Gilead Sciences Statement on Phase 3 Obeldesivir Clinical Trials in COVID-19: BIRCH Study to Stop Enrollment While OAKTREE Study Nears Full Enrollment

Foster City, Calif., September 28, 2023 – Gilead Sciences, Inc. (Nasdaq: GILD) today announced that it has stopped patient enrollment in BIRCH (Study GS-US-611-6273), a Phase 3 study evaluating the efficacy and safety of obeldesivir compared with placebo in non-hospitalized participants who are at high risk for developing severe COVID-19. This decision is based on lower-than-expected COVID-19 incidence rates and related hospitalizations or all-cause death by Day 29, which are primary endpoints in the study. The decision does not reflect any safety or efficacy concerns. Patients already enrolled will continue in the study which remains blinded.

The decision to stop enrolling patients in the BIRCH study does not impact the OAKTREE study (GS-US-611-6549), a Phase 3 study evaluating the safety and efficacy of obeldesivir compared with placebo in non-hospitalized participants without risk factors for developing severe COVID-19. OAKTREE is rapidly approaching full enrollment and will continue to enroll patients in the United States and Japan. Data from both studies will be shared with regulatory bodies as soon as possible.

Gilead is working to address the current unmet need for additional effective oral antiviral treatments that can be taken by people who have a standard-risk of developing severe disease.

More information about BIRCH (NCT05603143) and OAKTREE (NCT05715528) can be found at

Obeldesivir is an investigational product that has not been approved for any use in any country, and its safety and efficacy have not been established.

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, and cancer. Gilead operates in more than 35 countries worldwide, with headquarters in Foster City, California.

Forward-Looking Statements
This communication 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 within currently anticipated timelines or at all, and the possibility of unfavorable results from ongoing or additional clinical trials, including those involving  obeldesivir; the possibility that Gilead may make a strategic decision to discontinue development of obeldesivir, and as a result, obeldesivir may never be commercialized; uncertainties relating to regulatory applications and related filing and approval timelines; the risk that any regulatory approvals, if granted, may be subject to significant limitations on use; 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 June 30, 2023, 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.

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