Merck Advances Phase 3 Trial to Evaluate Investigational Islatravir as Once-Monthly Oral PrEP for Women at High Risk for Acquiring HIV-1

Collaboration with the Bill & Melinda Gates Foundation Seeks to Bring Forward a New HIV Prevention Option to Help Address the HIV Epidemic with Focus on Women in Sub-Saharan Africa.

KENILWORTH, N.J., November 16, 2020 – Merck (NYSE: MRK), known as MSD outside of the United States and Canada, today announced a collaboration with the Bill & Melinda Gates Foundation (the foundation) where the foundation is committing to provide funding to support a pivotal Phase 3 study investigating a once-monthly oral pre-exposure prophylaxis (PrEP)1 option in women and adolescent girls at high risk for acquiring HIV-1 infection in sub-Saharan Africa. The study, IMPOWER 22, will evaluate the efficacy and safety of islatravir — Merck’s novel investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI) under evaluation for both treatment and prevention — and is anticipated to begin by early 2021. More than half of new HIV infections globally occur in sub-Saharan Africa, with women accounting for nearly 60 percent of new infections in this region.

“Our collaboration with the Bill & Melinda Gates Foundation exemplifies our shared mission to end the global HIV epidemic through meaningful innovations in HIV prevention, including additional PrEPPrEP Prophylaxie Pré-Exposition. La PrEP est une stratégie qui permet à une personne séronégative exposée au VIH d'éliminer le risque d'infection, en prenant, de manière continue ou «à la demande», un traitement anti-rétroviral à base de Truvada®. options,” said Dr. Roy D. Baynes, senior vice president and head of global clinical development, chief medical officer, Merck Research Laboratories. “Islatravir is a promising antiviral candidate with evidence from ongoing clinical trials to support its development as a once-monthly oral PrEP agent. Through this collaboration, we can further explore the potential of islatravir as part of our work towards the collective global public health goal of reducing the number of new HIV infections.”

“The world will not be able to end the HIV epidemic until we can effectively prevent HIV acquisition in at-risk individuals and populations,” said Dr. Emilio Emini, director of the TB & HIV program, the Bill & Melinda Gates Foundation. “This collaboration will help advance HIV science and potentially offer a new option to prevent HIV acquisition among at-risk women, both in sub- Saharan Africa and globally.”

Per the agreement between the foundation and Merck, the foundation, in its role as a funder, intends to provide grant funding to the International Clinical Research Center (ICRC) at the University of Washington Department of Global Health, which is collaborating with Merck on the IMPOWER 22 study. This grant will support ICRC’s work with experienced trial sites in sub-Saharan Africa to enroll, follow and retain the large number of women required for this research.

Merck will be the trial sponsor, responsible for supplying the medicine, gaining regulatory and customs approvals, and providing operational expertise and resources for management of the trial, such as site monitoring and data reporting. Merck will be funding the IMPOWER 22 clinical trial in the United States.

“Globally, women continue to be underserved in HIV research and care. In 2019, women accounted for 48 percent of new infections, and in 2018, AIDS-related illnesses remained the leading cause of death for women during their reproductive years,” said Prof. Elizabeth Anne Bukusi, MBChB, PhD, senior principal clinical research scientist and co-director of the Research
Care Training Program at the Center for Microbiology Research of The Kenya Medical Research Institute, and a trial investigator. “We will not turn the tide on HIV globally until we turn the tide on the virus in Africa, and this clinical trial seeks to help advance this effort through its focus on women, especially younger women, who remain disproportionately at risk on this continent.”


Clinical Trials Program IMPOWER 22 is a randomized, active-controlled, double-blind, multisite Phase 3 study evaluating the efficacy and safety of islatravir administered orally once-monthly as PrEP in cisgender women who are at high risk for HIV-1 infection in sub-Saharan Africa and the United States. The active comparator for this study, emtricitabine/tenofovir disoproxil fumarate (FTC/TDF), will be administered orally once daily. Approximately 4,500 cisgender women and adolescent girls, ages 16 through 45, will be randomized (stratified by site and age) in a 1:1 ratio to receive either islatravir or FTC/TDF for the duration of the study.

Information on this study will be posted shortly on

Merck also plans to conduct additional studies in HIV prevention with islatravir in once- monthly oral PrEP. These studies will include IMPOWER 24, a global Phase 3 clinical trial to evaluate islatravir as a once-monthly oral agent for PrEP at sites across the world and among other key populations impacted by the epidemic, including men who have sex with men (MSM) and transgender women.

About Islatravir (MK-8591)

Islatravir (formerly MK-8591) is Merck’s investigational nucleoside reverse transcriptase translocation inhibitor (NRTTI) currently being evaluated in clinical trials for the treatment of HIV-1 infection in combination with other antiretrovirals, as well as for pre-exposure prophylaxis (PrEP) of HIV-1 infection as a single investigational agent, across a variety of formulations. In 2012, Merck licensed islatravir (4’-ethynyl-2-fluoro-2’-deoxyadenosine or EFdA) from the Yamasa Corporation based in Choshi, Japan.