-- If Approved, Bulevirtide Will Be the First Treatment Option for Adult Patients in the U. S. With Chronic Hepatitis Delta Virus Infection With Compensated Liver Disease --

Gilead Sciences, Inc. (Nasdaq: GILD) announced today that it has submitted a Biologics License Application (BLA) to the U.S. Food and Drug Administration (FDA) for bulevirtide for injection (2 mg), a potential first-in-class antiviral medicine for the treatment of chronic hepatitis delta virus (HDV) infection in adults with compensated liver disease; bulevirtide has been granted Breakthrough Therapy and Orphan Drug designations by the FDA. Bulevirtide is an investigational agent in the U.S. and the safety and efficacy have not been established. The BLA submission is supported by data from completed and ongoing Phase 2 studies and the ongoing Phase 3 MYR301 study which supports the safety and efficacy of bulevirtide 2 mg once daily after 24 weeks of therapy. In Europe, Hepcludex^® (bulevirtide) has been granted Conditional Marketing Authorization by the European Commission and PRIority MEdicines (PRIME) scheme eligibility by the European Medicines Agency (EMA), as the first approved treatment in Europe for adults with chronic HDV infection with compensated liver disease.

“Our goal is to bring safe and effective treatments to people living with the most severe form of chronic viral hepatitis that is associated with rapid progression to serious complications, including fibrosis, cirrhosis, and an increased risk of liver cancer and death,” said Merdad Parsey, MD, PhD, Chief Medical Officer, Gilead Sciences. “As a leader in hepatology, this filing is the latest milestone in Gilead’s ongoing efforts to address the needs of people living with liver diseases and leverages our deep understanding of chronic viral hepatitis. We look forward to working with the FDA with the goal of bringing this innovation to people living with HDV as quickly as possible.”

Interim results from the Phase 3 MYR301 study indicate that after 24 weeks of therapy, the proportion of people with HDV infection achieving the combined virological and biochemical response was 36.7% with bulevirtide 2 mg, 28% in participants receiving bulevirtide 10 mg and 0% in participants currently under observation who have not received antiviral treatment at this stage of the study. Treatment for 24 weeks with bulevirtide 2 mg had a statistically significant response (p<0.001) as compared to the no treatment group. Additionally, rapid alanine aminotransferase (ALT) reduction and normalization were observed in >50% of people with HDV in the bulevirtide 2 mg group compared with the no treatment group (5.9%). These results reinforce the efficacy of bulevirtide observed in completed Phase 2 studies for the treatment of HDV.

Based on these interim results, the safety profile of bulevirtide at 24 weeks is consistent with previously completed clinical studies. No serious adverse events (AEs), symptomatic elevations in bile salts or AEs leading to discontinuation related to bulevirtide were reported. The most common AEs observed with bulevirtide are raised levels of bile salts in the blood (which may affect more than 1 in 10 people), reactions at the site of injection (which may affect up to 1 in 10 people) and worsening of liver disease after stopping bulevirtide (which may affect up to 1 in 10 people).

About MYR301

MYR301 is an ongoing Phase 3 clinical trial evaluating the long-term efficacy and safety of bulevirtide in 150 people living with chronic HDV infection randomly allocated to treatment with either bulevirtide 2 mg once daily (n=49), bulevirtide 10 mg once daily (n=50) or no antiviral treatment (delayed treatment, n=51). In the initial MYR301 trial, treatment for 24 weeks with bulevirtide 10 mg had a statistically significant response (p<0.001) as compared to the no treatment group, with bulevirtide 2 mg having a numerically higher response rate compared to bulevirtide 10 mg. Rapid ALT reduction and normalization were observed in 38% of people taking bulevirtide 10 mg. Primary efficacy and safety data will be assessed at Week 48. After Week 48, participants in the delayed treatment group of the study will be 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 (<LoD) or ≥2log10 IU/ml decline from baseline and ALT normalization at Week 48. Secondary endpoints at Week 48 include undetectable HDV RNA and a change from baseline in liver stiffness measured by elastography.

About HDV

Chronic HDV infection 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 hepatitis B virus (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, hepatic decompensation and an increased risk of liver cancer and death. In the United States and Europe, there are approximately 230,000 people living with HDV infection; however, it remains underdiagnosed globally.

About Gilead Sciences in Liver Disease

For more than 20 years, Gilead has sought to address some of the biggest challenges in liver disease. The company has transformed the trajectory of multiple liver diseases through a relentless pursuit of innovation and pioneering access programs to bring meaningful therapies to people around the world. More work is required, and Gilead is committed to advancing innovative therapeutics to address the most pressing unmet needs in liver disease and overcoming barriers to better care.

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 and cancer. 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 receive FDA approval for bulevirtide for the treatment of chronic HDV infection in adults with compensated liver disease and the possibility of unfavorable results from ongoing or additional clinical studies involving bulevirtide. These and other risks, uncertainties and factors are described in detail in Gilead’s Quarterly Report on Form 10-Q for the quarter ended September 30, 2021, 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 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 Twitter (@GileadSciences) or call Gilead Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

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