additional pending and potential applications for Hepcludex, and the risk that any such approvals, if granted, may be subject to significant limitations on use or subject to withdrawal or other adverse actions by the applicable regulatory authority; the risk that physicians may not see the benefits of prescribing Hepcludex for the treatment of HDV; and any assumptions underlying any of the foregoing. These and other risks, uncertainties and factors are described in detail in Gilead's Quarterly Report on Form 10-Q for the quarter ended March 31, 2026, as filed with the U.S. Securities and Exchange Commission. These risks, uncertainties and other factors could cause actual results to differ materially from those referred to in the forward-looking statements. All statements other than statements of historical fact are statements that could be deemed forward-looking statements. The reader is cautioned that any such forward-looking statements are not guarantees of future performance and involve risks and uncertainties and is cautioned not to place undue reliance on these forward-looking statements. All forward-looking statements are based on information currently available to Gilead, and Gilead assumes no obligation and disclaims any intent to update any such forward-looking statements.

Hepcludex, Gilead and the Gilead logo are registered trademarks of Gilead Sciences, Inc., or its related companies.

U.S. full Prescribing Information for Hepcludex is available at www.gilead.com.

For more information about Gilead, please visit the company's website at www.gilead.com, follow Gilead on X/Twitter (@Gilead Sciences) and LinkedIn (@Gilead-Sciences).

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Priscilla White, Media

public_affairs@gilead.com

Jacquie Ross, Investors

investor_relations@gilead.com