Gilead and Merck Announce Phase 2 Data Showing a Treatment Switch to an Investigational Oral Once-Weekly Combination Regimen of Islatravir and Lenacapavir Maintained Viral Suppression in Adults at Week 48

– Novel Investigational Combination Regimen is Advancing to Phase 3 and has the Potential to Become the First Weekly Oral HIV Treatment –

Gilead Sciences, Inc. GILD and Merck MRK, known as MSD outside of the United States and Canada, today announced new results from a Phase 2 clinical study evaluating the investigational combination of islatravir, an investigational nucleoside reverse transcriptase translocation inhibitor, and lenacapavir, a first-in-class HIV-1 capsid inhibitor. These late-breaking data were presented during an oral session at IDWeek 2024, taking place in Los Angeles, and virtually, from October 16-19.

At 48 weeks, the novel investigational combination maintained a high rate (n=49; 94.2%) of viral suppression (HIV-1 RNA <50 copies/mL) in virologically suppressed adults, a secondary endpoint of the study. Zero participants had a viral load of ≥50 copies/mL at Week 48. Week 24 results, including the study's primary endpoint, were previously presented at the 31st Conference on Retroviruses and Opportunistic Infections (CROI).

"The future of HIV treatment is person-centered, with long-acting options tailored to help meet the needs and preferences of people affected by HIV," said Jared Baeten, MD, PhD, Senior Vice President, Virology Therapeutic Area Head, Gilead Sciences. "There is no ‘one size fits all' approach. The complexities of HIV care require putting people first in the development of biomedical innovations as we keep striving to offer options for all those living with HIV. These data presented at IDWeek demonstrate our commitment to continuous scientific discovery aimed at further transforming the HIV treatment landscape."

In this open-label, active-controlled study (NCT05052996), virologically suppressed adults (n=104) on Biktarvy^® (bictegravir 50 mg/emtricitabine 200 mg/tenofovir alafenamide 25 mg tablets, B/F/TAF) were randomly allocated in a 1:1 ratio to receive either oral islatravir 2 mg and lenacapavir 300 mg once a week (n=52) or to continue daily oral Biktarvy (n=52). The median age of participants was 40 years (20-76). Eighteen percent of participants were assigned female at birth, 50% were non-white, and 29% were Latine.

The proportion of individuals with HIV-1 RNA <50 c/mL at Week 48 by FDA snapshot algorithm (a secondary endpoint), showed that participants who switched to treatment with once-weekly islatravir and lenacapavir (ISL + LEN) or continued Biktarvy maintained comparable high rates of HIV suppression at Week 48 (94.2% v. 92.3%, respectively). No participants treated with either ISL + LEN or Biktarvy had a viral load of ≥ 50 copies/mL at Week 48 (another secondary endpoint).

Treatment-related-adverse events (TRAEs), as attributed by study investigator, were experienced by 19.2% of participants (n=10/52) in the ISL + LEN group and the most common were dry mouth (n=2/52; 3.8%) and nausea (n=2/52; 3.8%). TRAEs were reported by 5.8% of participants in the Biktarvy group (n=3/52). No grade 3 or 4 TRAEs related to the study drug were reported in either treatment group. Two participants (n=2/52; 3.8%) discontinued ISL + LEN due to adverse events unrelated to the drug. At Week 48 no significant differences were seen between treatment groups in mean change from baseline in CD4+ T-cell counts or absolute lymphocyte counts. No participants discontinued due to a decrease in CD4+ T-cell or lymphocyte counts.

"Daily single-tablet regimens have helped to transform HIV care but can be challenging for some people to maintain. Novel HIV treatment options that allow for less frequent oral dosing have the potential to help support adherence, and address stigma faced by some individuals taking daily oral therapy," said Dr. Elizabeth Rhee, Vice President, Global Clinical Development, Merck Research Laboratories. "We are pleased to see these encouraging 48-week data for this once-weekly oral combination regimen and advance to phase 3 clinical trials in collaboration with Gilead."

Along with these most recent study results, the potent antiviral activities, and pharmacokinetic profiles of islatravir and lenacapavir support their continued development as an investigational once-weekly oral combination regimen for use in people with HIV who are virologically suppressed. This investigational combination of weekly oral ISL 2 mg + LEN 300 mg is being further evaluated as a fixed-dose combination regimen in two Phase 3 studies (NCT06630286 and NCT06630299) in virologically suppressed people with HIV.

Islatravir in combination with lenacapavir is investigational and not approved anywhere globally. The safety and efficacy of the combination of islatravir and lenacapavir have not been established.

Lenacapavir is being studied in multiple ongoing early and late-stage development programs and has the potential to offer a diverse set of person-centric options for treatment that could uniquely fit into the lives of people with HIV. The use of lenacapavir for HIV treatment in virologically suppressed individuals is investigational and not approved anywhere globally.

Please see below for the U.S. Indication and Important Safety Information, including Boxed Warning, for Biktarvy.

There is currently no cure for HIV or AIDS.

About Islatravir (MK-8591) and Merck's HIV Research

Islatravir (MK-8591) is Merck's investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI) under evaluation in multiple ongoing early and late-stage clinical studies in combination with other antiretrovirals for the treatment of HIV-1. Studies with islatravir are designed to offer different dosing options as potential daily and once-weekly treatments. For an overview of Merck's HIV treatment and prevention clinical development program, please click here.

About Lenacapavir

The multi-stage mechanism of action of lenacapavir, is distinguishable from other currently approved classes of antiviral agents. While most antivirals act on just one stage of viral replication, lenacapavir is designed to inhibit HIV at multiple stages of its lifecycle.

Lenacapavir is being evaluated as a potential long-acting option in multiple ongoing and planned early and late-stage clinical studies in Gilead's HIV prevention and treatment research program. The goal is to offer both long-acting oral and injectable options with various dosing frequencies in combination with other antiretroviral agents for treatment or as a single agent for prevention. This approach aims to help address the individual needs and preferences of people with HIV and people who could benefit from pre-exposure prophylaxis (PrEP). The use of lenacapavir for HIV prevention is investigational and the safety and efficacy of lenacapavir for this use has not been established.

About Merck

At Merck, known as MSD outside of the United States and Canada, we are unified around our purpose: We use the power of leading-edge science to save and improve lives around the world. For more than 130 years, we have brought hope to humanity through the development of important medicines and vaccines. We aspire to be the premier research-intensive biopharmaceutical company in the world – and today, we are at the forefront of research to deliver innovative health solutions that advance the prevention and treatment of diseases in people and animals. We foster a diverse and inclusive global workforce and operate responsibly every day to enable a safe, sustainable and healthy future for all people and communities. For more information, visit www.merck.com and connect with us on X (formerly Twitter), Facebook, Instagram, YouTube and LinkedIn.

Merck's Commitment to HIV

For more than 35 years, Merck has been committed to scientific research and discovery in HIV leading to scientific breakthroughs that have helped change HIV treatment. Our work has been pioneering in the development of new options across multiple drug classes to help those impacted by HIV. Today, we are developing a series of antiviral options designed to help people manage HIV and protect people from HIV, with the goal of reducing the growing burden of infection worldwide. We want to ensure people are not defined by HIV and our work focuses on transformational innovations, collaborations with others in the global HIV community, and access initiatives aimed at the goal of helping to end the HIV epidemic for everyone.

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, Calif.

About Gilead Sciences in HIV

For 35 years, Gilead has been a leading innovator in the field of HIV, driving advances in treatment, prevention and cure research. Gilead researchers have developed 12 HIV medications, including the first single-tablet regimen to treat HIV, the first antiretroviral for pre-exposure prophylaxis (PrEP) to help reduce new HIV infections, and the first long-acting injectable HIV treatment medication administered twice-yearly. Our advances in medical research have helped to transform HIV into a treatable, preventable, chronic condition for millions of people.

Gilead is committed to continued scientific innovation to provide solutions for the evolving needs of people affected by HIV around the world. Through partnerships, collaborations, and charitable giving, the company also aims to improve education, expand access and address barriers to care, with the goal of ending the HIV epidemic for everyone, everywhere. Gilead is recognized as one of the leading funders of HIV-related programs in a report released by Funders Concerned About AIDS.

IMPORTANT U.S. SAFETY INFORMATION AND INDICATION FOR THE USE OF BIKTARVY

Biktarvy is indicated as a complete regimen for the treatment of human immunodeficiency virus type 1 (HIV-1) infection in adults and pediatric patients weighing at least 14 kg who have no antiretroviral treatment history or to replace the current antiretroviral regimen in those who are virologically-suppressed (HIV-1 RNA less than 50 copies per mL) on a stable antiretroviral regimen with no history of treatment failure and no known or suspected substitutions associated with resistance to bictegravir or tenofovir.

BOXED WARNING: POST TREATMENT ACUTE EXACERBATION OF HEPATITIS B

• Severe acute exacerbations of hepatitis B have been reported in patients who are coinfected with HIV-1 and HBV and have discontinued products containing emtricitabine (FTC) and/or tenofovir disoproxil fumarate (TDF), and may occur with discontinuation of BIKTARVY. Closely monitor hepatic function with both clinical and laboratory follow-up for at least several months in patients who are coinfected with HIV-1 and HBV and discontinue BIKTARVY. If appropriate, anti-hepatitis B therapy may be warranted.

Contraindications

• Coadministration: Do not use BIKTARVY with dofetilide or rifampin.

Warnings and precautions

• Drug interactions: See Contraindications and Drug Interactions sections. Consider the potential for drug interactions prior to and during BIKTARVY therapy and monitor for adverse reactions.

• Immune reconstitution syndrome, including the occurrence of autoimmune disorders with variable time to onset, has been reported.

• New onset or worsening renal impairment: Postmarketing cases of renal impairment, including acute renal failure, proximal renal tubulopathy (PRT), and Fanconi syndrome have been reported with tenofovir alafenamide (TAF)–containing products. Do not initiate BIKTARVY in patients with estimated creatinine clearance (CrCl) <30 mL/min except in virologically suppressed adults <15 mL/min who are receiving chronic hemodialysis. Patients with impaired renal function and/or taking nephrotoxic agents (including NSAIDs) are at increased risk of renal-related adverse reactions. Discontinue BIKTARVY in patients who develop clinically significant decreases in renal function or evidence of Fanconi syndrome. Renal monitoring: Prior to or when initiating BIKTARVY and during therapy, assess serum creatinine, CrCl, urine glucose, and urine protein in all patients as clinically appropriate. In patients with chronic kidney disease, assess serum phosphorus.

• Lactic acidosis and severe hepatomegaly with steatosis: Fatal cases have been reported with the use of nucleoside analogs, including FTC and TDF. Discontinue BIKTARVY if clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity develop, including hepatomegaly and steatosis in the absence of marked transaminase elevations.

Adverse reactions

• Most common adverse reactions (incidence ≥5%; all grades) in clinical studies through week 144 were diarrhea (6%), nausea (6%), and headache (5%).

Drug interactions

• Prescribing information: Consult the full prescribing information for BIKTARVY for more information on Contraindications, Warnings, and potentially significant drug interactions, including clinical comments.

• Enzymes/transporters: Drugs that induce P-gp or induce both CYP3A and UGT1A1 can substantially decrease the concentration of components of BIKTARVY. Drugs that inhibit P-gp, BCRP, or inhibit both CYP3A and UGT1A1 may significantly increase the concentrations of components of BIKTARVY. BIKTARVY can increase the concentration of drugs that are substrates of OCT2 or MATE1.

• Drugs affecting renal function: Coadministration of BIKTARVY with drugs that reduce renal function or compete for active tubular secretion may increase concentrations of FTC and tenofovir and the risk of adverse reactions.

Dosage and administration

• Dosage: Adult and pediatric patients weighing ≥25 kg: 1 tablet containing 50 mg bictegravir (BIC), 200 mg emtricitabine (FTC), and 25 mg tenofovir alafenamide (TAF) taken once daily with or without food. Pediatric patients weighing ≥14 kg to <25 kg: 1 tablet containing 30 mg BIC, 120 mg FTC, and 15 mg TAF taken once daily with or without food. For children unable to swallow a whole tablet, the tablet can be split and each part taken separately as long as all parts are ingested within approximately 10 minutes.

• Renal impairment: For patients weighing ≥25 kg, not recommended in patients with CrCl 15 to <30 mL/min, or <15 mL/min who are not receiving chronic hemodialysis, or <15 mL/min who are receiving chronic hemodialysis and have no antiretroviral treatment history. For patients weighing ≥14 kg to <25 kg, not recommended in patients with CrCl <30 mL/min.

• Hepatic impairment: Not recommended in patients with severe hepatic impairment.

• Prior to or when initiating: Test patients for HBV infection.

• Prior to or when initiating, and during treatment: As clinically appropriate, assess serum creatinine, CrCl, urine glucose, and urine protein in all patients. In patients with chronic kidney disease, assess serum phosphorus.

Pregnancy and lactation

• Pregnancy: BIKTARVY is recommended in pregnant individuals who are virologically suppressed on a stable ARV regimen with no known substitutions associated with resistance to any of the individual components of BIKTARVY. Lower plasma exposures of BIKTARVY were observed during pregnancy; therefore, viral load should be monitored closely during pregnancy. An Antiretroviral Pregnancy Registry (APR) has been established. Available data from the APR for BIC, FTC, or TAF show no difference in the rates of birth defects compared with a US reference population.

• Lactation: Individuals infected with HIV-1 should be informed of the potential risks of breastfeeding.

Gilead 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 and additional clinical trials or studies, including those involving lenacapavir; uncertainties relating to regulatory applications and related filing and approval timelines, including potential applications for indications currently under evaluation; the possibility that Gilead may make a strategic decision to discontinue development of these programs and, as a result, these programs may never be successfully commercialized for the indications currently under evaluation; 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, 2024, 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.

Forward-Looking Statement of Merck & Co., Inc., Rahway, N.J., USA

This news release of Merck & Co., Inc., Rahway, N.J., USA (the "company") includes "forward-looking statements" within the meaning of the safe harbor provisions of the U.S. Private Securities Litigation Reform Act of 1995. These statements are based upon the current beliefs and expectations of the company's management and are subject to significant risks and uncertainties. There can be no guarantees with respect to pipeline candidates that the candidates will receive the necessary regulatory approvals or that they will prove to be commercially successful. If underlying assumptions prove inaccurate or risks or uncertainties materialize, actual results may differ materially from those set forth in the forward-looking statements.

Risks and uncertainties include but are not limited to, general industry conditions and competition; general economic factors, including interest rate and currency exchange rate fluctuations; the impact of pharmaceutical industry regulation and health care legislation in the United States and internationally; global trends toward health care cost containment; technological advances, new products and patents attained by competitors; challenges inherent in new product development, including obtaining regulatory approval; the company's ability to accurately predict future market conditions; manufacturing difficulties or delays; financial instability of international economies and sovereign risk; dependence on the effectiveness of the company's patents and other protections for innovative products; and the exposure to litigation, including patent litigation, and/or regulatory actions.

The company undertakes no obligation to publicly update any forward-looking statement, whether as a result of new information, future events or otherwise. Additional factors that could cause results to differ materially from those described in the forward-looking statements can be found in the company's Annual Report on Form 10-K for the year ended December 31, 2023 and the company's other filings with the Securities and Exchange Commission (SEC) available at the SEC's Internet site (www.sec.gov).

U.S. full Prescribing Information for Biktarvy, including BOXED WARNING, is available at www.gilead.com.

Biktarvy, Gilead and the Gilead logo are registered trademarks of Gilead Sciences, Inc., or its related companies. All other marks are the property of their respective owners.

For more information about Gilead, please visit the company's website at www.gilead.com, follow Gilead on X (@Gilead Sciences) and LinkedIn, or call Gilead Public Affairs at 1-800-GILEAD-5 or 1-650-574-3000.

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