Final Data From the Phase 3 MYR301 Study Demonstrated Longer Treatment With Bulevirtide Was Associated With Sustaining Undetectability After Stopping Treatment

– 90% of Adults with Chronic Hepatitis Delta Virus (HDV) who Achieved Undetectable HDV RNA at 96 Weeks of Treatment with Bulevirtide Remained Undetectable for Almost 2 Years After Stopping Treatment –

Gilead Sciences Inc. (NASDAQ:GILD) today announced final results from the pivotal Phase 3 MYR301 study revealing that 36% (23 out of 64) of adults living with chronic hepatitis delta virus (HDV) treated with the first-in-class entry inhibitor bulevirtide at either a 2 mg or 10 mg dose maintained virologic suppression for almost two years after stopping treatment after achieving undetectable HDV RNA at end of treatment (EOT). In participants who sustained undetectability for one year after end of therapy, no relapses occurred in the second year of follow-up. In addition, sustained post-treatment undetectable HDV RNA was more frequent in participants with longer on-treatment HDV RNA undetectability at end of treatment: 90% (9/10) of those who had HDV RNA undetectability for ≥ 96 weeks at end of treatment remained HDV undetectable off-treatment. These new data, presented at the European Association for the Study of the Liver (EASL) Congress 2025, show the potential value of bulevirtide monotherapy for some adults living with chronic HDV, even after treatment has ended.

"HDV is the most severe form of viral hepatitis with more rapid progression towards liver cancer and liver-related death. Previous data have demonstrated the potential of bulevirtide as a safe and effective treatment option and, as EASL and the European Medicines Agency guidelines recommend, continued treatment is encouraged as long as people are experiencing a clinical benefit," said Professor Heiner Wedemeyer, Head and Chair of the Department of Gastroenterology, Hepatology, Infectious Diseases and Endocrinology at Hannover Medical School. "With today's results, we're now seeing the potential of bulevirtide to maintain virologic suppression and normalize markers of liver inflammation for a subset of people living with HDV, demonstrating a durable response, even after treatment cessation."

The findings (LBO-004) build on data, presented at The Liver Meeting^® 2024, hosted by the American Association for the Study of Liver Diseases (AASLD), from MYR301 which demonstrated a subset of participants treated with bulevirtide monotherapy had undetectable HDV RNA 48 weeks after stopping treatment. Today's presentation adds further insight by not only showing the durability of response post-treatment, but that sustained undetectability was more frequent in people with longer, on-treatment HDV RNA undetectability at the time of bulevirtide discontinuation. Furthermore, post-treatment hepatic serious adverse events (SAEs) were reported in 14% (20/142) of participants but were resolved in 85% (17/20) of these participants, most of whom restarted bulevirtide therapy.

"At Gilead, we are committed to advancing research and exploring the full potential of bulevirtide as a monotherapy, in combination, and at different doses, to help improve outcomes for people living with chronic HDV," said Anu Osinusi, Vice President, Clinical Research for Hepatitis, Respiratory and Emerging Viruses at Gilead. "Previous results from MYR301 demonstrated the potential benefits of long-term treatment with bulevirtide. With this new data, we now have valuable insight into the durability of the response even after treatment has ended."

HDV affects an estimated 4.5% of people living with chronic hepatitis B (HBV), with an estimated global prevalence of 12 million people. Bulevirtide 2 mg remains the only approved treatment for adults with chronic HDV and compensated liver disease in the European Economic Area (EEA), the UK, Switzerland and Australia and is not approved in the U.S. or elsewhere. Bulevirtide 10 mg is an investigational product and is not approved anywhere.

For more information on the EASL Congress 2025 and Gilead's presentations, please visit the congress website.

Marketing Authorization

In July 2023, the European Commission (EC) granted full Marketing Authorization (MA) for Hepcludex^® (bulevirtide) 2 mg for the treatment of adults with chronic HDV and compensated liver disease. Bulevirtide was initially granted a conditional MA from the EC in July 2020 to provide people living with HDV urgent access to treatment. Bulevirtide's conditional MA license in the UK was converted to a full MA in August 2023, and a full MA was granted in Switzerland in February 2024. In regions where bulevirtide is not approved, including the U.S., bulevirtide 2 mg is an investigational product. In these regions, health authorities have not established the safety and efficacy of bulevirtide. Bulevirtide 10 mg is an investigational product and is not approved anywhere globally.

About MYR301

MYR301 is a Phase 3 clinical trial evaluating the long-term efficacy and safety of bulevirtide in 150 people living with chronic HDV randomly allocated to treatment with bulevirtide 2 mg once daily (n=49), 10 mg once daily (n=50) or no antiviral treatment (delayed treatment, n=51). Primary efficacy and safety data was assessed at Week 48. After Week 48, participants in the delayed treatment group of the study were switched to bulevirtide 10 mg once daily for an additional 96 weeks. The total duration of treatment across all groups in the study is 144 weeks. The primary endpoint, combined response, is defined as an undetectable HDV RNA or ≥2log10 IU/ml decline from baseline and ALT normalization at Week 48. Secondary endpoints at Week 48 include undetectable HDV RNA (key secondary endpoint), ALT normalization, and a change from baseline in liver stiffness measured by transient elastography.

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. The company has helped to transform hepatitis C from a chronic condition into a curable condition. For individuals living with hepatitis B or hepatitis delta (HDV), Gilead's focus on advancing medicines drives hope that today's research will turn into tomorrow's cures. Beyond viral hepatitis, Gilead is working to deliver advanced treatments for people living with primary biliary cholangitis. The commitment of Gilead does not stop there. Through ground-breaking science and collaborative partnerships, the company strives to create healthier futures for everyone living with liver disease. Gilead remains devoted 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 bulevirtide; and the risk that any such approvals, if granted, may be subject to significant limitations on use; the risk that physicians may not see the benefits of prescribing bulevirtide 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, 2025, 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.

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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Blair Baumwell, Media

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Jacquie Ross, Investors

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